From 06662f07b04be024dde9d1e3905061997448103a Mon Sep 17 00:00:00 2001 From: David Goulet Date: Thu, 22 May 2014 13:25:24 -0400 Subject: [PATCH] Fix: improve and update lttng.h comments Signed-off-by: David Goulet --- include/lttng/lttng.h | 166 +++++++++++++++++++++++++++--------------- 1 file changed, 107 insertions(+), 59 deletions(-) diff --git a/include/lttng/lttng.h b/include/lttng/lttng.h index e59b2d31d..eda61d6be 100644 --- a/include/lttng/lttng.h +++ b/include/lttng/lttng.h @@ -375,42 +375,15 @@ struct lttng_handle { /* * Public LTTng control API - * - * For functions having an lttng domain type as parameter, if a bad value is - * given, NO default is applied and an error is returned. - * - * On success, all functions of the API return 0 or the size of the allocated - * array (in bytes). - * - * On error, a negative value is returned being a specific lttng-tools error - * code which can be humanly interpreted with lttng_strerror(err). - * - * Exceptions to this are noted below. - */ - -/* - * Create a handle used as a context for every request made to the library. - * - * This handle contains the session name and lttng domain on which the command - * will be executed. - * The returned pointer will be NULL in case of malloc() error. */ -extern struct lttng_handle *lttng_create_handle(const char *session_name, - struct lttng_domain *domain); - -/* - * Destroy an handle. - * - * It free(3) the data pointer returned by lttng_create_handle(), rendering it - * unusable. - */ -extern void lttng_destroy_handle(struct lttng_handle *handle); /* * Create a tracing session using a name and an optional URL. * * If _url_ is NULL, no consumer is created for the session. The name can't be * NULL here. + * + * Return 0 on success else a negative LTTng error code. */ extern int lttng_create_session(const char *name, const char *url); @@ -420,11 +393,11 @@ extern int lttng_create_session(const char *name, const char *url); * session will be set in overwrite mode and in mmap output since splice is not * supported. * - * If an url is given, it will be used to create a default snapshot output - * using it as a destination. If NULL, no output will be defined and an - * add-output call will be needed. + * Name can't be NULL. If an url is given, it will be used to create a default + * snapshot output using it as a destination. If NULL, no output will be + * defined and an add-output call will be needed. * - * Name can't be NULL. + * Return 0 on success else a negative LTTng error code. */ extern int lttng_create_session_snapshot(const char *name, const char *snapshot_url); @@ -437,18 +410,43 @@ extern int lttng_create_session_snapshot(const char *name, * switch-timer is forbidden. Synchronization beacons are sent to the relayd, * indexes are sent and metadata is checked for each packet. * - * Returns LTTNG_OK on success or a negative error code. + * Name can't be NULL. If no URL is given, the default is to send the data to + * net://127.0.0.1. The timer_interval is in usec and by default set to 1000000 + * (1 second). + * + * Return 0 on success else a negative LTTng error code. */ extern int lttng_create_session_live(const char *name, const char *url, unsigned int timer_interval); +/* + * Create an handle used as a context for every request made to the library. + * + * This handle contains the session name and domain on which the command will + * be executed. A domain is basically a tracer like the kernel or user space. + * + * Return an newly allocated handle that should be freed using + * lttng_destroy_handle. On error, NULL is returned. + */ +extern struct lttng_handle *lttng_create_handle(const char *session_name, + struct lttng_domain *domain); + +/* + * Destroy an handle that has been previously created with lttng_create_handle. + * + * It free the given pointer making it unusable. + */ +extern void lttng_destroy_handle(struct lttng_handle *handle); + /* * Destroy a tracing session. * - * The session will not be usable anymore, tracing will be stopped for all - * registered traces, and the tracing buffers will be flushed. + * The session will not be usable, tracing will be stopped thus buffers will be + * flushed. * * The name can't be NULL here. + * + * Return 0 on success else a negative LTTng error code. */ extern int lttng_destroy_session(const char *name); @@ -456,15 +454,17 @@ extern int lttng_destroy_session(const char *name); * List all the tracing sessions. * * Return the size (number of entries) of the "lttng_session" array. Caller - * must free(3). + * must free sessions. On