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  * This library is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU Lesser General Public License, version 2.1 only,
   7  * as published by the Free Software Foundation.
   8  *
   9  * This library is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
  12  * for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General Public License
  15  * along with this library; if not, write to the Free Software Foundation,
  16  * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  17  */
  18
  19 #ifndef LTTNG_SESSION_H
  20 #define LTTNG_SESSION_H
  21
  22 #ifdef __cplusplus
  23 extern "C" {
  24 #endif
  25
  26 struct lttng_session_descriptor;
  27 struct lttng_destruction_handle;
  28
  29 /*
  30  * Basic session information.
  31  *
  32  * The "enabled" field is only used when listing the sessions which indicate if
  33  * it's started or not.
  34  *
  35  * The structures should be initialized to zero before use.
  36  */
  37 #define LTTNG_SESSION_PADDING1             8
  38 struct lttng_session {
  39         char name[LTTNG_NAME_MAX];
  40         /*
  41          * Human-readable representation of the trace's destination.
  42          * In the case of a local tracing session, a path is provided:
  43          *     /path/to/the/output
  44          *
  45          * In the case of a remote (network) tracing session, the string has
  46          * the following format:
  47          *     net://hostname/path:ctrl_port [data: data_port]
  48          */
  49         char path[PATH_MAX];
  50         uint32_t enabled;       /* enabled/started: 1, disabled/stopped: 0 */
  51         uint32_t snapshot_mode;
  52         unsigned int live_timer_interval;       /* usec */
  53
  54         /*
  55          * End of public attributes.
  56          * The remaining fields are used to deal with ABI management concerns.
  57          */
  58
  59         /*
  60          * 32-bit architectures are already naturally aligned on 4 bytes after
  61          * 'live_timer_interval'. However, the offset does not result in a
  62          * natural alignment on 64-bit architectures. Adding 4 bytes of
  63          * padding here results in an aligned offset after 'alignement_padding'
  64          * for both bitnesses.
  65          *
  66          * This was added since not all compilers appear to align unions in the
  67          * same way. Some (e.g. MSVC) do not seem to impose an alignement
  68          * constraint while others (e.g. gcc, clang, icc) seem to align it to
  69          * ensure 'ptr' is naturally aligned.
  70          */
  71         char alignment_padding[4];
  72         union {
  73                 /*
  74                  * Ensure the 'extended' union has the same size for both
  75                  * 32-bit and 64-bit builds.
  76                  */
  77                 char padding[LTTNG_SESSION_PADDING1];
  78                 void *ptr;
  79         } extended;
  80 };
  81
  82 /*
  83  * Create a session on the session daemon from a session descriptor.
  84  *
  85  * See the session descriptor API description in session-descriptor.h
  86  *
  87  * Note that unspecified session descriptor parameters, such as a session's
  88  * name, are updated in the session descriptor if the creation of the session
  89  * succeeds. This allows users to query the session's auto-generated name
  90  * after its creation. Note that other attributes can be queried using the
  91  * session listing API.
  92  *
  93  * Returns LTTNG_OK on success. See lttng-error.h for the meaning of the other
  94  * return codes.
  95  */
  96 extern enum lttng_error_code lttng_create_session_ext(
  97                 struct lttng_session_descriptor *session_descriptor);
  98
  99 /*
 100  * Create a tracing session using a name and an optional URL.
 101  *
 102  * If _url_ is NULL, no consumer is created for the session. The name can't be
 103  * NULL here.
 104  *
 105  * Return 0 on success else a negative LTTng error code.
 106  */
 107 extern int lttng_create_session(const char *name, const char *url);
 108
 109 /*
 110  * Create a tracing session that will exclusively be used for snapshot meaning
 111  * the session will be in no output mode and every channel enabled for that
 112  * session will be set in overwrite mode and in mmap output since splice is not
 113  * supported.
 114  *
 115  * Name can't be NULL. If an url is given, it will be used to create a default
 116  * snapshot output using it as a destination. If NULL, no output will be
 117  * defined and an add-output call will be needed.
 118  *
 119  * Return 0 on success else a negative LTTng error code.
 120  */
 121 extern int lttng_create_session_snapshot(const char *name,
 122                 const char *snapshot_url);
 123
 124 /*
 125  * Create a session exclusively used for live reading.
 126  *
 127  * In this mode, the switch-timer parameter is forced for each UST channel, a
 128  * live-switch-timer is enabled for kernel channels, manually setting
 129  * switch-timer is forbidden. Synchronization beacons are sent to the relayd,
 130  * indexes are sent and metadata is checked for each packet.
 131  *
 132  * Name can't be NULL. If no URL is given, the default is to send the data to
 133  * net://127.0.0.1. The timer_interval is in usec.
