From 3c85df0a443c12439c9cd9c098f3b43b5612c7f2 Mon Sep 17 00:00:00 2001
From: Derek Collison <derek@nats.io>
Date: Sun, 14 Mar 2021 05:18:52 -0700
Subject: [PATCH] Truncate up to entry, no need for previous

Signed-off-by: Derek Collison <derek@nats.io>
---
 server/const.go          |  2 +-
 server/filestore_test.go | 34 ++++++++++++++++++++++++++++++++++
 server/raft.go           | 19 +++----------------
 3 files changed, 38 insertions(+), 17 deletions(-)

diff --git a/server/const.go b/server/const.go
index 752c0cee..5281968d 100644
--- a/server/const.go
+++ b/server/const.go
@@ -41,7 +41,7 @@ var (
 
 const (
 	// VERSION is the current version for the server.
-	VERSION = "2.2.0-RC.8.4"
+	VERSION = "2.2.0-RC.8.5"
 
 	// PROTO is the currently supported protocol.
 	// 0 was the original
diff --git a/server/filestore_test.go b/server/filestore_test.go
index 62370aa2..944c68c1 100644
--- a/server/filestore_test.go
+++ b/server/filestore_test.go
@@ -810,6 +810,40 @@ func TestFileStoreCompact(t *testing.T) {
 	}
 }
 
+func TestFileStoreCompactLastPlusOne(t *testing.T) {
+	storeDir, _ := ioutil.TempDir("", JetStreamStoreDir)
+	os.MkdirAll(storeDir, 0755)
+	defer os.RemoveAll(storeDir)
+
+	fs, err := newFileStore(FileStoreConfig{StoreDir: storeDir, BlockSize: 8192, AsyncFlush: false}, StreamConfig{Name: "zzz", Storage: FileStorage})
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+	defer fs.Stop()
+
+	subj, msg := "foo", make([]byte, 10_000)
+	for i := 0; i < 10_000; i++ {
+		if _, _, err := fs.StoreMsg(subj, nil, msg); err != nil {
+			t.Fatalf("Unexpected error: %v", err)
+		}
+	}
+	if state := fs.State(); state.Msgs != 10_000 {
+		t.Fatalf("Expected 1000000 msgs, got %d", state.Msgs)
+	}
+	if _, err := fs.Compact(10_001); err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+	state := fs.State()
+	if state.Msgs != 0 {
+		t.Fatalf("Expected no message but got %d", state.Msgs)
+	}
+	fmt.Printf("state is %+v\n", state)
+
+	fs.StoreMsg(subj, nil, msg)
+	state = fs.State()
+	fmt.Printf("state is %+v\n", state)
+}
+
 func TestFileStoreCompactPerf(t *testing.T) {
 	t.SkipNow()
 
diff --git a/server/raft.go b/server/raft.go
index 3299f38f..796fc44e 100644
--- a/server/raft.go
+++ b/server/raft.go
@@ -2210,25 +2210,12 @@ func (n *raft) attemptStepDown(newLeader string) {
 func (n *raft) truncateWal(ae *appendEntry) {
 	n.debug("Truncating and repairing WAL")
 
-	// Special case if already at 0.
-	if ae.pindex == 0 {
-		n.pindex = ae.pindex
-		n.pterm = ae.pterm
-		n.wal.Purge()
-		return
-	}
-
-	tindex := ae.pindex - 1
-	if err := n.wal.Truncate(tindex); err != nil {
+	if err := n.wal.Truncate(ae.pindex); err != nil {
 		n.setWriteErrLocked(err)
 		return
 	}
-	n.pindex = tindex
-	if nae, _ := n.loadEntry(tindex); nae != nil {
-		n.pterm = nae.term
-	} else {
-		n.pterm = ae.term
-	}
+	n.pindex = ae.pindex
+	n.pterm = ae.term
 }
 
 // processAppendEntry will process an appendEntry.