Track issue: #24875

What problem does this PR solve?

This PR uses pprof profile labels to collect CPU time group by SQL and plan digest.

What is changed and how it works?

The implementation is:

1: Use SQL digest and plan digest as the pprof labels.

// After parse and calculated SQL digest, set the sql digest label
ctx = pprof.WithLabels(ctx, pprof.Labels("sql_digest", sql_digest))
pprof.SetGoroutineLabels(ctx)

...

// After the optimizer generated plan, set the plan digest label.
ctx = pprof.WithLabels(ctx, pprof.Labels("plan_digest", plan_digest))
pprof.SetGoroutineLabels(ctx)

There is a special case, for execute stmt SQL, should use the prepare SQL digest as the sql_digest pprof label.

2. Start 2 background worker to fetch profile and analyze the profile data.

Using a buffer channel to avoid parse and output take too much time that infect the fetching profile work.

Other problem

Because the profile worker keep calling pprof.StartCPUProfile to fetch profile data, other place (such pprof profile HTTP API handler) call pprof.StartCPUProfile will be failed.

In order to solve this problem, other place should fetch profile data from profile worker instead of pprof.StartCPUProfile.

Check List

Tests

• Unit test

Side effects

• Performance regression
  • Consumes more CPU
  • Consumes more MEM

Release note

• No release note