From 67969a39c1eefb22ee9af210cc0ca350951c2b51 Mon Sep 17 00:00:00 2001
From: wangyuan21 <wangyuan21@baidu.com>
Date: Wed, 21 Jul 2021 16:23:39 +0800
Subject: [PATCH] Fix SETNX and MSETNX commands can't guarantee atomicity

---
 src/redis_cmd.cc    | 2 +-
 src/redis_string.cc | 3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/redis_cmd.cc b/src/redis_cmd.cc
index e8e1a103cee..5d7a7b56655 100644
--- a/src/redis_cmd.cc
+++ b/src/redis_cmd.cc
@@ -4321,7 +4321,7 @@ CommandAttributes redisCommandTable[] = {
     ADD_CMD("setex", 4, "write", 1, 1, 1, CommandSetEX),
     ADD_CMD("psetex", 4, "write", 1, 1, 1, CommandPSetEX),
     ADD_CMD("setnx", 3, "write", 1, 1, 1, CommandSetNX),
-    ADD_CMD("msetnx", -3, "write", 1, -1, 2, CommandMSetNX),
+    ADD_CMD("msetnx", -3, "write exclusive", 1, -1, 2, CommandMSetNX),
     ADD_CMD("mset", -3, "write", 1, -1, 2, CommandMSet),
     ADD_CMD("incrby", 3, "write", 1, 1, 1, CommandIncrBy),
     ADD_CMD("incrbyfloat", 3, "write", 1, 1, 1, CommandIncrByFloat),
diff --git a/src/redis_string.cc b/src/redis_string.cc
index 8bcbf4b3c32..f936cebc0fa 100644
--- a/src/redis_string.cc
+++ b/src/redis_string.cc
@@ -309,6 +309,9 @@ rocksdb::Status String::MSetNX(const std::vector<StringPair> &pairs, int ttl, in
   for (StringPair pair : pairs) {
     AppendNamespacePrefix(pair.key, &ns_key);
     LockGuard guard(storage_->GetLockManager(), ns_key);
+    if (Exists({pair.key}, &exists).ok() && exists == 1) {
+      return rocksdb::Status::OK();
+    }
     std::string bytes;
     Metadata metadata(kRedisString, false);
     metadata.expire = expire;