4e1ca4b8011fc3392394a09dc4f3f5303e07ee2c
[lttng-tools.git] / 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
24 typedef uint64_t notification_client_id;
25
26 struct notification_thread_handle {
27 /*
28 * Queue of struct notification command.
29 * event_pipe must be WRITE(2) to signal that a new command
30 * has been enqueued.
31 */
32 struct {
33 struct lttng_pipe *event_pipe;
34 struct cds_list_head list;
35 pthread_mutex_t lock;
36 } cmd_queue;
37 /*
38 * Read side of pipes used to receive channel status info collected
39 * by the various consumer daemons.
40 */
41 struct {
42 int ust32_consumer;
43 int ust64_consumer;
44 int kernel_consumer;
45 } channel_monitoring_pipes;
46 /* Used to wait for the launch of the notification thread. */
47 sem_t ready;
48 };
49
50 /**
51 * This thread maintains an internal state associating clients and triggers.
52 *
53 * In order to speed-up and simplify queries, hash tables providing the
54 * following associations are maintained:
55 *
56 * - client_socket_ht: associate a client's socket (fd) to its
57 * "struct notification_client".
58 * This hash table owns the "struct notification_client" which must
59 * thus be disposed-of on removal from the hash table.
60 *
61 * - client_id_ht: associate a client's id to its "struct notification_client"
62 * This hash table holds a _weak_ reference to the
63 * "struct notification_client".
64 *
65 * - channel_triggers_ht:
66 * associates a channel key to a list of
67 * struct lttng_trigger_list_nodes. The triggers in this list are
68 * those that have conditions that apply to a particular channel.
69 * A channel entry is only created when a channel is added; the
70 * list of triggers applying to such a channel is built at that
71 * moment.
72 * This hash table owns the list, but not the triggers themselves.
73 *
74 * - session_triggers_ht:
75 * associates a session name to a list of
76 * struct lttng_trigger_list_nodes. The triggers in this list are
77 * those that have conditions that apply to a particular session.
78 * A session entry is only created when a session is created; the
79 * list of triggers applying to this new session is built at that
80 * moment. This happens at the time of creation of a session_info.
81 * Likewise, the list is destroyed at the time of the session_info's
82 * destruction.
83 *
84 * - channel_state_ht:
85 * associates a pair (channel key, channel domain) to its last
86 * sampled state received from the consumer daemon
87 * (struct channel_state).
88 * This previous sample is kept to implement edge-triggered
89 * conditions as we need to detect the state transitions.
90 * This hash table owns the channel state.
91 *
92 * - notification_trigger_clients_ht:
93 * associates notification-emitting triggers to clients
94 * (struct notification_client_list) subscribed to those
95 * conditions.
96 * The condition's hash and match functions are used directly since
97 * all triggers in this hash table have the "notify" action.
98 * This hash table holds no ownership.
99 *
100 * - channels_ht:
101 * associates a channel_key to a struct channel_info. The hash table
102 * holds the ownership of the struct channel_info.
103 *
104 * - sessions_ht:
105 * associates a session_name (hash) to a struct session_info. The
106 * hash table holds no ownership of the struct session_info;
107 * the session_info structure is owned by the session's various
108 * channels through their struct channel_info (ref-counting is used).
109 *
110 * - triggers_ht:
111 * associates a trigger to a struct lttng_trigger_ht_element.
112 * The hash table holds the ownership of the
113 * lttng_trigger_ht_elements along with the triggers themselves.
114 * - triggers_by_name_uid_ht:
115 * associates a trigger (name, uid) tuple to
116 * a struct lttng_trigger_ht_element.
117 * The hash table does not hold any ownership and is used strictly
118 * for lookup on registration.
119 *
120 * The thread reacts to the following internal events:
121 * 1) creation of a tracing channel,
122 * 2) destruction of a tracing channel,
123 * 3) registration of a trigger,
124 * 4) unregistration of a trigger,
125 * 5) reception of a channel monitor sample from the consumer daemon.
126 * 6) Session rotation ongoing
127 * 7) Session rotation completed
128 *
129 * Events specific to notification-emitting triggers:
130 * 8) connection of a notification client,
131 * 9) disconnection of a notification client,
132 * 10) subscription of a client to a conditions' notifications,
133 * 11) unsubscription of a client from a conditions' notifications,
134 *
135 *
136 * 1) Creation of a tracing channel
137 * - notification_trigger_clients_ht is traversed to identify
138 * triggers which apply to this new channel,
139 * - triggers identified are added to the channel_triggers_ht.
