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/* Helloblock module -- An example of blocking command implementation
* with threads.
*
* -----------------------------------------------------------------------------
*
* Copyright (c) 2016, Salvatore Sanfilippo <antirez at gmail dot com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of Redis nor the names of its contributors may be used
* to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include "../redismodule.h"
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <unistd.h>
/* Reply callback for blocking command HELLO.BLOCK */
int HelloBlock_Reply(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
REDISMODULE_NOT_USED(argv);
REDISMODULE_NOT_USED(argc);
int *myint = RedisModule_GetBlockedClientPrivateData(ctx);
return RedisModule_ReplyWithLongLong(ctx,*myint);
}
/* Timeout callback for blocking command HELLO.BLOCK */
int HelloBlock_Timeout(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
REDISMODULE_NOT_USED(argv);
REDISMODULE_NOT_USED(argc);
return RedisModule_ReplyWithSimpleString(ctx,"Request timedout");
}
/* Private data freeing callback for HELLO.BLOCK command. */
void HelloBlock_FreeData(RedisModuleCtx *ctx, void *privdata) {
REDISMODULE_NOT_USED(ctx);
RedisModule_Free(privdata);
}
/* The thread entry point that actually executes the blocking part
* of the command HELLO.BLOCK. */
void *HelloBlock_ThreadMain(void *arg) {
void **targ = arg;
RedisModuleBlockedClient *bc = targ[0];
long long delay = (unsigned long)targ[1];
RedisModule_Free(targ);
sleep(delay);
int *r = RedisModule_Alloc(sizeof(int));
*r = rand();
RedisModule_UnblockClient(bc,r);
return NULL;
}
/* An example blocked client disconnection callback.
*
* Note that in the case of the HELLO.BLOCK command, the blocked client is now
* owned by the thread calling sleep(). In this specific case, there is not
* much we can do, however normally we could instead implement a way to
* signal the thread that the client disconnected, and sleep the specified
* amount of seconds with a while loop calling sleep(1), so that once we
* detect the client disconnection, we can terminate the thread ASAP. */
void HelloBlock_Disconnected(RedisModuleCtx *ctx, RedisModuleBlockedClient *bc) {
RedisModule_Log(ctx,"warning","Blocked client %p disconnected!",
(void*)bc);
/* Here you should cleanup your state / threads, and if possible
* call RedisModule_UnblockClient(), or notify the thread that will
* call the function ASAP. */
}
/* HELLO.BLOCK <delay> <timeout> -- Block for <count> seconds, then reply with
* a random number. Timeout is the command timeout, so that you can test
* what happens when the delay is greater than the timeout. */
int HelloBlock_RedisCommand(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
if (argc != 3) return RedisModule_WrongArity(ctx);
long long delay;
long long timeout;
if (RedisModule_StringToLongLong(argv[1],&delay) != REDISMODULE_OK) {
return RedisModule_ReplyWithError(ctx,"ERR invalid count");
}
if (RedisModule_StringToLongLong(argv[2],&timeout) != REDISMODULE_OK) {
return RedisModule_ReplyWithError(ctx,"ERR invalid count");
}
pthread_t tid;
RedisModuleBlockedClient *bc = RedisModule_BlockClient(ctx,HelloBlock_Reply,HelloBlock_Timeout,HelloBlock_FreeData,timeout);
/* Here we set a disconnection handler, however since this module will
* block in sleep() in a thread, there is not much we can do in the
* callback, so this is just to show you the API. */
RedisModule_SetDisconnectCallback(bc,HelloBlock_Disconnected);
/* Now that we setup a blocking client, we need to pass the control
* to the thread. However we need to pass arguments to the thread:
* the delay and a reference to the blocked client handle. */
void **targ = RedisModule_Alloc(sizeof(void*)*2);
targ[0] = bc;
targ[1] = (void*)(unsigned long) delay;
if (pthread_create(&tid,NULL,HelloBlock_ThreadMain,targ) != 0) {
RedisModule_AbortBlock(bc);
return RedisModule_ReplyWithError(ctx,"-ERR Can't start thread");
}
return REDISMODULE_OK;
}
/* The thread entry point that actually executes the blocking part
* of the command HELLO.KEYS.
