[lttng-tools.git] / include / lttng / notification / channel.h

/*
 * Copyright (C) 2017 - Jérémie Galarneau <jeremie.galarneau@efficios.com>
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License, version 2.1 only,
 * as published by the Free Software Foundation.
 *
 * This library is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#ifndef LTTNG_NOTIFICATION_CHANNEL_H
#define LTTNG_NOTIFICATION_CHANNEL_H

#ifdef __cplusplus
extern "C" {
#endif

struct lttng_endpoint;
struct lttng_condition;
struct lttng_notification;
struct lttng_notification_channel;

enum lttng_notification_channel_status {
	LTTNG_NOTIFICATION_CHANNEL_STATUS_NOTIFICATIONS_DROPPED = 1,
	LTTNG_NOTIFICATION_CHANNEL_STATUS_OK = 0,
	LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR = -1,
	LTTNG_NOTIFICATION_CHANNEL_STATUS_CLOSED = -2,
	LTTNG_NOTIFICATION_CHANNEL_STATUS_ALREADY_SUBSCRIBED = -3,
	/* Condition unknown. */
	LTTNG_NOTIFICATION_CHANNEL_STATUS_UNKNOWN_CONDITION = -4,
	LTTNG_NOTIFICATION_CHANNEL_STATUS_INVALID = -5,
	LTTNG_NOTIFICATION_CHANNEL_STATUS_UNSUPPORTED_VERSION = -6,
};

/**
 * A notification channel is used to receive notifications from various
 * LTTng components.
 *
 * Notification channels connect a client to an LTTng endpoint
 * (see lttng/endpoint.h) and allows client to subscribe and unsubscribe
 * to various types of notifications which are associated to conditions.
 *
 * In order to emit a notification, a condition must be associated to a
 * notify action within a trigger. A client wishing to consume such
 * conditions must explicitly subscribe to them by using an equivalent
 * condition.
 */

/*
 * Create a notification channel connected to a given endpoint.
 *
 * The only supported endpoint, at the moment, is the
 * lttng_session_daemon_notification_endpoint, which is a singleton
 * declared in the lttng/endpoint.h header.
 *
 * Returns an lttng_notification_channel on success, NULL on failure.
 * The returned lttng_notification_channel must be destroyed using
 * the lttng_notification_channel_destroy() function.
 */
extern struct lttng_notification_channel *lttng_notification_channel_create(
		struct lttng_endpoint *endpoint);

/*
 * Get the next notification received on a notification channel.
 *
 * This call will block until a notification is received on the notification
 * channel or until the endpoint closes the connection.
 *
 * The returned notification's ownership is transferred to the caller and
 * it must be destroyed using lttng_notification_destroy().
 *
 * Notifications can be dropped if a client consumes the notifications sent
 * through the notification channel too slowly.
 *
 * Returns LTTNG_NOTIFICATION_CHANNEL_STATUS_OK and a notification on success,
 * LTTNG_NOTIFICATION_CHANNEL_STATUS_INVALID if an invalid parameter was
 * provided, or LTTNG_NOTIFICATION_CHANNEL_STATUS_NOTIFICATIONS_DROPPED if
 * notifications were dropped.
 */
extern enum lttng_notification_channel_status
lttng_notification_channel_get_next_notification(
		struct lttng_notification_channel *channel,
		struct lttng_notification **notification);

/*
 * Subscribe to notifications of a condition through a notification channel.
 *
 * The caller retains the ownership of the condition passed through this call
 * and it can be disposed-of at any moment after this call.
 *
 * An error will be reported if the client tries to subscribe to the same
 * condition multiple times without unsubscribing.
 *
 * Returns LTTNG_NOTIFICATION_CHANNEL_STATUS_OK on success,
 * LTTNG_NOTIFICATION_CHANNEL_STATUS_INVALID if an invalid parameter was
 * provided, or LTTNG_NOTIFICATION_CHANNEL_STATUS_ALREADY_SUBSCRIBED if the
 * client was already subscribed to the condition through this channel.
 */
extern enum lttng_notification_channel_status
lttng_notification_channel_subscribe(
		struct lttng_notification_channel *channel,
		const struct lttng_condition *condition);

