[babeltrace.git] / src / plugins / ctf / lttng-live / lttng-live.c

/*
 * SPDX-License-Identifier: MIT
 *
 * Copyright 2019 Francis Deslauriers <francis.deslauriers@efficios.com>
 * Copyright 2016 Jérémie Galarneau <jeremie.galarneau@efficios.com>
 * Copyright 2016 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * Babeltrace CTF LTTng-live Client Component
 */

#define BT_COMP_LOG_SELF_COMP self_comp
#define BT_LOG_OUTPUT_LEVEL log_level
#define BT_LOG_TAG "PLUGIN/SRC.CTF.LTTNG-LIVE"
#include "logging/comp-logging.h"

#include <inttypes.h>
#include <stdbool.h>
#include <unistd.h>

#include <glib.h>

#include "common/assert.h"
#include <babeltrace2/babeltrace.h>
#include "compat/compiler.h"
#include <babeltrace2/types.h>

#include "plugins/common/muxing/muxing.h"
#include "plugins/common/param-validation/param-validation.h"

#include "data-stream.h"
#include "metadata.h"
#include "lttng-live.h"

#define MAX_QUERY_SIZE                      (256*1024)
#define URL_PARAM                           "url"
#define INPUTS_PARAM                        "inputs"
#define SESS_NOT_FOUND_ACTION_PARAM         "session-not-found-action"
#define SESS_NOT_FOUND_ACTION_CONTINUE_STR  "continue"
#define SESS_NOT_FOUND_ACTION_FAIL_STR      "fail"
#define SESS_NOT_FOUND_ACTION_END_STR       "end"

#define print_dbg(fmt, ...)     BT_COMP_LOGD(fmt, ## __VA_ARGS__)

static
const char *lttng_live_iterator_status_string(
                enum lttng_live_iterator_status status)
{
        switch (status) {
        case LTTNG_LIVE_ITERATOR_STATUS_CONTINUE:
                return "LTTNG_LIVE_ITERATOR_STATUS_CONTINUE";
        case LTTNG_LIVE_ITERATOR_STATUS_AGAIN:
                return "LTTNG_LIVE_ITERATOR_STATUS_AGAIN";
        case LTTNG_LIVE_ITERATOR_STATUS_END:
                return "LTTNG_LIVE_ITERATOR_STATUS_END";
        case LTTNG_LIVE_ITERATOR_STATUS_OK:
                return "LTTNG_LIVE_ITERATOR_STATUS_OK";
        case LTTNG_LIVE_ITERATOR_STATUS_INVAL:
                return "LTTNG_LIVE_ITERATOR_STATUS_INVAL";
        case LTTNG_LIVE_ITERATOR_STATUS_ERROR:
                return "LTTNG_LIVE_ITERATOR_STATUS_ERROR";
        case LTTNG_LIVE_ITERATOR_STATUS_NOMEM:
                return "LTTNG_LIVE_ITERATOR_STATUS_NOMEM";
        case LTTNG_LIVE_ITERATOR_STATUS_UNSUPPORTED:
                return "LTTNG_LIVE_ITERATOR_STATUS_UNSUPPORTED";
        default:
                bt_common_abort();
        }
}

static
const char *lttng_live_stream_state_string(enum lttng_live_stream_state state)
{
        switch (state) {
        case LTTNG_LIVE_STREAM_ACTIVE_NO_DATA:
                return "ACTIVE_NO_DATA";
        case LTTNG_LIVE_STREAM_QUIESCENT_NO_DATA:
                return "QUIESCENT_NO_DATA";
        case LTTNG_LIVE_STREAM_QUIESCENT:
                return "QUIESCENT";
        case LTTNG_LIVE_STREAM_ACTIVE_DATA:
                return "ACTIVE_DATA";
        case LTTNG_LIVE_STREAM_EOF:
                return "EOF";
        default:
                return "ERROR";
        }
}

void lttng_live_stream_iterator_set_state(struct lttng_live_stream_iterator *stream_iter,
                enum lttng_live_stream_state new_state)
{
        bt_self_component *self_comp = stream_iter->self_comp;
        bt_logging_level log_level = stream_iter->log_level;

        BT_COMP_LOGD("Setting live stream iterator state: viewer-stream-id=%" PRIu64
                ", old-state=%s, new-state=%s",
                stream_iter->viewer_stream_id,
                lttng_live_stream_state_string(stream_iter->state),
                lttng_live_stream_state_string(new_state));

        stream_iter->state = new_state;
}

#define LTTNG_LIVE_LOGD_STREAM_ITER(live_stream_iter) \
        do { \
                BT_COMP_LOGD("Live stream iterator state=%s, " \
                        "last-inact-ts-is-set=%d, last-inact-ts-value=%" PRId64 "), " \
                        "curr-inact-ts %" PRId64, \
                        lttng_live_stream_state_string(live_stream_iter->state), \
                        live_stream_iter->last_inactivity_ts.is_set, \
                        live_stream_iter->last_inactivity_ts.value, \
                        live_stream_iter->current_inactivity_ts); \
        } while (0);

BT_HIDDEN
bool lttng_live_graph_is_canceled(struct lttng_live_msg_iter *msg_iter)
{
        bool ret;

        if (!msg_iter) {
                ret = false;
                goto end;
        }

        ret = bt_self_message_iterator_is_interrupted(
                msg_iter->self_msg_iter);

end:
        return ret;
}

static
struct lttng_live_trace *lttng_live_session_borrow_trace_by_id(struct lttng_live_session *session,
                uint64_t trace_id)
{
        uint64_t trace_idx;
        struct lttng_live_trace *ret_trace = NULL;

        for (trace_idx = 0; trace_idx < session->traces->len; trace_idx++) {
                struct lttng_live_trace *trace =
                        g_ptr_array_index(session->traces, trace_idx);
                if (trace->id == trace_id) {
                        ret_trace = trace;
                        goto end;
                }
        }

end:
        return ret_trace;
}

static
void lttng_live_destroy_trace(struct lttng_live_trace *trace)
{
        bt_logging_level log_level = trace->log_level;
        bt_self_component *self_comp = trace->self_comp;

        BT_COMP_LOGD("Destroying live trace: trace-id=%"PRIu64, trace->id);

        BT_ASSERT(trace->stream_iterators);
        g_ptr_array_free(trace->stream_iterators, TRUE);

        BT_TRACE_PUT_REF_AND_RESET(trace->trace);
        BT_TRACE_CLASS_PUT_REF_AND_RESET(trace->trace_class);

        lttng_live_metadata_fini(trace);
        g_free(trace);
}

static
struct lttng_live_trace *lttng_live_create_trace(struct lttng_live_session *session,
                uint64_t trace_id)
{
        struct lttng_live_trace *trace = NULL;
        bt_logging_level log_level = session->log_level;
        bt_self_component *self_comp = session->self_comp;

        BT_COMP_LOGD("Creating live trace: "
                "session-id=%"PRIu64", trace-id=%"PRIu64,
                session->id, trace_id);
        trace = g_new0(struct lttng_live_trace, 1);
        if (!trace) {
                BT_COMP_LOGE_APPEND_CAUSE(self_comp,
                        "Failed to allocate live trace");
                goto error;
        }
        trace->log_level = session->log_level;
        trace->self_comp = session->self_comp;
        trace->session = session;
        trace->id = trace_id;
        trace->trace_class = NULL;
        trace->trace = NULL;
        trace->stream_iterators = g_ptr_array_new_with_free_func(
                (GDestroyNotify) lttng_live_stream_iterator_destroy);
        BT_ASSERT(trace->stream_iterators);
        trace->metadata_stream_state = LTTNG_LIVE_METADATA_STREAM_STATE_NEEDED;
        g_ptr_array_add(session->traces, trace);

        goto end;
error:
        g_free(trace);
        trace = NULL;
end:
        return trace;
}

BT_HIDDEN
struct lttng_live_trace *lttng_live_session_borrow_or_create_trace_by_id(
                struct lttng_live_session *session, uint64_t trace_id)
{
        struct lttng_live_trace *trace;

        trace = lttng_live_session_borrow_trace_by_id(session, trace_id);
        if (trace) {
                goto end;
        }

        /* The session is the owner of the newly created trace. */
        trace = lttng_live_create_trace(session, trace_id);

end:
        return trace;
}

BT_HIDDEN
int lttng_live_add_session(struct lttng_live_msg_iter *lttng_live_msg_iter,
                uint64_t session_id, const char *hostname,
                const char *session_name)
{
        int ret = 0;
        struct lttng_live_session *session;
        bt_logging_level log_level = lttng_live_msg_iter->log_level;
        bt_self_component *self_comp = lttng_live_msg_iter->self_comp;

        BT_COMP_LOGD("Adding live session: "
                "session-id=%" PRIu64 ", hostname=\"%s\" session-name=\"%s\"",
                session_id, hostname, session_name);

        session = g_new0(struct lttng_live_session, 1);
        if (!session) {
                BT_COMP_LOGE_APPEND_CAUSE(self_comp,
                        "Failed to allocate live session");
                goto error;
        }

        session->log_level = lttng_live_msg_iter->log_level;
        session->self_comp = lttng_live_msg_iter->self_comp;
        session->id = session_id;
        session->traces = g_ptr_array_new_with_free_func(
                (GDestroyNotify) lttng_live_destroy_trace);
        BT_ASSERT(session->traces);
        session->lttng_live_msg_iter = lttng_live_msg_iter;
        session->new_streams_needed = true;
        session->hostname = g_string_new(hostname);
        BT_ASSERT(session->hostname);

        session->session_name = g_string_new(session_name);
        BT_ASSERT(session->session_name);

        g_ptr_array_add(lttng_live_msg_iter->sessions, session);
        goto end;
error:
        g_free(session);
        ret = -1;
end:
        return ret;
}

static
void lttng_live_destroy_session(struct lttng_live_session *session)
{
        bt_logging_level log_level;
        bt_self_component *self_comp;

        if (!session) {
                goto end;
        }

        log_level = session->log_level;
        self_comp = session->self_comp;
        BT_COMP_LOGD("Destroying live session: "
                "session-id=%"PRIu64", session-name=\"%s\"",
                session->id, session->session_name->str);
        if (session->id != -1ULL) {
                if (lttng_live_session_detach(session)) {
                        if (!lttng_live_graph_is_canceled(
                                        session->lttng_live_msg_iter)) {
                                /* Old relayd cannot detach sessions. */
                                BT_COMP_LOGD("Unable to detach lttng live session %" PRIu64,
                                        session->id);
                        }
                }
                session->id = -1ULL;
        }

        if (session->traces) {
                g_ptr_array_free(session->traces, TRUE);
        }

        if (session->hostname) {
                g_string_free(session->hostname, TRUE);
        }
        if (session->session_name) {
                g_string_free(session->session_name, TRUE);
        }
        g_free(session);

end:
        return;
}

static
void lttng_live_msg_iter_destroy(struct lttng_live_msg_iter *lttng_live_msg_iter)
{
        if (!lttng_live_msg_iter) {
                goto end;
        }

        if (lttng_live_msg_iter->sessions) {
                g_ptr_array_free(lttng_live_msg_iter->sessions, TRUE);
        }

        if (lttng_live_msg_iter->viewer_connection) {
                live_viewer_connection_destroy(lttng_live_msg_iter->viewer_connection);
        }
        BT_ASSERT(lttng_live_msg_iter->lttng_live_comp);
        BT_ASSERT(lttng_live_msg_iter->lttng_live_comp->has_msg_iter);

