} channel_monitoring_pipes;
};
+/**
+ * This thread maintains an internal state associating clients and triggers.
+ *
+ * In order to speed-up and simplify queries, hash tables providing the
+ * following associations are maintained:
+ *
+ * - client_socket_ht: associate a client's socket (fd) to its "struct client"
+ * This hash table owns the "struct client" which must thus be
+ * disposed-of on removal from the hash table.
+ *
+ * - channel_triggers_ht:
+ * associates a channel key to a list of
+ * struct lttng_trigger_list_nodes. The triggers in this list are
+ * those that have conditions that apply to this channel.
+ * A channel entry is only created when a channel is added; the
+ * list of triggers applying to such a channel is built at that
+ * moment.
+ * This hash table owns the list, but not the triggers themselves.
+ *
+ * - channel_state_ht:
+ * associates a pair (channel key, channel domain) to its last
+ * sampled state received from the consumer daemon
+ * (struct channel_state).
+ * This previous sample is kept to implement edge-triggered
+ * conditions as we need to detect the state transitions.
+ * This hash table owns the channel state.
+ *
+ * - notification_trigger_clients_ht:
+ * associates notification-emitting triggers to clients
+ * (struct notification_client_list) subscribed to those
+ * conditions.
+ * The condition's hash and match functions are used directly since
+ * all triggers in this hash table have the "notify" action.
+ * This hash table holds no ownership.
+ *
+ * - channels_ht:
+ * associates a channel_key to a struct channel_info. The hash table
+ * holds the ownership of the struct channel_info.
+ *
+ * - triggers_ht:
+ * associated a condition to a struct lttng_trigger_ht_element.
+ * The hash table holds the ownership of the
+ * lttng_trigger_ht_elements along with the triggers themselves.
+ *
+ * The thread reacts to the following internal events:
+ * 1) creation of a tracing channel,
+ * 2) destruction of a tracing channel,
+ * 3) registration of a trigger,
+ * 4) unregistration of a trigger,
+ * 5) reception of a channel monitor sample from the consumer daemon.
+ *
+ * Events specific to notification-emitting triggers:
+ * 6) connection of a notification client,
+ * 7) disconnection of a notification client,
+ * 8) subscription of a client to a conditions' notifications,
+ * 9) unsubscription of a client from a conditions' notifications,
+ *
+ *
+ * 1) Creation of a tracing channel
+ * - notification_trigger_clients_ht is traversed to identify
+ * triggers which apply to this new channel,
+ * - triggers identified are added to the channel_triggers_ht.
+ * - add channel to channels_ht
+ *
+ * 2) Destruction of a tracing channel
+ * - remove entry from channel_triggers_ht, releasing the list wrapper and
+ * elements,
+ * - remove entry from the channel_state_ht.
+ * - remove channel from channels_ht
+ *
+ * 3) Registration of a trigger
+ * - if the trigger's action is of type "notify",
+ * - traverse the list of conditions of every client to build a list of
+ * clients which have to be notified when this trigger's condition is met,
+ * - add list of clients (even if it is empty) to the
+ * notification_trigger_clients_ht,
+ * - add trigger to channel_triggers_ht (if applicable),
+ * - add trigger to triggers_ht
+ *
+ * 4) Unregistration of a trigger
+ * - if the trigger's action is of type "notify",
+ * - remove the trigger from the notification_trigger_clients_ht,
+ * - remove trigger from channel_triggers_ht (if applicable),
+ * - remove trigger from triggers_ht
+ *
+ * 5) Reception of a channel monitor sample from the consumer daemon
+ * - evaluate the conditions associated with the triggers found in
+ * the channel_triggers_ht,
+ * - if a condition evaluates to "true" and the condition is of type
+ * "notify", query the notification_trigger_clients_ht and send
+ * a notification to the clients.
+ *
+ * 6) Connection of a client
+ * - add client socket to the client_socket_ht.
+ *
+ * 7) Disconnection of a client
+ * - remove client socket from the client_socket_ht,
+ * - traverse all conditions to which the client is subscribed and remove
+ * the client from the notification_trigger_clients_ht.
+ *
+ * 8) Subscription of a client to a condition's notifications
+ * - Add the condition to the client's list of subscribed conditions,
+ * - Look-up notification_trigger_clients_ht and add the client to
+ * list of clients.
+ *
+ * 9) Unsubscription of a client to a condition's notifications
+ * - Remove the condition from the client's list of subscribed conditions,
+ * - Look-up notification_trigger_clients_ht and remove the client
+ * from the list of clients.
+ */
struct notification_thread_state {
int notification_channel_socket;
struct lttng_poll_event events;
projects / lttng-tools.git / blobdiff