doc/man/lttng-add-trigger.1.txt

   1 lttng-add-trigger(1)
   2 =====================
   3 :revdate: 17 January 2020
   4
   5
   6 NAME
   7 ----
   8 lttng-add-trigger - Create LTTng triggers
   9
  10
  11 SYNOPSIS
  12 --------
  13
  14 [verse]
  15 *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *add-trigger* [--id ID]
  16       [--fire-every N] [--fire-once-after N]
  17       --condition CONDITION-NAME CONDITION-ARGS
  18       --action ACTION-NAME ACTION-ARGS
  19       [--action ACTION-NAME ACTION-ARGS]...
  20
  21
  22 DESCRIPTION
  23 -----------
  24
  25 The `lttng add-trigger` command is used to create triggers.  A
  26 trigger is an association between a *condition* and one or more
  27 *actions*.  When the condition associated to a trigger is met, the
  28 actions associated to that trigger are executed.  The tracing does not
  29 have to be active for the conditions to be met, and triggers are
  30 independent from tracing sessions.
  31
  32 By default, a trigger fires every time its condition is met.  The
  33 '--fire-every' and '--fire-once-after' options can be used to change
  34 this mode.
  35
  36 The syntax by which conditions and actions are specified is described
  37 below.
  38
  39 Conditions
  40 ~~~~~~~~~~
  41
  42 Conditions are specified with the `--condition` option, followed by a
  43 condition name, and possibly some more arguments, depending on the
  44 specific condition.  There must be exactly one condition given in the
  45 `lttng add-trigger` invocation.
  46
  47 The available conditions are:
  48
  49 Event rule: `on-event [event rule arguments]`::
  50     This type of condition is met when the tracer encounters an event
  51     matching the given even rule.  The arguments describing the event
  52     rule are the same as those describing the event rules of the
  53     man:lttng-enable-event(1) command, with these exceptions:
  54
  55     - It is not possible to use filter operands that use values from
  56       the context.
  57
  58 Actions
  59 ~~~~~~~
  60
  61 Actions are specified with the `--action` option, followed by an action
  62 name, and possibly some more arguments, depending on the specific
  63 action.  There must be at least one action given in the
  64 `lttng add-trigger` invocation.
  65
  66 The available actions are:
  67
  68 Notify: *notify*::
  69     This action causes the LTTng session daemon to send a notification,
  70     through its notification mechanism (see man:lttng-sessiond(8)).
  71     Some details about the condition evaluation are sent along with the
  72     notification.
  73
  74 Start session: *start-session* session-name::
  75     This action causes the LTTng session daemon to start tracing for the
  76     session with the given name.  If no session with the given name exist
  77     at the time the condition is met, nothing is done.
  78
  79 Stop session: *stop-session* session-name::
  80     This action causes the LTTng session daemon to stop tracing for the
  81     session with the given name.  If no session with the given name exist
  82     at the time the condition is met, nothing is done.
  83
  84 Rotate session: *rotate-session* session-name::
  85     This action causes the LTTng session daemon to rotate the session
  86     with the given name.  See  man:lttng-rotate(1) for more information
  87     about the session rotation concept.  If no session with the given
  88     name exist at the time the condition is met, nothing is done.
  89
  90 Snapshot session: *snapshot-session* session-name::
  91     This action causes the LTTng session daemon to take a snapshot of the
  92     session with the given name.  See man:lttng-snapshot(1) for more
  93     information about the session snapshot concept.  If no session with
  94     the given name exist at the time the condition is met, nothing is
  95     done.
  96
  97 OPTIONS
  98 -------
  99
 100 option:--id='ID'::
 101     Set the id of the trigger to 'ID'.  If omitted, an id will
 102     automatically be assigned to the trigger by the session daemon.
 103 +
 104 If a trigger with the specified 'ID' already exists, the trigger
 105 creation will fail.
 106
 107 option:--fire-every 'N'::
 108     Execute the trigger's actions every 'N' times the condition is met.
 109
 110 option:--fire-once-after 'N'::
 111     Execute the trigger's actions once after 'N' times the condition is
 112     met, then never after that.
 113
 114 include::common-cmd-help-options.txt[]
 115
 116
 117 include::common-cmd-footer.txt[]
 118
 119
 120 SEE ALSO
 121 --------
 122 man:lttng-list-triggers(1),
 123 man:lttng-remove-trigger(1),
 124 man:lttng(1)