        /* All stream iterators must be destroyed at this point. */
        BT_ASSERT(lttng_live_msg_iter->active_stream_iter == 0);
        lttng_live_msg_iter->lttng_live_comp->has_msg_iter = false;

        g_free(lttng_live_msg_iter);

end:
        return;
}

BT_HIDDEN
void lttng_live_msg_iter_finalize(bt_self_message_iterator *self_msg_iter)
{
        struct lttng_live_msg_iter *lttng_live_msg_iter;

        BT_ASSERT(self_msg_iter);

        lttng_live_msg_iter = bt_self_message_iterator_get_data(self_msg_iter);
        BT_ASSERT(lttng_live_msg_iter);
        lttng_live_msg_iter_destroy(lttng_live_msg_iter);
}

static
enum lttng_live_iterator_status lttng_live_iterator_next_check_stream_state(
                struct lttng_live_stream_iterator *lttng_live_stream)
{
        bt_logging_level log_level = lttng_live_stream->log_level;
        bt_self_component *self_comp = lttng_live_stream->self_comp;

        switch (lttng_live_stream->state) {
        case LTTNG_LIVE_STREAM_QUIESCENT:
        case LTTNG_LIVE_STREAM_ACTIVE_DATA:
                break;
        case LTTNG_LIVE_STREAM_ACTIVE_NO_DATA:
                /* Invalid state. */
                BT_COMP_LOGF("Unexpected stream state \"ACTIVE_NO_DATA\"");
                bt_common_abort();
        case LTTNG_LIVE_STREAM_QUIESCENT_NO_DATA:
                /* Invalid state. */
                BT_COMP_LOGF("Unexpected stream state \"QUIESCENT_NO_DATA\"");
                bt_common_abort();
        case LTTNG_LIVE_STREAM_EOF:
                break;
        }
        return LTTNG_LIVE_ITERATOR_STATUS_OK;
}

/*
 * For active no data stream, fetch next index. As a result of that it can
 * become either:
 * - quiescent: won't have events for a bit,
 * - have data: need to get that data and produce the event,
 * - have no data on this stream at this point: need to retry (AGAIN) or return
 *   EOF.
 */
static
enum lttng_live_iterator_status lttng_live_iterator_next_handle_one_no_data_stream(
                struct lttng_live_msg_iter *lttng_live_msg_iter,
                struct lttng_live_stream_iterator *lttng_live_stream)
{
        bt_logging_level log_level = lttng_live_msg_iter->log_level;
        bt_self_component *self_comp = lttng_live_msg_iter->self_comp;
        enum lttng_live_iterator_status ret = LTTNG_LIVE_ITERATOR_STATUS_OK;
        enum lttng_live_stream_state orig_state = lttng_live_stream->state;
        struct packet_index index;

        if (lttng_live_stream->trace->metadata_stream_state ==
                        LTTNG_LIVE_METADATA_STREAM_STATE_NEEDED) {
                BT_COMP_LOGD("Need to get an update for the metadata stream before proceeding further with this stream: "
                        "stream-name=\"%s\"", lttng_live_stream->name->str);
                ret = LTTNG_LIVE_ITERATOR_STATUS_CONTINUE;
                goto end;
        }

        if (lttng_live_stream->trace->session->new_streams_needed) {
                BT_COMP_LOGD("Need to get an update of all streams before proceeding further with this stream: "
                        "stream-name=\"%s\"", lttng_live_stream->name->str);
                ret = LTTNG_LIVE_ITERATOR_STATUS_CONTINUE;
                goto end;
        }

        if (lttng_live_stream->state != LTTNG_LIVE_STREAM_ACTIVE_NO_DATA &&
                        lttng_live_stream->state != LTTNG_LIVE_STREAM_QUIESCENT_NO_DATA) {
                goto end;
        }
        ret = lttng_live_get_next_index(lttng_live_msg_iter, lttng_live_stream,
                        &index);
        if (ret != LTTNG_LIVE_ITERATOR_STATUS_OK) {
                goto end;
        }

        BT_ASSERT_DBG(lttng_live_stream->state != LTTNG_LIVE_STREAM_EOF);

        if (lttng_live_stream->state == LTTNG_LIVE_STREAM_QUIESCENT) {
                uint64_t last_inact_ts = lttng_live_stream->last_inactivity_ts.value,
                         curr_inact_ts = lttng_live_stream->current_inactivity_ts;

                if (orig_state == LTTNG_LIVE_STREAM_QUIESCENT_NO_DATA &&
                                last_inact_ts == curr_inact_ts) {
                        /*
                         * Because the stream is in the QUIESCENT_NO_DATA
                         * state, we can assert that the last_inactivity_ts was
                         * set and can be safely used in the `if` above.
                         */
                        BT_ASSERT(lttng_live_stream->last_inactivity_ts.is_set);

                        ret = LTTNG_LIVE_ITERATOR_STATUS_AGAIN;
                        LTTNG_LIVE_LOGD_STREAM_ITER(lttng_live_stream);
                } else {
                        ret = LTTNG_LIVE_ITERATOR_STATUS_CONTINUE;
                }
                goto end;
        }

        lttng_live_stream->base_offset = index.offset;
        lttng_live_stream->offset = index.offset;
        lttng_live_stream->len = index.packet_size / CHAR_BIT;

        BT_COMP_LOGD("Setting live stream reading info: stream-name=\"%s\", "
                        "viewer-stream-id=%" PRIu64 ", stream-base-offset=%" PRIu64
                        ", stream-offset=%" PRIu64 ", stream-len=%" PRIu64,
                        lttng_live_stream->name->str,
                        lttng_live_stream->viewer_stream_id,
                        lttng_live_stream->base_offset,
                        lttng_live_stream->offset, lttng_live_stream->len);

end:
        if (ret == LTTNG_LIVE_ITERATOR_STATUS_OK) {
                ret = lttng_live_iterator_next_check_stream_state(lttng_live_stream);
        }
        return ret;
}

/*
 * Creation of the message requires the ctf trace class to be created
 * beforehand, but the live protocol gives us all streams (including metadata)
 * at once. So we split it in three steps: getting streams, getting metadata
 * (which creates the ctf trace class), and then creating the per-stream
 * messages.
 */
static
enum lttng_live_iterator_status lttng_live_get_session(
                struct lttng_live_msg_iter *lttng_live_msg_iter,
                struct lttng_live_session *session)
{
        bt_logging_level log_level = lttng_live_msg_iter->log_level;
        bt_self_component *self_comp = lttng_live_msg_iter->self_comp;
        enum lttng_live_iterator_status status;
        uint64_t trace_idx;

        if (!session->attached) {
                BT_COMP_LOGD("Attach to session: session-id=%" PRIu64,
                        session->id);
                enum lttng_live_viewer_status attach_status =
                        lttng_live_session_attach(session,
                                lttng_live_msg_iter->self_msg_iter);
                if (attach_status != LTTNG_LIVE_VIEWER_STATUS_OK) {
                        if (lttng_live_graph_is_canceled(lttng_live_msg_iter)) {
                                /*
                                 * Clear any causes appended in
                                 * `lttng_live_attach_session()` as we want to
                                 * return gracefully since the graph was
                                 * cancelled.
                                 */
                                bt_current_thread_clear_error();
                                status = LTTNG_LIVE_ITERATOR_STATUS_AGAIN;
                        } else {
                                status = LTTNG_LIVE_ITERATOR_STATUS_ERROR;
                                BT_COMP_LOGE_APPEND_CAUSE(self_comp,
                                        "Error attaching to LTTng live session");
                        }
                        goto end;
                }
        }

        BT_COMP_LOGD("Updating all streams and metadata for session: "
                "session-id=%" PRIu64 ", session-name=\"%s\"",
                session->id, session->session_name->str);

        status = lttng_live_session_get_new_streams(session,
                lttng_live_msg_iter->self_msg_iter);
        if (status != LTTNG_LIVE_ITERATOR_STATUS_OK &&
                        status != LTTNG_LIVE_ITERATOR_STATUS_END) {
                goto end;
        }

        trace_idx = 0;
        while (trace_idx < session->traces->len) {
                struct lttng_live_trace *trace =
                        g_ptr_array_index(session->traces, trace_idx);

                status = lttng_live_metadata_update(trace);
                switch (status) {
                case LTTNG_LIVE_ITERATOR_STATUS_END:
                case LTTNG_LIVE_ITERATOR_STATUS_OK:
                        trace_idx++;
                        break;
                case LTTNG_LIVE_ITERATOR_STATUS_CONTINUE:
                case LTTNG_LIVE_ITERATOR_STATUS_AGAIN:
                        goto end;
                default:
                        BT_COMP_LOGE_APPEND_CAUSE(self_comp,
                                "Error updating trace metadata: "
                                "stream-iter-status=%s, trace-id=%"PRIu64,
                                lttng_live_iterator_status_string(status),
                                trace->id);
                        goto end;
                }
        }

        /*
         * Now that we have the metadata we can initialize the downstream
         * iterator.
         */
        status = lttng_live_lazy_msg_init(session,
                lttng_live_msg_iter->self_msg_iter);

end:
        return status;
}

static
void lttng_live_force_new_streams_and_metadata(struct lttng_live_msg_iter *lttng_live_msg_iter)
{
        uint64_t session_idx, trace_idx;
        bt_logging_level log_level = lttng_live_msg_iter->log_level;
        bt_self_component *self_comp = lttng_live_msg_iter->self_comp;

        for (session_idx = 0; session_idx < lttng_live_msg_iter->sessions->len;
                        session_idx++) {
                struct lttng_live_session *session =
                        g_ptr_array_index(lttng_live_msg_iter->sessions, session_idx);
                BT_COMP_LOGD("Force marking session as needing new streams: "
                                "session-id=%" PRIu64, session->id);
                session->new_streams_needed = true;
                for (trace_idx = 0; trace_idx < session->traces->len;
                                trace_idx++) {
                        struct lttng_live_trace *trace =
                                g_ptr_array_index(session->traces, trace_idx);
                        BT_COMP_LOGD("Force marking trace metadata state as needing an update: "
                                        "session-id=%" PRIu64 ", trace-id=%" PRIu64,
                                        session->id, trace->id);

                        BT_ASSERT(trace->metadata_stream_state !=
                                LTTNG_LIVE_METADATA_STREAM_STATE_CLOSED);

                        trace->metadata_stream_state = LTTNG_LIVE_METADATA_STREAM_STATE_NEEDED;
                }
        }
}

static
enum lttng_live_iterator_status
lttng_live_iterator_handle_new_streams_and_metadata(
                struct lttng_live_msg_iter *lttng_live_msg_iter)
{
        enum lttng_live_iterator_status status;
        enum lttng_live_viewer_status viewer_status;
        bt_logging_level log_level = lttng_live_msg_iter->log_level;
        bt_self_component *self_comp = lttng_live_msg_iter->self_comp;
        uint64_t session_idx = 0, nr_sessions_opened = 0;
        struct lttng_live_session *session;
        enum session_not_found_action sess_not_found_act =
                lttng_live_msg_iter->lttng_live_comp->params.sess_not_found_act;

