tests checkpoints immediately and gives more of a time buffer (#4432)

pkg/ingester/checkpoint_test.go

@@ -330,11 +330,15 @@ func TestIngesterWALBackpressureCheckpoint(t *testing.T) {
 }
 
 func expectCheckpoint(t *testing.T, walDir string, shouldExist bool, max time.Duration) {
+	once := make(chan struct{}, 1)
+	once <- struct{}{}
+
 	deadline := time.After(max)
 	for {
 		select {
 		case <-deadline:
 			require.Fail(t, "timeout while waiting for checkpoint existence:", shouldExist)
+		case <-once: // Trick to ensure we check immediately before deferring to ticker.
 		default:
 			<-time.After(max / 10) // check 10x over the duration
 		}
@@ -637,7 +641,7 @@ func TestIngesterWALReplaysUnorderedToOrdered(t *testing.T) {
 
 			if waitForCheckpoint {
 				// Ensure we have checkpointed now
-				expectCheckpoint(t, walDir, true, ingesterConfig.WAL.CheckpointDuration*2) // give a bit of buffer
+				expectCheckpoint(t, walDir, true, ingesterConfig.WAL.CheckpointDuration*10) // give a bit of buffer
 
 				// Add some more data after the checkpoint
 				tmp := end