From 95c17c0cb24ebfff814b0c10e21d1a12b02fb478 Mon Sep 17 00:00:00 2001
From: antirez <antirez@gmail.com>
Date: Thu, 13 Oct 2016 16:57:40 +0200
Subject: [PATCH] Modules: AbortBlock() API implemented.

---
 src/module.c         | 10 +++++++++-
 src/modules/INTRO.md |  1 +
 src/redismodule.h    |  2 ++
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/module.c b/src/module.c
index 91cd5309..66c09a42 100644
--- a/src/module.c
+++ b/src/module.c
@@ -3140,6 +3140,13 @@ int RM_UnblockClient(RedisModuleBlockedClient *bc, void *privdata) {
     return REDISMODULE_OK;
 }
 
+/* Abort a blocked client blocking operation: the client will be unblocked
+ * without firing the reply callback. */
+int RM_AbortBlock(RedisModuleBlockedClient *bc) {
+    bc->reply_callback = NULL;
+    return RM_UnblockClient(bc,NULL);
+}
+
 /* This function will check the moduleUnblockedClients queue in order to
  * call the reply callback and really unblock the client.
  *
@@ -3163,7 +3170,7 @@ void moduleHandleBlockedClients(void) {
         /* Release the lock during the loop, as long as we don't
          * touch the shared list. */
 
-        if (c != NULL) {
+        if (c != NULL && bc->reply_callback != NULL) {
             RedisModuleCtx ctx = REDISMODULE_CTX_INIT;
             ctx.flags |= REDISMODULE_CTX_BLOCKED_REPLY;
             ctx.blocked_privdata = bc->privdata;
@@ -3545,5 +3552,6 @@ void moduleRegisterCoreAPI(void) {
     REGISTER_API(IsBlockedReplyRequest);
     REGISTER_API(IsBlockedTimeoutRequest);
     REGISTER_API(GetBlockedClientPrivateData);
+    REGISTER_API(AbortBlock);
     REGISTER_API(Milliseconds);
 }
diff --git a/src/modules/INTRO.md b/src/modules/INTRO.md
index e5576b7f..3ac6a467 100644
--- a/src/modules/INTRO.md
+++ b/src/modules/INTRO.md
@@ -6,6 +6,7 @@ The modules documentation is composed of the following files:
 * `INTRO.md` (this file). An overview about Redis Modules system and API. It's a good idea to start your reading here.
 * `API.md` is generated from module.c top comments of RedisMoule functions. It is a good reference in order to understand how each function works.
 * `TYPES.md` covers the implementation of native data types into modules.
+* `BLOCK.md` shows how to write blocking commands that will not reply immediately, but will block the client, without blocking the Redis server, and will provide a reply whenever will be possible.
 
 Redis modules make possible to extend Redis functionality using external
 modules, implementing new Redis commands at a speed and with features
diff --git a/src/redismodule.h b/src/redismodule.h
index 104de958..a07c0948 100644
--- a/src/redismodule.h
+++ b/src/redismodule.h
@@ -200,6 +200,7 @@ int REDISMODULE_API_FUNC(RedisModule_UnblockClient)(RedisModuleBlockedClient *bc
 int REDISMODULE_API_FUNC(RedisModule_IsBlockedReplyRequest)(RedisModuleCtx *ctx);
 int REDISMODULE_API_FUNC(RedisModule_IsBlockedTimeoutRequest)(RedisModuleCtx *ctx);
 void *REDISMODULE_API_FUNC(RedisModule_GetBlockedClientPrivateData)(RedisModuleCtx *ctx);
+int REDISMODULE_API_FUNC(RedisModule_AbortBlock)(RedisModuleBlockedClient *bc);
 long long REDISMODULE_API_FUNC(RedisModule_Milliseconds)(void);
 
 /* This is included inline inside each Redis module. */
@@ -307,6 +308,7 @@ static int RedisModule_Init(RedisModuleCtx *ctx, const char *name, int ver, int
     REDISMODULE_GET_API(IsBlockedReplyRequest);
     REDISMODULE_GET_API(IsBlockedTimeoutRequest);
     REDISMODULE_GET_API(GetBlockedClientPrivateData);
+    REDISMODULE_GET_API(AbortBlock);
     REDISMODULE_GET_API(Milliseconds);
 
     RedisModule_SetModuleAttribs(ctx,name,ver,apiver);