140 * - add channel to channels_ht
141 * - if it is the first channel of a session, a session_info is created and
142 * added to the sessions_ht. A list of the triggers associated with that
143 * session is built, and it is added to session_triggers_ht.
144 *
145 * 2) Destruction of a tracing channel
146 * - remove entry from channel_triggers_ht, releasing the list wrapper and
147 * elements,
148 * - remove entry from the channel_state_ht.
149 * - remove channel from channels_ht
150 * - if it was the last known channel of a session, the session_info
151 * structure is torndown, which in return destroys the list of triggers
152 * applying to that session.
153 *
154 * 3) Registration of a trigger
155 * - if the trigger's action is of type "notify",
156 * - traverse the list of conditions of every client to build a list of
157 * clients which have to be notified when this trigger's condition is met,
158 * - add list of clients (even if it is empty) to the
159 * notification_trigger_clients_ht,
160 * - add trigger to channel_triggers_ht (if applicable),
161 * - add trigger to session_triggers_ht (if applicable),
162 * - add trigger to triggers_by_name_uid_ht
163 * - add trigger to triggers_ht
164 * - evaluate the trigger's condition right away to react if that condition
165 * is true from the beginning.
166 *
167 * 4) Unregistration of a trigger
168 * - if the trigger's action is of type "notify",
169 * - remove the trigger from the notification_trigger_clients_ht,
170 * - remove trigger from channel_triggers_ht (if applicable),
171 * - remove trigger from session_triggers_ht (if applicable),
172 * - remove trigger from triggers_by_name_uid_ht
173 * - remove trigger from triggers_ht
174 *
175 * 5) Reception of a channel monitor sample from the consumer daemon
176 * - evaluate the conditions associated with the triggers found in
177 * the channel_triggers_ht,
178 * - if a condition evaluates to "true" and the condition is of type
179 * "notify", query the notification_trigger_clients_ht and send
180 * a notification to the clients.
181 *
182 * 6) Session rotation ongoing
183 *
184 * 7) Session rotation completed
185 *
186 * 8) Connection of a client
187 * - add client socket to the client_socket_ht,
188 * - add client socket to the client_id_ht.
189 *
190 * 9) Disconnection of a client
191 * - remove client socket from the client_id_ht,
192 * - remove client socket from the client_socket_ht,
193 * - traverse all conditions to which the client is subscribed and remove
194 * the client from the notification_trigger_clients_ht.
195 *
196 * 10) Subscription of a client to a condition's notifications
197 * - Add the condition to the client's list of subscribed conditions,
198 * - Look-up notification_trigger_clients_ht and add the client to
199 * list of clients.
200 * - Evaluate the condition for the client that subscribed if the trigger
201 * was already registered.
202 *
203 * 11) Unsubscription of a client to a condition's notifications
204 * - Remove the condition from the client's list of subscribed conditions,
205 * - Look-up notification_trigger_clients_ht and remove the client
206 * from the list of clients.
207 */
208 struct notification_thread_state {
209 int notification_channel_socket;
210 struct lttng_poll_event events;
211 struct cds_lfht *client_socket_ht;
212 struct cds_lfht *client_id_ht;
213 struct cds_lfht *channel_triggers_ht;
214 struct cds_lfht *session_triggers_ht;
215 struct cds_lfht *channel_state_ht;
216 struct cds_lfht *notification_trigger_clients_ht;
217 struct cds_lfht *channels_ht;
218 struct cds_lfht *sessions_ht;
219 struct cds_lfht *triggers_ht;
220 struct cds_lfht *triggers_by_name_uid_ht;
221 struct {
222 uint64_t name_offset;
223 } trigger_id;
224 notification_client_id next_notification_client_id;
225 struct action_executor *executor;
226 };
227
228 /* notification_thread_data takes ownership of the channel monitor pipes. */
229 struct notification_thread_handle *notification_thread_handle_create(
230 struct lttng_pipe *ust32_channel_monitor_pipe,
231 struct lttng_pipe *ust64_channel_monitor_pipe,
232 struct lttng_pipe *kernel_channel_monitor_pipe);
233 void notification_thread_handle_destroy(
234 struct notification_thread_handle *handle);
235 struct lttng_thread *launch_notification_thread(
236 struct notification_thread_handle *handle);
237
238 #endif /* NOTIFICATION_THREAD_H */
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