Fix live-comm: merge TCP socket write-write sequence in a single write

[lttng-tools.git] / src / bin / lttng-relayd / live.c

diff --git a/src/bin/lttng-relayd/live.c b/src/bin/lttng-relayd/live.c
index f00270bea4c84ab4727047594443191e028965ef..9029a5955a4ad2a4f7551fb033e371914b905bee 100644 (file)
--- a/src/bin/lttng-relayd/live.c
+++ b/src/bin/lttng-relayd/live.c
@@ -1482,13 +1482,15 @@ error_put:
 static
 int viewer_get_packet(struct relay_connection *conn)
 {
-       int ret, send_data = 0;
+       int ret;
        char *data = NULL;
-       uint32_t len = 0;
-       ssize_t read_len;
        struct lttng_viewer_get_packet get_packet_info;
        struct lttng_viewer_trace_packet reply;
        struct relay_viewer_stream *vstream = NULL;
+       bool skip_send_data = false;
+       uint32_t send_len = sizeof(reply);
+       uint32_t packet_data_len = 0;
+       ssize_t read_len;
 
        DBG2("Relay get data packet");
 
@@ -1506,21 +1508,26 @@ int viewer_get_packet(struct relay_connection *conn)
 
        vstream = viewer_stream_get_by_id(be64toh(get_packet_info.stream_id));
        if (!vstream) {
+               skip_send_data = true;
                DBG("Client requested packet of unknown stream id %" PRIu64,
                                be64toh(get_packet_info.stream_id));
                reply.status = htobe32(LTTNG_VIEWER_GET_PACKET_ERR);
-               goto send_reply_nolock;
+       } else {
+               packet_data_len = be32toh(get_packet_info.len);
+               send_len += packet_data_len;
        }
 
-       pthread_mutex_lock(&vstream->stream->lock);
-
-       len = be32toh(get_packet_info.len);
-       data = zmalloc(len);
+       data = zmalloc(send_len);
        if (!data) {
                PERROR("relay data zmalloc");
                goto error;
        }
 
+       if (skip_send_data) {
+               goto send_reply_nolock;
+       }
+
+       pthread_mutex_lock(&vstream->stream->lock);
        ret = lseek(vstream->stream_fd->fd, be64toh(get_packet_info.offset),
                        SEEK_SET);
        if (ret < 0) {
@@ -1528,16 +1535,17 @@ int viewer_get_packet(struct relay_connection *conn)
                        be64toh(get_packet_info.offset));
                goto error;
        }
-       read_len = lttng_read(vstream->stream_fd->fd, data, len);
-       if (read_len < len) {
+       read_len = lttng_read(vstream->stream_fd->fd,
+                       data + sizeof(reply),
+                       packet_data_len);
+       if (read_len < packet_data_len) {
                PERROR("Relay reading trace file, fd: %d, offset: %" PRIu64,
                                vstream->stream_fd->fd,
                                be64toh(get_packet_info.offset));
                goto error;
        }
        reply.status = htobe32(LTTNG_VIEWER_GET_PACKET_OK);
-       reply.len = htobe32(len);
-       send_data = 1;
+       reply.len = htobe32(packet_data_len);
        goto send_reply;
 
 error:
@@ -1548,26 +1556,19 @@ send_reply:
                pthread_mutex_unlock(&vstream->stream->lock);
        }
 send_reply_nolock:
-       reply.flags = htobe32(reply.flags);
 
        health_code_update();
 
-       ret = send_response(conn->sock, &reply, sizeof(reply));
+       memcpy(data, &reply, sizeof(reply));
+       health_code_update();
+       ret = send_response(conn->sock, data, send_len);
+       health_code_update();
        if (ret < 0) {
+               PERROR("sendmsg of packet data failed");
                goto end_free;
        }
-       health_code_update();
-
-       if (send_data) {
-               health_code_update();
-               ret = send_response(conn->sock, data, len);
-               if (ret < 0) {
-                       goto end_free;
-               }
-               health_code_update();
-       }
 
-       DBG("Sent %u bytes for stream %" PRIu64, len,
+       DBG("Sent %u bytes for stream %" PRIu64, send_len,
                        be64toh(get_packet_info.stream_id));
 
 end_free: