include/lttng/session.h

   1 /*
   2  * Copyright (C) 2014 David Goulet <dgoulet@efficios.com>
   3  * Copyright (C) 2019 Jérémie Galarneau <jeremie.galarneau@efficios.com>
   4  *
   5  * SPDX-License-Identifier: LGPL-2.1-only
   6  *
   7  */
   8
   9 #ifndef LTTNG_SESSION_H
  10 #define LTTNG_SESSION_H
  11
  12 #ifdef __cplusplus
  13 extern "C" {
  14 #endif
  15
  16 #include <lttng/constant.h>
  17 #include <lttng/lttng-export.h>
  18
  19 struct lttng_handle;
  20 struct lttng_session_descriptor;
  21 struct lttng_destruction_handle;
  22
  23 /*
  24  * Basic session information.
  25  *
  26  * The "enabled" field is only used when listing the sessions which indicate if
  27  * it's started or not.
  28  *
  29  * The structures should be initialized to zero before use.
  30  */
  31 #define LTTNG_SESSION_PADDING1             8
  32 struct lttng_session {
  33         char name[LTTNG_NAME_MAX];
  34         /*
  35          * Human-readable representation of the trace's destination.
  36          * In the case of a local tracing session, a path is provided:
  37          *     /path/to/the/output
  38          *
  39          * In the case of a remote (network) tracing session, the string has
  40          * the following format:
  41          *     net://hostname/path:ctrl_port [data: data_port]
  42          */
  43         char path[PATH_MAX];
  44         uint32_t enabled;       /* enabled/started: 1, disabled/stopped: 0 */
  45         uint32_t snapshot_mode;
  46         unsigned int live_timer_interval;       /* usec */
  47
  48         /*
  49          * End of public attributes.
  50          * The remaining fields are used to deal with ABI management concerns.
  51          */
  52
  53         /*
  54          * 32-bit architectures are already naturally aligned on 4 bytes after
  55          * 'live_timer_interval'. However, the offset does not result in a
  56          * natural alignment on 64-bit architectures. Adding 4 bytes of
  57          * padding here results in an aligned offset after 'alignement_padding'
  58          * for both bitnesses.
  59          *
  60          * This was added since not all compilers appear to align unions in the
  61          * same way. Some (e.g. MSVC) do not seem to impose an alignement
  62          * constraint while others (e.g. gcc, clang, icc) seem to align it to
  63          * ensure 'ptr' is naturally aligned.
  64          */
  65         char alignment_padding[4];
  66         union {
  67                 /*
  68                  * Ensure the 'extended' union has the same size for both
  69                  * 32-bit and 64-bit builds.
  70                  */
  71                 char padding[LTTNG_SESSION_PADDING1];
  72                 void *ptr;
  73         } extended;
  74 };
  75
  76 /*
  77  * Create a session on the session daemon from a session descriptor.
  78  *
  79  * See the session descriptor API description in session-descriptor.h
  80  *
  81  * Note that unspecified session descriptor parameters, such as a session's
  82  * name, are updated in the session descriptor if the creation of the session
  83  * succeeds. This allows users to query the session's auto-generated name
  84  * after its creation. Note that other attributes can be queried using the
  85  * session listing API.
  86  *
  87  * Returns LTTNG_OK on success. See lttng-error.h for the meaning of the other
  88  * return codes.
  89  */
  90 LTTNG_EXPORT extern enum lttng_error_code lttng_create_session_ext(
  91                 struct lttng_session_descriptor *session_descriptor);
  92
  93 /*
  94  * Create a tracing session using a name and an optional URL.
  95  *
  96  * If _url_ is NULL, no consumer is created for the session. The name can't be
  97  * NULL here.
  98  *
  99  * Return 0 on success else a negative LTTng error code.
 100  */
 101 LTTNG_EXPORT extern int lttng_create_session(const char *name, const char *url);
 102
 103 /*
 104  * Create a tracing session that will exclusively be used for snapshot meaning
 105  * the session will be in no output mode and every channel enabled for that
 106  * session will be set in overwrite mode and in mmap output since splice is not
 107  * supported.
 108  *
 109  * Name can't be NULL. If an url is given, it will be used to create a default
 110  * snapshot output using it as a destination. If NULL, no output will be
 111  * defined and an add-output call will be needed.
