profiler: add go_num_goroutine metric

[felixge]

What does this PR do?

Add a new metric capturing the number of active goroutines. See commit messages for details.

Motivation

This will help users to investigate goroutine leaks.

Reviewer's Checklist

• Changed code has unit tests for its functionality at or near 100% coverage.
• There is a benchmark for any new code, or changes to existing code.
• If this interacts with the agent in a new way, a system test has been added.

For Datadog employees:

• If this PR touches code that handles credentials of any kind, such as Datadog API keys, I've requested a review from @DataDog/security-design-and-guidance.
• This PR doesn't touch any of that.

Unsure? Have a question? Request a review!

[pr-commenter]

Benchmarks

Benchmark execution time: 2023-09-15 10:04:09

Comparing candidate commit 1ee2035 in PR branch felix.geisendoerfer/PROF-8077-goroutine-metric with baseline commit 3679975 in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 40 metrics, 1 unstable metrics.

[nsrip-dd]

LGTM! If you'd like, we can wait until the backend changes are deployed to validate this using the unit-of-work app from this PR? I don't feel strongly about that, though. Up to you :)

[felixge]

I think we should merge it. We can manually kick off a test-app run on main once the backend changes are ready.

Also, let's try out this new merge queue thing, I've been told it's working now.

[felixge]

/merge

[dd-devflow]

🚂 MergeQueue

Pull request added to the queue.

This build is going to start soon! (estimated merge in less than 0s)

you can cancel this operation by commenting your pull request with /merge -c!

[dd-devflow]

🚨 MergeQueue

not able to merge the branch in the target branch

Details

Error: PUT https://api.github.com/repos/DataDog/dd-trace-go/pulls/2217/merge: 405 5 of 5 required status checks are expected. You're not authorized to push to this branch. Visit https://docs.github.com/articles/about-protected-branches/ for more information. []

FullStacktrace:
activity error (type: github.GithubService_MergePullRequest, scheduledEventID: 41, startedEventID: 42, identity: 1@github-worker-96b967b77-knmkl@): PUT https://api.github.com/repos/DataDog/dd-trace-go/pulls/2217/merge: 405 5 of 5 required status checks are expected. You're not authorized to push to this branch. Visit https://docs.github.com/articles/about-protected-branches/ for more information. [] (type: ErrorResponse, retryable: true)

If you need support, contact us on slack #ci-interfaces with those details!

[felixge]

/merge

[dd-devflow]

🚂 MergeQueue

Pull request added to the queue.

This build is going to start soon! (estimated merge in less than 0s)

you can cancel this operation by commenting your pull request with /merge -c!

[dd-devflow]

🚨 MergeQueue

not able to merge the branch in the target branch

Details

Error: PUT https://api.github.com/repos/DataDog/dd-trace-go/pulls/2217/merge: 405 5 of 5 required status checks are expected. []

FullStacktrace:
activity error (type: github.GithubService_MergePullRequest, scheduledEventID: 41, startedEventID: 42, identity: 1@github-worker-96b967b77-ttrnk@): PUT https://api.github.com/repos/DataDog/dd-trace-go/pulls/2217/merge: 405 5 of 5 required status checks are expected. [] (type: ErrorResponse, retryable: true)

If you need support, contact us on slack #ci-interfaces with those details!

[mimfgg]

/merge

[dd-devflow]

🚨 MergeQueue

You are not allowed to use the merge queue towards main.

If you need support, contact us on slack #ci-interfaces with those details!

[felixge]

/merge

[dd-devflow]

🚂 MergeQueue

Pull request added to the queue.

This build is going to start soon! (estimated merge in less than 0s)

you can cancel this operation by commenting your pull request with /merge -c!