From 47c87eb71c65acddd004ff63bab7c6c18d0af123 Mon Sep 17 00:00:00 2001
From: Todd Beets <todd@beetsme.net>
Date: Wed, 14 Dec 2022 14:34:27 -0800
Subject: [PATCH] fix and test for clustered mem store asset no-quorum if
 leader restarted

---
 server/jetstream_cluster_3_test.go | 83 ++++++++++++++++++++++++++++++
 server/raft.go                     |  9 ----
 2 files changed, 83 insertions(+), 9 deletions(-)

diff --git a/server/jetstream_cluster_3_test.go b/server/jetstream_cluster_3_test.go
index c03bdee3..11be3931 100644
--- a/server/jetstream_cluster_3_test.go
+++ b/server/jetstream_cluster_3_test.go
@@ -2286,3 +2286,86 @@ func TestJetStreamClusterAfterPeerRemoveZeroState(t *testing.T) {
 		return nil
 	})
 }
+
+func TestJetStreamClusterMemLeaderRestart(t *testing.T) {
+	// Test if R3 clustered mem store asset leader server restarted, that asset remains stable with final quorum
+	c := createJetStreamClusterExplicit(t, "R3S", 3)
+	defer c.shutdown()
+
+	ml := c.leader()
+	nc, jsc := jsClientConnect(t, ml)
+	defer nc.Close()
+
+	_, err := jsc.AddStream(&nats.StreamConfig{
+		Name:     "foo",
+		Storage:  nats.MemoryStorage,
+		Subjects: []string{"foo.*"},
+		Replicas: 3,
+	})
+	require_NoError(t, err)
+
+	// load up messages
+	toSend := 10000
+	for i := 1; i <= toSend; i++ {
+		msg := []byte("Hello World")
+		if _, err = jsc.Publish("foo.a", msg); err != nil {
+			t.Fatalf("unexpected publish error: %v", err)
+		}
+	}
+
+	osi, err := jsc.StreamInfo("foo")
+	require_NoError(t, err)
+	// make sure 10000 msgs
+	require_True(t, osi.State.Msgs == uint64(toSend))
+
+	// Shutdown the stream leader server
+	rs := c.serverByName(osi.Cluster.Leader)
+	rs.Shutdown()
+
+	// Make sure that we have a META leader (there can always be a re-election)
+	c.waitOnLeader()
+
+	// Should still have quorum and a new leader
+	checkFor(t, time.Second, 200*time.Millisecond, func() error {
+		osi, err = jsc.StreamInfo("foo")
+		if err != nil {
+			return fmt.Errorf("expected healthy stream asset, got %s", err.Error())
+		}
+		if osi.Cluster.Leader == "" {
+			return fmt.Errorf("expected healthy stream asset with new leader")
+		}
+		if osi.State.Msgs != uint64(toSend) {
+			return fmt.Errorf("expected healthy stream asset %d messages, got %d messages", toSend, osi.State.Msgs)
+		}
+		return nil
+	})
+
+	// Now restart the old leader peer (old stream state)
+	oldrs := rs
+	rs, _ = RunServerWithConfig(rs.getOpts().ConfigFile)
+	defer rs.Shutdown()
+
+	// Replaced old with new server
+	for i := 0; i < len(c.servers); i++ {
+		if c.servers[i] == oldrs {
+			c.servers[i] = rs
+		}
+	}
+
+	// Wait for cluster to be formed
+	checkClusterFormed(t, c.servers...)
+
+	// Make sure that we have a leader (there can always be a re-election)
+	c.waitOnLeader()
+
+	// Can we get stream info after return
+	osi, err = jsc.StreamInfo("foo")
+	if err != nil {
+		t.Fatalf("expected stream asset info return, got %s", err.Error())
+	}
+
+	// When asset leader came back did we re-form with quorum
+	if osi.Cluster.Leader == "" {
+		t.Fatalf("expected a current leader after old leader restarted")
+	}
+}
diff --git a/server/raft.go b/server/raft.go
index 1bcfd745..7f0ad3fb 100644
--- a/server/raft.go
+++ b/server/raft.go
@@ -951,15 +951,6 @@ func (n *raft) InstallSnapshot(data []byte) error {
 		return errCatchupsRunning
 	}
 
-	// We don't store snapshots for memory based WALs.
-	// This matches loadSnapshot logic now.
-	// But we should compact.
-	if _, ok := n.wal.(*memStore); ok {
-		n.wal.Compact(n.applied)
-		n.Unlock()
-		return nil
-	}
-
 	var state StreamState
 	n.wal.FastState(&state)