src/bin/lttng-sessiond/notification-thread.h

   1 /*
   2  * Copyright (C) 2017 Jérémie Galarneau <jeremie.galarneau@efficios.com>
   3  *
   4  * SPDX-License-Identifier: GPL-2.0-only
   5  *
   6  */
   7
   8 #ifndef NOTIFICATION_THREAD_H
   9 #define NOTIFICATION_THREAD_H
  10
  11 #include <urcu/list.h>
  12 #include <urcu.h>
  13 #include <urcu/rculfhash.h>
  14 #include <lttng/trigger/trigger.h>
  15 #include <common/pipe.h>
  16 #include <common/compat/poll.h>
  17 #include <common/hashtable/hashtable.h>
  18 #include <pthread.h>
  19 #include <semaphore.h>
  20 #include "thread.h"
  21
  22
  23 typedef uint64_t notification_client_id;
  24
  25 struct notification_thread_handle {
  26         /*
  27          * Queue of struct notification command.
  28          * event_pipe must be WRITE(2) to signal that a new command
  29          * has been enqueued.
  30          */
  31         struct {
  32                 struct lttng_pipe *event_pipe;
  33                 struct cds_list_head list;
  34                 pthread_mutex_t lock;
  35         } cmd_queue;
  36         /*
  37          * Read side of pipes used to receive channel status info collected
  38          * by the various consumer daemons.
  39          */
  40         struct {
  41                 int ust32_consumer;
  42                 int ust64_consumer;
  43                 int kernel_consumer;
  44         } channel_monitoring_pipes;
  45         /* Used to wait for the launch of the notification thread. */
  46         sem_t ready;
  47 };
  48
  49 /**
  50  * This thread maintains an internal state associating clients and triggers.
  51  *
  52  * In order to speed-up and simplify queries, hash tables providing the
  53  * following associations are maintained:
  54  *
  55  *   - client_socket_ht: associate a client's socket (fd) to its
  56  *             "struct notification_client".
  57  *             This hash table owns the "struct notification_client" which must
  58  *             thus be disposed-of on removal from the hash table.
  59  *
  60  *   - client_id_ht: associate a client's id to its "struct notification_client"
  61  *             This hash table holds a _weak_ reference to the
  62  *             "struct notification_client".
  63  *
  64  *   - channel_triggers_ht:
  65  *             associates a channel key to a list of
  66  *             struct lttng_trigger_list_nodes. The triggers in this list are
  67  *             those that have conditions that apply to a particular channel.
  68  *             A channel entry is only created when a channel is added; the
  69  *             list of triggers applying to such a channel is built at that
  70  *             moment.
  71  *             This hash table owns the list, but not the triggers themselves.
  72  *
  73  *   - session_triggers_ht:
  74  *             associates a session name to a list of
  75  *             struct lttng_trigger_list_nodes. The triggers in this list are
  76  *             those that have conditions that apply to a particular session.
  77  *             A session entry is only created when a session is created; the
  78  *             list of triggers applying to this new session is built at that
  79  *             moment. This happens at the time of creation of a session_info.
  80  *             Likewise, the list is destroyed at the time of the session_info's
  81  *             destruction.
  82  *
  83  *   - channel_state_ht:
  84  *             associates a pair (channel key, channel domain) to its last
  85  *             sampled state received from the consumer daemon
  86  *             (struct channel_state).
  87  *             This previous sample is kept to implement edge-triggered
  88  *             conditions as we need to detect the state transitions.
  89  *             This hash table owns the channel state.
  90  *
  91  *   - notification_trigger_clients_ht:
  92  *             associates notification-emitting triggers to clients
  93  *             (struct notification_client_list) subscribed to those
  94  *             conditions.
  95  *             The condition's hash and match functions are used directly since
  96  *             all triggers in this hash table have the "notify" action.
  97  *             This hash table holds no ownership.
  98  *
  99  *   - channels_ht:
 100  *             associates a channel_key to a struct channel_info. The hash table
 101  *             holds the ownership of the struct channel_info.
 102  *
 103  *   - sessions_ht:
 104  *             associates a session_name (hash) to a struct session_info. The
 105  *             hash table holds no ownership of the struct session_info;
 106  *             the session_info structure is owned by the session's various
 107  *             channels through their struct channel_info (ref-counting is used).
 108  *
 109  *   - triggers_ht:
 110  *             associates a condition to a struct lttng_trigger_ht_element.
 111  *             The hash table holds the ownership of the
 112  *             lttng_trigger_ht_elements along with the triggers themselves.
 113  *
 114  * The thread reacts to the following internal events:
 115  *   1) creation of a tracing channel,
 116  *   2) destruction of a tracing channel,
 117  *   3) registration of a trigger,
 118  *   4) unregistration of a trigger,
 119  *   5) reception of a channel monitor sample from the consumer daemon.
