From 8a6ddab56894302e72feff70900455357f6b5e50 Mon Sep 17 00:00:00 2001
From: Wang Yuan <wangyuan21@baidu.com>
Date: Wed, 21 Jul 2021 17:32:08 +0800
Subject: [PATCH] Fix SETNX and MSETNX commands can't guarantee atomicity
 (#337)

---
 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 ff4b52f5c14..8c164a39c7a 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 d56a8c4b211..773aef7d6db 100644
--- a/src/redis_string.cc
+++ b/src/redis_string.cc
@@ -354,6 +354,9 @@ 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;