Leak test pdutil.TestScheduler

[djshow832]

Bug Report

[2021-10-14T07:19:31.756Z] goleak: Errors on successful test run: found unexpected goroutines:
[2021-10-14T07:19:31.756Z] [Goroutine 265 in state chan receive, with github.com/pingcap/tidb/br/pkg/pdutil.TestScheduler.func5 on top of the stack:
[2021-10-14T07:19:31.756Z] goroutine 265 [chan receive]:
[2021-10-14T07:19:31.756Z] github.com/pingcap/tidb/br/pkg/pdutil.TestScheduler.func5(0xc00060e2a0)
[2021-10-14T07:19:31.756Z] 	/home/jenkins/agent/workspace/tidb_ghpr_check_2/go/src/github.com/pingcap/tidb/br/pkg/pdutil/pd_serial_test.go:74 +0x34
[2021-10-14T07:19:31.756Z] created by github.com/pingcap/tidb/br/pkg/pdutil.TestScheduler
[2021-10-14T07:19:31.756Z] 	/home/jenkins/agent/workspace/tidb_ghpr_check_2/go/src/github.com/pingcap/tidb/br/pkg/pdutil/pd_serial_test.go:73 +0x825
[2021-10-14T07:19:31.756Z] ]
[2021-10-14T07:19:31.756Z] FAIL	github.com/pingcap/tidb/br/pkg/pdutil	0.674s

See https://ci.pingcap.net/blue/organizations/jenkins/tidb_ghpr_check_2/detail/tidb_ghpr_check_2/38433/pipeline

[tisonkun]

@unconsolable please take a look at this test. Possibly we should handle schedulerPauseCh gracefully.

[unconsolable]

tidb/br/pkg/pdutil/pd_serial_test.go

Lines 70 to 76 in ae346a5

	_, err = pdController.pauseSchedulersAndConfigWith(ctx, []string{scheduler}, cfg, mock)
	require.NoError(t, err)
	go func() {
	<-schedulerPauseCh
	}()
	err = pdController.resumeSchedulerWith(ctx, []string{scheduler}, mock)

IMHO this goroutine creation should be removed, as pauseSchedulersAndConfigWith success, it will create a goroutine and select on it.

tidb/br/pkg/pdutil/pd.go

Lines 448 to 450 in ae346a5

	case <-p.schedulerPauseCh:
	log.Info("exit pause scheduler and configs successful")
	return

Also, in (*PdController).Close(), it will close the chan and the pdClient. as in this scenario pdClient is nill, we can close the channel in defer.

[github-actions]

Please check whether the issue should be labeled with 'affects-x.y' or 'fixes-x.y.z', and then remove 'needs-more-info' label.