Implement: CLUSTER REPLICATE NO ONE

src/cluster_legacy.c

@@ -7029,7 +7029,36 @@ int clusterCommandSpecial(client *c) {
         clusterDelNode(n);
         clusterDoBeforeSleep(CLUSTER_TODO_UPDATE_STATE | CLUSTER_TODO_SAVE_CONFIG);
         addReply(c, shared.ok);
-    } else if (!strcasecmp(c->argv[1]->ptr, "replicate") && c->argc == 3) {
+    } else if (!strcasecmp(c->argv[1]->ptr, "replicate") && (c->argc == 3 || c->argc == 4)) {
+        /* CLUSTER REPLICATE (<NODE ID> | NO ONE)*/
+        if (c->argc == 4) {
+            /* CLUSTER REPLICATE NO ONE */
+            if (strcasecmp(c->argv[2]->ptr, "NO") != 0 || strcasecmp(c->argv[3]->ptr, "ONE") != 0) {
+                addReplySubcommandSyntaxError(c);
+                return 1;
+            }
+            if (nodeIsPrimary(myself)) {
+                addReply(c, shared.ok);
+                return 1;
+            }
+            sds client = catClientInfoShortString(sdsempty(), c, server.hide_user_data_from_log);
+            serverLog(LL_NOTICE, "Stop replication and turning myself into empty primary (request from '%s').", client);
+            sdsfree(client);
+            clusterSetNodeAsPrimary(myself);
+            clusterPromoteSelfToPrimary();
+            emptyData(-1, server.repl_replica_lazy_flush ? EMPTYDB_ASYNC : EMPTYDB_NO_FLAGS, NULL);
+            clusterCloseAllSlots();
+            resetManualFailover();
+
+            // moving new primary to its own shard.
+            char new_shard_id[CLUSTER_NAMELEN];
+            getRandomHexChars(new_shard_id, CLUSTER_NAMELEN);
+            updateShardId(myself, new_shard_id);
+
+            clusterDoBeforeSleep(CLUSTER_TODO_UPDATE_STATE | CLUSTER_TODO_SAVE_CONFIG | CLUSTER_TODO_BROADCAST_ALL);
+            addReply(c, shared.ok);
+            return 1;
+        }
         /* CLUSTER REPLICATE <NODE ID> */
         /* Lookup the specified node in our table. */
         clusterNode *n = clusterLookupNode(c->argv[2]->ptr, sdslen(c->argv[2]->ptr));

src/commands.def

@@ -768,7 +768,9 @@ struct COMMAND_ARG CLUSTER_REPLICAS_Args[] = {
 
 #ifndef SKIP_CMD_HISTORY_TABLE
 /* CLUSTER REPLICATE history */
-#define CLUSTER_REPLICATE_History NULL
+commandHistory CLUSTER_REPLICATE_History[] = {
+{"8.1.0","Added support of 'NO ONE' arg instead of <node-id> resulting into detaching replica from primary node."},
+};
 #endif
 
 #ifndef SKIP_CMD_TIPS_TABLE
@@ -781,9 +783,21 @@ struct COMMAND_ARG CLUSTER_REPLICAS_Args[] = {
 #define CLUSTER_REPLICATE_Keyspecs NULL
 #endif
 
+/* CLUSTER REPLICATE args no_one argument table */
+struct COMMAND_ARG CLUSTER_REPLICATE_args_no_one_Subargs[] = {
+{MAKE_ARG("no",ARG_TYPE_PURE_TOKEN,-1,"NO",NULL,NULL,CMD_ARG_NONE,0,NULL)},
+{MAKE_ARG("one",ARG_TYPE_PURE_TOKEN,-1,"ONE",NULL,NULL,CMD_ARG_NONE,0,NULL)},
+};
+
+/* CLUSTER REPLICATE args argument table */
+struct COMMAND_ARG CLUSTER_REPLICATE_args_Subargs[] = {
+{MAKE_ARG("node-id",ARG_TYPE_STRING,-1,NULL,NULL,NULL,CMD_ARG_NONE,0,NULL)},
+{MAKE_ARG("no-one",ARG_TYPE_BLOCK,-1,NULL,NULL,"8.1.0",CMD_ARG_NONE,2,NULL),.subargs=CLUSTER_REPLICATE_args_no_one_Subargs},
+};
+
 /* CLUSTER REPLICATE argument table */
 struct COMMAND_ARG CLUSTER_REPLICATE_Args[] = {
-{MAKE_ARG("node-id",ARG_TYPE_STRING,-1,NULL,NULL,NULL,CMD_ARG_NONE,0,NULL)},
+{MAKE_ARG("args",ARG_TYPE_ONEOF,-1,NULL,NULL,NULL,CMD_ARG_NONE,2,NULL),.subargs=CLUSTER_REPLICATE_args_Subargs},
 };
 