*
* Note: this implementation is very simple on purpose, so no duplicated
* keys (returned by SCAN) are filtered. However adding such a functionality
* would be trivial just using any data structure implementing a dictionary
* in order to filter the duplicated items. */
void *HelloKeys_ThreadMain(void *arg) {
RedisModuleBlockedClient *bc = arg;
RedisModuleCtx *ctx = RedisModule_GetThreadSafeContext(bc);
long long cursor = 0;
size_t replylen = 0;
RedisModule_ReplyWithArray(ctx,REDISMODULE_POSTPONED_LEN);
do {
RedisModule_ThreadSafeContextLock(ctx);
RedisModuleCallReply *reply = RedisModule_Call(ctx,
"SCAN","l",(long long)cursor);
RedisModule_ThreadSafeContextUnlock(ctx);
RedisModuleCallReply *cr_cursor =
RedisModule_CallReplyArrayElement(reply,0);
RedisModuleCallReply *cr_keys =
RedisModule_CallReplyArrayElement(reply,1);
RedisModuleString *s = RedisModule_CreateStringFromCallReply(cr_cursor);
RedisModule_StringToLongLong(s,&cursor);
RedisModule_FreeString(ctx,s);
size_t items = RedisModule_CallReplyLength(cr_keys);
for (size_t j = 0; j < items; j++) {
RedisModuleCallReply *ele =
RedisModule_CallReplyArrayElement(cr_keys,j);
RedisModule_ReplyWithCallReply(ctx,ele);
replylen++;
}
RedisModule_FreeCallReply(reply);
} while (cursor != 0);
RedisModule_ReplySetArrayLength(ctx,replylen);
RedisModule_FreeThreadSafeContext(ctx);
RedisModule_UnblockClient(bc,NULL);
return NULL;
}
/* HELLO.KEYS -- Return all the keys in the current database without blocking
* the server. The keys do not represent a point-in-time state so only the keys
* that were in the database from the start to the end are guaranteed to be
* there. */
int HelloKeys_RedisCommand(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
REDISMODULE_NOT_USED(argv);
if (argc != 1) return RedisModule_WrongArity(ctx);
pthread_t tid;
/* Note that when blocking the client we do not set any callback: no
* timeout is possible since we passed '0', nor we need a reply callback
* because we'll use the thread safe context to accumulate a reply. */
RedisModuleBlockedClient *bc = RedisModule_BlockClient(ctx,NULL,NULL,NULL,0);
/* Now that we setup a blocking client, we need to pass the control
* to the thread. However we need to pass arguments to the thread:
* the reference to the blocked client handle. */
if (pthread_create(&tid,NULL,HelloKeys_ThreadMain,bc) != 0) {
RedisModule_AbortBlock(bc);
return RedisModule_ReplyWithError(ctx,"-ERR Can't start thread");
}
return REDISMODULE_OK;
}
/* This function must be present on each Redis module. It is used in order to
* register the commands into the Redis server. */
int RedisModule_OnLoad(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
REDISMODULE_NOT_USED(argv);
REDISMODULE_NOT_USED(argc);
if (RedisModule_Init(ctx,"helloblock",1,REDISMODULE_APIVER_1)
== REDISMODULE_ERR) return REDISMODULE_ERR;
if (RedisModule_CreateCommand(ctx,"hello.block",
HelloBlock_RedisCommand,"",0,0,0) == REDISMODULE_ERR)
return REDISMODULE_ERR;
if (RedisModule_CreateCommand(ctx,"hello.keys",
HelloKeys_RedisCommand,"",0,0,0) == REDISMODULE_ERR)
return REDISMODULE_ERR;
return REDISMODULE_OK;
}
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