        BT_COMP_LOGD("Update data and metadata of all sessions: "
                "live-msg-iter-addr=%p", lttng_live_msg_iter);
        /*
         * In a remotely distant future, we could add a "new
         * session" flag to the protocol, which would tell us that we
         * need to query for new sessions even though we have sessions
         * currently ongoing.
         */
        if (lttng_live_msg_iter->sessions->len == 0) {
                if (sess_not_found_act != SESSION_NOT_FOUND_ACTION_CONTINUE) {
                        BT_COMP_LOGD("No session found. Exiting in accordance with the `session-not-found-action` parameter");
                        status = LTTNG_LIVE_ITERATOR_STATUS_END;
                        goto end;
                } else {
                        BT_COMP_LOGD("No session found. Try creating a new one in accordance with the `session-not-found-action` parameter");
                        /*
                         * Retry to create a viewer session for the requested
                         * session name.
                         */
                        viewer_status = lttng_live_create_viewer_session(lttng_live_msg_iter);
                        if (viewer_status != LTTNG_LIVE_VIEWER_STATUS_OK) {
                                if (viewer_status == LTTNG_LIVE_VIEWER_STATUS_ERROR) {
                                        status = LTTNG_LIVE_ITERATOR_STATUS_ERROR;
                                        BT_COMP_LOGE_APPEND_CAUSE(self_comp,
                                                "Error creating LTTng live viewer session");
                                } else if (viewer_status == LTTNG_LIVE_VIEWER_STATUS_INTERRUPTED) {
                                        status = LTTNG_LIVE_ITERATOR_STATUS_AGAIN;
                                } else {
                                        bt_common_abort();
                                }
                                goto end;
                        }
                }
        }

        for (session_idx = 0; session_idx < lttng_live_msg_iter->sessions->len;
                        session_idx++) {
                session = g_ptr_array_index(lttng_live_msg_iter->sessions,
                                session_idx);
                status = lttng_live_get_session(lttng_live_msg_iter, session);
                switch (status) {
                case LTTNG_LIVE_ITERATOR_STATUS_OK:
                        break;
                case LTTNG_LIVE_ITERATOR_STATUS_END:
                        status = LTTNG_LIVE_ITERATOR_STATUS_OK;
                        break;
                default:
                        goto end;
                }
                if (!session->closed) {
                        nr_sessions_opened++;
                }
        }

        if (sess_not_found_act != SESSION_NOT_FOUND_ACTION_CONTINUE &&
                        nr_sessions_opened == 0) {
                status = LTTNG_LIVE_ITERATOR_STATUS_END;
        } else {
                status = LTTNG_LIVE_ITERATOR_STATUS_OK;
        }

end:
        return status;
}

static
enum lttng_live_iterator_status emit_inactivity_message(
                struct lttng_live_msg_iter *lttng_live_msg_iter,
                struct lttng_live_stream_iterator *stream_iter,
                const bt_message **message, uint64_t timestamp)
{
        enum lttng_live_iterator_status ret = LTTNG_LIVE_ITERATOR_STATUS_OK;
        bt_logging_level log_level = lttng_live_msg_iter->log_level;
        bt_self_component *self_comp = lttng_live_msg_iter->self_comp;
        bt_message *msg = NULL;

        BT_ASSERT(stream_iter->trace->clock_class);

        BT_COMP_LOGD("Emitting inactivity message for stream: ctf-stream-id=%" PRIu64
                ", viewer-stream-id=%" PRIu64 ", timestamp=%" PRIu64,
                stream_iter->ctf_stream_class_id.value,
                stream_iter->viewer_stream_id, timestamp);

        msg = bt_message_message_iterator_inactivity_create(
                lttng_live_msg_iter->self_msg_iter,
                stream_iter->trace->clock_class, timestamp);
        if (!msg) {
                BT_COMP_LOGE_APPEND_CAUSE(self_comp,
                        "Error emitting message iterator inactivity message");
                goto error;
        }

        *message = msg;
end:
        return ret;

error:
        ret = LTTNG_LIVE_ITERATOR_STATUS_ERROR;
        bt_message_put_ref(msg);
        goto end;
}

static
enum lttng_live_iterator_status lttng_live_iterator_next_handle_one_quiescent_stream(
                struct lttng_live_msg_iter *lttng_live_msg_iter,
                struct lttng_live_stream_iterator *lttng_live_stream,
                const bt_message **message)
{
        enum lttng_live_iterator_status ret = LTTNG_LIVE_ITERATOR_STATUS_OK;

        if (lttng_live_stream->state != LTTNG_LIVE_STREAM_QUIESCENT) {
                return LTTNG_LIVE_ITERATOR_STATUS_OK;
        }

        /*
         * Check if we already sent an inactivty message downstream for this
         * `current_inactivity_ts` value.
         */
        if (lttng_live_stream->last_inactivity_ts.is_set &&
                        lttng_live_stream->current_inactivity_ts ==
                                lttng_live_stream->last_inactivity_ts.value) {
                lttng_live_stream_iterator_set_state(lttng_live_stream,
                        LTTNG_LIVE_STREAM_QUIESCENT_NO_DATA);

                ret = LTTNG_LIVE_ITERATOR_STATUS_CONTINUE;
                goto end;
        }

        ret = emit_inactivity_message(lttng_live_msg_iter, lttng_live_stream,
                message, lttng_live_stream->current_inactivity_ts);

        lttng_live_stream->last_inactivity_ts.value =
                lttng_live_stream->current_inactivity_ts;
        lttng_live_stream->last_inactivity_ts.is_set = true;
end:
        return ret;
}

static
int live_get_msg_ts_ns(struct lttng_live_stream_iterator *stream_iter,
                struct lttng_live_msg_iter *lttng_live_msg_iter,
                const bt_message *msg, int64_t last_msg_ts_ns,
                int64_t *ts_ns)
{
        const bt_clock_class *clock_class = NULL;
        const bt_clock_snapshot *clock_snapshot = NULL;
        int ret = 0;
        bt_logging_level log_level = lttng_live_msg_iter->log_level;
        bt_self_component *self_comp = lttng_live_msg_iter->self_comp;

        BT_ASSERT_DBG(msg);
        BT_ASSERT_DBG(ts_ns);

        BT_COMP_LOGD("Getting message's timestamp: iter-data-addr=%p, msg-addr=%p, "
                "last-msg-ts=%" PRId64, lttng_live_msg_iter, msg,
                last_msg_ts_ns);

        switch (bt_message_get_type(msg)) {
        case BT_MESSAGE_TYPE_EVENT:
                clock_class = bt_message_event_borrow_stream_class_default_clock_class_const(
                                msg);
                BT_ASSERT_DBG(clock_class);

                clock_snapshot = bt_message_event_borrow_default_clock_snapshot_const(
                        msg);
                break;
        case BT_MESSAGE_TYPE_PACKET_BEGINNING:
                clock_class = bt_message_packet_beginning_borrow_stream_class_default_clock_class_const(
                        msg);
                BT_ASSERT(clock_class);

                clock_snapshot = bt_message_packet_beginning_borrow_default_clock_snapshot_const(
                        msg);
                break;
        case BT_MESSAGE_TYPE_PACKET_END:
                clock_class = bt_message_packet_end_borrow_stream_class_default_clock_class_const(
                        msg);
                BT_ASSERT(clock_class);

                clock_snapshot = bt_message_packet_end_borrow_default_clock_snapshot_const(
                        msg);
                break;
        case BT_MESSAGE_TYPE_DISCARDED_EVENTS:
                clock_class = bt_message_discarded_events_borrow_stream_class_default_clock_class_const(
                        msg);
                BT_ASSERT(clock_class);

                clock_snapshot = bt_message_discarded_events_borrow_beginning_default_clock_snapshot_const(
                        msg);
                break;
        case BT_MESSAGE_TYPE_DISCARDED_PACKETS:
                clock_class = bt_message_discarded_packets_borrow_stream_class_default_clock_class_const(
                        msg);
                BT_ASSERT(clock_class);

                clock_snapshot = bt_message_discarded_packets_borrow_beginning_default_clock_snapshot_const(
                        msg);
                break;
        case BT_MESSAGE_TYPE_MESSAGE_ITERATOR_INACTIVITY:
                clock_snapshot = bt_message_message_iterator_inactivity_borrow_clock_snapshot_const(
                        msg);
                break;
        default:
                /* All the other messages have a higher priority */
                BT_COMP_LOGD_STR("Message has no timestamp: using the last message timestamp.");
                *ts_ns = last_msg_ts_ns;
                goto end;
        }

        clock_class = bt_clock_snapshot_borrow_clock_class_const(clock_snapshot);
        BT_ASSERT_DBG(clock_class);

        ret = bt_clock_snapshot_get_ns_from_origin(clock_snapshot, ts_ns);
        if (ret) {
                BT_COMP_LOGE_APPEND_CAUSE(self_comp,
                        "Cannot get nanoseconds from Epoch of clock snapshot: "
                        "clock-snapshot-addr=%p", clock_snapshot);
                goto error;
        }

        goto end;

error:
        ret = -1;

end:
        if (ret == 0) {
                BT_COMP_LOGD("Found message's timestamp: "
                        "iter-data-addr=%p, msg-addr=%p, "
                        "last-msg-ts=%" PRId64 ", ts=%" PRId64,
                        lttng_live_msg_iter, msg, last_msg_ts_ns, *ts_ns);
        }

        return ret;
}

static
enum lttng_live_iterator_status lttng_live_iterator_next_handle_one_active_data_stream(
                struct lttng_live_msg_iter *lttng_live_msg_iter,
                struct lttng_live_stream_iterator *lttng_live_stream,
                const bt_message **message)
{
        enum lttng_live_iterator_status ret = LTTNG_LIVE_ITERATOR_STATUS_OK;
        bt_logging_level log_level = lttng_live_msg_iter->log_level;
        bt_self_component *self_comp = lttng_live_msg_iter->self_comp;
        enum ctf_msg_iter_status status;
        uint64_t session_idx, trace_idx;

        for (session_idx = 0; session_idx < lttng_live_msg_iter->sessions->len;
                        session_idx++) {
                struct lttng_live_session *session =
                        g_ptr_array_index(lttng_live_msg_iter->sessions, session_idx);

                if (session->new_streams_needed) {
                        BT_COMP_LOGD("Need an update for streams: "
                                        "session-id=%" PRIu64, session->id);
                        ret = LTTNG_LIVE_ITERATOR_STATUS_CONTINUE;
                        goto end;
                }
                for (trace_idx = 0; trace_idx < session->traces->len;
                                trace_idx++) {
                        struct lttng_live_trace *trace =
                                g_ptr_array_index(session->traces, trace_idx);
                        if (trace->metadata_stream_state == LTTNG_LIVE_METADATA_STREAM_STATE_NEEDED) {
                                BT_COMP_LOGD("Need an update for metadata stream: "
                                                "session-id=%" PRIu64 ", trace-id=%" PRIu64,
                                                session->id, trace->id);
                                ret = LTTNG_LIVE_ITERATOR_STATUS_CONTINUE;
                                goto end;
                        }
                }
        }

        if (lttng_live_stream->state != LTTNG_LIVE_STREAM_ACTIVE_DATA) {
                ret = LTTNG_LIVE_ITERATOR_STATUS_ERROR;
                BT_COMP_LOGE_APPEND_CAUSE(self_comp,
                        "Invalid state of live stream iterator"
                        "stream-iter-status=%s",
                        lttng_live_stream_state_string(lttng_live_stream->state));
                goto end;
        }

        status = ctf_msg_iter_get_next_message(
                lttng_live_stream->msg_iter, message);
        switch (status) {
        case CTF_MSG_ITER_STATUS_EOF:
                ret = LTTNG_LIVE_ITERATOR_STATUS_END;
                break;
        case CTF_MSG_ITER_STATUS_OK:
                ret = LTTNG_LIVE_ITERATOR_STATUS_OK;
                break;
        case CTF_MSG_ITER_STATUS_AGAIN:
                /*
                 * Continue immediately (end of packet). The next
                 * get_index may return AGAIN to delay the following
                 * attempt.
                 */
                ret = LTTNG_LIVE_ITERATOR_STATUS_CONTINUE;
                break;
        case CTF_MSG_ITER_STATUS_ERROR:
        default:
                ret = LTTNG_LIVE_ITERATOR_STATUS_ERROR;
                BT_COMP_LOGE_APPEND_CAUSE(self_comp,
                        "CTF message iterator failed to get next message: "
                        "msg-iter=%p, msg-iter-status=%s",
                        lttng_live_stream->msg_iter,
                        ctf_msg_iter_status_string(status));
                break;
        }

end:
        return ret;
}

static
enum lttng_live_iterator_status lttng_live_iterator_close_stream(
                struct lttng_live_msg_iter *lttng_live_msg_iter,
                struct lttng_live_stream_iterator *stream_iter,
                const bt_message **curr_msg)
{
        enum lttng_live_iterator_status live_status =
                LTTNG_LIVE_ITERATOR_STATUS_OK;
        bt_logging_level log_level = lttng_live_msg_iter->log_level;
        bt_self_component *self_comp = lttng_live_msg_iter->self_comp;

