Teardown the notification thread after the sessiond clean-up
[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 #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 */
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