When in cluster mode we should be more permissive about what we retur…

…n with MGET. Currently we check if all keys are the same slot but we could retunr if all slots are on this node instead.

Signed-off-by: John Sully <[email protected]>

src/cluster.c

@@ -1057,8 +1057,14 @@ getNodeByQuery(client *c, struct serverCommand *cmd, robj **argv, int argc, int
                 }
             } else {
                 /* If it is not the first key/channel, make sure it is exactly
-                 * the same key/channel as the first we saw. */
-                if (slot != thisslot) {
+                 * the same key/channel as the first we saw or an allowed crossslot situation. */
+                int prevent_crossslot = (cmd_flags & CMD_WRITE) // eliminate issues with client->current_slot
+                    || pubsubshard_included // pubsub does not benefit and too many edge cases
+                    || c->cmd->proc == execCommand // We do not permit crossslot transactions to prevent client code which will break when cluster topology changes
+                    // finally, if any key is migrating we cannot permit the crossslot since we don't check if the specific keys are affected
+                    //  this could potentially be relaxed in the future.
+                    || migrating_slot || importing_slot || getMigratingSlotDest(slot) != NULL || getImportingSlotSource(slot) != NULL;
+                if (slot != thisslot && prevent_crossslot) {
                     /* Error: multiple keys from different slots. */
                     getKeysFreeResult(&result);
                     if (error_code) *error_code = CLUSTER_REDIR_CROSS_SLOT;

src/server.c

@@ -5388,7 +5388,8 @@ sds genValkeyInfoString(dict *section_dict, int all_sections, int everything) {
             "executable:%s\r\n", server.executable ? server.executable : "",
             "config_file:%s\r\n", server.configfile ? server.configfile : "",
             "io_threads_active:%i\r\n", server.io_threads_active,
-            "availability_zone:%s\r\n", server.availability_zone));
+            "availability_zone:%s\r\n", server.availability_zone,
+            "features:%s\r\n", "cluster_mget"));
         /* clang-format on */
 
         /* Conditional properties */