ev

This is an execution visualizer for Go.

Usage

You underscore import the package into your main program, and do no further changes there.

import _ "github.com/calmh/ev"

This does nothing unless the environment variable EV_INTERVAL is set at startup. If it is, resource usage statistics are printed to stdout every EV_INTERVAL milliseconds together with your program's normal output.

jb@syno:~/s/g/c/ev $ EV_INTERVAL=1000 testprog
Hello, world!
ev pid 11866 @1459409325892: 5 gr, 1 ms user, 3 ms sys, 299 KiB alloc, 4472 objs, 299 KiB totalloc, 1636 KiB sys, 736 KiB heap, 288 KiB stack, 4096 KiB nextgc, 0 ms gcpause, 0 gcs
ev pid 11866 @1459409326896: 5 gr, 2 ms user, 3 ms sys, 308 KiB alloc, 4500 objs, 308 KiB totalloc, 1892 KiB sys, 640 KiB heap, 384 KiB stack, 4096 KiB nextgc, 0 ms gcpause, 0 gcs
ev pid 11866 @1459409327897: 5 gr, 2 ms user, 4 ms sys, 310 KiB alloc, 4515 objs, 310 KiB totalloc, 1892 KiB sys, 608 KiB heap, 416 KiB stack, 4096 KiB nextgc, 0 ms gcpause, 0 gcs

You can interpret this data manually if you like but it's more powerful to use the program ev to visualize the trace. To do this, simply pipe the output through ev. It will filter out the execution trace lines but pass on other output.

jb@syno:~/s/g/c/ev $ EV_INTERVAL=1000 testprog | ev
Hello, world!

You can of course also pipe a saved log to ev.

ev starts a web server, by default on localhost port 8080. Visit that with your browser and you'll get a nice overview of what's going on.