From 3213e8de921ef55896f740fb55e9469bbe2a22c4 Mon Sep 17 00:00:00 2001
From: antirez <antirez@gmail.com>
Date: Wed, 19 Sep 2018 12:02:37 +0200
Subject: Module cluster flags: add RM_SetClusterFlags() API.

---
 src/cluster.c     |  5 +++++
 src/module.c      | 26 ++++++++++++++++++++++++++
 src/redismodule.h |  2 ++
 3 files changed, 33 insertions(+)

diff --git a/src/cluster.c b/src/cluster.c
index 381ff827e..e82f256c2 100644
--- a/src/cluster.c
+++ b/src/cluster.c
@@ -3877,6 +3877,11 @@ int verifyClusterConfigWithData(void) {
     int j;
     int update_config = 0;
 
+    /* Return ASAP if a module disabled cluster redirections. In that case
+     * every master can store keys about every possible hash slot. */
+    if (server.cluster_module_flags & CLUSTER_MODULE_FLAG_NO_REDIRECTION)
+        return C_OK;
+
     /* If this node is a slave, don't perform the check at all as we
      * completely depend on the replication stream. */
     if (nodeIsSlave(myself)) return C_OK;
diff --git a/src/module.c b/src/module.c
index 9b7365fe2..57e7c92f3 100644
--- a/src/module.c
+++ b/src/module.c
@@ -4132,6 +4132,31 @@ int RM_GetClusterNodeInfo(RedisModuleCtx *ctx, const char *id, char *ip, char *m
     return REDISMODULE_OK;
 }
 
+/* Set Redis Cluster flags in order to change the normal behavior of
+ * Redis Cluster, especially with the goal of disabling certain functions.
+ * This is useful for modules that use the Cluster API in order to create
+ * a different distributed system, but still want to use the Redis Cluster
+ * message bus. Flags that can be set:
+ *
+ *  CLUSTER_MODULE_FLAG_NO_FAILOVER
+ *  CLUSTER_MODULE_FLAG_NO_REDIRECTION
+ *
+ * With the following effects:
+ *
+ *  NO_FAILOVER: prevent Redis Cluster slaves to failover a failing master.
+ *               Also disables the replica migration feature.
+ *
+ *  NO_REDIRECTION: Every node will accept any key, without trying to perform
+ *                  partitioning according to the user Redis Cluster algorithm.
+ *                  Slots informations will still be propagated across the
+ *                  cluster, but without effects. */
+void RM_SetClusterFlags(RedisModuleCtx *ctx, uint64_t flags) {
+    if (flags & REDISMODULE_CLUSTER_FLAG_NO_FAILOVER)
+        server.cluster_module_flags |= CLUSTER_MODULE_FLAG_NO_FAILOVER;
+    if (flags & REDISMODULE_CLUSTER_FLAG_NO_REDIRECTION)
+        server.cluster_module_flags |= CLUSTER_MODULE_FLAG_NO_REDIRECTION;
+}
+
 /* --------------------------------------------------------------------------
  * Modules Timers API
  *
@@ -4708,4 +4733,5 @@ void moduleRegisterCoreAPI(void) {
     REGISTER_API(BlockedClientDisconnected);
     REGISTER_API(SetDisconnectCallback);
     REGISTER_API(GetBlockedClientHandle);
+    REGISTER_API(SetClusterFlags);
 }
diff --git a/src/redismodule.h b/src/redismodule.h
index d37865643..77fac9e63 100644
--- a/src/redismodule.h
+++ b/src/redismodule.h
@@ -307,6 +307,7 @@ size_t REDISMODULE_API_FUNC(RedisModule_GetClusterSize)(void);
 void REDISMODULE_API_FUNC(RedisModule_GetRandomBytes)(unsigned char *dst, size_t len);
 void REDISMODULE_API_FUNC(RedisModule_GetRandomHexChars)(char *dst, size_t len);
 void REDISMODULE_API_FUNC(RedisModule_SetDisconnectCallback)(RedisModuleBlockedClient *bc, RedisModuleDisconnectFunc callback);
+void REDISMODULE_API_FUNC(RedisModule_SetClusterFlags)(RedisModuleCtx *ctx, uint64_t flags);
 #endif
 
 /* This is included inline inside each Redis module. */
@@ -444,6 +445,7 @@ static int RedisModule_Init(RedisModuleCtx *ctx, const char *name, int ver, int
     REDISMODULE_GET_API(GetClusterSize);
     REDISMODULE_GET_API(GetRandomBytes);
     REDISMODULE_GET_API(GetRandomHexChars);
+    REDISMODULE_GET_API(SetClusterFlags);
 #endif
 
     if (RedisModule_IsModuleNameBusy && RedisModule_IsModuleNameBusy(name)) return REDISMODULE_ERR;
-- 
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