 120  *   6) Session rotation ongoing
 121  *   7) Session rotation completed
 122  *
 123  * Events specific to notification-emitting triggers:
 124  *   8) connection of a notification client,
 125  *   9) disconnection of a notification client,
 126  *   10) subscription of a client to a conditions' notifications,
 127  *   11) unsubscription of a client from a conditions' notifications,
 128  *
 129  *
 130  * 1) Creation of a tracing channel
 131  *    - notification_trigger_clients_ht is traversed to identify
 132  *      triggers which apply to this new channel,
 133  *      - triggers identified are added to the channel_triggers_ht.
 134  *    - add channel to channels_ht
 135  *    - if it is the first channel of a session, a session_info is created and
 136  *      added to the sessions_ht. A list of the triggers associated with that
 137  *      session is built, and it is added to session_triggers_ht.
 138  *
 139  * 2) Destruction of a tracing channel
 140  *    - remove entry from channel_triggers_ht, releasing the list wrapper and
 141  *      elements,
 142  *    - remove entry from the channel_state_ht.
 143  *    - remove channel from channels_ht
 144  *    - if it was the last known channel of a session, the session_info
 145  *      structure is torndown, which in return destroys the list of triggers
 146  *      applying to that session.
 147  *
 148  * 3) Registration of a trigger
 149  *    - if the trigger's action is of type "notify",
 150  *      - traverse the list of conditions of every client to build a list of
 151  *        clients which have to be notified when this trigger's condition is met,
 152  *        - add list of clients (even if it is empty) to the
 153  *          notification_trigger_clients_ht,
 154  *    - add trigger to channel_triggers_ht (if applicable),
 155  *    - add trigger to session_triggers_ht (if applicable),
 156  *    - add trigger to triggers_ht
 157  *    - evaluate the trigger's condition right away to react if that condition
 158  *      is true from the beginning.
 159  *
 160  * 4) Unregistration of a trigger
 161  *    - if the trigger's action is of type "notify",
 162  *      - remove the trigger from the notification_trigger_clients_ht,
 163  *    - remove trigger from channel_triggers_ht (if applicable),
 164  *    - remove trigger from session_triggers_ht (if applicable),
 165  *    - remove trigger from triggers_ht
 166  *
 167  * 5) Reception of a channel monitor sample from the consumer daemon
 168  *    - evaluate the conditions associated with the triggers found in
 169  *      the channel_triggers_ht,
 170  *      - if a condition evaluates to "true" and the condition is of type
 171  *        "notify", query the notification_trigger_clients_ht and send
 172  *        a notification to the clients.
 173  *
 174  * 6) Session rotation ongoing
 175  *
 176  * 7) Session rotation completed
 177  *
 178  * 8) Connection of a client
 179  *    - add client socket to the client_socket_ht,
 180  *    - add client socket to the client_id_ht.
 181  *
 182  * 9) Disconnection of a client
 183  *    - remove client socket from the client_id_ht,
 184  *    - remove client socket from the client_socket_ht,
 185  *    - traverse all conditions to which the client is subscribed and remove
 186  *      the client from the notification_trigger_clients_ht.
 187  *
 188  * 10) Subscription of a client to a condition's notifications
 189  *    - Add the condition to the client's list of subscribed conditions,
 190  *    - Look-up notification_trigger_clients_ht and add the client to
 191  *      list of clients.
 192  *    - Evaluate the condition for the client that subscribed if the trigger
 193  *      was already registered.
 194  *
 195  * 11) Unsubscription of a client to a condition's notifications
 196  *    - Remove the condition from the client's list of subscribed conditions,
 197  *    - Look-up notification_trigger_clients_ht and remove the client
 198  *      from the list of clients.
 199  */
 200 struct notification_thread_state {
 201         int notification_channel_socket;
 202         struct lttng_poll_event events;
 203         struct cds_lfht *client_socket_ht;
 204         struct cds_lfht *client_id_ht;
 205         struct cds_lfht *channel_triggers_ht;
 206         struct cds_lfht *session_triggers_ht;
 207         struct cds_lfht *channel_state_ht;
 208         struct cds_lfht *notification_trigger_clients_ht;
 209         struct cds_lfht *channels_ht;
 210         struct cds_lfht *sessions_ht;
 211         struct cds_lfht *triggers_ht;
 212         notification_client_id next_notification_client_id;
 213 };
 214
 215 /* notification_thread_data takes ownership of the channel monitor pipes. */
 216 struct notification_thread_handle *notification_thread_handle_create(
 217                 struct lttng_pipe *ust32_channel_monitor_pipe,
 218                 struct lttng_pipe *ust64_channel_monitor_pipe,
 219                 struct lttng_pipe *kernel_channel_monitor_pipe);
 220 void notification_thread_handle_destroy(
 221                 struct notification_thread_handle *handle);
 222 struct lttng_thread *launch_notification_thread(
 223                 struct notification_thread_handle *handle);
 224
 225 #endif /* NOTIFICATION_THREAD_H */