        BT_COMP_LOGD("Closing live stream iterator: stream-name=\"%s\", "
                        "viewer-stream-id=%" PRIu64, stream_iter->name->str,
                        stream_iter->viewer_stream_id);

        /*
         * The viewer has hung up on us so we are closing the stream. The
         * `ctf_msg_iter` should simply realize that it needs to close the
         * stream properly by emitting the necessary stream end message.
         */
        enum ctf_msg_iter_status status = ctf_msg_iter_get_next_message(
                stream_iter->msg_iter, curr_msg);

        if (status == CTF_MSG_ITER_STATUS_ERROR) {
                BT_COMP_LOGE_APPEND_CAUSE(self_comp,
                        "Error getting the next message from CTF message iterator");
                live_status = LTTNG_LIVE_ITERATOR_STATUS_ERROR;
                goto end;
        } else if (status == CTF_MSG_ITER_STATUS_EOF) {
                BT_COMP_LOGI("Reached the end of the live stream iterator.");
                live_status = LTTNG_LIVE_ITERATOR_STATUS_END;
                goto end;
        }

        BT_ASSERT(status == CTF_MSG_ITER_STATUS_OK);

end:
        return live_status;
}

/*
 * helper function:
 *            handle_no_data_streams()
 *              retry:
 *                - for each ACTIVE_NO_DATA stream:
 *                  - query relayd for stream data, or quiescence info.
 *                    - if need metadata, get metadata, goto retry.
 *                    - if new stream, get new stream as ACTIVE_NO_DATA, goto retry
 *                  - if quiescent, move to QUIESCENT streams
 *                  - if fetched data, move to ACTIVE_DATA streams
 *                (at this point each stream either has data, or is quiescent)
 *
 *
 * iterator_next:
 *            handle_new_streams_and_metadata()
 *                  - query relayd for known streams, add them as ACTIVE_NO_DATA
 *                  - query relayd for metadata
 *
 *            call handle_active_no_data_streams()
 *
 *            handle_quiescent_streams()
 *                - if at least one stream is ACTIVE_DATA:
 *                  - peek stream event with lowest timestamp -> next_ts
 *                  - for each quiescent stream
 *                    - if next_ts >= quiescent end
 *                      - set state to ACTIVE_NO_DATA
 *                - else
 *                  - for each quiescent stream
 *                      - set state to ACTIVE_NO_DATA
 *
 *            call handle_active_no_data_streams()
 *
 *            handle_active_data_streams()
 *                - if at least one stream is ACTIVE_DATA:
 *                    - get stream event with lowest timestamp from heap
 *                    - make that stream event the current message.
 *                    - move this stream heap position to its next event
 *                      - if we need to fetch data from relayd, move
 *                        stream to ACTIVE_NO_DATA.
 *                    - return OK
 *                - return AGAIN
 *
 * end criterion: ctrl-c on client. If relayd exits or the session
 * closes on the relay daemon side, we keep on waiting for streams.
 * Eventually handle --end timestamp (also an end criterion).
 *
 * When disconnected from relayd: try to re-connect endlessly.
 */
static
enum lttng_live_iterator_status lttng_live_iterator_next_msg_on_stream(
                struct lttng_live_msg_iter *lttng_live_msg_iter,
                struct lttng_live_stream_iterator *stream_iter,
                const bt_message **curr_msg)
{
        bt_logging_level log_level = lttng_live_msg_iter->log_level;
        bt_self_component *self_comp = lttng_live_msg_iter->self_comp;
        enum lttng_live_iterator_status live_status;

        BT_COMP_LOGD("Advancing live stream iterator until next message if possible: "
                "stream-name=\"%s\", viewer-stream-id=%" PRIu64,
                stream_iter->name->str, stream_iter->viewer_stream_id);

        if (stream_iter->has_stream_hung_up) {
                /*
                 * The stream has hung up and the stream was properly closed
                 * during the last call to the current function. Return _END
                 * status now so that this stream iterator is removed for the
                 * stream iterator list.
                 */
                live_status = LTTNG_LIVE_ITERATOR_STATUS_END;
                goto end;
        }

retry:
        LTTNG_LIVE_LOGD_STREAM_ITER(stream_iter);

        /*
         * Make sure we have the most recent metadata and possibly some new
         * streams.
         */
        live_status = lttng_live_iterator_handle_new_streams_and_metadata(
                lttng_live_msg_iter);
        if (live_status != LTTNG_LIVE_ITERATOR_STATUS_OK) {
                goto end;
        }

        live_status = lttng_live_iterator_next_handle_one_no_data_stream(
                lttng_live_msg_iter, stream_iter);
        if (live_status != LTTNG_LIVE_ITERATOR_STATUS_OK) {
                if (live_status == LTTNG_LIVE_ITERATOR_STATUS_END) {
                        /*
                         * We overwrite `live_status` since `curr_msg` is
                         * likely set to a valid message in this function.
                         */
                        live_status = lttng_live_iterator_close_stream(
                                lttng_live_msg_iter, stream_iter, curr_msg);
                }
                goto end;
        }

        live_status = lttng_live_iterator_next_handle_one_quiescent_stream(
                lttng_live_msg_iter, stream_iter, curr_msg);
        if (live_status != LTTNG_LIVE_ITERATOR_STATUS_OK) {
                BT_ASSERT(!*curr_msg);
                goto end;
        }
        if (*curr_msg) {
                goto end;
        }
        live_status = lttng_live_iterator_next_handle_one_active_data_stream(
                lttng_live_msg_iter, stream_iter, curr_msg);
        if (live_status != LTTNG_LIVE_ITERATOR_STATUS_OK) {
                BT_ASSERT(!*curr_msg);
        }

end:
        if (live_status == LTTNG_LIVE_ITERATOR_STATUS_CONTINUE) {
                BT_COMP_LOGD("Ask the relay daemon for an updated view of the data and metadata streams");
                goto retry;
        }

        BT_COMP_LOGD("Returning from advancing live stream iterator: status=%s"
                        "stream-name=\"%s\", viewer-stream-id=%" PRIu64,
                        lttng_live_iterator_status_string(live_status),
                        stream_iter->name->str, stream_iter->viewer_stream_id);

        return live_status;
}

static
bool is_discarded_packet_or_event_message(const bt_message *msg)
{
        const enum bt_message_type msg_type = bt_message_get_type(msg);

        return msg_type == BT_MESSAGE_TYPE_DISCARDED_EVENTS ||
                        msg_type == BT_MESSAGE_TYPE_DISCARDED_PACKETS;
}

static
enum lttng_live_iterator_status adjust_discarded_packets_message(
                bt_self_message_iterator *iter,
                const bt_stream *stream,
                const bt_message *msg_in, bt_message **msg_out,
                uint64_t new_begin_ts)
{
        enum lttng_live_iterator_status status = LTTNG_LIVE_ITERATOR_STATUS_OK;
        enum bt_property_availability availability;
        const bt_clock_snapshot *clock_snapshot;
        uint64_t end_ts;
        uint64_t count;

        clock_snapshot = bt_message_discarded_packets_borrow_end_default_clock_snapshot_const(msg_in);
        end_ts = bt_clock_snapshot_get_value(clock_snapshot);

        availability = bt_message_discarded_packets_get_count(msg_in, &count);
        BT_ASSERT_DBG(availability == BT_PROPERTY_AVAILABILITY_AVAILABLE);

        *msg_out = bt_message_discarded_packets_create_with_default_clock_snapshots(
                iter, stream, new_begin_ts, end_ts);
        if (!*msg_out) {
                status = LTTNG_LIVE_ITERATOR_STATUS_NOMEM;
                goto end;
        }

        bt_message_discarded_packets_set_count(*msg_out, count);
end:
        return status;
}

static
enum lttng_live_iterator_status adjust_discarded_events_message(
                bt_self_message_iterator *iter,
                const bt_stream *stream,
                const bt_message *msg_in, bt_message **msg_out,
                uint64_t new_begin_ts)
{
        enum lttng_live_iterator_status status = LTTNG_LIVE_ITERATOR_STATUS_OK;
        enum bt_property_availability availability;
        const bt_clock_snapshot *clock_snapshot;
        uint64_t end_ts;
        uint64_t count;

        clock_snapshot = bt_message_discarded_events_borrow_end_default_clock_snapshot_const(msg_in);
        end_ts = bt_clock_snapshot_get_value(clock_snapshot);

        availability = bt_message_discarded_events_get_count(msg_in, &count);
        BT_ASSERT_DBG(availability == BT_PROPERTY_AVAILABILITY_AVAILABLE);

        *msg_out = bt_message_discarded_events_create_with_default_clock_snapshots(
                iter, stream, new_begin_ts, end_ts);
        if (!*msg_out) {
                status = LTTNG_LIVE_ITERATOR_STATUS_NOMEM;
                goto end;
        }

        bt_message_discarded_events_set_count(*msg_out, count);
end:
        return status;
}

static
enum lttng_live_iterator_status handle_late_message(
                struct lttng_live_msg_iter *lttng_live_msg_iter,
                struct lttng_live_stream_iterator *stream_iter,
                int64_t late_msg_ts_ns, const bt_message *late_msg)
{
        bt_self_component *self_comp = lttng_live_msg_iter->self_comp;
        bt_logging_level log_level = lttng_live_msg_iter->log_level;
        const bt_clock_class *clock_class;
        const bt_stream_class *stream_class;
        enum bt_clock_class_cycles_to_ns_from_origin_status ts_ns_status;
        int64_t last_inactivity_ts_ns;
        enum lttng_live_iterator_status stream_iter_status = LTTNG_LIVE_ITERATOR_STATUS_OK;
        enum lttng_live_iterator_status adjust_status;
        bt_message *adjusted_message;

        /*
         * The timestamp of the current message is before the last message sent
         * by this component. We CANNOT send it as is.
         *
         * The only expected scenario in which that could happen is the
         * following, everything else is a bug in this component, relay deamon,
         * or CTF parser.
         *
         * Expected scenario: The CTF message iterator emitted discarded
         * packets and discarded events with synthesized beginning and end
         * timestamps from the bounds of the last known packet and the newly
         * decoded packet header. The CTF message iterator is not aware of
         * stream inactivity beacons. Hence, we have to adjust the beginning
         * timestamp of those types of messages if a stream signalled its
         * inactivity up until _after_ the last known packet's beginning
         * timestamp.
         *
         * Otherwise, the monotonicity guarantee of message timestamps would
         * not be preserved.
         *
         * In short, the only scenario in which it's okay and fixable to
         * received a late message is when:
         *  1. the late message is a discarded packets or discarded events
         *      message,
         *  2. this stream produced an inactivity message downstream, and
         *  3. the timestamp of the late message is within the inactivity
         *      timespan we sent downstream through the inactivity message.
         */