/*
 * Unsubscribe to notifications of a condition through a notification channel.
 *
 * The caller retains the ownership of the condition passed through this call
 * and it can be disposed-of at any moment after this call.
 *
 * An error will be reported if the client tries to unsubscribe to from a
 * conditions' notifications to which it was not previously subscribed.
 *
 * Returns LTTNG_NOTIFICATION_CHANNEL_STATUS_OK on success,
 * LTTNG_NOTIFICATION_CHANNEL_STATUS_INVALID if an invalid parameter was
 * provided, or LTTNG_NOTIFICATION_CHANNEL_STATUS_UNKNOWN_CONDITION if the
 * client was not already subscribed to the condition through this channel.
 */
extern enum lttng_notification_channel_status
lttng_notification_channel_unsubscribe(
		struct lttng_notification_channel *channel,
		const struct lttng_condition *condition);

/*
 * Closes and destroys (frees) a notification channel.
 */
extern void lttng_notification_channel_destroy(
		struct lttng_notification_channel *channel);

#ifdef __cplusplus
}
#endif

#endif /* LTTNG_NOTIFICATION_CHANNEL_H */
Commit	Line	Data
a58c490f JG	1	/*
	2	* Copyright (C) 2017 - Jérémie Galarneau <jeremie.galarneau@efficios.com>
	3	*
	4	* This library is free software; you can redistribute it and/or modify it
	5	* under the terms of the GNU Lesser General Public License, version 2.1 only,
	6	* as published by the Free Software Foundation.
	7	*
	8	* This library 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 Lesser General Public License
	11	* for more details.
	12	*
	13	* You should have received a copy of the GNU Lesser General Public License
	14	* along with this library; if not, write to the Free Software Foundation,
	15	* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	16	*/
	17
	18	#ifndef LTTNG_NOTIFICATION_CHANNEL_H
	19	#define LTTNG_NOTIFICATION_CHANNEL_H
	20
	21	#ifdef __cplusplus
	22	extern "C" {
	23	#endif
	24
	25	struct lttng_endpoint;
	26	struct lttng_condition;
	27	struct lttng_notification;
	28	struct lttng_notification_channel;
	29
a58c490f JG	30	enum lttng_notification_channel_status {
	31	LTTNG_NOTIFICATION_CHANNEL_STATUS_NOTIFICATIONS_DROPPED = 1,
	32	LTTNG_NOTIFICATION_CHANNEL_STATUS_OK = 0,
	33	LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR = -1,
	34	LTTNG_NOTIFICATION_CHANNEL_STATUS_CLOSED = -2,
	35	LTTNG_NOTIFICATION_CHANNEL_STATUS_ALREADY_SUBSCRIBED = -3,
	36	/* Condition unknown. */
	37	LTTNG_NOTIFICATION_CHANNEL_STATUS_UNKNOWN_CONDITION = -4,
	38	LTTNG_NOTIFICATION_CHANNEL_STATUS_INVALID = -5,
	39	LTTNG_NOTIFICATION_CHANNEL_STATUS_UNSUPPORTED_VERSION = -6,
	40	};
	41
92eda4bd JG	42	/**
	43	* A notification channel is used to receive notifications from various
	44	* LTTng components.
	45	*
	46	* Notification channels connect a client to an LTTng endpoint
	47	* (see lttng/endpoint.h) and allows client to subscribe and unsubscribe
	48	* to various types of notifications which are associated to conditions.
	49	*
	50	* In order to emit a notification, a condition must be associated to a
	51	* notify action within a trigger. A client wishing to consume such
	52	* conditions must explicitly subscribe to them by using an equivalent
	53	* condition.
	54	*/
	55
	56	/*
	57	* Create a notification channel connected to a given endpoint.
	58	*
	59	* The only supported endpoint, at the moment, is the
	60	* lttng_session_daemon_notification_endpoint, which is a singleton
	61	* declared in the lttng/endpoint.h header.
	62	*
