[lttng-dev] Notification event from lttng-relayd on trace rotation completion?

[Christoffer Ahlbin]

What is the recommended approach to have an external process notified
that a trace session rotation has completed on the lttng-relayd end?

I'm trying out the trace rotation functionality available in 2.11
(pre-release) and will be running a trace session inside a Linux
container (userspace tracepoints only), and running lttng-relayd on
the container host. I would then like to have a third process, a
"collector"-like process, that will also be running on the container
host and will have the responsibility of collecting completeted trace
chunks (i.e. rotated chunks) and push them further along into a trace
analysis pipeline.

So far I've looked at using inotify to watch the lttng-traces/
directory, and the idea would be to infer a trace rotation based on
that the destination directories post rotation are named on the format
"%Y%m%dT%H%M%S%z-%Y%m%dT%H%M%S%z-<seqno>". But I'm not entirely
satisifed with that approach. Ideally I would be able to be notified
more explicitly that a rotation completed.


Any thoughts and recommendations are most welcome.

Thanks

Christoffer Ahlbin