Make sure purge works with redeliveries pending

Signed-off-by: Derek Collison <derek@nats.io>

server/observable.go

@@ -1317,9 +1317,21 @@ func (o *Observable) purge(sseq uint64) {
 		o.pending = nil
 		if o.ptmr != nil {
 			o.ptmr.Stop()
-			o.ptmr = nil
+			// Do not nil this out here. This allows checkPending to fire
+			// and still be ok and not panic.
 		}
 	}
+	// We need to remove all those being queued for redelivery under o.rdq
+	if len(o.rdq) > 0 {
+		var newRDQ []uint64
+		for _, sseq := range o.rdq {
+			if sseq >= o.sseq {
+				newRDQ = append(newRDQ, sseq)
+			}
+		}
+		// Replace with new list. Most of the time this will be nil.
+		o.rdq = newRDQ
+	}
 	o.mu.Unlock()
 }
 

test/jetstream_test.go

@@ -2108,6 +2108,91 @@ func TestJetStreamMsgSetPurgeWithObservable(t *testing.T) {
 	}
 }
 
+func TestJetStreamMsgSetPurgeWithObservableAndRedelivery(t *testing.T) {
+	cases := []struct {
+		name    string
+		mconfig *server.MsgSetConfig
+	}{
+		{"MemoryStore", &server.MsgSetConfig{Name: "DC", Storage: server.MemoryStorage}},
+		{"FileStore", &server.MsgSetConfig{Name: "DC", Storage: server.FileStorage}},
+	}
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			s := RunBasicJetStreamServer()
+			defer s.Shutdown()
+
+			mset, err := s.GlobalAccount().AddMsgSet(c.mconfig)
+			if err != nil {
+				t.Fatalf("Unexpected error adding message set: %v", err)
+			}
+			defer mset.Delete()
+
+			nc := clientConnectToServer(t, s)
+			defer nc.Close()
+
+			// Send 100 msgs
+			for i := 0; i < 100; i++ {
+				nc.Publish("DC", []byte("OK!"))
+			}
+			nc.Flush()
+			if stats := mset.Stats(); stats.Msgs != 100 {
+				t.Fatalf("Expected %d messages, got %d", 100, stats.Msgs)
+			}
+			// Now create an observable and make sure it functions properly.
+			// This will test redelivery state and purge of the msgset.
+			wcfg := &server.ObservableConfig{
+				Durable:    "WQ",
+				DeliverAll: true,
+				AckPolicy:  server.AckExplicit,
+				AckWait:    20 * time.Millisecond,
+			}
+			o, err := mset.AddObservable(wcfg)
+			if err != nil {
+				t.Fatalf("Expected no error with registered interest, got %v", err)
+			}
+			defer o.Delete()
+			nextSubj := o.RequestNextMsgSubject()
+			for i := 0; i < 50; i++ {
+				// Do not ack these.
+				if _, err := nc.Request(nextSubj, nil, time.Second); err != nil {
+					t.Fatalf("Unexpected error: %v", err)
+				}
+			}
+			// Now wait to make sure we are in a redelivered state.
+			time.Sleep(wcfg.AckWait * 2)
+			// Now do purge.
+			mset.Purge()
+			if stats := mset.Stats(); stats.Msgs != 0 {
+				t.Fatalf("Expected %d messages, got %d", 0, stats.Msgs)
+			}
+			// Now get the state and check that we did the right thing.
+			// Pending should be cleared, and msgset sequences should have been set
+			// to the total messages before purge + 1.
+			state := o.Info().State
+			if len(state.Pending) != 0 {
+				t.Fatalf("Expected no pending, got %d", len(state.Pending))
+			}
+			if state.Delivered.SetSeq != 101 {
+				t.Fatalf("Expected to have setseq now at next seq of 101, got %d", state.Delivered.SetSeq)
+			}
+			// Check AckFloors which should have also been adjusted.
+			if state.AckFloor.SetSeq != 100 {
+				t.Fatalf("Expected ackfloor for setseq to be 100, got %d", state.AckFloor.SetSeq)
+			}
+			if state.AckFloor.ObsSeq != 50 {
+				t.Fatalf("Expected ackfloor for obsseq to be 75, got %d", state.AckFloor.ObsSeq)
+			}
+			// Also make sure we can get new messages correctly.
+			nc.Request("DC", []byte("OK-22"), time.Second)
+			if msg, err := nc.Request(nextSubj, nil, time.Second); err != nil {
+				t.Fatalf("Unexpected error: %v", err)
+			} else if string(msg.Data) != "OK-22" {
+				t.Fatalf("Received wrong message, wanted 'OK-22', got %q", msg.Data)
+			}
+		})
+	}
+}
+
 func TestJetStreamInterestRetentionMsgSet(t *testing.T) {
 	cases := []struct {
 		name    string