error, a negative LTTng error code is returned. */ extern int lttng_list_sessions(struct lttng_session **sessions); /* * List the registered domain(s) of a session. * + * Session name CAN NOT be NULL. + * * Return the size (number of entries) of the "lttng_domain" array. Caller - * must free(3). + * must free domains. On error, a negative LTTng error code is returned. */ extern int lttng_list_domains(const char *session_name, struct lttng_domain **domains); @@ -472,8 +472,10 @@ extern int lttng_list_domains(const char *session_name, /* * List the channel(s) of a session. * + * The handle CAN NOT be NULL. + * * Return the size (number of entries) of the "lttng_channel" array. Caller - * must free(3). + * must free channels. On error, a negative LTTng error code is returned. */ extern int lttng_list_channels(struct lttng_handle *handle, struct lttng_channel **channels); @@ -481,8 +483,10 @@ extern int lttng_list_channels(struct lttng_handle *handle, /* * List the event(s) of a session channel. * - * Return the size (number of entries) of the "lttng_event" array. - * Caller must free(3). + * Both handle and channel_name CAN NOT be NULL. + * + * Return the size (number of entries) of the "lttng_event" array. Caller must + * free events. On error a negative LTTng error code is returned. */ extern int lttng_list_events(struct lttng_handle *handle, const char *channel_name, struct lttng_event **events); @@ -490,8 +494,10 @@ extern int lttng_list_events(struct lttng_handle *handle, /* * List the available tracepoints of a specific lttng domain. * - * Return the size (number of entries) of the "lttng_event" array. - * Caller must free(3). + * The handle CAN NOT be NULL. + * + * Return the size (number of entries) of the "lttng_event" array. Caller must + * free events. On error a negative LTTng error code is returned. */ extern int lttng_list_tracepoints(struct lttng_handle *handle, struct lttng_event **events); @@ -499,8 +505,11 @@ extern int lttng_list_tracepoints(struct lttng_handle *handle, /* * List the available tracepoints fields of a specific lttng domain. * + * The handle CAN NOT be NULL. + * * Return the size (number of entries) of the "lttng_event_field" array. - * Caller must free(3). + * Caller must free fields. On error a negative LTTng error code is + * returned. */ extern int lttng_list_tracepoint_fields(struct lttng_handle *handle, struct lttng_event_field **fields); @@ -508,20 +517,20 @@ extern int lttng_list_tracepoint_fields(struct lttng_handle *handle, /* * Check if a session daemon is alive. * - * Return 1 if alive or 0 if not. On error returns a negative value. + * Return 1 if alive or 0 if not. On error, returns a negative negative LTTng + * error code. */ extern int lttng_session_daemon_alive(void); /* * Set the tracing group for the *current* flow of execution. * - * On success, returns 0 else a negative value on error being a lttng error - * code found in lttng-error.h + * On success, returns 0 else a negative LTTng error code. */ extern int lttng_set_tracing_group(const char *name); /* - * Return a human-readable error message for an lttng-tools error code. + * Return a human-readable error message for a LTTng error code. * * Parameter MUST be a negative value or else you'll get a generic message. */ @@ -532,26 +541,32 @@ extern const char *lttng_strerror(int code); * No consumer will be spawned and all fds/commands will go through the socket * path given (socket_path). * - * NOTE: At the moment, if you use the liblttng-kconsumer, you can only use the - * command socket. The error socket is not supported yet for roaming consumers. + * NOTE that this is not recommended unless you absolutely know what you are + * doing. + * + * Return 0 on success else a negative LTTng error code. */ extern int lttng_register_consumer(struct lttng_handle *handle, const char *socket_path); /* - * Start tracing for *all* registered traces (kernel and user-space). + * Start tracing for *all* domain(s) in the session. + * + * Return 0 on success else a negative LTTng error code. */ extern int lttng_start_tracing(const char *session_name); /* - * Stop tracing for *all* registered traces (kernel and user-space). + * Stop tracing for *all* domain(s) in the session. * * This call will wait for data availability for each domain of the session so * this can take an abritrary amount of time. However, when returning you have - * the guarantee that the data is ready to be read and analyse. Use the + * the guarantee that the data is ready to be read and analyze. Use the * _no_wait call below