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

   1 /*
   2  * Copyright (C) 2017 - Jérémie Galarneau <jeremie.galarneau@efficios.com>
   3  *
   4  * This program is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License, version 2 only, as
   6  * published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
  11  * more details.
  12  *
  13  * You should have received a copy of the GNU General Public License along with
  14  * this program; if not, write to the Free Software Foundation, Inc., 51
  15  * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  16  */
  17
  18 #ifndef NOTIFICATION_THREAD_H
  19 #define NOTIFICATION_THREAD_H
  20
  21 #include <urcu/list.h>
  22 #include <urcu.h>
  23 #include <urcu/rculfhash.h>
  24 #include <lttng/trigger/trigger.h>
  25 #include <common/pipe.h>
  26 #include <common/compat/poll.h>
  27 #include <common/hashtable/hashtable.h>
  28 #include <pthread.h>
  29 #include <semaphore.h>
  30 #include "thread.h"
  31
  32 struct notification_thread_handle {
  33         /*
  34          * Queue of struct notification command.
  35          * event_pipe must be WRITE(2) to signal that a new command
  36          * has been enqueued.
  37          */
  38         struct {
  39                 struct lttng_pipe *event_pipe;
  40                 struct cds_list_head list;
  41                 pthread_mutex_t lock;
  42         } cmd_queue;
  43         /*
  44          * Read side of pipes used to receive channel status info collected
  45          * by the various consumer daemons.
  46          */
  47         struct {
  48                 int ust32_consumer;
  49                 int ust64_consumer;
  50                 int kernel_consumer;
  51         } channel_monitoring_pipes;
  52         /* Used to wait for the launch of the notification thread. */
  53         sem_t ready;
  54 };
  55
  56 /**
  57  * This thread maintains an internal state associating clients and triggers.
  58  *
  59  * In order to speed-up and simplify queries, hash tables providing the
  60  * following associations are maintained:
  61  *
  62  *   - client_socket_ht: associate a client's socket (fd) to its "struct client"
  63  *             This hash table owns the "struct client" which must thus be
  64  *             disposed-of on removal from the hash table.
  65  *
  66  *   - channel_triggers_ht:
  67  *             associates a channel key to a list of
  68  *             struct lttng_trigger_list_nodes. The triggers in this list are
  69  *             those that have conditions that apply to a particular channel.
  70  *             A channel entry is only created when a channel is added; the
  71  *             list of triggers applying to such a channel is built at that
  72  *             moment.
  73  *             This hash table owns the list, but not the triggers themselves.
  74  *
  75  *   - session_triggers_ht:
  76  *             associates a session name to a list of
  77  *             struct lttng_trigger_list_nodes. The triggers in this list are
  78  *             those that have conditions that apply to a particular session.
  79  *             A session entry is only created when a session is created; the
  80  *             list of triggers applying to this new session is built at that
  81  *             moment. This happens at the time of creation of a session_info.
  82  *             Likewise, the list is destroyed at the time of the session_info's
  83  *             destruction.
  84  *
  85  *   - channel_state_ht:
  86  *             associates a pair (channel key, channel domain) to its last
  87  *             sampled state received from the consumer daemon
  88  *             (struct channel_state).
  89  *             This previous sample is kept to implement edge-triggered
  90  *             conditions as we need to detect the state transitions.
  91  *             This hash table owns the channel state.
  92  *
  93  *   - notification_trigger_clients_ht:
  94  *             associates notification-emitting triggers to clients
  95  *             (struct notification_client_list) subscribed to those
  96  *             conditions.
  97  *             The condition's hash and match functions are used directly since
  98  *             all triggers in this hash table have the "notify" action.
  99  *             This hash table holds no ownership.
 100  *
 101  *   - channels_ht:
 102  *             associates a channel_key to a struct channel_info. The hash table
 103  *             holds the ownership of the struct channel_info.
 104  *
 105  *   - sessions_ht:
 106  *             associates a session_name (hash) to a struct session_info. The
 107  *             hash table holds no ownership of the struct session_info;
 108  *             the session_info structure is owned by the session's various
 109  *             channels through their struct channel_info (ref-counting is used).
 110  *
 111  *   - triggers_ht:
 112  *             associates a condition to a struct lttng_trigger_ht_element.
