Prevent cluster from crashing when a read-only MULTI follows a read-write one

CHANGELOG.md

@@ -4,6 +4,8 @@ All notable changes to this project will be documented in this file.
 ## Unreleased
 - Updated rocksdb dependency to v5.15.10.
 - Added `TYPE` command.
+- A read-only MULTI immediatelly after a read-write MULTI could
+  cause the cluster to crash.
 
 ## 0.3.3 (2018-09-14)
 

src/redis/Transaction.cc

@@ -131,6 +131,8 @@ bool Transaction::deserialize(const std::string &src) {
 
 void Transaction::clear() {
   requests.clear();
+  phantom = false;
+  hasWrites = false;
 }
 
 std::string Transaction::getFusedCommand() const {

test/multi.cc

@@ -122,6 +122,25 @@ TEST_F(Multi, HandlerBasicSanity) {
   replies.clear();
   ASSERT_REPLY(tunnel(leaderID)->exec("EXEC"), "ERR EXEC without MULTI");
   ASSERT_REPLY(tunnel(leaderID)->exec("HGET", "myhash", "f1"), "v1");
+
+  // Read MULTI-EXEC right after a write
+  replies.clear();
+  replies.push_back(tunnel(leaderID)->exec("MULTI"));
+  replies.push_back(tunnel(leaderID)->exec("SET", "abc", "123"));
+  replies.push_back(tunnel(leaderID)->exec("EXEC"));
+
+  ASSERT_REPLY(replies[0], "OK");
+  ASSERT_REPLY(replies[1], "QUEUED");
+  ASSERT_REPLY_DESCRIBE(replies[2], "1) OK\n");
+
+  replies.clear();
+  replies.push_back(tunnel(leaderID)->exec("MULTI"));
+  replies.push_back(tunnel(leaderID)->exec("GET", "abc"));
+  replies.push_back(tunnel(leaderID)->exec("EXEC"));
+
+  ASSERT_REPLY(replies[0], "OK");
+  ASSERT_REPLY(replies[1], "QUEUED");
+  ASSERT_REPLY_DESCRIBE(replies[2], "1) \"123\"\n");
 }
 
 TEST_F(Multi, WithRaft) {