        BT_COMP_LOGD("Handling late message on live stream iterator: "
                "stream-name=\"%s\", viewer-stream-id=%" PRIu64,
                stream_iter->name->str, stream_iter->viewer_stream_id);

        if (!stream_iter->last_inactivity_ts.is_set) {
                BT_COMP_LOGE_APPEND_CAUSE(self_comp, "Invalid live stream state: "
                        "have a late message when no inactivity message "
                        "was ever sent for that stream.");
                stream_iter_status = LTTNG_LIVE_ITERATOR_STATUS_ERROR;
                goto end;
        }

        if (!is_discarded_packet_or_event_message(late_msg)) {
                BT_COMP_LOGE_APPEND_CAUSE(self_comp, "Invalid live stream state: "
                        "have a late message that is not a packet discarded or "
                        "event discarded message: late-msg-type=%s",
                        bt_common_message_type_string(bt_message_get_type(late_msg)));
                stream_iter_status = LTTNG_LIVE_ITERATOR_STATUS_ERROR;
                goto end;
        }

        stream_class = bt_stream_borrow_class_const(stream_iter->stream);
        clock_class = bt_stream_class_borrow_default_clock_class_const(stream_class);

        ts_ns_status = bt_clock_class_cycles_to_ns_from_origin(clock_class,
                        stream_iter->last_inactivity_ts.value, &last_inactivity_ts_ns);
        if (ts_ns_status != BT_CLOCK_CLASS_CYCLES_TO_NS_FROM_ORIGIN_STATUS_OK) {
                BT_COMP_LOGE_APPEND_CAUSE(self_comp,"Error converting last "
                        "inactivity message timestamp to nanoseconds");
                stream_iter_status = LTTNG_LIVE_ITERATOR_STATUS_ERROR;
                goto end;
        }

        if (last_inactivity_ts_ns <= late_msg_ts_ns) {
                BT_COMP_LOGE_APPEND_CAUSE(self_comp, "Invalid live stream state: "
                        "have a late message that is none included in a stream "
                        "inactivity timespan: last-inactivity-ts-ns=%" PRIu64
                        "late-msg-ts-ns=%" PRIu64, last_inactivity_ts_ns, late_msg_ts_ns);
                stream_iter_status = LTTNG_LIVE_ITERATOR_STATUS_ERROR;
                goto end;
        }

        /*
         * We now know that it's okay for this message to be late, we can now
         * adjust its timestamp to ensure monotonicity.
         */
        BT_COMP_LOGD("Adjusting the timestamp of late message: late-msg-type=%s, "
                "msg-new-ts-ns=%" PRIu64,
                bt_common_message_type_string(bt_message_get_type(late_msg)),
                stream_iter->last_inactivity_ts.value);
        switch (bt_message_get_type(late_msg)) {
        case BT_MESSAGE_TYPE_DISCARDED_EVENTS:
                adjust_status = adjust_discarded_events_message(
                                lttng_live_msg_iter->self_msg_iter,
                                stream_iter->stream,
                                late_msg, &adjusted_message,
                                stream_iter->last_inactivity_ts.value);
                break;
        case BT_MESSAGE_TYPE_DISCARDED_PACKETS:
                adjust_status = adjust_discarded_packets_message(
                                lttng_live_msg_iter->self_msg_iter,
                                stream_iter->stream,
                                late_msg, &adjusted_message,
                                stream_iter->last_inactivity_ts.value);
                break;
        default:
                bt_common_abort();
        }

        if (adjust_status != LTTNG_LIVE_ITERATOR_STATUS_OK) {
                stream_iter_status = adjust_status;
                goto end;
        }

        BT_ASSERT_DBG(adjusted_message);
        stream_iter->current_msg = adjusted_message;
        stream_iter->current_msg_ts_ns = last_inactivity_ts_ns;
        bt_message_put_ref(late_msg);

end:
        return stream_iter_status;
}

static
enum lttng_live_iterator_status next_stream_iterator_for_trace(
                struct lttng_live_msg_iter *lttng_live_msg_iter,
                struct lttng_live_trace *live_trace,
                struct lttng_live_stream_iterator **youngest_trace_stream_iter)
{
        struct lttng_live_stream_iterator *youngest_candidate_stream_iter = NULL;
        bt_logging_level log_level = lttng_live_msg_iter->log_level;
        bt_self_component *self_comp = lttng_live_msg_iter->self_comp;
        enum lttng_live_iterator_status stream_iter_status;;
        int64_t youngest_candidate_msg_ts = INT64_MAX;
        uint64_t stream_iter_idx;

        BT_ASSERT_DBG(live_trace);
        BT_ASSERT_DBG(live_trace->stream_iterators);

        BT_COMP_LOGD("Finding the next stream iterator for trace: "
                "trace-id=%"PRIu64, live_trace->id);
        /*
         * Update the current message of every stream iterators of this trace.
         * The current msg of every stream must have a timestamp equal or
         * larger than the last message returned by this iterator. We must
         * ensure monotonicity.
         */
        stream_iter_idx = 0;
        while (stream_iter_idx < live_trace->stream_iterators->len) {
                bool stream_iter_is_ended = false;
                struct lttng_live_stream_iterator *stream_iter =
                        g_ptr_array_index(live_trace->stream_iterators,
                                stream_iter_idx);

                /*
                 * If there is no current message for this stream, go fetch
                 * one.
                 */
                while (!stream_iter->current_msg) {
                        const bt_message *msg = NULL;
                        int64_t curr_msg_ts_ns = INT64_MAX;

                        stream_iter_status = lttng_live_iterator_next_msg_on_stream(
                                lttng_live_msg_iter, stream_iter, &msg);

                        if (stream_iter_status == LTTNG_LIVE_ITERATOR_STATUS_END) {
                                stream_iter_is_ended = true;
                                break;
                        }

                        if (stream_iter_status != LTTNG_LIVE_ITERATOR_STATUS_OK) {
                                goto end;
                        }

                        BT_ASSERT_DBG(msg);

                        BT_COMP_LOGD("Live stream iterator returned message: msg-type=%s"
                                        "stream-name=\"%s\", viewer-stream-id=%" PRIu64,
                                        bt_common_message_type_string(bt_message_get_type(msg)),
                                        stream_iter->name->str, stream_iter->viewer_stream_id);

                        /*
                         * Get the timestamp in nanoseconds from origin of this
                         * messsage.
                         */
                        live_get_msg_ts_ns(stream_iter, lttng_live_msg_iter,
                                msg, lttng_live_msg_iter->last_msg_ts_ns,
                                &curr_msg_ts_ns);

                        /*
                         * Check if the message of the current live stream
                         * iterator occurred at the exact same time or after the
                         * last message returned by this component's message
                         * iterator. If not, we need to handle it with care.
                         */
                        if (curr_msg_ts_ns >= lttng_live_msg_iter->last_msg_ts_ns) {
                                stream_iter->current_msg = msg;
                                stream_iter->current_msg_ts_ns = curr_msg_ts_ns;
                        } else {
                                /*
                                 * We received a message from the past. This
                                 * may be fixable but it can also be an error.
                                 */
                                stream_iter_status = handle_late_message(
                                                lttng_live_msg_iter, stream_iter,
                                                curr_msg_ts_ns, msg);
                                if (stream_iter_status != LTTNG_LIVE_ITERATOR_STATUS_OK) {
                                        BT_COMP_LOGE_APPEND_CAUSE(self_comp,
                                                "Late message could not be handled correctly: "
                                                "lttng-live-msg-iter-addr=%p, "
                                                "stream-name=\"%s\", "
                                                "curr-msg-ts=%" PRId64
                                                ", last-msg-ts=%" PRId64,
                                                lttng_live_msg_iter,
                                                stream_iter->name->str,
                                                curr_msg_ts_ns,
                                                lttng_live_msg_iter->last_msg_ts_ns);
                                        stream_iter_status = LTTNG_LIVE_ITERATOR_STATUS_ERROR;
                                        goto end;
                                }
                        }
                }

                BT_ASSERT_DBG(stream_iter != youngest_candidate_stream_iter);

                if (!stream_iter_is_ended) {
                        if (G_UNLIKELY(youngest_candidate_stream_iter == NULL) ||
                                        stream_iter->current_msg_ts_ns < youngest_candidate_msg_ts) {
                                /*
                                 * Update the current best candidate message
                                 * for the stream iterator of this live trace
                                 * to be forwarded downstream.
                                 */
                                youngest_candidate_msg_ts = stream_iter->current_msg_ts_ns;
                                youngest_candidate_stream_iter = stream_iter;
                        } else if (stream_iter->current_msg_ts_ns == youngest_candidate_msg_ts) {
                                /*
                                 * Order the messages in an arbitrary but
                                 * deterministic way.
                                 */
                                BT_ASSERT_DBG(stream_iter != youngest_candidate_stream_iter);
                                int ret = common_muxing_compare_messages(
                                        stream_iter->current_msg,
                                        youngest_candidate_stream_iter->current_msg);
                                if (ret < 0) {
                                        /*
                                         * The `youngest_candidate_stream_iter->current_msg`
                                         * should go first. Update the next
                                         * iterator and the current timestamp.
                                         */
                                        youngest_candidate_msg_ts = stream_iter->current_msg_ts_ns;
                                        youngest_candidate_stream_iter = stream_iter;
                                } else if (ret == 0) {
                                        /*
                                         * Unable to pick which one should go
                                         * first.
                                         */
                                        BT_COMP_LOGW("Cannot deterministically pick next live stream message iterator because they have identical next messages: "
                                                "stream-iter-addr=%p"
                                                "stream-iter-addr=%p",
                                                stream_iter,
                                                youngest_candidate_stream_iter);
                                }
                        }

                        stream_iter_idx++;
                } else {
                        /*
                         * The live stream iterator has ended. That
                         * iterator is removed from the array, but
                         * there is no need to increment
                         * stream_iter_idx as
                         * g_ptr_array_remove_index_fast replaces the
                         * removed element with the array's last
                         * element.
                         */
                        g_ptr_array_remove_index_fast(
                                live_trace->stream_iterators,
                                stream_iter_idx);
                }
        }

        if (youngest_candidate_stream_iter) {
                *youngest_trace_stream_iter = youngest_candidate_stream_iter;
                stream_iter_status = LTTNG_LIVE_ITERATOR_STATUS_OK;
        } else {
                /*
                 * The only case where we don't have a candidate for this trace
                 * is if we reached the end of all the iterators.
                 */
                BT_ASSERT(live_trace->stream_iterators->len == 0);
                stream_iter_status = LTTNG_LIVE_ITERATOR_STATUS_END;
        }

end:
        return stream_iter_status;
}

static
enum lttng_live_iterator_status next_stream_iterator_for_session(
                struct lttng_live_msg_iter *lttng_live_msg_iter,
                struct lttng_live_session *session,
                struct lttng_live_stream_iterator **youngest_session_stream_iter)
{
        bt_self_component *self_comp = lttng_live_msg_iter->self_comp;
        bt_logging_level log_level = lttng_live_msg_iter->log_level;
        enum lttng_live_iterator_status stream_iter_status;
        uint64_t trace_idx = 0;
        int64_t youngest_candidate_msg_ts = INT64_MAX;
        struct lttng_live_stream_iterator *youngest_candidate_stream_iter = NULL;

