Avoid shard id update of replica if not matching with primary shard id

Signed-off-by: Harkrishn Patro <harkrisp@amazon.com>

src/cluster_legacy.c

@@ -914,6 +914,12 @@ static void updateAnnouncedHumanNodename(clusterNode *node, char *new) {
 
 
 static void updateShardId(clusterNode *node, const char *shard_id) {
+    /* Shard id update of replica independently will corrupt the config file. */
+    if (shard_id && nodeIsSlave(node) && memcmp(clusterNodeGetMaster(node)->shard_id, shard_id, CLUSTER_NAMELEN) != 0) {
+        serverLog(LL_NOTICE, "Shard id %.40s update request for node id %.40s diverges from existing primary shard id %.40s, rejecting!", shard_id, node->name, clusterNodeGetMaster(node)->shard_id);
+        return;
+    }
+
     if (shard_id && memcmp(node->shard_id, shard_id, CLUSTER_NAMELEN) != 0) {
         clusterRemoveNodeFromShard(node);
         memcpy(node->shard_id, shard_id, CLUSTER_NAMELEN);