Docs: document trigger condition and action ownership in 2.13+

[lttng-tools.git] / include / lttng / trigger / trigger.h

/*
 * Copyright (C) 2017 Jérémie Galarneau <jeremie.galarneau@efficios.com>
 *
 * SPDX-License-Identifier: LGPL-2.1-only
 *
 */

#ifndef LTTNG_TRIGGER_H
#define LTTNG_TRIGGER_H

#include <sys/types.h>
#include <inttypes.h>

struct lttng_action;
struct lttng_condition;
struct lttng_trigger;
/* A set of triggers. */
struct lttng_triggers;

#ifdef __cplusplus
extern "C" {
#endif

enum lttng_register_trigger_status {
	LTTNG_REGISTER_TRIGGER_STATUS_OK = 0,
	LTTNG_REGISTER_TRIGGER_STATUS_INVALID = -1,
};

enum lttng_trigger_status {
	LTTNG_TRIGGER_STATUS_OK = 0,
	LTTNG_TRIGGER_STATUS_ERROR = -1,
	LTTNG_TRIGGER_STATUS_UNKNOWN = -2,
	LTTNG_TRIGGER_STATUS_INVALID = -3,
	LTTNG_TRIGGER_STATUS_UNSET = -4,
	LTTNG_TRIGGER_STATUS_UNSUPPORTED = -5,
	LTTNG_TRIGGER_STATUS_PERMISSION_DENIED = -6,
};

enum lttng_trigger_firing_policy {
	LTTNG_TRIGGER_FIRING_POLICY_EVERY_N = 0,
	LTTNG_TRIGGER_FIRING_POLICY_ONCE_AFTER_N = 1,
};

/*
 * Create a trigger object associating a condition and an action.
 *
 * A trigger associates a condition and an action to take whenever the
 * condition evaluates to true. Such actions can, for example, consist
 * in the emission of a notification to clients listening through
 * notification channels.
 *
 * Prior to 2.13, the caller had to retain the ownership of both the condition
 * and action. Both objects had to be kept alive for the lifetime of the trigger
 * object. This is no longer the case as the condition and action objects are
 * internally reference counted. It is safe to destroy a condition and an action
 * after using them to create a trigger. However, they should no longer be used.
 *
 * If the action is a notification action with capture descriptors,
 * the condition must be an event rule condition.
 *
 * A trigger must be registered in order to become activate and can
 * be destroyed after its registration.
 *
 * Returns a trigger object on success, NULL on error.
 * Trigger objects must be destroyed using the lttng_trigger_destroy()
 * function.
 */
extern struct lttng_trigger *lttng_trigger_create(
		struct lttng_condition *condition, struct lttng_action *action);

/*
 * Set the user identity (uid) of a trigger.
 *
 * Only available for the root user (uid 0).
 *
 * Returns LTTNG_TRIGGER_STATUS_OK on success,
 * LTTNG_TRIGGER_STATUS_EPERM if not authorized,
 * LTTNG_TRIGGER_STATUS_INVALID if invalid parameters are passed.
 */
extern enum lttng_trigger_status lttng_trigger_set_owner_uid(
		struct lttng_trigger *trigger, uid_t uid);

/*
 * Get the user identity (uid) of a trigger.
 *
 * Returns LTTNG_TRIGGER_STATUS_OK on success,
 * LTTNG_TRIGGER_STATUS_UNSET if unset,
 * LTTNG_TRIGGER_STATUS_INVALID if invalid parameters are passed.
 */
extern enum lttng_trigger_status lttng_trigger_get_owner_uid(
		const struct lttng_trigger *trigger, uid_t *uid);

/*
 * Get the condition of a trigger.
 *
 * The caller acquires no ownership of the returned condition.
 *
 * Returns a condition on success, NULL on error.
 */
extern struct lttng_condition *lttng_trigger_get_condition(
		struct lttng_trigger *trigger);

const struct lttng_condition *lttng_trigger_get_const_condition(
		const struct lttng_trigger *trigger);

/*
 * Get the action of a trigger.
 *
 * The caller acquires no ownership of the returned action.
 *
 * Returns an action on success, NULL on error.
 */
extern struct lttng_action *lttng_trigger_get_action(
		struct lttng_trigger *trigger);

const struct lttng_action *lttng_trigger_get_const_action(
		const struct lttng_trigger *trigger);

