Fix: return NULL on trace chunk registry failure

[lttng-tools.git] / doc / man / lttng-enable-rotation.1.txt

lttng-enable-rotation(1)
========================


NAME
----
lttng-enable-rotation - Set a tracing session's rotation schedule


SYNOPSIS
--------
[verse]
*lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *enable-rotation* [option:--session='SESSION']
      (option:--timer='PERIOD' | option:--size='SIZE' | option:--timer='PERIOD' option:--size='SIZE')


DESCRIPTION
-----------
The `lttng enable-rotation` command sets a rotation schedule for the
current tracing session, or for the tracing session named 'SESSION' if
provided. See man:lttng-rotate(1) for more information about the
concepts of a tracing session _rotation_ and a _trace chunk_.

With the option:--timer option, the rotation schedule is set so that an
automatic rotation occurs at least every 'PERIOD' (microseconds without
a unit suffix).

With the option:--size option, the rotation schedule is set
so that an automatic rotation occurs every time the total size of the
flushed part of the current trace chunk is at least 'SIZE' (bytes
without a unit suffix).

For both option:--timer and option:--size options, LTTng checks the
schedule condition periodically using the monitor timers of the tracing
session's channels (see the nloption:--monitor-timer option of the
man:lttng-enable-channel(1) command). This means that:

* With the option:--timer option, the automatic rotation can occur when
  the elapsed time since the last automatic rotation is slightly greater
  than 'PERIOD'. The exact precision is governed by the monitor timer's
  precision, which relies on the precision of the platform's
  implementation of POSIX timers.

* With the option:--size option, the automatic rotation can occur when
  the size of the flushed part of the current trace chunk is greater
  than 'SIZE'.

You can combine the option:--timer and option:--size options.

The naming convention of a trace chunk archive which an automatic
rotation creates is the same as with the immediate rotation command,
man:lttng-rotate(1).

You can unset a rotation schedule with the man:lttng-disable-rotation(1)
command.

See <<limitations,LIMITATIONS>> for important limitations regarding
this command.


include::common-cmd-options-head.txt[]


Rotation schedule condition
~~~~~~~~~~~~~~~~~~~~~~~~~~~
option:--size='SIZE'::
    Set a rotation schedule so that an automatic rotation occurs every
    time the total size of the flushed part of the current trace chunk
    is at least 'SIZE' bytes. The `k` (kiB), `M` (MiB), and `G` (GiB)
    suffixes are supported.

option:--timer='PERIOD'::
    Set a rotation schedule so that an automatic rotation occurs at
    least every 'PERIOD' microseconds. The `ms` (milliseconds), `s`
    (seconds), `m` (minutes), and `h` (hours) suffixes are supported.


Target
~~~~~~
option:-s 'SESSION', option:--session='SESSION'::
    Set a rotation schedule for the tracing session named 'SESSION'
    instead of the current tracing session.


include::common-cmd-help-options.txt[]


[[limitations]]
LIMITATIONS
-----------
The `lttng enable-rotation` command only works when:

* The tracing session is created in normal mode or in network streaming
  mode (see man:lttng-create(1)).

* No channel was created with a configured trace file count or size
  limit (see the nloption:--tracefile-size and
  nloption:--tracefile-count options in man:lttng-enable-channel(1)).

For a given tracing session, LTTng only performs an automatic rotation
when no other rotation is currently happening.


include::common-cmd-footer.txt[]


SEE ALSO
--------
man:lttng-rotate(1),
man:lttng-disable-rotation(1),
man:lttng(1)