how to get each rule's time cost in bazel build

Question

I want to get the time every rule costs when executing a bazel build. I found aspect in bazel,use that feature I can print each rule's finish time in log file.

However I found aspect of a rule executing after the rule executing, with that I can't get when a rule start executing.

So Is there any way to extend a rule before it executing?

Answer 1

Bazel has builtin performance profiling which provides lots of details. Run your build with --profile=/tmp/profile.gz and then load the resulting file into chrome://tracing in any Chrome instance. You'll get something like this (from the docs):

Note that due to bazelbuild/bazel#12965 you may need to manually un-gzip it before loading into Chrome.

There's also documentation on the profile file format if you want to write a tool to analyze it yourself.