kvserver: de-flake TestStoreRangeMergeRHSLeaseExpiration

The test is setting up a race where a RHS leaseholder which is about to
get merged away loses the lease, while serving reads and writes.

The test set up these reads and writes so that they would all get to at
least the span acquisition stage. However, requests could bounce early
on the leaseholder check (which we've moved around recently), which
would deadlock the test.

Looking at the test, it's a little surprising that the replica sometimes
does not realize it is supposed to get a lease, but this is one of the
wonkier multiTestContext plus manual clock setup plus a maze of
interceptors, so it's not too surprising and, as I decided, not
worth looking into. Instead, the fix is to tolerate that not all
requests will make it to the latch, which seems like a sane assumption;
the test does not rely on it, it would just like it to happen so that
the intended regression test takes place.

Before this commit,

> make stress PKG=./pkg/kv/kvserver/ TESTS=TestStoreRangeMergeRHSLeaseExpiration TESTTIMEOUT=1m 2>&1 | tee log

failed in ~1-2 minutes. Runs just fine for 10+ minutes now.

Closes #47503.

Release note: None

pkg/kv/kvserver/client_merge_test.go

@@ -1426,9 +1426,7 @@ func TestStoreRangeMergeRHSLeaseExpiration(t *testing.T) {
 
 	// Manually heartbeat the liveness on the first store to ensure it's
 	// considered live. The automatic heartbeat might not come for a while.
-	if err := mtc.heartbeatLiveness(ctx, 0); err != nil {
-		t.Fatal(err)
-	}
+	require.NoError(t, mtc.heartbeatLiveness(ctx, 0))
 
 	// Send several get and put requests to the the RHS. The first of these to
 	// arrive will acquire the lease; the remaining requests will wait for that
@@ -1448,9 +1446,17 @@ func TestStoreRangeMergeRHSLeaseExpiration(t *testing.T) {
 	//
 	// This race has since been fixed by installing the mergeComplete channel
 	// before the new lease.
-	reqErrs := make(chan error)
+	reqErrs := make(chan *roachpb.Error) // closed when all reqs done
+	var wg sync.WaitGroup
+	wg.Add(reqConcurrency)
+	go func() {
+		wg.Wait()
+		close(reqErrs)
+	}()
+
 	for i := 0; i < reqConcurrency; i++ {
 		go func(i int) {
+			defer wg.Done()
 			// For this test to have a shot at triggering a race, this log message
 			// must be interleaved with the "new range lease" message, like so:
 			//
@@ -1471,7 +1477,7 @@ func TestStoreRangeMergeRHSLeaseExpiration(t *testing.T) {
 			_, pErr := kv.SendWrappedWith(ctx, mtc.stores[0].TestSender(), roachpb.Header{
 				RangeID: rhsDesc.RangeID,
 			}, req)
-			reqErrs <- pErr.GoError()
+			reqErrs <- pErr
 		}(i)
 		time.Sleep(time.Millisecond)
 	}
@@ -1482,24 +1488,28 @@ func TestStoreRangeMergeRHSLeaseExpiration(t *testing.T) {
 	// merge to complete without depending too heavily on implementation
 	// details.
 	for i := 0; i < reqConcurrency; i++ {
-		<-reqAcquiredLatch
+		select {
+		case <-reqAcquiredLatch:
+			// Latch acquired.
+		case pErr := <-reqErrs:
+			// Requests may never make it to the latch acquisition if s1 has not
+			// yet learned s2's lease is expired. Instead, we'll see a
+			// NotLeaseholderError.
+			require.IsType(t, &roachpb.NotLeaseHolderError{}, pErr.GetDetail())
+		}
 	}
 	time.Sleep(50 * time.Millisecond)
 
 	// Finally, allow the merge to complete. It should complete successfully.
 	close(finishMerge)
-	if err := <-mergeErr; err != nil {
-		t.Fatal(err)
-	}
+	require.NoError(t, <-mergeErr)
 
 	// Because the merge completed successfully, r2 has ceased to exist. We
-	// therefore *must* see either a RangeNotFound or a NotLeaseHolderError
-	// error from every pending get and put request. Anything else is a
-	// consistency error (or a bug in the test).
-	for i := 0; i < reqConcurrency; i++ {
-		if err := <-reqErrs; !testutils.IsError(err, "(r2 was not found|not lease holder)") {
-			t.Fatalf("expected error from req during merge, but got %v", err)
-		}
+	// therefore *must* see only RangeNotFoundErrors here from every pending get
+	// and put request. Anything else is a consistency error (or a bug in the
+	// test).
+	for pErr := range reqErrs {
+		require.IsType(t, &roachpb.RangeNotFoundError{}, pErr.GetDetail())
 	}
 }