to avoid this behavior. * * The session_name can't be NULL. + * + * Return 0 on success else a negative LTTng error code. */ extern int lttng_stop_tracing(const char *session_name); @@ -564,11 +579,14 @@ extern int lttng_stop_tracing_no_wait(const char *session_name); /* * Add context to event(s) for a specific channel (or for all). * - * If channel_name is NULL, a lookup of the event's channel is done. If both - * are NULL, the context is applied to all events of all channels. + * If the channel_name is NULL and they are no channel for the domain, the + * default channel is created (channel0). The context is then added on ALL + * channels since no name was specified. + * + * The event_name is ignored since adding a context to an event is not possible + * for now. * - * Note that whatever event_name value is, a context can not be added to an - * event, so we just ignore it for now. + * Return 0 on success else a negative LTTng error code. */ extern int lttng_add_context(struct lttng_handle *handle, struct lttng_event_context *ctx, const char *event_name, @@ -578,10 +596,12 @@ extern int lttng_add_context(struct lttng_handle *handle, * Create or enable an event (or events) for a channel. * * If the event you are trying to enable does not exist, it will be created, - * else it is enabled. - * If channel_name is NULL, the default channel is used (channel0). + * else it is enabled. If channel_name is NULL, the default channel is used + * (channel0). * * The handle and ev params can not be NULL. + * + * Return 0 on success else a negative LTTng error code. */ extern int lttng_enable_event(struct lttng_handle *handle, struct lttng_event *ev, const char *channel_name); @@ -596,6 +616,8 @@ extern int lttng_enable_event(struct lttng_handle *handle, * if not found. * If filter_expression is NULL, an event without associated filter is * created. + * + * Return 0 on success else a negative LTTng error code. */ extern int lttng_enable_event_with_filter(struct lttng_handle *handle, struct lttng_event *event, const char *channel_name, @@ -612,6 +634,8 @@ extern int lttng_enable_event_with_filter(struct lttng_handle *handle, * If filter_expression is NULL, an event without associated filter is * created. * If exclusion count is zero, the event will be created without exclusions. + * + * Return 0 on success else a negative LTTng error code. */ extern int lttng_enable_event_with_exclusions(struct lttng_handle *handle, struct lttng_event *event, const char *channel_name, @@ -622,6 +646,8 @@ extern int lttng_enable_event_with_exclusions(struct lttng_handle *handle, * Create or enable a channel. * * The chan and handle params can not be NULL. + * + * Return 0 on success else a negative LTTng error code. */ extern int lttng_enable_channel(struct lttng_handle *handle, struct lttng_channel *chan); @@ -631,6 +657,8 @@ extern int lttng_enable_channel(struct lttng_handle *handle, * * If name is NULL, all events are disabled. * If channel_name is NULL, the default channel is used (channel0). + * + * Return 0 on success else a negative LTTng error code. */ extern int lttng_disable_event(struct lttng_handle *handle, const char *name, const char *channel_name); @@ -638,6 +666,9 @@ extern int lttng_disable_event(struct lttng_handle *handle, /* * Disable channel. * + * Name and handle CAN NOT be NULL. + * + * Return 0 on success else a negative LTTng error code. */ extern int lttng_disable_channel(struct lttng_handle *handle, const char *name); @@ -646,6 +677,8 @@ extern int lttng_disable_channel(struct lttng_handle *handle, * Calibrate LTTng overhead. * * The chan and handle params can not be NULL. + * + * Return 0 on success else a negative LTTng error code. */ extern int lttng_calibrate(struct lttng_handle *handle, struct lttng_calibrate *calibrate); @@ -667,6 +700,21 @@ extern void lttng_channel_set_default_attr(struct lttng_domain *domain, * * Default port are 5342 and 5343 respectively for control and data which uses * the TCP protocol. + * + * URL format: proto://[HOST|IP][:PORT1[:PORT2]][/TRACE_PATH] + * + * Possible protocols are: + * > file://... + * Local filesystem full path. + * + * > net[6]://... + * This will use the default network transport layer which is TCP for both + * control (PORT1) and data port (PORT2). + * + * > tcp[6]://... + * TCP only streaming. For this one, both data and control URL must be given. + * + * Return 0 on success else a negative LTTng error code. */ extern int lttng_set_consumer_url(struct lttng_handle *handle, const char *control_url, const char *data_url); -- 2.34.1