聘请等待消息

Question

我正在使用hiredis C库连接到redis服务器。我无法弄清楚订阅新消息后如何等待新消息。

我的代码如下所示：

signal(SIGPIPE, SIG_IGN );
  struct event_base *base = event_base_new();

  redisAsyncContext *c = redisAsyncConnect("127.0.0.1", 6379);
  if (c->err) {
    /* Let *c leak for now... */
    printf("Error: %s\n", c->errstr);
    return 1;
  }

  redisLibeventAttach(c, base);
  redisAsyncSetConnectCallback(c, connectCallback);
  redisAsyncSetDisconnectCallback(c, disconnectCallback);
  redisAsyncCommand(c, NULL, NULL, "SET key %b", argv[argc - 1],
                    strlen(argv[argc - 1]));
  redisAsyncCommand(c, getCallback, (char*) "end-1", "GET key");
  redisAsyncCommand(c, getCallback, (char*) "end-1", "SUBSCRIBE foo");

现在如何告诉hiredis在频道上等待消息？

Answer 1

您无需告诉hiredis您需要在通道上等待：事件循环将仅在先前已注册的Redis连接上等待。

这是一个完整的示例：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include "hiredis.h"
#include "async.h"
#include "adapters/libevent.h"

void subCallback(redisAsyncContext *c, void *r, void *priv) {
    redisReply *reply = r;
    if (reply == NULL) return;
    if ( reply->type == REDIS_REPLY_ARRAY && reply->elements == 3 ) {
        if ( strcmp( reply->element[0]->str, "subscribe" ) != 0 ) {
            printf( "Received[%s] channel %s: %s\n",
                    (char*)priv,
                    reply->element[1]->str,
                    reply->element[2]->str );
        }
    }
}

void connectCallback(const redisAsyncContext *c, int status) {
    if (status != REDIS_OK) {
        printf("Error: %s\n", c->errstr);
        return;
    }
    printf("Connected...\n");
}

void disconnectCallback(const redisAsyncContext *c, int status) {
    if (status != REDIS_OK) {
        printf("Error: %s\n", c->errstr);
        return;
    }
    printf("Disconnected...\n");
}

int main (int argc, char **argv) {
    signal(SIGPIPE, SIG_IGN);
    struct event_base *base = event_base_new();

    redisAsyncContext *c = redisAsyncConnect("127.0.0.1", 6379);
    if (c->err) {
        /* Let *c leak for now... */
        printf("Error: %s\n", c->errstr);
        return 1;
    }

    redisLibeventAttach(c,base);
    redisAsyncSetConnectCallback(c,connectCallback);
    redisAsyncSetDisconnectCallback(c,disconnectCallback);
    redisAsyncCommand(c, subCallback, (char*) "sub", "SUBSCRIBE foo");

    event_base_dispatch(base);
    return 0;
}

您可以通过使用以下命令发布内容来对其进行测试：

redis-cli publish foo something

event_base_dispatch函数是实际启动事件循环并使其等待Redis订阅的函数。