redis 客户端与服务器建立连接过程

参考：https://blog.youkuaiyun.com/fishmai/article/details/78515355
客户端main方法

int main(int argc, char **argv) {
    int firstarg;

    config.hostip = sdsnew("127.0.0.1");
    config.hostport = 6379;
    config.hostsocket = NULL;
    config.repeat = 1;
    config.interval = 0;
    config.dbnum = 0;
    config.interactive = 0;
    config.shutdown = 0;
    config.monitor_mode = 0;
    config.pubsub_mode = 0;
    config.latency_mode = 0;
    config.latency_history = 0;
    config.cluster_mode = 0;
    config.slave_mode = 0;
    config.getrdb_mode = 0;
    config.rdb_filename = NULL;
    config.pipe_mode = 0;
    config.bigkeys = 0;
    config.stdinarg = 0;
    config.auth = NULL;
    config.eval = NULL;
    if (!isatty(fileno(stdout)) && (getenv("FAKETTY") == NULL))
        config.output = OUTPUT_RAW;
    else
        config.output = OUTPUT_STANDARD;
    config.mb_delim = sdsnew("\n");
    cliInitHelp();

    firstarg = parseOptions(argc,argv);
    argc -= firstarg;
    argv += firstarg;
   #先根据配置的指定参数，如果指定了某个参数就进入某个模式下，否则到最后cliconnect,进入交互模式
    /* Latency mode */
    if (config.latency_mode) {
        if (cliConnect(0) == REDIS_ERR) exit(1);
        latencyMode();
    }

    /* Slave mode */
    if (config.slave_mode) {
        if (cliConnect(0) == REDIS_ERR) exit(1);
        slaveMode();
    }

    /* Get RDB mode. */
    if (config.getrdb_mode) {
        if (cliConnect(0) == REDIS_ERR) exit(1);
        getRDB();
    }

    /* Pipe mode */
    if (config.pipe_mode) {
        if (cliConnect(0) == REDIS_ERR) exit(1);
        pipeMode();
    }

    /* Find big keys */
    if (config.bigkeys) {
        if (cliConnect(0) == REDIS_ERR) exit(1);
        findBigKeys();
    }

    /* Stat mode */
    if (config.stat_mode) {
        if (cliConnect(0) == REDIS_ERR) exit(1);
        if (config.interval == 0) config.interval = 1000000;
        statMode();
    }

    /* Start interactive mode when no command is provided */
    if (argc == 0 && !config.eval) {
        /* Note that in repl mode we don't abort on connection error.
         * A new attempt will be performed for every command send. */
        cliConnect(0);
        repl();
    }

    /* Otherwise, we have some arguments to execute */
    if (cliConnect(0) != REDIS_OK) exit(1);
    if (config.eval) {
        return evalMode(argc,argv);
    } else {
        return noninteractive(argc,convertToSds(argc,argv));
    }
}

看下cliConnect方法

/* Connect to the server. If force is not zero the connection is performed
 * even if there is already a connected socket. */
static int cliConnect(int force) {
    if (context == NULL || force) {
        if (context != NULL)
            redisFree(context);
#根据ip port信息或是socket信息建立连接
        if (config.hostsocket == NULL) {
            context = redisConnect(config.hostip,config.hostport);
        } else {
            context = redisConnectUnix(config.hostsocket);
        }

        if (context->err) {
            fprintf(stderr,"Could not connect to Redis at ");
            if (config.hostsocket == NULL)
                fprintf(stderr,"%s:%d: %s\n",config.hostip,config.hostport,context->errstr);
            else
                fprintf(stderr,"%s: %s\n",config.hostsocket,context->errstr);
            redisFree(context);
            context = NULL;
            return REDIS_ERR;
        }
#上面返回一个连接的conetxt
        /* Set aggressive KEEP_ALIVE socket option in the Redis context socket
         * in order to prevent timeouts caused by the execution of long
         * commands. At the same time this improves the detection of real
         * errors. */
        anetKeepAlive(NULL, context->fd, REDIS_CLI_KEEPALIVE_INTERVAL);
        #进行auth和selectdb
        /* Do AUTH and select the right DB. */
        if (cliAuth() != REDIS_OK)
            return REDIS_ERR;
        if (cliSelect() != REDIS_OK)
            return REDIS_ERR;
    }
    return REDIS_OK;
}

连接到redis

/* Connect to a Redis instance. On error the field error in the returned
 * context will be set to the return value of the error function.
 * When no set of reply functions is given, the default set will be used. */
redisContext *redisConnect(const char *ip, int port) {
    redisContext *c = redisContextInit();
    c->flags |= REDIS_BLOCK;
    redisContextConnectTcp(c,ip,port,NULL);
    return c;
}

