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 "action-executor.h"
  12 #include "thread.h"
  13 #include <common/compat/poll.h>
  14 #include <common/hashtable/hashtable.h>
  15 #include <common/pipe.h>
  16 #include <lttng/trigger/trigger.h>
  17 #include <pthread.h>
  18 #include <semaphore.h>
  19 #include <urcu.h>
  20 #include <urcu/list.h>
  21 #include <urcu/rculfhash.h>
  22
  23 typedef uint64_t notification_client_id;
  24
  25 struct notification_event_trigger_source_element {
  26         int fd;
  27         struct cds_list_head node;
  28 };
  29
  30 struct notification_trigger_tokens_ht_element {
  31     uint64_t token;
  32     struct lttng_trigger *trigger;
  33     struct cds_lfht_node node;
  34     /* call_rcu delayed reclaim. */
  35     struct rcu_head rcu_node;
  36 };
  37
  38 struct notification_thread_handle {
  39         /*
  40          * Queue of struct notification command.
  41          * event_pipe must be WRITE(2) to signal that a new command
  42          * has been enqueued.
  43          */
  44         struct {
  45                 struct lttng_pipe *event_pipe;
  46                 struct cds_list_head list;
  47                 pthread_mutex_t lock;
  48         } cmd_queue;
  49         /*
  50          * Read side of pipes used to receive channel status info collected
  51          * by the various consumer daemons.
  52          */
  53         struct {
  54                 int ust32_consumer;
  55                 int ust64_consumer;
  56                 int kernel_consumer;
  57         } channel_monitoring_pipes;
  58         /*
  59          * Read side of pipes used to reveice event trigger generetated by
  60          * registered applications
  61          */
  62         struct {
  63                 /* List of notification_event_trigger_source_element */
  64                 struct cds_list_head list;
  65                 pthread_mutex_t lock;
  66                 int kernel_tracer;
  67         } event_trigger_sources;
  68         /* Used to wait for the launch of the notification thread. */
  69         sem_t ready;
  70 };
  71
  72 /**
  73  * This thread maintains an internal state associating clients and triggers.
  74  *
  75  * In order to speed-up and simplify queries, hash tables providing the
  76  * following associations are maintained:
  77  *
  78  *   - client_socket_ht: associate a client's socket (fd) to its
  79  *             "struct notification_client".
  80  *             This hash table owns the "struct notification_client" which must
  81  *             thus be disposed-of on removal from the hash table.
  82  *
  83  *   - client_id_ht: associate a client's id to its "struct notification_client"
  84  *             This hash table holds a _weak_ reference to the
  85  *             "struct notification_client".
  86  *
  87  *   - channel_triggers_ht:
  88  *             associates a channel key to a list of
  89  *             struct lttng_trigger_list_nodes. The triggers in this list are
  90  *             those that have conditions that apply to a particular channel.
  91  *             A channel entry is only created when a channel is added; the
  92  *             list of triggers applying to such a channel is built at that
  93  *             moment.
  94  *             This hash table owns the list, but not the triggers themselves.
  95  *
  96  *   - session_triggers_ht:
  97  *             associates a session name to a list of
  98  *             struct lttng_trigger_list_nodes. The triggers in this list are
  99  *             those that have conditions that apply to a particular session.
 100  *             A session entry is only created when a session is created; the
 101  *             list of triggers applying to this new session is built at that
 102  *             moment. This happens at the time of creation of a session_info.
 103  *             Likewise, the list is destroyed at the time of the session_info's
 104  *             destruction.
 105  *
 106  *   - channel_state_ht:
 107  *             associates a pair (channel key, channel domain) to its last
 108  *             sampled state received from the consumer daemon
 109  *             (struct channel_state).
 110  *             This previous sample is kept to implement edge-triggered
 111  *             conditions as we need to detect the state transitions.
 112  *             This hash table owns the channel state.
 113  *
 114  *   - notification_trigger_clients_ht:
 115  *             associates notification-emitting triggers to clients
 116  *             (struct notification_client_list) subscribed to those
 117  *             conditions.
 118  *             The condition's hash and match functions are used directly since
 119  *             all triggers in this hash table have the "notify" action.
 120  *             This hash table holds no ownership.
 121  *
 122  *   - channels_ht:
 123  *             associates a channel_key to a struct channel_info. The hash table
 124  *             holds the ownership of the struct channel_info.
 125  *
 126  *   - sessions_ht:
 127  *             associates a session_name (hash) to a struct session_info. The
 128  *             hash table holds no ownership of the struct session_info;
 129  *             the session_info structure is owned by the session's various
 130  *             channels through their struct channel_info (ref-counting is used).
 131  *
 132  *   - triggers_ht:
 133  *             associates a trigger to a struct lttng_trigger_ht_element.
 134  *             The hash table holds the ownership of the
 135  *             lttng_trigger_ht_elements along with the triggers themselves.
 136  *   - triggers_by_name_ht:
 137  *             associates a trigger name to a struct lttng_trigger_ht_element.
 138  *             The hash table does not hold any ownership and is used strictly
 139  *             for lookup on registration.
 140  *
 141  * The thread reacts to the following internal events:
 142  *   1) creation of a tracing channel,
 143  *   2) destruction of a tracing channel,
 144  *   3) registration of a trigger,
 145  *   4) unregistration of a trigger,
 146  *   5) reception of a channel monitor sample from the consumer daemon.
