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