table of contents
LTTNG-ADD-CONTEXT(1) | LTTng Manual | LTTNG-ADD-CONTEXT(1) |
NAME¶
lttng-add-context - Add context fields to an LTTng channel
SYNOPSIS¶
Add context fields to a channel:
lttng [GENERAL OPTIONS] add-context
(--kernel | --userspace | --jul | --log4j)
[--session=SESSION] [--channel=CHANNEL]
--type=TYPE [--type=TYPE]...
List the available context fields:
lttng [GENERAL OPTIONS] add-context --list
DESCRIPTION¶
The lttng add-context command adds one or more context fields to a channel.
Channels are created with the lttng-enable-channel(1) command.
When context fields are added to a channel, all the events emitted within this channel contain the dynamic values of those context fields.
If the --session option is omitted, the current tracing session is used. If the --channel option is omitted, the context fields are added to all the selected tracing session’s channels.
Many context fields can be added to a channel at once by repeating the --type option.
perf counters are available as per-CPU (perf:cpu: prefix) as well as per-thread (perf:thread: prefix) counters. Currently, per-CPU counters can only be used in the Linux kernel tracing domain, while per-thread counters can only be used in the user space tracing domain.
It is also possible to enable PMU counters by raw ID using the perf:cpu:raw:rN:NAME (Linux kernel tracing domain) or perf:thread:raw:rN:NAME (user space tracing domain), with:
N
NAME
Application-specific context fields can be added to a channel using the following syntax:
$app.PROVIDER:TYPE
with:
PROVIDER
TYPE
Note
Make sure to single-quote the type when running the command from a shell, as $ is a special character for variable substitution in most shells.
Use the --list option without other arguments to list the available context field names.
See the LIMITATIONS section below for a list of limitations to consider.
OPTIONS¶
General options are described in lttng(1).
Domain¶
One of:
-j, --jul
-k, --kernel
-l, --log4j
-u, --userspace
Target¶
-c CHANNEL, --channel=CHANNEL
-s SESSION, --session=SESSION
Context¶
--list
-t TYPE, --type=TYPE
Program information¶
-h, --help
This option, like lttng-help(1), attempts to launch /usr/bin/man to view the command’s man page. The path to the man pager can be overridden by the LTTNG_MAN_BIN_PATH environment variable.
--list-options
LIMITATIONS¶
As of this version of LTTng, it is not possible to add context fields to a channel once its tracing session has been started (see lttng-start(1)) at least once.
ENVIRONMENT VARIABLES¶
LTTNG_ABORT_ON_ERROR
LTTNG_HOME
LTTNG_MAN_BIN_PATH
LTTNG_SESSION_CONFIG_XSD_PATH
LTTNG_SESSIOND_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
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
$LTTNG_HOME/.lttng
$LTTNG_HOME/.lttng/sessions
/etc/lttng/sessions
Note
$LTTNG_HOME defaults to $HOME when not explicitly set.
EXIT STATUS¶
0
1
2
3
4
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¶
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¶
5 Februrary 2018 | LTTng 2.12.3 |