	63	* Returns an lttng_notification_channel on success, NULL on failure.
	64	* The returned lttng_notification_channel must be destroyed using
	65	* the lttng_notification_channel_destroy() function.
	66	*/
a58c490f JG	67	extern struct lttng_notification_channel *lttng_notification_channel_create(
	68	struct lttng_endpoint *endpoint);
	69
92eda4bd JG	70	/*
	71	* Get the next notification received on a notification channel.
	72	*
	73	* This call will block until a notification is received on the notification
	74	* channel or until the endpoint closes the connection.
	75	*
	76	* The returned notification's ownership is transferred to the caller and
	77	* it must be destroyed using lttng_notification_destroy().
	78	*
	79	* Notifications can be dropped if a client consumes the notifications sent
	80	* through the notification channel too slowly.
	81	*
53d80915	82	* Returns LTTNG_NOTIFICATION_CHANNEL_STATUS_OK and a notification on success,
92eda4bd JG	83	* LTTNG_NOTIFICATION_CHANNEL_STATUS_INVALID if an invalid parameter was
	84	* provided, or LTTNG_NOTIFICATION_CHANNEL_STATUS_NOTIFICATIONS_DROPPED if
	85	* notifications were dropped.
	86	*/
a58c490f JG	87	extern enum lttng_notification_channel_status
	88	lttng_notification_channel_get_next_notification(
	89	struct lttng_notification_channel *channel,
	90	struct lttng_notification **notification);
	91
92eda4bd JG	92	/*
	93	* Subscribe to notifications of a condition through a notification channel.
	94	*
	95	* The caller retains the ownership of the condition passed through this call
	96	* and it can be disposed-of at any moment after this call.
	97	*
	98	* An error will be reported if the client tries to subscribe to the same
	99	* condition multiple times without unsubscribing.
	100	*
	101	* Returns LTTNG_NOTIFICATION_CHANNEL_STATUS_OK on success,
	102	* LTTNG_NOTIFICATION_CHANNEL_STATUS_INVALID if an invalid parameter was
	103	* provided, or LTTNG_NOTIFICATION_CHANNEL_STATUS_ALREADY_SUBSCRIBED if the
	104	* client was already subscribed to the condition through this channel.
	105	*/
a58c490f JG	106	extern enum lttng_notification_channel_status
	107	lttng_notification_channel_subscribe(
	108	struct lttng_notification_channel *channel,
	109	const struct lttng_condition *condition);
	110
92eda4bd JG	111	/*
	112	* Unsubscribe to notifications of a condition through a notification channel.
	113	*
	114	* The caller retains the ownership of the condition passed through this call
	115	* and it can be disposed-of at any moment after this call.
	116	*
	117	* An error will be reported if the client tries to unsubscribe to from a
	118	* conditions' notifications to which it was not previously subscribed.
	119	*
	120	* Returns LTTNG_NOTIFICATION_CHANNEL_STATUS_OK on success,
	121	* LTTNG_NOTIFICATION_CHANNEL_STATUS_INVALID if an invalid parameter was
	122	* provided, or LTTNG_NOTIFICATION_CHANNEL_STATUS_UNKNOWN_CONDITION if the
	123	* client was not already subscribed to the condition through this channel.
	124	*/
a58c490f JG	125	extern enum lttng_notification_channel_status
	126	lttng_notification_channel_unsubscribe(
	127	struct lttng_notification_channel *channel,
	128	const struct lttng_condition *condition);
	129
92eda4bd JG	130	/*
	131	* Closes and destroys (frees) a notification channel.
	132	*/
a58c490f JG	133	extern void lttng_notification_channel_destroy(
	134	struct lttng_notification_channel *channel);
	135
	136	#ifdef __cplusplus
	137	}
	138	#endif
	139
	140	#endif /* LTTNG_NOTIFICATION_CHANNEL_H */