discovery.process and pyroscope.java

[korniltsev]

PR Description

discovery.process is pretty simple
There are couple of things worth noting for pyroscope.java

We bundle two versions of async-profiler one for musl, second for glibc. The musl one is compiled with static stdc++ because alpine often does not have stdc++ installed by default. asprof is compiled statically, so that we have 1 binary instead of 2.
libAsyncProfiler.so absolute path should be exactly the same on host as inside container.

This is the layout of the bundled .tar.gz

// asprof
// glibc / libasyncProfiler.so
// musl / libasyncProfiler.so

Extracted to this layout on the host. And shared library is copied to the target process at the same path via /proc/pid/root/...

./grafana-agent-asprof-musl-f97eb5b45a225752d7b26bb0fd4f2e37d1ddf5d5
./grafana-agent-asprof-musl-f97eb5b45a225752d7b26bb0fd4f2e37d1ddf5d5/bin
./grafana-agent-asprof-musl-f97eb5b45a225752d7b26bb0fd4f2e37d1ddf5d5/bin/asprof
./grafana-agent-asprof-musl-f97eb5b45a225752d7b26bb0fd4f2e37d1ddf5d5/lib
./grafana-agent-asprof-musl-f97eb5b45a225752d7b26bb0fd4f2e37d1ddf5d5/lib/libasyncProfiler.so
./grafana-agent-asprof-glibc-f97eb5b45a225752d7b26bb0fd4f2e37d1ddf5d5
./grafana-agent-asprof-glibc-f97eb5b45a225752d7b26bb0fd4f2e37d1ddf5d5/bin
./grafana-agent-asprof-glibc-f97eb5b45a225752d7b26bb0fd4f2e37d1ddf5d5/bin/asprof
./grafana-agent-asprof-glibc-f97eb5b45a225752d7b26bb0fd4f2e37d1ddf5d5/lib
./grafana-agent-asprof-glibc-f97eb5b45a225752d7b26bb0fd4f2e37d1ddf5d5/lib/libasyncProfiler.so

It is loaded from bin/apsorf binary as 'bin/../lib/libasyncProfiler.so`

asprof is built from upstream main branch with these changes to makefile https://gist.github.com/korniltsev/972f8ee37f3280af6757d7b8fec445d0

I had one interesting bug when my unpacking code was overwriting shared libraries in the target process root fs causing SIGSEGV in jvm->dlopen("libAsyncProfiler.so") so now it does not overwrite files.

Which issue(s) this PR fixes

Notes to the Reviewer

PR Checklist

• CHANGELOG.md updated
• Documentation added
• Tests updated
• Config converters updated

[cyriltovena]

Really simple, love it so far !

[github-actions]

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[cyriltovena]

Docs are good to me.

[clayton-cornell]

Some doc suggestions

[clayton-cornell]

Docs look good to me now ;-)