/*
 * Get the name of a trigger.
 *
 * The caller does not assume the ownership of the returned name.
 * The name shall only only be used for the duration of the trigger's
 * lifetime, or until a different name is set.
 *
 * Returns LTTNG_TRIGGER_STATUS_OK and a pointer to the trigger's name on
 * success, LTTNG_TRIGGER_STATUS_INVALID if an invalid parameter is passed,
 * or LTTNG_TRIGGER_STATUS_UNSET if a name was not set prior to this call.
 */
extern enum lttng_trigger_status lttng_trigger_get_name(
		const struct lttng_trigger *trigger, const char **name);

/*
 * Set the trigger name.
 *
 * A name is optional.
 * A name will be assigned on trigger registration if no name is set.
 *
 * The name is copied.
 *
 * Return LTTNG_TRIGGER_STATUS_OK on success, LTTNG_TRIGGER_STATUS_INVALID
 * if invalid parameters are passed.
 */
extern enum lttng_trigger_status lttng_trigger_set_name(
		struct lttng_trigger *trigger, const char *name);

/*
 * Set the trigger firing policy.
 *
 * This is optional. By default a trigger is set to fire each time the
 * associated condition occurs.
 *
 * Threshold is the number of times the condition must be hit before the policy
 * is enacted.
 *
 * Return LTTNG_TRIGGER_STATUS_OK on success, LTTNG_TRIGGER_STATUS_INVALID
 * if invalid parameters are passed.
 */
extern enum lttng_trigger_status lttng_trigger_set_firing_policy(
		struct lttng_trigger *trigger,
		enum lttng_trigger_firing_policy policy_type,
		uint64_t threshold);

/*
 * Get the trigger firing policy.
 *
 * Threshold is the number of time the condition must be hit before the policy is
 * enacted.
 *
 * Return LTTNG_TRIGGER_STATUS_OK on success, LTTNG_TRIGGER_STATUS_INVALID
 * if invalid parameters are passed.
 */
extern enum lttng_trigger_status lttng_trigger_get_firing_policy(
		const struct lttng_trigger *trigger,
		enum lttng_trigger_firing_policy *policy_type,
		uint64_t *threshold);

/*
 * Destroy (frees) a trigger object.
 */
extern void lttng_trigger_destroy(struct lttng_trigger *trigger);

/*
 * Register a trigger to the session daemon.
 *
 * The trigger can be destroyed after this call.
 *
 * Return 0 on success, a negative LTTng error code on error.
 */
extern int lttng_register_trigger(struct lttng_trigger *trigger);

/*
 * Unregister a trigger from the session daemon.
 *
 * The trigger can be destroyed after this call.
 *
 * Return 0 on success, a negative LTTng error code on error.
 */
extern int lttng_unregister_trigger(const struct lttng_trigger *trigger);

/*
 * List triggers for the current user.
 *
 * On success, a newly-allocated trigger set is returned.
 *
 * The trigger set must be destroyed by the caller (see
 * lttng_triggers_destroy()).
 *
 * Returns LTTNG_OK on success, else a suitable LTTng error code.
 */
extern enum lttng_error_code lttng_list_triggers(
		struct lttng_triggers **triggers);

/*
 * Get a trigger from the set at a given index.
 *
 * Note that the trigger set maintains the ownership of the returned trigger.
 * It must not be destroyed by the user, nor should a reference to it be held
 * beyond the lifetime of the trigger set.
 *
 * Returns a trigger, or NULL on error.
 */
extern const struct lttng_trigger *lttng_triggers_get_at_index(
		const struct lttng_triggers *triggers, unsigned int index);

/*
 * Get the number of triggers in a trigger set.
 *
 * Return LTTNG_TRIGGER_STATUS_OK on success,
 * LTTNG_TRIGGER_STATUS_INVALID when invalid parameters are passed.
 */
extern enum lttng_trigger_status lttng_triggers_get_count(
		const struct lttng_triggers *triggers, unsigned int *count);

/*
 * Destroy a trigger set.
 */
extern void lttng_triggers_destroy(struct lttng_triggers *triggers);


#ifdef __cplusplus
}
#endif

#endif /* LTTNG_TRIGGER_H */