 113  *             The hash table holds the ownership of the
 114  *             lttng_trigger_ht_elements along with the triggers themselves.
 115  *
 116  * The thread reacts to the following internal events:
 117  *   1) creation of a tracing channel,
 118  *   2) destruction of a tracing channel,
 119  *   3) registration of a trigger,
 120  *   4) unregistration of a trigger,
 121  *   5) reception of a channel monitor sample from the consumer daemon.
 122  *   6) Session rotation ongoing
 123  *   7) Session rotation completed
 124  *
 125  * Events specific to notification-emitting triggers:
 126  *   8) connection of a notification client,
 127  *   9) disconnection of a notification client,
 128  *   10) subscription of a client to a conditions' notifications,
 129  *   11) unsubscription of a client from a conditions' notifications,
 130  *
 131  *
 132  * 1) Creation of a tracing channel
 133  *    - notification_trigger_clients_ht is traversed to identify
 134  *      triggers which apply to this new channel,
 135  *      - triggers identified are added to the channel_triggers_ht.
 136  *    - add channel to channels_ht
 137  *    - if it is the first channel of a session, a session_info is created and
 138  *      added to the sessions_ht. A list of the triggers associated with that
 139  *      session is built, and it is added to session_triggers_ht.
 140  *
 141  * 2) Destruction of a tracing channel
 142  *    - remove entry from channel_triggers_ht, releasing the list wrapper and
 143  *      elements,
 144  *    - remove entry from the channel_state_ht.
 145  *    - remove channel from channels_ht
 146  *    - if it was the last known channel of a session, the session_info
 147  *      structure is torndown, which in return destroys the list of triggers
 148  *      applying to that session.
 149  *
 150  * 3) Registration of a trigger
 151  *    - if the trigger's action is of type "notify",
 152  *      - traverse the list of conditions of every client to build a list of
 153  *        clients which have to be notified when this trigger's condition is met,
 154  *        - add list of clients (even if it is empty) to the
 155  *          notification_trigger_clients_ht,
 156  *    - add trigger to channel_triggers_ht (if applicable),
 157  *    - add trigger to session_triggers_ht (if applicable),
 158  *    - add trigger to triggers_ht
 159  *    - evaluate the trigger's condition right away to react if that condition
 160  *      is true from the beginning.
 161  *
 162  * 4) Unregistration of a trigger
 163  *    - if the trigger's action is of type "notify",
 164  *      - remove the trigger from the notification_trigger_clients_ht,
 165  *    - remove trigger from channel_triggers_ht (if applicable),
 166  *    - remove trigger from session_triggers_ht (if applicable),
 167  *    - remove trigger from triggers_ht
 168  *
 169  * 5) Reception of a channel monitor sample from the consumer daemon
 170  *    - evaluate the conditions associated with the triggers found in
 171  *      the channel_triggers_ht,
 172  *      - if a condition evaluates to "true" and the condition is of type
 173  *        "notify", query the notification_trigger_clients_ht and send
 174  *        a notification to the clients.
 175  *
 176  * 6) Session rotation ongoing
 177  *
 178  * 7) Session rotation completed
 179  *
 180  * 8) Connection of a client
 181  *    - add client socket to the client_socket_ht.
 182  *
 183  * 9) Disconnection of a client
 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 *channel_triggers_ht;
 205         struct cds_lfht *session_triggers_ht;
 206         struct cds_lfht *channel_state_ht;
 207         struct cds_lfht *notification_trigger_clients_ht;
 208         struct cds_lfht *channels_ht;
 209         struct cds_lfht *sessions_ht;
 210         struct cds_lfht *triggers_ht;
 211 };
 212
 213 /* notification_thread_data takes ownership of the channel monitor pipes. */
 214 struct notification_thread_handle *notification_thread_handle_create(
 215                 struct lttng_pipe *ust32_channel_monitor_pipe,
 216                 struct lttng_pipe *ust64_channel_monitor_pipe,
 217                 struct lttng_pipe *kernel_channel_monitor_pipe);
 218 void notification_thread_handle_destroy(
 219                 struct notification_thread_handle *handle);
 220 struct lttng_thread *launch_notification_thread(
 221                 struct notification_thread_handle *handle);
 222
 223 #endif /* NOTIFICATION_THREAD_H */