[lttng-dev] [LTTng] Domains

[Sebastien Boisvert]

I have a question pertaining to the user experience.

I don't know though if it makes sense though from a implementation point-of-view. 

But I think it makes sense for the user experience.


Would it make sense to auto-detect the domain when the user does not provide it (-u or -k or -j or -p or -l) ?

My understanding is that there are 2 domains: kernel and userspace.

Since Java/Python/Log4j are bits in userspace, I would expect them to be in the userspace category.


If I enable an event without providing a domain, I am told that there is an error.


sboisvert at Z1:~/gydle-optical-aligner.build$ lttng enable-event 'gydle_om:*'
Error: Please specify a domain (-k/-u/-j).
Error: Command error

So, if I don't specify it, lttng tells me to provide the domain (-k, -i, or -u).

In the help, there are more domains though. There are 5 to be exact.


sboisvert at Z1:~/gydle-optical-aligner.build$ lttng enable-event --help|head -n 13|tail -n 5
  -k, --kernel             Apply to the kernel tracer
  -u, --userspace          Apply to the user-space tracer
  -j, --jul                Apply to Java application using JUL
  -l, --log4j              Apply for Java application using LOG4j
  -p, --python             Apply for Python application



The stuff provided to "lttng enable-event" is a string, so the fact that LTTng kernel tracepoints have no namespaces
is not a problem I think.

So if the event name is in the list of kernel tracepoints, then use "-k", otherwise, use "-u".