From 12f5ea365577ca370835e2bf782c823eb6a4ed91 Mon Sep 17 00:00:00 2001
From: Derek Collison <derek@nats.io>
Date: Tue, 1 Feb 2022 14:03:53 -0800
Subject: [PATCH] When a consumer had not filtered subject and was attached to
 a interest policy retention stream we could incorrectly drop messages.

Signed-off-by: Derek Collison <derek@nats.io>
---
 server/jetstream_test.go | 47 ++++++++++++++++++++++++++++++++++++++++
 server/stream.go         |  4 ++--
 2 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/server/jetstream_test.go b/server/jetstream_test.go
index 2eee7c5576f..00e75bc05b2 100644
--- a/server/jetstream_test.go
+++ b/server/jetstream_test.go
@@ -14642,6 +14642,53 @@ func TestJetStreamMaxMsgsPerSubjectWithDiscardNew(t *testing.T) {
 	}
 }
 
+// Issue #2836
+func TestJetStreamInterestRetentionBug(t *testing.T) {
+	s := RunBasicJetStreamServer()
+	defer s.Shutdown()
+
+	if config := s.JetStreamConfig(); config != nil {
+		defer removeDir(t, config.StoreDir)
+	}
+
+	nc, js := jsClientConnect(t, s)
+	defer nc.Close()
+
+	_, err := js.AddStream(&nats.StreamConfig{
+		Name:      "TEST",
+		Subjects:  []string{"foo.>"},
+		Retention: nats.InterestPolicy,
+	})
+	require_NoError(t, err)
+
+	_, err = js.AddConsumer("TEST", &nats.ConsumerConfig{Durable: "c1", AckPolicy: nats.AckExplicitPolicy})
+	require_NoError(t, err)
+
+	test := func(token string, fseq, msgs uint64) {
+		t.Helper()
+		subj := fmt.Sprintf("foo.%s", token)
+		_, err = js.Publish(subj, nil)
+		require_NoError(t, err)
+		si, err := js.StreamInfo("TEST")
+		require_NoError(t, err)
+		if si.State.FirstSeq != fseq {
+			t.Fatalf("Expected first to be %d, got %d", fseq, si.State.FirstSeq)
+		}
+		if si.State.Msgs != msgs {
+			t.Fatalf("Expected msgs to be %d, got %d", msgs, si.State.Msgs)
+		}
+	}
+
+	test("bar", 1, 1)
+
+	// Create second filtered consumer.
+	_, err = js.AddConsumer("TEST", &nats.ConsumerConfig{Durable: "c2", FilterSubject: "foo.foo", AckPolicy: nats.AckExplicitPolicy})
+	require_NoError(t, err)
+
+	test("bar", 1, 2)
+
+}
+
 ///////////////////////////////////////////////////////////////////////////
 // Simple JetStream Benchmarks
 ///////////////////////////////////////////////////////////////////////////
diff --git a/server/stream.go b/server/stream.go
index 6e579dc0815..4e5c9c4193a 100644
--- a/server/stream.go
+++ b/server/stream.go
@@ -2923,10 +2923,10 @@ func (mset *stream) processJetStreamMsg(subject, reply string, hdr, msg []byte,
 		if numConsumers == 0 {
 			noInterest = true
 		} else if mset.numFilter > 0 {
-			// Assume none.
+			// Assume no interest and check to disqualify.
 			noInterest = true
 			for _, o := range mset.consumers {
-				if o.cfg.FilterSubject != _EMPTY_ && subjectIsSubsetMatch(subject, o.cfg.FilterSubject) {
+				if o.cfg.FilterSubject == _EMPTY_ || subjectIsSubsetMatch(subject, o.cfg.FilterSubject) {
 					noInterest = false
 					break
 				}