 112  *
 113  * Return 0 on success else a negative LTTng error code.
 114  */
 115 LTTNG_EXPORT extern int lttng_create_session_snapshot(const char *name,
 116                 const char *snapshot_url);
 117
 118 /*
 119  * Create a session exclusively used for live reading.
 120  *
 121  * In this mode, the switch-timer parameter is forced for each UST channel, a
 122  * live-switch-timer is enabled for kernel channels, manually setting
 123  * switch-timer is forbidden. Synchronization beacons are sent to the relayd,
 124  * indexes are sent and metadata is checked for each packet.
 125  *
 126  * Name can't be NULL. If no URL is given, the default is to send the data to
 127  * net://127.0.0.1. The timer_interval is in usec.
 128  *
 129  * Return 0 on success else a negative LTTng error code.
 130  */
 131 LTTNG_EXPORT extern int lttng_create_session_live(const char *name, const char *url,
 132                 unsigned int timer_interval);
 133
 134 /*
 135  * Destroy a tracing session.
 136  *
 137  * The session will not be usable, tracing will be stopped thus buffers will be
 138  * flushed.
 139  *
 140  * This call will wait for data availability for each domain of the session,
 141  * which can take an arbitrary amount of time. However, when returning the
 142  * tracing data is guaranteed to be ready to be read and analyzed.
 143  *
 144  * lttng_destroy_session_no_wait() may be used if such a guarantee is not
 145  * needed.
 146  *
 147  * The name can't be NULL here.
 148  *
 149  * Return 0 on success else a negative LTTng error code.
 150  */
 151 LTTNG_EXPORT extern int lttng_destroy_session(const char *name);
 152
 153 /*
 154  * Destroy a tracing session.
 155  *
 156  * Performs the same function as lttng_destroy_session(), but provides
 157  * an lttng_destruction_handle which can be used to wait for the completion
 158  * of the session's destruction. The lttng_destroy_handle can also be used
 159  * obtain the status and archive location of any implicit session
 160  * rotation that may have occurred during the session's destruction.
 161  *
 162  * Returns LTTNG_OK on success. The returned handle is owned by the caller
 163  * and must be free'd using lttng_destruction_handle_destroy().
 164  */
 165 LTTNG_EXPORT extern enum lttng_error_code lttng_destroy_session_ext(const char *session_name,
 166                 struct lttng_destruction_handle **handle);
 167
 168 /*
 169  * Behaves exactly like lttng_destroy_session but does not wait for data
 170  * availability.
 171  */
 172 LTTNG_EXPORT extern int lttng_destroy_session_no_wait(const char *name);
 173
 174 /*
 175  * List all the tracing sessions.
 176  *
 177  * Return the number of entries of the "lttng_session" array. The caller
 178  * must free the returned sessions array directly using free().
 179  *
 180  * On error, a negative LTTng error code is returned.
 181  */
 182 LTTNG_EXPORT extern int lttng_list_sessions(struct lttng_session **sessions);
 183
 184 /*
 185  * Get the creation time of an lttng_session object on the session daemon.
 186  *
 187  * This function must only be used with lttng_session objects returned
 188  * by lttng_list_sessions() or lttng_session_create().
 189  *
 190  * The creation time returned is a UNIX timestamp; the number of seconds since
 191  * Epoch (1970-01-01 00:00:00 +0000 (UTC)).
 192  *
 193  * Returns LTTNG_OK on success. See lttng-error.h for the meaning of the other
 194  * return codes.
 195  */
 196 LTTNG_EXPORT extern enum lttng_error_code lttng_session_get_creation_time(
 197                 const struct lttng_session *session, uint64_t *creation_time);
 198
 199 /*
 200  * Set the shared memory path for a session.
 201  *
 202  * Sets the (optional) file system path where shared memory buffers will
 203  * be created for the session. This is useful for buffer extraction on
 204  * crash, when used with filesystems like pramfs.
 205  *
 206  * Return 0 on success else a negative LTTng error code.
 207  */
 208 LTTNG_EXPORT extern int lttng_set_session_shm_path(const char *session_name,
 209                 const char *shm_path);
 210
 211 #ifdef __cplusplus
 212 }
 213 #endif
 214
 215 #endif /* LTTNG_SESSION_H */