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 #include <lttng/constant.h>
  27
  28 struct lttng_handle;
  29 struct lttng_session_descriptor;
  30 struct lttng_destruction_handle;
  31
  32 /*
  33  * Basic session information.
  34  *
  35  * The "enabled" field is only used when listing the sessions which indicate if
  36  * it's started or not.
  37  *
  38  * The structures should be initialized to zero before use.
  39  */
  40 #define LTTNG_SESSION_PADDING1             8
  41 struct lttng_session {
  42         char name[LTTNG_NAME_MAX];
  43         /*
  44          * Human-readable representation of the trace's destination.
  45          * In the case of a local tracing session, a path is provided:
  46          *     /path/to/the/output
  47          *
  48          * In the case of a remote (network) tracing session, the string has
  49          * the following format:
  50          *     net://hostname/path:ctrl_port [data: data_port]
  51          */
  52         char path[PATH_MAX];
  53         uint32_t enabled;       /* enabled/started: 1, disabled/stopped: 0 */
  54         uint32_t snapshot_mode;
  55         unsigned int live_timer_interval;       /* usec */
  56
  57         /*
  58          * End of public attributes.
  59          * The remaining fields are used to deal with ABI management concerns.
  60          */
  61
  62         /*
  63          * 32-bit architectures are already naturally aligned on 4 bytes after
  64          * 'live_timer_interval'. However, the offset does not result in a
  65          * natural alignment on 64-bit architectures. Adding 4 bytes of
  66          * padding here results in an aligned offset after 'alignement_padding'
  67          * for both bitnesses.
  68          *
  69          * This was added since not all compilers appear to align unions in the
  70          * same way. Some (e.g. MSVC) do not seem to impose an alignement
  71          * constraint while others (e.g. gcc, clang, icc) seem to align it to
  72          * ensure 'ptr' is naturally aligned.
  73          */
  74         char alignment_padding[4];
  75         union {
  76                 /*
  77                  * Ensure the 'extended' union has the same size for both
  78                  * 32-bit and 64-bit builds.
  79                  */
  80                 char padding[LTTNG_SESSION_PADDING1];
  81                 void *ptr;
  82         } extended;
  83 };
  84
  85 /*
  86  * Create a session on the session daemon from a session descriptor.
  87  *
  88  * See the session descriptor API description in session-descriptor.h
  89  *
  90  * Note that unspecified session descriptor parameters, such as a session's
  91  * name, are updated in the session descriptor if the creation of the session
  92  * succeeds. This allows users to query the session's auto-generated name
  93  * after its creation. Note that other attributes can be queried using the
  94  * session listing API.
  95  *
  96  * Returns LTTNG_OK on success. See lttng-error.h for the meaning of the other
  97  * return codes.
  98  */
  99 extern enum lttng_error_code lttng_create_session_ext(
 100                 struct lttng_session_descriptor *session_descriptor);
 101
 102 /*
 103  * Create a tracing session using a name and an optional URL.
 104  *
 105  * If _url_ is NULL, no consumer is created for the session. The name can't be
 106  * NULL here.
 107  *
 108  * Return 0 on success else a negative LTTng error code.
 109  */
 110 extern int lttng_create_session(const char *name, const char *url);
 111
 112 /*
 113  * Create a tracing session that will exclusively be used for snapshot meaning
 114  * the session will be in no output mode and every channel enabled for that
 115  * session will be set in overwrite mode and in mmap output since splice is not
 116  * supported.
 117  *
 118  * Name can't be NULL. If an url is given, it will be used to create a default
 119  * snapshot output using it as a destination. If NULL, no output will be
 120  * defined and an add-output call will be needed.
 121  *
 122  * Return 0 on success else a negative LTTng error code.
 123  */
 124 extern int lttng_create_session_snapshot(const char *name,
 125                 const char *snapshot_url);
 126
 127 /*
 128  * Create a session exclusively used for live reading.
 129  *
 130  * In this mode, the switch-timer parameter is forced for each UST channel, a
 131  * live-switch-timer is enabled for kernel channels, manually setting
 132  * switch-timer is forbidden. Synchronization beacons are sent to the relayd,
 133  * indexes are sent and metadata is checked for each packet.
 134  *
 135  * Name can't be NULL. If no URL is given, the default is to send the data to
 136  * net://127.0.0.1. The timer_interval is in usec.
 137  *
 138  * Return 0 on success else a negative LTTng error code.
 139  */
 140 extern int lttng_create_session_live(const char *name, const char *url,
 141                 unsigned int timer_interval);
 142
 143 /*
 144  * Destroy a tracing session.
 145  *
 146  * The session will not be usable, tracing will be stopped thus buffers will be
 147  * flushed.
 148  *
 149  * This call will wait for data availability for each domain of the session,
 150  * which can take an arbitrary amount of time. However, when returning the
 151  * tracing data is guaranteed to be ready to be read and analyzed.
 152  *
 153  * lttng_destroy_session_no_wait() may be used if such a guarantee is not
 154  * needed.
 155  *
 156  * The name can't be NULL here.
 157  *
 158  * Return 0 on success else a negative LTTng error code.
 159  */
 160 extern int lttng_destroy_session(const char *name);
 161
 162 /*
 163  * Destroy a tracing session.
 164  *
 165  * Performs the same function as lttng_destroy_session(), but provides
 166  * an lttng_destruction_handle which can be used to wait for the completion
 167  * of the session's destruction. The lttng_destroy_handle can also be used
 168  * obtain the status and archive location of any implicit session
 169  * rotation that may have occurred during the session's destruction.
 170  *
 171  * Returns LTTNG_OK on success. The returned handle is owned by the caller
 172  * and must be free'd using lttng_destruction_handle_destroy().
 173  */
 174 extern enum lttng_error_code lttng_destroy_session_ext(const char *session_name,
 175                 struct lttng_destruction_handle **handle);
 176
 177 /*
 178  * Behaves exactly like lttng_destroy_session but does not wait for data
 179  * availability.
 180  */
 181 extern int lttng_destroy_session_no_wait(const char *name);
 182
 183 /*
 184  * List all the tracing sessions.
 185  *
 186  * Return the number of entries of the "lttng_session" array. The caller
 187  * must free the returned sessions array directly using free().
 188  *
 189  * On error, a negative LTTng error code is returned.
 190  */
 191 extern int lttng_list_sessions(struct lttng_session **sessions);
 192
 193 /*
 194  * Get the creation time of an lttng_session object on the session daemon.
 195  *
 196  * This function must only be used with lttng_session objects returned
 197  * by lttng_list_sessions() or lttng_session_create().
 198  *
 199  * The creation time returned is a UNIX timestamp; the number of seconds since
 200  * Epoch (1970-01-01 00:00:00 +0000 (UTC)).
 201  *
 202  * Returns LTTNG_OK on success. See lttng-error.h for the meaning of the other
 203  * return codes.
 204  */
 205 extern enum lttng_error_code lttng_session_get_creation_time(
 206                 const struct lttng_session *session, uint64_t *creation_time);
 207
 208 /*
 209  * Set the shared memory path for a session.
 210  *
 211  * Sets the (optional) file system path where shared memory buffers will
 212  * be created for the session. This is useful for buffer extraction on
 213  * crash, when used with filesystems like pramfs.
 214  *
 215  * Return 0 on success else a negative LTTng error code.
 216  */
 217 extern int lttng_set_session_shm_path(const char *session_name,
 218                 const char *shm_path);
 219
 220 #ifdef __cplusplus
 221 }
 222 #endif
 223
 224 #endif /* LTTNG_SESSION_H */