 /********** CLUSTER RESET ********************/
@@ -1024,7 +1038,7 @@ struct COMMAND_STRUCT CLUSTER_Subcommands[] = {
 {MAKE_CMD("myshardid","Returns the shard ID of a node.","O(1)","7.2.0",CMD_DOC_NONE,NULL,NULL,"cluster",COMMAND_GROUP_CLUSTER,CLUSTER_MYSHARDID_History,0,CLUSTER_MYSHARDID_Tips,1,clusterCommand,2,CMD_LOADING|CMD_STALE,0,CLUSTER_MYSHARDID_Keyspecs,0,NULL,0)},
 {MAKE_CMD("nodes","Returns the cluster configuration for a node.","O(N) where N is the total number of Cluster nodes","3.0.0",CMD_DOC_NONE,NULL,NULL,"cluster",COMMAND_GROUP_CLUSTER,CLUSTER_NODES_History,0,CLUSTER_NODES_Tips,1,clusterCommand,2,CMD_LOADING|CMD_STALE,0,CLUSTER_NODES_Keyspecs,0,NULL,0)},
 {MAKE_CMD("replicas","Lists the replica nodes of a primary node.","O(N) where N is the number of replicas.","5.0.0",CMD_DOC_NONE,NULL,NULL,"cluster",COMMAND_GROUP_CLUSTER,CLUSTER_REPLICAS_History,0,CLUSTER_REPLICAS_Tips,1,clusterCommand,3,CMD_ADMIN|CMD_STALE,0,CLUSTER_REPLICAS_Keyspecs,0,NULL,1),.args=CLUSTER_REPLICAS_Args},
-{MAKE_CMD("replicate","Configure a node as replica of a primary node.","O(1)","3.0.0",CMD_DOC_NONE,NULL,NULL,"cluster",COMMAND_GROUP_CLUSTER,CLUSTER_REPLICATE_History,0,CLUSTER_REPLICATE_Tips,0,clusterCommand,3,CMD_NO_ASYNC_LOADING|CMD_ADMIN|CMD_STALE,0,CLUSTER_REPLICATE_Keyspecs,0,NULL,1),.args=CLUSTER_REPLICATE_Args},
+{MAKE_CMD("replicate","Configure a node as replica of a primary node or detaches replica from primary.","O(1)","3.0.0",CMD_DOC_NONE,NULL,NULL,"cluster",COMMAND_GROUP_CLUSTER,CLUSTER_REPLICATE_History,1,CLUSTER_REPLICATE_Tips,0,clusterCommand,-3,CMD_NO_ASYNC_LOADING|CMD_ADMIN|CMD_STALE,0,CLUSTER_REPLICATE_Keyspecs,0,NULL,1),.args=CLUSTER_REPLICATE_Args},
 {MAKE_CMD("reset","Resets a node.","O(N) where N is the number of known nodes. The command may execute a FLUSHALL as a side effect.","3.0.0",CMD_DOC_NONE,NULL,NULL,"cluster",COMMAND_GROUP_CLUSTER,CLUSTER_RESET_History,0,CLUSTER_RESET_Tips,0,clusterCommand,-2,CMD_ADMIN|CMD_STALE|CMD_NOSCRIPT,0,CLUSTER_RESET_Keyspecs,0,NULL,1),.args=CLUSTER_RESET_Args},
 {MAKE_CMD("saveconfig","Forces a node to save the cluster configuration to disk.","O(1)","3.0.0",CMD_DOC_NONE,NULL,NULL,"cluster",COMMAND_GROUP_CLUSTER,CLUSTER_SAVECONFIG_History,0,CLUSTER_SAVECONFIG_Tips,0,clusterCommand,2,CMD_NO_ASYNC_LOADING|CMD_ADMIN|CMD_STALE,0,CLUSTER_SAVECONFIG_Keyspecs,0,NULL,0)},
 {MAKE_CMD("set-config-epoch","Sets the configuration epoch for a new node.","O(1)","3.0.0",CMD_DOC_NONE,NULL,NULL,"cluster",COMMAND_GROUP_CLUSTER,CLUSTER_SET_CONFIG_EPOCH_History,0,CLUSTER_SET_CONFIG_EPOCH_Tips,0,clusterCommand,3,CMD_NO_ASYNC_LOADING|CMD_ADMIN|CMD_STALE,0,CLUSTER_SET_CONFIG_EPOCH_Keyspecs,0,NULL,1),.args=CLUSTER_SET_CONFIG_EPOCH_Args},