        BT_COMP_LOGD("Finding the next stream iterator for session: "
                "session-id=%"PRIu64, session->id);
        /*
         * Make sure we are attached to the session and look for new streams
         * and metadata.
         */
        stream_iter_status = lttng_live_get_session(lttng_live_msg_iter, session);
        if (stream_iter_status != LTTNG_LIVE_ITERATOR_STATUS_OK &&
                        stream_iter_status != LTTNG_LIVE_ITERATOR_STATUS_CONTINUE &&
                        stream_iter_status != LTTNG_LIVE_ITERATOR_STATUS_END) {
                goto end;
        }

        BT_ASSERT_DBG(session->traces);

        while (trace_idx < session->traces->len) {
                bool trace_is_ended = false;
                struct lttng_live_stream_iterator *stream_iter;
                struct lttng_live_trace *trace =
                        g_ptr_array_index(session->traces, trace_idx);

                stream_iter_status = next_stream_iterator_for_trace(
                        lttng_live_msg_iter, trace, &stream_iter);
                if (stream_iter_status == LTTNG_LIVE_ITERATOR_STATUS_END) {
                        /*
                         * All the live stream iterators for this trace are
                         * ENDed. Remove the trace from this session.
                         */
                        trace_is_ended = true;
                } else if (stream_iter_status != LTTNG_LIVE_ITERATOR_STATUS_OK) {
                        goto end;
                }

                if (!trace_is_ended) {
                        BT_ASSERT_DBG(stream_iter);

                        if (G_UNLIKELY(youngest_candidate_stream_iter == NULL) ||
                                        stream_iter->current_msg_ts_ns < youngest_candidate_msg_ts) {
                                youngest_candidate_msg_ts = stream_iter->current_msg_ts_ns;
                                youngest_candidate_stream_iter = stream_iter;
                        } else if (stream_iter->current_msg_ts_ns == youngest_candidate_msg_ts) {
                                /*
                                 * Order the messages in an arbitrary but
                                 * deterministic way.
                                 */
                                int ret = common_muxing_compare_messages(
                                        stream_iter->current_msg,
                                        youngest_candidate_stream_iter->current_msg);
                                if (ret < 0) {
                                        /*
                                         * The `youngest_candidate_stream_iter->current_msg`
                                         * should go first. Update the next iterator
                                         * and the current timestamp.
                                         */
                                        youngest_candidate_msg_ts = stream_iter->current_msg_ts_ns;
                                        youngest_candidate_stream_iter = stream_iter;
                                } else if (ret == 0) {
                                        /* Unable to pick which one should go first. */
                                        BT_COMP_LOGW("Cannot deterministically pick next live stream message iterator because they have identical next messages: "
                                                "stream-iter-addr=%p" "stream-iter-addr=%p",
                                                stream_iter, youngest_candidate_stream_iter);
                                }
                        }
                        trace_idx++;
                } else {
                        /*
                         * trace_idx is not incremented since
                         * g_ptr_array_remove_index_fast replaces the
                         * element at trace_idx with the array's last element.
                         */
                        g_ptr_array_remove_index_fast(session->traces,
                                trace_idx);
                }
        }
        if (youngest_candidate_stream_iter) {
                *youngest_session_stream_iter = youngest_candidate_stream_iter;
                stream_iter_status = LTTNG_LIVE_ITERATOR_STATUS_OK;
        } else {
                /*
                 * The only cases where we don't have a candidate for this
                 * trace is:
                 *  1. if we reached the end of all the iterators of all the
                 *  traces of this session,
                 *  2. if we never had live stream iterator in the first place.
                 *
                 * In either cases, we return END.
                 */
                BT_ASSERT(session->traces->len == 0);
                stream_iter_status = LTTNG_LIVE_ITERATOR_STATUS_END;
        }
end:
        return stream_iter_status;
}

static inline
void put_messages(bt_message_array_const msgs, uint64_t count)
{
        uint64_t i;

        for (i = 0; i < count; i++) {
                BT_MESSAGE_PUT_REF_AND_RESET(msgs[i]);
        }
}

BT_HIDDEN
bt_message_iterator_class_next_method_status lttng_live_msg_iter_next(
                bt_self_message_iterator *self_msg_it,
                bt_message_array_const msgs, uint64_t capacity,
                uint64_t *count)
{
        bt_message_iterator_class_next_method_status status;
        enum lttng_live_viewer_status viewer_status;
        struct lttng_live_msg_iter *lttng_live_msg_iter =
                bt_self_message_iterator_get_data(self_msg_it);
        struct lttng_live_component *lttng_live =
                lttng_live_msg_iter->lttng_live_comp;
        bt_self_component *self_comp = lttng_live_msg_iter->self_comp;
        bt_logging_level log_level = lttng_live_msg_iter->log_level;
        enum lttng_live_iterator_status stream_iter_status;
        uint64_t session_idx;

        *count = 0;

        BT_ASSERT_DBG(lttng_live_msg_iter);

        if (G_UNLIKELY(lttng_live_msg_iter->was_interrupted)) {
                /*
                 * The iterator was interrupted in a previous call to the
                 * `_next()` method. We currently do not support generating
                 * messages after such event. The babeltrace2 CLI should never
                 * be running the graph after being interrupted. So this check
                 * is to prevent other graph users from using this live
                 * iterator in an messed up internal state.
                 */
                status = BT_MESSAGE_ITERATOR_CLASS_NEXT_METHOD_STATUS_ERROR;
                BT_COMP_LOGE_APPEND_CAUSE(self_comp,
                        "Message iterator was interrupted during a previous call to the `next()` and currently does not support continuing after such event.");
                goto end;
        }

        /*
         * Clear all the invalid message reference that might be left over in
         * the output array.
         */
        memset(msgs, 0, capacity * sizeof(*msgs));

        /*
         * If no session are exposed on the relay found at the url provided by
         * the user, session count will be 0. In this case, we return status
         * end to return gracefully.
         */
        if (lttng_live_msg_iter->sessions->len == 0) {
                if (lttng_live->params.sess_not_found_act !=
                                SESSION_NOT_FOUND_ACTION_CONTINUE) {
                        status = BT_MESSAGE_ITERATOR_CLASS_NEXT_METHOD_STATUS_END;
                        goto end;
                } else {
                        /*
                         * The are no more active session for this session
                         * name. Retry to create a viewer session for the
                         * requested session name.
                         */
                        viewer_status = lttng_live_create_viewer_session(lttng_live_msg_iter);
                        if (viewer_status != LTTNG_LIVE_VIEWER_STATUS_OK) {
                                if (viewer_status == LTTNG_LIVE_VIEWER_STATUS_ERROR) {
                                        status = BT_MESSAGE_ITERATOR_CLASS_NEXT_METHOD_STATUS_ERROR;
                                        BT_COMP_LOGE_APPEND_CAUSE(self_comp,
                                                "Error creating LTTng live viewer session");
                                } else if (viewer_status == LTTNG_LIVE_VIEWER_STATUS_INTERRUPTED) {
                                        status = BT_MESSAGE_ITERATOR_CLASS_NEXT_METHOD_STATUS_AGAIN;
                                } else {
                                        bt_common_abort();
                                }
                                goto end;
                        }
                }
        }

        if (lttng_live_msg_iter->active_stream_iter == 0) {
                lttng_live_force_new_streams_and_metadata(lttng_live_msg_iter);
        }

        /*
         * Here the muxing of message is done.
         *
         * We need to iterate over all the streams of all the traces of all the
         * viewer sessions in order to get the message with the smallest
         * timestamp. In this case, a session is a viewer session and there is
         * one viewer session per consumer daemon. (UST 32bit, UST 64bit and/or
         * kernel). Each viewer session can have multiple traces, for example,
         * 64bit UST viewer sessions could have multiple per-pid traces.
         *
         * We iterate over the streams of each traces to update and see what is
         * their next message's timestamp. From those timestamps, we select the
         * message with the smallest timestamp as the best candidate message
         * for that trace and do the same thing across all the sessions.
         *
         * We then compare the timestamp of best candidate message of all the
         * sessions to pick the message with the smallest timestamp and we
         * return it.
         */
        while (*count < capacity) {
                struct lttng_live_stream_iterator *youngest_stream_iter = NULL,
                          *candidate_stream_iter = NULL;
                int64_t youngest_msg_ts_ns = INT64_MAX;

                BT_ASSERT_DBG(lttng_live_msg_iter->sessions);
                session_idx = 0;
                while (session_idx < lttng_live_msg_iter->sessions->len) {
                        struct lttng_live_session *session =
                                g_ptr_array_index(lttng_live_msg_iter->sessions,
                                        session_idx);

                        /* Find the best candidate message to send downstream. */
                        stream_iter_status = next_stream_iterator_for_session(
                                lttng_live_msg_iter, session,
                                &candidate_stream_iter);

                        /* If we receive an END status, it means that either:
                         * - Those traces never had active streams (UST with no
                         *   data produced yet),
                         * - All live stream iterators have ENDed.*/
                        if (stream_iter_status == LTTNG_LIVE_ITERATOR_STATUS_END) {
                                if (session->closed && session->traces->len == 0) {
                                        /*
                                         * Remove the session from the list.
                                         * session_idx is not modified since
                                         * g_ptr_array_remove_index_fast
                                         * replaces the the removed element with
                                         * the array's last element.
                                         */
                                        g_ptr_array_remove_index_fast(
                                                lttng_live_msg_iter->sessions,
                                                session_idx);
                                } else {
                                        session_idx++;
                                }
                                continue;
                        }

                        if (stream_iter_status != LTTNG_LIVE_ITERATOR_STATUS_OK) {
                                goto return_status;
                        }

                        if (G_UNLIKELY(youngest_stream_iter == NULL) ||
                                        candidate_stream_iter->current_msg_ts_ns < youngest_msg_ts_ns) {
                                youngest_msg_ts_ns = candidate_stream_iter->current_msg_ts_ns;
                                youngest_stream_iter = candidate_stream_iter;
                        } else if (candidate_stream_iter->current_msg_ts_ns == youngest_msg_ts_ns) {
                                /*
                                 * The currently selected message to be sent
                                 * downstream next has the exact same timestamp
                                 * that of the current candidate message. We
                                 * must break the tie in a predictable manner.
                                 */
                                BT_COMP_LOGD_STR("Two of the next message candidates have the same timestamps, pick one deterministically.");
                                /*
                                 * Order the messages in an arbitrary but
                                 * deterministic way.
                                 */
                                int ret = common_muxing_compare_messages(
                                        candidate_stream_iter->current_msg,
                                        youngest_stream_iter->current_msg);
                                if (ret < 0) {
                                        /*
                                         * The `candidate_stream_iter->current_msg`
                                         * should go first. Update the next
                                         * iterator and the current timestamp.
                                         */
                                        youngest_msg_ts_ns = candidate_stream_iter->current_msg_ts_ns;
                                        youngest_stream_iter = candidate_stream_iter;
                                } else if (ret == 0) {
                                        /* Unable to pick which one should go first. */
                                        BT_COMP_LOGW("Cannot deterministically pick next live stream message iterator because they have identical next messages: "
                                                "next-stream-iter-addr=%p" "candidate-stream-iter-addr=%p",
                                                youngest_stream_iter, candidate_stream_iter);
                                }
                        }

