include/lttng/session.h

   1 /*
   2  * Copyright (C) 2014 - David Goulet <dgoulet@efficios.com>
   3  *
   4  * This library is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU Lesser General Public License, version 2.1 only,
   6  * as published by the Free Software Foundation.
   7  *
   8  * This library is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
  11  * for more details.
  12  *
  13  * You should have received a copy of the GNU Lesser General Public License
  14  * along with this library; if not, write to the Free Software Foundation,
  15  * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  16  */
  17
  18 #ifndef LTTNG_SESSION_H
  19 #define LTTNG_SESSION_H
  20
  21 #ifdef __cplusplus
  22 extern "C" {
  23 #endif
  24
  25 /*
  26  * Basic session information.
  27  *
  28  * The "enabled" field is only used when listing the sessions which indicate if
  29  * it's started or not.
  30  *
  31  * The structures should be initialized to zero before use.
  32  */
  33 #define LTTNG_SESSION_PADDING1             12
  34 struct lttng_session {
  35         char name[LTTNG_NAME_MAX];
  36         /* The path where traces are written */
  37         char path[PATH_MAX];
  38         uint32_t enabled;       /* enabled/started: 1, disabled/stopped: 0 */
  39         uint32_t snapshot_mode;
  40         unsigned int live_timer_interval;       /* usec */
  41
  42         char padding[LTTNG_SESSION_PADDING1];
  43 };
  44
  45 /*
  46  * Create a tracing session using a name and an optional URL.
  47  *
  48  * If _url_ is NULL, no consumer is created for the session. The name can't be
  49  * NULL here.
  50  *
  51  * Return 0 on success else a negative LTTng error code.
  52  */
  53 extern int lttng_create_session(const char *name, const char *url);
  54
  55 /*
  56  * Create a tracing session that will exclusively be used for snapshot meaning
  57  * the session will be in no output mode and every channel enabled for that
  58  * session will be set in overwrite mode and in mmap output since splice is not
  59  * supported.
  60  *
  61  * Name can't be NULL. If an url is given, it will be used to create a default
  62  * snapshot output using it as a destination. If NULL, no output will be
  63  * defined and an add-output call will be needed.
  64  *
  65  * Return 0 on success else a negative LTTng error code.
  66  */
  67 extern int lttng_create_session_snapshot(const char *name,
  68                 const char *snapshot_url);
  69
  70 /*
  71  * Create a session exclusively used for live reading.
  72  *
  73  * In this mode, the switch-timer parameter is forced for each UST channel, a
  74  * live-switch-timer is enabled for kernel channels, manually setting
  75  * switch-timer is forbidden. Synchronization beacons are sent to the relayd,
  76  * indexes are sent and metadata is checked for each packet.
  77  *
  78  * Name can't be NULL. If no URL is given, the default is to send the data to
  79  * net://127.0.0.1. The timer_interval is in usec and by default set to 1000000
  80  * (1 second).
  81  *
  82  * Return 0 on success else a negative LTTng error code.
  83  */
  84 extern int lttng_create_session_live(const char *name, const char *url,
  85                 unsigned int timer_interval);
  86
  87 /*
  88  * Clear a tracing session.
  89  *
  90  * Clear the data buffers and trace data.
  91  *
  92  * For sessions saving trace data to disk and streaming over the network to a
  93  * relay daemon, the buffers content and existing stream files are cleared when
  94  * the clear command is issued.
  95  *
  96  * For snapshot sessions (flight recorder), only the buffer content is cleared.
  97  * Prior snapshots are individually recorded to disk, and are therefore
  98  * untouched by this "clear" command.
  99  *
 100  * For live sessions streaming over network to a relay daemon, the buffers
 101  * will be cleared, and the files on the relay daemon side will be cleared as
 102  * well. However, any active live trace viewer currently reading an existing
 103  * trace packet will be able to proceed to read that packet entirely before
 104  * skipping over cleared stream data.
 105  *
 106  * The clear command guarantees that no trace data preceding the instant it is
 107  * called will be in the resulting trace.
 108  *
 109  * Trace data produced from the moment it is called and when the
 110  * function returned might be present in the resulting trace.
 111  *
 112  * Return 0 on success else a negative LTTng error code.
 113  *
 114  * Important error codes:
 115  *    LTTNG_ERR_CLEAR_RELAY_DISALLOW
 116  *    LTTNG_ERR_CLEAR_NOT_AVAILABLE
 117  *    LTTNG_ERR_CLEAR_NOT_AVAILABLE_RELAY
 118  *    LTTNG_ERR_CLEAR_FAIL_CONSUMER
 119 */
 120 extern int lttng_clear_session(const char *name);
 121
 122 /*
 123  * Destroy a tracing session.
 124  *
 125  * The session will not be usable, tracing will be stopped thus buffers will be
 126  * flushed.
 127  *
 128  * This call will wait for data availability for each domain of the session,
 129  * which can take an arbitrary amount of time. However, when returning the
 130  * tracing data is guaranteed to be ready to be read and analyzed.
 131  *
 132  * lttng_destroy_session_no_wait() may be used if such a guarantee is not
 133  * needed.
 134  *
 135  * The name can't be NULL here.
 136  *
 137  * Return 0 on success else a negative LTTng error code.
 138  */
 139 extern int lttng_destroy_session(const char *name);
 140
 141 /*
 142  * Behaves exactly like lttng_destroy_session but does not wait for data
 143  * availability.
 144  */
 145 extern int lttng_destroy_session_no_wait(const char *name);
 146
 147 /*
 148  * List all the tracing sessions.
 149  *
 150  * Return the size (number of entries) of the "lttng_session" array. Caller
 151  * must free sessions. On error, a negative LTTng error code is returned.
 152  */
 153 extern int lttng_list_sessions(struct lttng_session **sessions);
 154
 155 /*
 156  * Set the shared memory path for a session.
 157  *
 158  * Sets the (optional) file system path where shared memory buffers will
 159  * be created for the session. This is useful for buffer extraction on
 160  * crash, when used with filesystems like pramfs.
 161  *
 162  * Return 0 on success else a negative LTTng error code.
 163  */
 164 extern int lttng_set_session_shm_path(const char *session_name,
 165                 const char *shm_path);
 166
 167 /*
 168  * Add PID to session tracker.
 169  *
 170  * A pid argument >= 0 adds the PID to the session tracker.
 171  * A pid argument of -1 means "track all PIDs".
 172  *
 173  * Return 0 on success else a negative LTTng error code.
 174  */
 175 extern int lttng_track_pid(struct lttng_handle *handle, int pid);
 176
 177 /*
 178  * Remove PID from session tracker.
 179  *
 180  * A pid argument >= 0 removes the PID from the session tracker.
 181  * A pid argument of -1 means "untrack all PIDs".
 182  *
 183  * Return 0 on success else a negative LTTng error code.
 184  */
 185 extern int lttng_untrack_pid(struct lttng_handle *handle, int pid);
 186
 187 /*
 188  * List PIDs in the tracker.
 189  *
 190  * enabled is set to whether the PID tracker is enabled.
 191  * pids is set to an allocated array of PIDs currently tracked. On
 192  * success, pids must be freed by the caller.
 193  * nr_pids is set to the number of entries contained by the pids array.
 194  *
 195  * Returns 0 on success, else a negative LTTng error code.
 196  */
 197 extern int lttng_list_tracker_pids(struct lttng_handle *handle,
 198                 int *enabled, int32_t **pids, size_t *nr_pids);
 199
 200 #ifdef __cplusplus
 201 }
 202 #endif
 203
 204 #endif /* LTTNG_SESSION_H */