src/commands/cluster-replicate.json

@@ -1,21 +1,50 @@
 {
     "REPLICATE": {
-        "summary": "Configure a node as replica of a primary node.",
+        "summary": "Configure a node as replica of a primary node or detaches replica from primary.",
         "complexity": "O(1)",
         "group": "cluster",
         "since": "3.0.0",
-        "arity": 3,
+        "arity": -3,
         "container": "CLUSTER",
         "function": "clusterCommand",
+        "history": [
+            [
+                "8.1.0",
+                "Added support of 'NO ONE' arg instead of <node-id> resulting into detaching replica from primary node."
+            ]
+        ],
         "command_flags": [
             "NO_ASYNC_LOADING",
             "ADMIN",
             "STALE"
         ],
         "arguments": [
             {
-                "name": "node-id",
-                "type": "string"
+                "name": "args",
+                "type": "oneof",
+                "arguments": [
+                    {
+                        "name": "node-id",
+                        "type": "string"
+                    },
+                    {
+                        "name": "no-one",
+                        "type": "block",
+                        "since": "8.1.0",
+                        "arguments": [
+                            {
+                                "name": "no",
+                                "type": "pure-token",
+                                "token": "NO"
+                            },
+                            {
+                                "name": "one",
+                                "type": "pure-token",
+                                "token": "ONE"
+                            }
+                        ]
+                    }
+                ]
             }
         ],
         "reply_schema": {

tests/unit/cluster/replica-detach.tcl

@@ -0,0 +1,50 @@
+proc find_slots_for_node {node_idx node_id_to_find} {
+    set shards_cfg [R $node_idx CLUSTER SHARDS]
+    foreach shard_cfg $shards_cfg {
+        set nodes [dict get $shard_cfg nodes]
+        foreach node $nodes {
+            if {[dict get $node id] eq $node_id_to_find} {
+                return [dict get $shard_cfg slots]
+            }
+        }
+    }
+    return [list]
+}
+
+start_cluster 3 3 {tags {external:skip cluster}} {
+    test "Cluster should start ok" {
+        wait_for_cluster_state ok
+    }
+
+    test "CLUSTER REPLICATE NO ONE should turn node into empty primary" {
+        set replica_node 3
+        set replica_node_id [R $replica_node CLUSTER MYID]
+        # make sure node is replica
+        wait_for_condition 100 100 {
+            [string first "slave" [R $replica_node ROLE]] >= 0
+        } else {
+            puts "R $replica_node ROLE: [R $replica_node ROLE]"
+            fail "R $replica_node didn't assume replica role in time"
+        }
+
+        assert_equal "OK" [R $replica_node CLUSTER REPLICATE NO ONE]
+
+        # make sure node is turned into primary
+        wait_for_condition 100 100 {
+            [string first "master" [R $replica_node ROLE]] >= 0
+        } else {
+            puts "R $replica_node ROLE: [R $replica_node ROLE]"
+            fail "R $replica_node didn't assume primary role in time"
+        }
+
+        # checking that new primary has no slots across all nodes
+        foreach node_idx {0 1 2 3 4 5} {
+            wait_for_condition 100 100 {
+                [llength [find_slots_for_node $node_idx $replica_node_id]] == 0
+            } else {
+                puts "R $node_idx still returns node $replica_node_id owning slots: [find_slots_for_node $node_idx $replica_node_id]"
+                fail "R $node_idx didn't refresh topology after detaching replica $replica_node/$replica_node_id"
+            }
+        }
+    }
+}