lttng-enable-rotation

Synopsis

lttng [GENERAL OPTIONS] enable-rotation [--session=SESSION]
      (--timer=PERIOD | --size=SIZE | --timer=PERIOD --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 lttng-rotate(1) for more information about the concepts of a tracing session rotation and a trace chunk.

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

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

• With the --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 --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 --timer and --size options.

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

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

See Limitations for important limitations regarding this command.

Options

General options are described in lttng(1).

Limitations

The lttng enable-rotation command only works when:

• The tracing session is created in normal mode or in network streaming mode (see lttng-create(1)).
• No channel was created with a configured trace file count or size limit (see the --tracefile-size and --tracefile-count options in lttng-enable-channel(1)).

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

Environment Variables

LTTNG_ABORT_ON_ERROR

Set to 1 to abort the process after the first error is encountered.

LTTNG_HOME

Overrides the $HOME environment variable. Useful when the user running the commands has a non-writable home directory.

LTTNG_MAN_BIN_PATH

Absolute path to the man pager to use for viewing help information about LTTng commands (using lttng-help(1) or lttng COMMAND --help).

LTTNG_SESSION_CONFIG_XSD_PATH

Path in which the session.xsd session configuration XML schema may be found.

LTTNG_SESSIOND_PATH

Full session daemon binary path.

The --sessiond-path option has precedence over this environment variable.

Note that the lttng-create(1) command can spawn an LTTng session daemon automatically if none is running. See lttng-sessiond(8) for the environment variables influencing the execution of the session daemon.

Files

$LTTNG_HOME/.lttngrc

User LTTng runtime configuration.

This is where the per-user current tracing session is stored between executions of lttng(1). The current tracing session can be set with lttng-set-session(1). See lttng-create(1) for more information about tracing sessions.

$LTTNG_HOME/lttng-traces

Default output directory of LTTng traces. This can be overridden with the --output option of the lttng-create(1) command.

$LTTNG_HOME/.lttng

User LTTng runtime and configuration directory.

$LTTNG_HOME/.lttng/sessions

Default location of saved user tracing sessions (see lttng-save(1) and lttng-load(1)).

/usr/local/etc/lttng/sessions

System-wide location of saved tracing sessions (see lttng-save(1) and lttng-load(1)).

Exit Status

0

Success

1

Command error

2

Undefined command

3

Fatal error

4

Command warning (something went wrong during the command)

Bugs

If you encounter any issue or usability problem, please report it on the LTTng bug tracker <https://bugs.lttng.org/projects/lttng-tools>.

Resources

• LTTng project website <https://lttng.org>
• LTTng documentation <https://lttng.org/docs>
• Git repositories <http://git.lttng.org>
• GitHub organization <http://github.com/lttng>
• Continuous integration <http://ci.lttng.org/>
• Mailing list <http://lists.lttng.org> for support and development: lttng-dev@lists.lttng.org
• IRC channel <irc://irc.oftc.net/lttng>: #lttng on irc.oftc.net

Copyrights

This program is part of the LTTng-tools project.

LTTng-tools is distributed under the GNU General Public License version 2 <http://www.gnu.org/licenses/old-licenses/gpl-2.0.en.html>. See the LICENSE <https://github.com/lttng/lttng-tools/blob/master/LICENSE> file for details.

Thanks

Special thanks to Michel Dagenais and the DORSAL laboratory <http://www.dorsal.polymtl.ca/> at École Polytechnique de Montréal for the LTTng journey.

Also thanks to the Ericsson teams working on tracing which helped us greatly with detailed bug reports and unusual test cases.

See Also

lttng-rotate(1), lttng-disable-rotation(1), lttng(1)

Referenced By

lttng(1), lttng-disable-rotation(1), lttng-regenerate(1), lttng-rotate(1), lttng-snapshot(1), lttng-stop(1).