 134  *
 135  * Return 0 on success else a negative LTTng error code.
 136  */
 137 extern int lttng_create_session_live(const char *name, const char *url,
 138                 unsigned int timer_interval);
 139
 140 /*
 141  * Destroy a tracing session.
 142  *
 143  * The session will not be usable, tracing will be stopped thus buffers will be
 144  * flushed.
 145  *
 146  * This call will wait for data availability for each domain of the session,
 147  * which can take an arbitrary amount of time. However, when returning the
 148  * tracing data is guaranteed to be ready to be read and analyzed.
 149  *
 150  * lttng_destroy_session_no_wait() may be used if such a guarantee is not
 151  * needed.
 152  *
 153  * The name can't be NULL here.
 154  *
 155  * Return 0 on success else a negative LTTng error code.
 156  */
 157 extern int lttng_destroy_session(const char *name);
 158
 159 /*
 160  * Destroy a tracing session.
 161  *
 162  * Performs the same function as lttng_destroy_session(), but provides
 163  * an lttng_destruction_handle which can be used to wait for the completion
 164  * of the session's destruction. The lttng_destroy_handle can also be used
 165  * obtain the status and archive location of any implicit session
 166  * rotation that may have occurred during the session's destruction.
 167  *
 168  * Returns LTTNG_OK on success. The returned handle is owned by the caller
 169  * and must be free'd using lttng_destruction_handle_destroy().
 170  */
 171 extern enum lttng_error_code lttng_destroy_session_ext(const char *session_name,
 172                 struct lttng_destruction_handle **handle);
 173
 174 /*
 175  * Behaves exactly like lttng_destroy_session but does not wait for data
 176  * availability.
 177  */
 178 extern int lttng_destroy_session_no_wait(const char *name);
 179
 180 /*
 181  * List all the tracing sessions.
 182  *
 183  * Return the number of entries of the "lttng_session" array. The caller
 184  * must free the returned sessions array directly using free().
 185  *
 186  * On error, a negative LTTng error code is returned.
 187  */
 188 extern int lttng_list_sessions(struct lttng_session **sessions);
 189
 190 /*
 191  * Get the creation time of an lttng_session object on the session daemon.
 192  *
 193  * This function must only be used with lttng_session objects returned
 194  * by lttng_list_sessions() or lttng_session_create().
 195  *
 196  * The creation time returned is a UNIX timestamp; the number of seconds since
 197  * Epoch (1970-01-01 00:00:00 +0000 (UTC)).
 198  *
 199  * Returns LTTNG_OK on success. See lttng-error.h for the meaning of the other
 200  * return codes.
 201  */
 202 extern enum lttng_error_code lttng_session_get_creation_time(
 203                 const struct lttng_session *session, uint64_t *creation_time);
 204
 205 /*
 206  * Set the shared memory path for a session.
 207  *
 208  * Sets the (optional) file system path where shared memory buffers will
 209  * be created for the session. This is useful for buffer extraction on
 210  * crash, when used with filesystems like pramfs.
 211  *
 212  * Return 0 on success else a negative LTTng error code.
 213  */
 214 extern int lttng_set_session_shm_path(const char *session_name,
 215                 const char *shm_path);
 216
 217 /*
 218  * Add PID to session tracker.
 219  *
 220  * A pid argument >= 0 adds the PID to the session tracker.
 221  * A pid argument of -1 means "track all PIDs".
 222  *
 223  * Return 0 on success else a negative LTTng error code.
 224  */
 225 extern int lttng_track_pid(struct lttng_handle *handle, int pid);
 226
 227 /*
 228  * Remove PID from session tracker.
 229  *
 230  * A pid argument >= 0 removes the PID from the session tracker.
 231  * A pid argument of -1 means "untrack all PIDs".
 232  *
 233  * Return 0 on success else a negative LTTng error code.
 234  */
 235 extern int lttng_untrack_pid(struct lttng_handle *handle, int pid);
 236
 237 /*
 238  * List PIDs in the tracker.
 239  *
 240  * enabled is set to whether the PID tracker is enabled.
 241  * pids is set to an allocated array of PIDs currently tracked. On
 242  * success, pids must be freed by the caller.
 243  * nr_pids is set to the number of entries contained by the pids array.
 244  *
 245  * Returns 0 on success, else a negative LTTng error code.
 246  */
 247 extern int lttng_list_tracker_pids(struct lttng_handle *handle,
 248                 int *enabled, int32_t **pids, size_t *nr_pids);
 249
 250 #ifdef __cplusplus
 251 }
 252 #endif
 253
 254 #endif /* LTTNG_SESSION_H */