Module cluster flags: initial vars / defines added.

src/cluster.c

@@ -5438,6 +5438,10 @@ clusterNode *getNodeByQuery(client *c, struct redisCommand *cmd, robj **argv, in
     /* Set error code optimistically for the base case. */
     if (error_code) *error_code = CLUSTER_REDIR_NONE;
 
+    /* Modules can turn off Redis Cluster redirection: this is useful
+     * when writing a module that implements a completely different
+     * distributed system. */
+
     /* We handle all the cases as if they were EXEC commands, so we have
      * a common code path for everything */
     if (cmd->proc == execCommand) {

src/cluster.h

@@ -100,6 +100,13 @@ typedef struct clusterLink {
 #define CLUSTERMSG_TYPE_MODULE 9        /* Module cluster API message. */
 #define CLUSTERMSG_TYPE_COUNT 10        /* Total number of message types. */
 
+/* Flags that a module can set in order to prevent certain Redis Cluster
+ * features to be enabled. Useful when implementing a different distributed
+ * system on top of Redis Cluster message bus, using modules. */
+#define MODULE_CLUSTER_FLAG_NONE 0
+#define MODULE_CLUSTER_FLAG_NO_FAILOVER (1<<1)
+#define MODULE_CLUSTER_FLAG_NO_REDIRECTION (1<<2)
+
 /* This structure represent elements of node->fail_reports. */
 typedef struct clusterNodeFailReport {
     struct clusterNode *node;  /* Node reporting the failure condition. */

src/redismodule.h

@@ -117,6 +117,10 @@
 #define REDISMODULE_NODE_FAIL       (1<<4)
 #define REDISMODULE_NODE_NOFAILOVER (1<<5)
 
+#define REDISMODULE_CLUSTER_FLAG_NONE 0
+#define REDISMODULE_CLUSTER_FLAG_NO_FAILOVER (1<<1)
+#define REDISMODULE_CLUSTER_FLAG_NO_REDIRECTION (1<<2)
+
 #define REDISMODULE_NOT_USED(V) ((void) V)
 
 /* This type represents a timer handle, and is returned when a timer is

src/server.c

@@ -1621,6 +1621,7 @@ void initServerConfig(void) {
     server.cluster_announce_ip = CONFIG_DEFAULT_CLUSTER_ANNOUNCE_IP;
     server.cluster_announce_port = CONFIG_DEFAULT_CLUSTER_ANNOUNCE_PORT;
     server.cluster_announce_bus_port = CONFIG_DEFAULT_CLUSTER_ANNOUNCE_BUS_PORT;
+    server.cluster_module_flags = MODULE_CLUSTER_FLAG_NONE;
     server.migrate_cached_sockets = dictCreate(&migrateCacheDictType,NULL);
     server.next_client_id = 1; /* Client IDs, start from 1 .*/
     server.loading_process_events_interval_bytes = (1024*1024*2);

src/server.h

@@ -1232,6 +1232,10 @@ struct redisServer {
     char *cluster_announce_ip;  /* IP address to announce on cluster bus. */
     int cluster_announce_port;     /* base port to announce on cluster bus. */
     int cluster_announce_bus_port; /* bus port to announce on cluster bus. */
+    int cluster_module_flags;      /* Set of flags that Redis modules are able
+                                      to set in order to suppress certain
+                                      native Redis Cluster features. Check the
+                                      REDISMODULE_CLUSTER_FLAG_*. */
     /* Scripting */
     lua_State *lua; /* The Lua interpreter. We use just one for all clients */
     client *lua_client;   /* The "fake client" to query Redis from Lua */