diff options
Diffstat (limited to 'doc/developer/tracing.rst')
| -rw-r--r-- | doc/developer/tracing.rst | 27 |
1 files changed, 26 insertions, 1 deletions
diff --git a/doc/developer/tracing.rst b/doc/developer/tracing.rst index ee0a6be008..c194ae1270 100644 --- a/doc/developer/tracing.rst +++ b/doc/developer/tracing.rst @@ -57,7 +57,7 @@ run the target in non-forking mode (no ``-d``) and use LTTng as usual (refer to LTTng user manual). When using USDT probes with LTTng, follow the example in `this article <https://lttng.org/blog/2019/10/15/new-dynamic-user-space-tracing-in-lttng/>`_. -To trace with dtrace or SystemTap, compile with :option:`--enable-usdt=yes` and +To trace with dtrace or SystemTap, compile with `--enable-usdt=yes` and use your tracer as usual. To see available USDT probes:: @@ -308,6 +308,31 @@ Limitations Tracers do not like ``fork()`` or ``dlopen()``. LTTng has some workarounds for this involving interceptor libraries using ``LD_PRELOAD``. +If you're running FRR in a typical daemonizing way (``-d`` to the daemons) +you'll need to run the daemons like so: + +.. code-block:: shell + + LD_PRELOAD=liblttng-ust-fork.so <daemon> + + +If you're using systemd this you can accomplish this for all daemons by +modifying ``frr.service`` like so: + +.. code-block:: diff + + --- a/frr.service + +++ b/frr.service + @@ -7,6 +7,7 @@ Before=network.target + OnFailure=heartbeat-failed@%n.service + + [Service] + +Environment="LD_PRELOAD=liblttng-ust-fork.so" + Nice=-5 + Type=forking + NotifyAccess=all + + USDT tracepoints are relatively high overhead and probably shouldn't be used for "flight recorder" functionality, i.e. enabling and passively recording all events for monitoring purposes. It's generally okay to use LTTng like this, |