1 files changed, 218 insertions, 0 deletions
diff --git a/src/modules/helloblock.c b/src/modules/helloblock.c
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+++ b/src/modules/helloblock.c
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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;
+}