From a1cc8e6e465b9c414de0fd03ac6d32b2ce93ffe6 Mon Sep 17 00:00:00 2001
From: tidwall <joshbaker77@gmail.com>
Date: Tue, 12 Apr 2022 15:43:44 -0700
Subject: [PATCH] Fix eof error for incomplete commands.

This commit fixes an issue where Tile38 will fail to start
because the AOF file contains a partially written command, which
is caused by the server not having enough disk space to complete
the previous write.

This was discovered and reported by a Theresa D on the Tile38
Slack channel.
---
 internal/server/aof.go | 50 +++++++++++++++++++-----------------------
 1 file changed, 22 insertions(+), 28 deletions(-)

diff --git a/internal/server/aof.go b/internal/server/aof.go
index 6b440e21..f90ab6e6 100644
--- a/internal/server/aof.go
+++ b/internal/server/aof.go
@@ -55,29 +55,27 @@ func (s *Server) loadAOF() (err error) {
 	var buf []byte
 	var args [][]byte
 	var packet [0xFFFF]byte
-	var zeros int
 	for {
 		n, err := s.aof.Read(packet[:])
 		if err != nil {
-			if err == io.EOF {
-				if len(buf) > 0 {
-					return io.ErrUnexpectedEOF
-				}
-				if zeros > 0 {
-					// Trailing zeros in AOF. Truncate the file so it's sane.
-					// See issue #230 for more information. Force a warning.
-					log.Infof("Truncating %d zeros from AOF (issue #230)", zeros)
-					s.aofsz -= zeros
-					if err := s.aof.Truncate(int64(s.aofsz)); err != nil {
-						return err
-					}
-					if _, err := s.aof.Seek(int64(s.aofsz), 0); err != nil {
-						return err
-					}
-				}
-				return nil
+			if err != io.EOF {
+				return err
 			}
-			return err
+			if len(buf) > 0 {
+				// There was an incomplete command or other data at the end of
+				// the AOF file. Attempt to recover the file by truncating the
+				// file at the end position of the last complete command.
+				log.Warnf("Truncating %d bytes due to an incomplete command\n",
+					len(buf))
+				s.aofsz -= len(buf)
+				if err := s.aof.Truncate(int64(s.aofsz)); err != nil {
+					return err
+				}
+				if _, err := s.aof.Seek(int64(s.aofsz), 0); err != nil {
+					return err
+				}
+			}
+			return nil
 		}
 		s.aofsz += n
 		data := packet[:n]
@@ -86,15 +84,11 @@ func (s *Server) loadAOF() (err error) {
 		}
 		var complete bool
 		for {
-			if len(data) > 0 {
-				if data[0] == 0 {
-					zeros++
-					data = data[1:]
-					continue
-				}
-				if zeros > 0 {
-					return clientErrorf("Zeros found in AOF file (issue #230)")
-				}
+			if len(data) > 0 && data[0] == 0 {
+				// Zeros found in AOF file (issue #230).
+				// Just ignore it and move the next byte.
+				data = data[1:]
+				continue
 			}
 			complete, args, _, data, err = redcon.ReadNextCommand(data, args[:0])
 			if err != nil {