multitenantccl/tenantcostserver: deflake TestDataDriven

[ajwerner]

Fixes #93462

The scope for the outer test instead of per file subtest was creating problems for leaktest.

Release note: None

[cockroach-teamcity]

This change is 

[renatolabs]

Thanks!

To keep things documented (aka, I don't understand the fix): why is this the fix? I see other datadriven tests where the log.Scope(t).Close(t) call is outside the function passed to Walk, and that doesn't seem to cause problems. Moreover, this test hasn't really changed much recently.

I also started a bisection when I filed the issue, and apparently #92930 made this test flaky.

[ajwerner]

From what I could tell, the goroutines were logging goroutines which get launched from here:

cockroach/pkg/util/log/flags.go

Line 91 in 4640c58

func ApplyConfig(config logconfig.Config) (logShutdownFn func(), err error) {

The way that leaktest works is that it makes sure that all goroutines which exist after the test are done existed before it started. The race here was that we launched these goroutines under log.Scope (here) but they had not yet started by the time leaktest picked its snapshot. So, by choosing to not start the logging goroutines until after leaktest picks its snapshot, we remove the hazard of the async goroutines having not yet started.

[renatolabs]

Thanks!

[ajwerner]

TFTR!

bors r+

[craig]

Build failed (retrying...):

• Bazel Essential CI (Cockroach)

[craig]

Build failed (retrying...):

• Bazel Essential CI (Cockroach)

[craig]

Build failed (retrying...):

• Bazel Essential CI (Cockroach)

[craig]

Build succeeded:

• Bazel Essential CI (Cockroach)