                        session_idx++;
                }

                if (!youngest_stream_iter) {
                        stream_iter_status = LTTNG_LIVE_ITERATOR_STATUS_AGAIN;
                        goto return_status;
                }

                BT_ASSERT_DBG(youngest_stream_iter->current_msg);
                /* Ensure monotonicity. */
                BT_ASSERT_DBG(lttng_live_msg_iter->last_msg_ts_ns <=
                        youngest_stream_iter->current_msg_ts_ns);

                /*
                 * Insert the next message to the message batch. This will set
                 * stream iterator current messsage to NULL so that next time
                 * we fetch the next message of that stream iterator
                 */
                BT_MESSAGE_MOVE_REF(msgs[*count], youngest_stream_iter->current_msg);
                (*count)++;

                /* Update the last timestamp in nanoseconds sent downstream. */
                lttng_live_msg_iter->last_msg_ts_ns = youngest_msg_ts_ns;
                youngest_stream_iter->current_msg_ts_ns = INT64_MAX;

                stream_iter_status = LTTNG_LIVE_ITERATOR_STATUS_OK;
        }

return_status:
        switch (stream_iter_status) {
        case LTTNG_LIVE_ITERATOR_STATUS_OK:
        case LTTNG_LIVE_ITERATOR_STATUS_AGAIN:
                /*
                 * If we gathered messages, return _OK even if the graph was
                 * interrupted. This allows for the components downstream to at
                 * least get the thoses messages. If the graph was indeed
                 * interrupted there should not be another _next() call as the
                 * application will tear down the graph. This component class
                 * doesn't support restarting after an interruption.
                 */
                if (*count > 0) {
                        status = BT_MESSAGE_ITERATOR_CLASS_NEXT_METHOD_STATUS_OK;
                } else {
                        status = BT_MESSAGE_ITERATOR_CLASS_NEXT_METHOD_STATUS_AGAIN;
                }
                break;
        case LTTNG_LIVE_ITERATOR_STATUS_END:
                status = BT_MESSAGE_ITERATOR_CLASS_NEXT_METHOD_STATUS_END;
                break;
        case LTTNG_LIVE_ITERATOR_STATUS_NOMEM:
                BT_COMP_LOGE_APPEND_CAUSE(self_comp,
                        "Memory error preparing the next batch of messages: "
                        "live-iter-status=%s",
                        lttng_live_iterator_status_string(stream_iter_status));
                status = BT_MESSAGE_ITERATOR_CLASS_NEXT_METHOD_STATUS_MEMORY_ERROR;
                break;
        case LTTNG_LIVE_ITERATOR_STATUS_ERROR:
        case LTTNG_LIVE_ITERATOR_STATUS_INVAL:
        case LTTNG_LIVE_ITERATOR_STATUS_UNSUPPORTED:
                BT_COMP_LOGE_APPEND_CAUSE(self_comp,
                        "Error preparing the next batch of messages: "
                        "live-iter-status=%s",
                        lttng_live_iterator_status_string(stream_iter_status));

                status = BT_MESSAGE_ITERATOR_CLASS_NEXT_METHOD_STATUS_ERROR;
                /* Put all existing messages on error. */
                put_messages(msgs, *count);
                break;
        default:
                bt_common_abort();
        }

end:
        return status;
}

static
struct lttng_live_msg_iter *lttng_live_msg_iter_create(
                struct lttng_live_component *lttng_live_comp,
                bt_self_message_iterator *self_msg_it)
{
        bt_self_component *self_comp = lttng_live_comp->self_comp;
        bt_logging_level log_level = lttng_live_comp->log_level;

        struct lttng_live_msg_iter *lttng_live_msg_iter =
                g_new0(struct lttng_live_msg_iter, 1);
        if (!lttng_live_msg_iter) {
                BT_COMP_LOGE_APPEND_CAUSE(self_comp,
                        "Failed to allocate lttng_live_msg_iter");
                goto end;
        }

        lttng_live_msg_iter->log_level = lttng_live_comp->log_level;
        lttng_live_msg_iter->self_comp = lttng_live_comp->self_comp;
        lttng_live_msg_iter->lttng_live_comp = lttng_live_comp;
        lttng_live_msg_iter->self_msg_iter = self_msg_it;

        lttng_live_msg_iter->active_stream_iter = 0;
        lttng_live_msg_iter->last_msg_ts_ns = INT64_MIN;
        lttng_live_msg_iter->was_interrupted = false;

        lttng_live_msg_iter->sessions = g_ptr_array_new_with_free_func(
                (GDestroyNotify) lttng_live_destroy_session);
        BT_ASSERT(lttng_live_msg_iter->sessions);

end:
        return lttng_live_msg_iter;

}

BT_HIDDEN
bt_message_iterator_class_initialize_method_status lttng_live_msg_iter_init(
                bt_self_message_iterator *self_msg_it,
                bt_self_message_iterator_configuration *config,
                bt_self_component_port_output *self_port)
{
        bt_message_iterator_class_initialize_method_status status;
        struct lttng_live_component *lttng_live;
        struct lttng_live_msg_iter *lttng_live_msg_iter;
        enum lttng_live_viewer_status viewer_status;
        bt_logging_level log_level;
        bt_self_component *self_comp =
                bt_self_message_iterator_borrow_component(self_msg_it);

        lttng_live = bt_self_component_get_data(self_comp);
        log_level = lttng_live->log_level;
        self_comp = lttng_live->self_comp;


        /* There can be only one downstream iterator at the same time. */
        BT_ASSERT(!lttng_live->has_msg_iter);
        lttng_live->has_msg_iter = true;

        lttng_live_msg_iter = lttng_live_msg_iter_create(lttng_live,
                self_msg_it);
        if (!lttng_live_msg_iter) {
                status = BT_MESSAGE_ITERATOR_CLASS_INITIALIZE_METHOD_STATUS_MEMORY_ERROR;
                BT_COMP_LOGE_APPEND_CAUSE(self_comp,
                        "Failed to create lttng_live_msg_iter");
                goto error;
        }

         viewer_status = live_viewer_connection_create(self_comp, NULL,
                log_level, lttng_live->params.url->str, false,
                lttng_live_msg_iter, &lttng_live_msg_iter->viewer_connection);
        if (viewer_status != LTTNG_LIVE_VIEWER_STATUS_OK) {
                if (viewer_status == LTTNG_LIVE_VIEWER_STATUS_ERROR) {
                        BT_COMP_LOGE_APPEND_CAUSE(self_comp,
                                "Failed to create viewer connection");
                } else if (viewer_status == LTTNG_LIVE_VIEWER_STATUS_INTERRUPTED) {
                        /*
                         * Interruption in the _iter_init() method is not
                         * supported. Return an error.
                         */
                        BT_COMP_LOGE_APPEND_CAUSE(self_comp,
                                "Interrupted while creating viewer connection");
                }
                goto error;
        }

        viewer_status = lttng_live_create_viewer_session(lttng_live_msg_iter);
        if (viewer_status != LTTNG_LIVE_VIEWER_STATUS_OK) {
                if (viewer_status == LTTNG_LIVE_VIEWER_STATUS_ERROR) {
                        BT_COMP_LOGE_APPEND_CAUSE(self_comp,
                                "Failed to create viewer session");
                } else if (viewer_status == LTTNG_LIVE_VIEWER_STATUS_INTERRUPTED) {
                        /*
                         * Interruption in the _iter_init() method is not
                         * supported. Return an error.
                         */
                        BT_COMP_LOGE_APPEND_CAUSE(self_comp,
                                "Interrupted when creating viewer session");
                }
                goto error;
        }

        if (lttng_live_msg_iter->sessions->len == 0) {
                switch (lttng_live->params.sess_not_found_act) {
                case SESSION_NOT_FOUND_ACTION_CONTINUE:
                        BT_COMP_LOGI("Unable to connect to the requested live viewer session. Keep trying to connect because of "
                                "%s=\"%s\" component parameter: url=\"%s\"",
                                SESS_NOT_FOUND_ACTION_PARAM,
                                SESS_NOT_FOUND_ACTION_CONTINUE_STR,
                                lttng_live->params.url->str);
                        break;
                case SESSION_NOT_FOUND_ACTION_FAIL:
                        BT_COMP_LOGE_APPEND_CAUSE(self_comp,
                                "Unable to connect to the requested live viewer session. Fail the message iterator initialization because of %s=\"%s\" "
                                "component parameter: url =\"%s\"",
                                SESS_NOT_FOUND_ACTION_PARAM,
                                SESS_NOT_FOUND_ACTION_FAIL_STR,
                                lttng_live->params.url->str);
                        goto error;
                case SESSION_NOT_FOUND_ACTION_END:
                        BT_COMP_LOGI("Unable to connect to the requested live viewer session. End gracefully at the first _next() "
                                "call because of %s=\"%s\" component parameter: "
                                "url=\"%s\"", SESS_NOT_FOUND_ACTION_PARAM,
                                SESS_NOT_FOUND_ACTION_END_STR,
                                lttng_live->params.url->str);
                        break;
                default:
                        bt_common_abort();
                }
        }

        bt_self_message_iterator_set_data(self_msg_it, lttng_live_msg_iter);
        status = BT_MESSAGE_ITERATOR_CLASS_INITIALIZE_METHOD_STATUS_OK;
        goto end;

error:
        status = BT_MESSAGE_ITERATOR_CLASS_INITIALIZE_METHOD_STATUS_ERROR;
        lttng_live_msg_iter_destroy(lttng_live_msg_iter);
end:
        return status;
}

static struct bt_param_validation_map_value_entry_descr list_sessions_params[] = {
        { URL_PARAM, BT_PARAM_VALIDATION_MAP_VALUE_ENTRY_MANDATORY, { .type = BT_VALUE_TYPE_STRING } },
        BT_PARAM_VALIDATION_MAP_VALUE_ENTRY_END
};

static
bt_component_class_query_method_status lttng_live_query_list_sessions(
                const bt_value *params, const bt_value **result,
                bt_self_component_class *self_comp_class,
                bt_logging_level log_level)
{
        bt_component_class_query_method_status status;
        const bt_value *url_value = NULL;
        const char *url;
        struct live_viewer_connection *viewer_connection = NULL;
        enum lttng_live_viewer_status viewer_status;
        enum bt_param_validation_status validation_status;
        gchar *validate_error = NULL;

        validation_status = bt_param_validation_validate(params,
                list_sessions_params, &validate_error);
        if (validation_status == BT_PARAM_VALIDATION_STATUS_MEMORY_ERROR) {
                status = BT_COMPONENT_CLASS_QUERY_METHOD_STATUS_MEMORY_ERROR;
                goto error;
        } else if (validation_status == BT_PARAM_VALIDATION_STATUS_VALIDATION_ERROR) {
                status = BT_COMPONENT_CLASS_QUERY_METHOD_STATUS_ERROR;
                BT_COMP_CLASS_LOGE_APPEND_CAUSE(self_comp_class, "%s",
                        validate_error);
                goto error;
        }

        url_value = bt_value_map_borrow_entry_value_const(params, URL_PARAM);
        url = bt_value_string_get(url_value);

        viewer_status = live_viewer_connection_create(NULL, self_comp_class,
                log_level, url, true, NULL, &viewer_connection);
        if (viewer_status != LTTNG_LIVE_VIEWER_STATUS_OK) {
                if (viewer_status == LTTNG_LIVE_VIEWER_STATUS_ERROR) {
                        BT_COMP_CLASS_LOGE_APPEND_CAUSE(self_comp_class,
                                "Failed to create viewer connection");
                        status = BT_COMPONENT_CLASS_QUERY_METHOD_STATUS_ERROR;
                } else if (viewer_status == LTTNG_LIVE_VIEWER_STATUS_INTERRUPTED) {
                        status = BT_COMPONENT_CLASS_QUERY_METHOD_STATUS_AGAIN;
                } else {
                        bt_common_abort();
                }
                goto error;
        }

        status = live_viewer_connection_list_sessions(viewer_connection,
                result);
        if (status != BT_COMPONENT_CLASS_QUERY_METHOD_STATUS_OK) {
                BT_COMP_CLASS_LOGE_APPEND_CAUSE(self_comp_class,
                        "Failed to list viewer sessions");
                goto error;
        }

        goto end;

error:
        BT_VALUE_PUT_REF_AND_RESET(*result);

        if (status >= 0) {
                status = BT_COMPONENT_CLASS_QUERY_METHOD_STATUS_ERROR;
        }

end:
        if (viewer_connection) {
                live_viewer_connection_destroy(viewer_connection);
        }

        g_free(validate_error);

        return status;
}

static
bt_component_class_query_method_status lttng_live_query_support_info(
                const bt_value *params, const bt_value **result,
                bt_self_component_class *self_comp_class,
                bt_logging_level log_level)
{
        bt_component_class_query_method_status status =
                BT_COMPONENT_CLASS_QUERY_METHOD_STATUS_OK;
        const bt_value *input_type_value;
        const bt_value *input_value;
        double weight = 0;
        struct bt_common_lttng_live_url_parts parts = { 0 };