 147  *   6) Session rotation ongoing
 148  *   7) Session rotation completed
 149  *
 150  * Events specific to notification-emitting triggers:
 151  *   8) connection of a notification client,
 152  *   9) disconnection of a notification client,
 153  *   10) subscription of a client to a conditions' notifications,
 154  *   11) unsubscription of a client from a conditions' notifications,
 155  *
 156  *
 157  * 1) Creation of a tracing channel
 158  *    - notification_trigger_clients_ht is traversed to identify
 159  *      triggers which apply to this new channel,
 160  *      - triggers identified are added to the channel_triggers_ht.
 161  *    - add channel to channels_ht
 162  *    - if it is the first channel of a session, a session_info is created and
 163  *      added to the sessions_ht. A list of the triggers associated with that
 164  *      session is built, and it is added to session_triggers_ht.
 165  *
 166  * 2) Destruction of a tracing channel
 167  *    - remove entry from channel_triggers_ht, releasing the list wrapper and
 168  *      elements,
 169  *    - remove entry from the channel_state_ht.
 170  *    - remove channel from channels_ht
 171  *    - if it was the last known channel of a session, the session_info
 172  *      structure is torndown, which in return destroys the list of triggers
 173  *      applying to that session.
 174  *
 175  * 3) Registration of a trigger
 176  *    - if the trigger's action is of type "notify",
 177  *      - traverse the list of conditions of every client to build a list of
 178  *        clients which have to be notified when this trigger's condition is met,
 179  *        - add list of clients (even if it is empty) to the
 180  *          notification_trigger_clients_ht,
 181  *    - add trigger to channel_triggers_ht (if applicable),
 182  *    - add trigger to session_triggers_ht (if applicable),
 183  *    - add trigger to triggers_by_name_ht
 184  *    - add trigger to triggers_ht
 185  *    - evaluate the trigger's condition right away to react if that condition
 186  *      is true from the beginning.
 187  *
 188  * 4) Unregistration of a trigger
 189  *    - if the trigger's action is of type "notify",
 190  *      - remove the trigger from the notification_trigger_clients_ht,
 191  *    - remove trigger from channel_triggers_ht (if applicable),
 192  *    - remove trigger from session_triggers_ht (if applicable),
 193  *    - remove trigger to triggers_by_name_ht
 194  *    - remove trigger from triggers_ht
 195  *
 196  * 5) Reception of a channel monitor sample from the consumer daemon
 197  *    - evaluate the conditions associated with the triggers found in
 198  *      the channel_triggers_ht,
 199  *      - if a condition evaluates to "true" and the condition is of type
 200  *        "notify", query the notification_trigger_clients_ht and send
 201  *        a notification to the clients.
 202  *
 203  * 6) Session rotation ongoing
 204  *
 205  * 7) Session rotation completed
 206  *
 207  * 8) Connection of a client
 208  *    - add client socket to the client_socket_ht,
 209  *    - add client socket to the client_id_ht.
 210  *
 211  * 9) Disconnection of a client
 212  *    - remove client socket from the client_id_ht,
 213  *    - remove client socket from the client_socket_ht,
 214  *    - traverse all conditions to which the client is subscribed and remove
 215  *      the client from the notification_trigger_clients_ht.
 216  *
 217  * 10) Subscription of a client to a condition's notifications
 218  *    - Add the condition to the client's list of subscribed conditions,
 219  *    - Look-up notification_trigger_clients_ht and add the client to
 220  *      list of clients.
 221  *    - Evaluate the condition for the client that subscribed if the trigger
 222  *      was already registered.
 223  *
 224  * 11) Unsubscription of a client to a condition's notifications
 225  *    - Remove the condition from the client's list of subscribed conditions,
 226  *    - Look-up notification_trigger_clients_ht and remove the client
 227  *      from the list of clients.
 228  */
 229 struct notification_thread_state {
 230         int notification_channel_socket;
 231         struct lttng_poll_event events;
 232         struct cds_lfht *client_socket_ht;
 233         struct cds_lfht *client_id_ht;
 234         struct cds_lfht *channel_triggers_ht;
 235         struct cds_lfht *session_triggers_ht;
 236         struct cds_lfht *channel_state_ht;
 237         struct cds_lfht *notification_trigger_clients_ht;
 238         struct cds_lfht *channels_ht;
 239         struct cds_lfht *sessions_ht;
 240         struct cds_lfht *triggers_ht;
 241         struct cds_lfht *triggers_by_name_ht;
 242         struct cds_lfht *trigger_tokens_ht;
 243         struct {
 244                 uint64_t token_generator;
 245                 uint64_t name_offset;
 246         } trigger_id;
 247         notification_client_id next_notification_client_id;
 248         struct action_executor *executor;
 249 };
 250
 251 /* notification_thread_data takes ownership of the channel monitor pipes. */
 252 struct notification_thread_handle *notification_thread_handle_create(
 253                 struct lttng_pipe *ust32_channel_monitor_pipe,
 254                 struct lttng_pipe *ust64_channel_monitor_pipe,
 255                 struct lttng_pipe *kernel_channel_monitor_pipe,
 256                 int kernel_notification_monitor_fd);
 257 void notification_thread_handle_destroy(
 258                 struct notification_thread_handle *handle);
 259 struct lttng_thread *launch_notification_thread(
 260                 struct notification_thread_handle *handle);
 261
 262 #endif /* NOTIFICATION_THREAD_H */