Stop recording after given time or on trigger.

[theldoria]

I want to apply uftrace to a cyclically running application, which may never stop.
However, I want to be able to record anyway and get the results after:

• a given max. time and/or
• using a trigger (probably examined in a Lua or Pathon script), e.g. after a specific function was entered for the N'th time

I would really love if recording would be done into a cyclic buffer, so I could stop recording on an user defined trigger (a watchpoint of a variable examined at any function enter/leave would be enough for may use case).

My question: is something like that possible?

EDIT: spelling

[namhyung]

I think we have two options for now.

1. use signal trigger like -S INT@finish : Ctrl-C (to the target process) will finish the tracing
2. setup function trigger like -T yourFunc@finish : it will finish the tracing as yourFunc is called

[honggyukim]

Hi @theldoria, I also think the features you mentioned can be useful, but we need time to implement those features.

@namhyung From my experience, I feel like sending a signal is not user-friendly. I think time based trace on/off is more useful and easy to use as @theldoria suggested.

How about this usage? (when recording a trace for t-fork.)

$ uftrace record -T 100ms@trace_on -T 500ms@finish -- t-fork

We can distinguish if <symbol> is a function name or a time unit by checking its first character.

But it might take time for implementation because I don't have much time these days.

[honggyukim]

I've created an issue at #1699.

[alexmyczko]

there is the timeout command. timout seconds uftrace parameters...

[namhyung]

Right, then it can emulate the time-based trigger using a signal. It seems timeout would send a TERM signal after the given time.

https://man7.org/linux/man-pages/man1/timeout.1.html