        /* Used by the logging macros */
        __attribute__((unused)) bt_self_component *self_comp = NULL;

        *result = NULL;
        input_type_value = bt_value_map_borrow_entry_value_const(params,
                "type");
        if (!input_type_value) {
                BT_COMP_CLASS_LOGE_APPEND_CAUSE(self_comp_class,
                        "Missing expected `type` parameter.");
                goto error;
        }

        if (!bt_value_is_string(input_type_value)) {
                BT_COMP_CLASS_LOGE_APPEND_CAUSE(self_comp_class,
                        "`type` parameter is not a string value.");
                goto error;
        }

        if (strcmp(bt_value_string_get(input_type_value), "string") != 0) {
                /* We don't handle file system paths */
                goto create_result;
        }

        input_value = bt_value_map_borrow_entry_value_const(params, "input");
        if (!input_value) {
                BT_COMP_CLASS_LOGE_APPEND_CAUSE(self_comp_class,
                        "Missing expected `input` parameter.");
                goto error;
        }

        if (!bt_value_is_string(input_value)) {
                BT_COMP_CLASS_LOGE_APPEND_CAUSE(self_comp_class,
                        "`input` parameter is not a string value.");
                goto error;
        }

        parts = bt_common_parse_lttng_live_url(bt_value_string_get(input_value),
                NULL, 0);
        if (parts.session_name) {
                /*
                 * Looks pretty much like an LTTng live URL: we got the
                 * session name part, which forms a complete URL.
                 */
                weight = .75;
        }

create_result:
        *result = bt_value_real_create_init(weight);
        if (!*result) {
                status = BT_COMPONENT_CLASS_QUERY_METHOD_STATUS_MEMORY_ERROR;
                goto error;
        }

        goto end;

error:
        if (status >= 0) {
                status = BT_COMPONENT_CLASS_QUERY_METHOD_STATUS_ERROR;
        }

        BT_ASSERT(!*result);

end:
        bt_common_destroy_lttng_live_url_parts(&parts);
        return status;
}

BT_HIDDEN
bt_component_class_query_method_status lttng_live_query(
                bt_self_component_class_source *comp_class,
                bt_private_query_executor *priv_query_exec,
                const char *object, const bt_value *params,
                __attribute__((unused)) void *method_data,
                const bt_value **result)
{
        bt_component_class_query_method_status status =
                BT_COMPONENT_CLASS_QUERY_METHOD_STATUS_OK;
        bt_self_component *self_comp = NULL;
        bt_self_component_class *self_comp_class =
                bt_self_component_class_source_as_self_component_class(comp_class);
        bt_logging_level log_level = bt_query_executor_get_logging_level(
                bt_private_query_executor_as_query_executor_const(
                        priv_query_exec));

        if (strcmp(object, "sessions") == 0) {
                status = lttng_live_query_list_sessions(params, result,
                        self_comp_class, log_level);
        } else if (strcmp(object, "babeltrace.support-info") == 0) {
                status = lttng_live_query_support_info(params, result,
                        self_comp_class, log_level);
        } else {
                BT_COMP_LOGI("Unknown query object `%s`", object);
                status = BT_COMPONENT_CLASS_QUERY_METHOD_STATUS_UNKNOWN_OBJECT;
                goto end;
        }

end:
        return status;
}

static
void lttng_live_component_destroy_data(struct lttng_live_component *lttng_live)
{
        if (!lttng_live) {
                return;
        }
        if (lttng_live->params.url) {
                g_string_free(lttng_live->params.url, TRUE);
        }
        g_free(lttng_live);
}

BT_HIDDEN
void lttng_live_component_finalize(bt_self_component_source *component)
{
        void *data = bt_self_component_get_data(
                bt_self_component_source_as_self_component(component));

        if (!data) {
                return;
        }
        lttng_live_component_destroy_data(data);
}

static
enum session_not_found_action parse_session_not_found_action_param(
        const bt_value *no_session_param)
{
        enum session_not_found_action action;
        const char *no_session_act_str = bt_value_string_get(no_session_param);

        if (strcmp(no_session_act_str, SESS_NOT_FOUND_ACTION_CONTINUE_STR) == 0) {
                action = SESSION_NOT_FOUND_ACTION_CONTINUE;
        } else if (strcmp(no_session_act_str, SESS_NOT_FOUND_ACTION_FAIL_STR) == 0) {
                action = SESSION_NOT_FOUND_ACTION_FAIL;
        } else {
                BT_ASSERT(strcmp(no_session_act_str, SESS_NOT_FOUND_ACTION_END_STR) == 0);
                action = SESSION_NOT_FOUND_ACTION_END;
        }

        return action;
}

static struct bt_param_validation_value_descr inputs_elem_descr = {
        .type = BT_VALUE_TYPE_STRING,
};

static const char *sess_not_found_action_choices[] = {
        SESS_NOT_FOUND_ACTION_CONTINUE_STR,
        SESS_NOT_FOUND_ACTION_FAIL_STR,
        SESS_NOT_FOUND_ACTION_END_STR,
};

static struct bt_param_validation_map_value_entry_descr params_descr[] = {
        { INPUTS_PARAM, BT_PARAM_VALIDATION_MAP_VALUE_ENTRY_MANDATORY, { BT_VALUE_TYPE_ARRAY, .array = {
                .min_length = 1,
                .max_length = 1,
                .element_type = &inputs_elem_descr,
        } } },
        { SESS_NOT_FOUND_ACTION_PARAM, BT_PARAM_VALIDATION_MAP_VALUE_ENTRY_OPTIONAL, { BT_VALUE_TYPE_STRING, .string = {
                .choices = sess_not_found_action_choices,
        } } },
        BT_PARAM_VALIDATION_MAP_VALUE_ENTRY_END
};

static
bt_component_class_initialize_method_status lttng_live_component_create(
                const bt_value *params,
                bt_logging_level log_level,
                bt_self_component *self_comp,
                struct lttng_live_component **component)
{
        struct lttng_live_component *lttng_live = NULL;
        const bt_value *inputs_value;
        const bt_value *url_value;
        const bt_value *value;
        const char *url;
        enum bt_param_validation_status validation_status;
        gchar *validation_error = NULL;
        bt_component_class_initialize_method_status status;

        validation_status = bt_param_validation_validate(params, params_descr,
                &validation_error);
        if (validation_status == BT_PARAM_VALIDATION_STATUS_MEMORY_ERROR) {
                status = BT_COMPONENT_CLASS_INITIALIZE_METHOD_STATUS_MEMORY_ERROR;
                goto error;
        } else if (validation_status == BT_PARAM_VALIDATION_STATUS_VALIDATION_ERROR) {
                BT_COMP_LOGE_APPEND_CAUSE(self_comp, "%s", validation_error);
                status = BT_COMPONENT_CLASS_INITIALIZE_METHOD_STATUS_ERROR;
                goto error;
        }

        lttng_live = g_new0(struct lttng_live_component, 1);
        if (!lttng_live) {
                status = BT_COMPONENT_CLASS_INITIALIZE_METHOD_STATUS_MEMORY_ERROR;
                goto end;
        }
        lttng_live->log_level = log_level;
        lttng_live->self_comp = self_comp;
        lttng_live->max_query_size = MAX_QUERY_SIZE;
        lttng_live->has_msg_iter = false;

        inputs_value =
                bt_value_map_borrow_entry_value_const(params, INPUTS_PARAM);
        url_value =
                bt_value_array_borrow_element_by_index_const(inputs_value, 0);
        url = bt_value_string_get(url_value);

        lttng_live->params.url = g_string_new(url);
        if (!lttng_live->params.url) {
                status = BT_COMPONENT_CLASS_INITIALIZE_METHOD_STATUS_MEMORY_ERROR;
                goto error;
        }

        value = bt_value_map_borrow_entry_value_const(params,
                SESS_NOT_FOUND_ACTION_PARAM);
        if (value) {
                lttng_live->params.sess_not_found_act =
                        parse_session_not_found_action_param(value);
        } else {
                BT_COMP_LOGI("Optional `%s` parameter is missing: "
                        "defaulting to `%s`.",
                        SESS_NOT_FOUND_ACTION_PARAM,
                        SESS_NOT_FOUND_ACTION_CONTINUE_STR);
                lttng_live->params.sess_not_found_act =
                        SESSION_NOT_FOUND_ACTION_CONTINUE;
        }

        status = BT_COMPONENT_CLASS_INITIALIZE_METHOD_STATUS_OK;
        goto end;

error:
        lttng_live_component_destroy_data(lttng_live);
        lttng_live = NULL;
end:
        g_free(validation_error);

        *component = lttng_live;
        return status;
}

BT_HIDDEN
bt_component_class_initialize_method_status lttng_live_component_init(
                bt_self_component_source *self_comp_src,
                bt_self_component_source_configuration *config,
                const bt_value *params,
                __attribute__((unused)) void *init_method_data)
{
        struct lttng_live_component *lttng_live;
        bt_component_class_initialize_method_status ret;
        bt_self_component *self_comp =
                bt_self_component_source_as_self_component(self_comp_src);
        bt_logging_level log_level = bt_component_get_logging_level(
                bt_self_component_as_component(self_comp));
        bt_self_component_add_port_status add_port_status;

        ret = lttng_live_component_create(params, log_level, self_comp, &lttng_live);
        if (ret != BT_COMPONENT_CLASS_INITIALIZE_METHOD_STATUS_OK) {
                goto error;
        }

        add_port_status = bt_self_component_source_add_output_port(
                self_comp_src, "out", NULL, NULL);
        if (add_port_status != BT_SELF_COMPONENT_ADD_PORT_STATUS_OK) {
                ret = (int) add_port_status;
                goto end;
        }

        bt_self_component_set_data(self_comp, lttng_live);
        goto end;

error:
        lttng_live_component_destroy_data(lttng_live);
        lttng_live = NULL;
end:
        return ret;
}