How to use tracing-flame? Getting empty file.

[rjzak]

I have a server app that I'm working on and wish to use tracing-flame to generate a flame chart. It just creates an empty file though.

I create the flame layer and have let guard = flame_layer.flush_on_drop();. But the server never exits on it's own, just at Control-C to stop it, or if I stop the service with the service command. Is it because the program doesn't exit on it's own that maybe the guard isn't properly dropped? The Drop should still be handled accordingly, correct? If not, how can I trigger the flame graph data to be saved to disk right before Control-C?

[mladedav]

When default handlers run, they just exit without unwinding and running drops like an unwinding panic does.

You can try using the ctrlc crate or another one that will allow you to handle other signals like sigterm too.

[rjzak]

Makes sense. How would I have the ctrlc hook, which handles forced exit, to have the flamegraph saved? An explicit drop of the guard?

[mladedav]

I suppose calling flush should be enough.