初始化context

static redisContext *redisContextInit(void) {
    redisContext *c;

    c = calloc(1,sizeof(redisContext));
    if (c == NULL)
        return NULL;

    c->err = 0;
    c->errstr[0] = '\0';
    c->obuf = sdsempty();
    c->reader = redisReaderCreate();
    return c;
}

redisContextConnectTcp 建立tcp连接

int redisContextConnectTcp(redisContext *c, const char *addr, int port, struct timeval *timeout) {
    int s, rv;
    char _port[6];  /* strlen("65535"); */
    struct addrinfo hints, *servinfo, *p;
    int blocking = (c->flags & REDIS_BLOCK);

    snprintf(_port, 6, "%d", port);
    memset(&hints,0,sizeof(hints));
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;

    if ((rv = getaddrinfo(addr,_port,&hints,&servinfo)) != 0) {
        __redisSetError(c,REDIS_ERR_OTHER,gai_strerror(rv));
        return REDIS_ERR;
    }
    for (p = servinfo; p != NULL; p = p->ai_next) {
        if ((s = socket(p->ai_family,p->ai_socktype,p->ai_protocol)) == -1)
            continue;

        if (redisSetBlocking(c,s,0) != REDIS_OK)
            goto error;
        if (connect(s,p->ai_addr,p->ai_addrlen) == -1) {
            if (errno == EHOSTUNREACH) {
                close(s);
                continue;
            } else if (errno == EINPROGRESS && !blocking) {
                /* This is ok. */
            } else {
                if (redisContextWaitReady(c,s,timeout) != REDIS_OK)
                    goto error;
            }
        }
        if (blocking && redisSetBlocking(c,s,1) != REDIS_OK)
            goto error;
        if (redisSetTcpNoDelay(c,s) != REDIS_OK)
            goto error;

        c->fd = s;
        c->flags |= REDIS_CONNECTED;
        rv = REDIS_OK;
        goto end;
    }
    if (p == NULL) {
        char buf[128];
        snprintf(buf,sizeof(buf),"Can't create socket: %s",strerror(errno));
        __redisSetError(c,REDIS_ERR_OTHER,buf);
        goto error;
    }

error:
    rv = REDIS_ERR;
end:
    freeaddrinfo(servinfo);
    return rv;  // Need to return REDIS_OK if alright
}

服务端在initServer的时候创建了事件监听，注册了acceptTcpHandler方法进行处理

void initServer() {
    int j;

    signal(SIGHUP, SIG_IGN);
    signal(SIGPIPE, SIG_IGN);
    setupSignalHandlers();

    if (server.syslog_enabled) {
        openlog(server.syslog_ident, LOG_PID | LOG_NDELAY | LOG_NOWAIT,
            server.syslog_facility);
    }

    server.current_client = NULL;
    server.clients = listCreate();
    server.clients_to_close = listCreate();
    server.slaves = listCreate();
    server.monitors = listCreate();
    server.unblocked_clients = listCreate();
    server.ready_keys = listCreate();

    createSharedObjects();
    adjustOpenFilesLimit();
    server.el = aeCreateEventLoop(server.maxclients+1024);
    server.db = zmalloc(sizeof(redisDb)*server.dbnum);

    if (server.port != 0) {
        server.ipfd = anetTcpServer(server.neterr,server.port,server.bindaddr);
        if (server.ipfd == ANET_ERR) {
            redisLog(REDIS_WARNING, "Opening port %d: %s",
                server.port, server.neterr);
            exit(1);
        }
    }
    if (server.unixsocket != NULL) {
        unlink(server.unixsocket); /* don't care if this fails */
        server.sofd = anetUnixServer(server.neterr,server.unixsocket,server.unixsocketperm);
        if (server.sofd == ANET_ERR) {
            redisLog(REDIS_WARNING, "Opening socket: %s", server.neterr);
            exit(1);
        }
    }
    if (server.ipfd < 0 && server.sofd < 0) {
        redisLog(REDIS_WARNING, "Configured to not listen anywhere, exiting.");
        exit(1);
    }
    for (j = 0; j < server.dbnum; j++) {
        server.db[j].dict = dictCreate(&dbDictType,NULL);
        server.db[j].expires = dictCreate(&keyptrDictType,NULL);
        server.db[j].blocking_keys = dictCreate(&keylistDictType,NULL);
        server.db[j].ready_keys = dictCreate(&setDictType,NULL);
        server.db[j].watched_keys = dictCreate(&keylistDictType,NULL);
        server.db[j].id = j;
    }
    server.pubsub_channels = dictCreate(&keylistDictType,NULL);
    server.pubsub_patterns = listCreate();
    listSetFreeMethod(server.pubsub_patterns,freePubsubPattern);
    listSetMatchMethod(server.pubsub_patterns,listMatchPubsubPattern);
    server.cronloops = 0;
    server.rdb_child_pid = -1;
    server.aof_child_pid = -1;
    aofRewriteBufferReset();
    server.aof_buf = sdsempty();
    server.lastsave = time(NULL); /* At startup we consider the DB saved. */
    server.lastbgsave_try = 0;    /* At startup we never tried to BGSAVE. */
    server.rdb_save_time_last = -1;
    server.rdb_save_time_start = -1;
    server.dirty = 0;
    server.stat_numcommands = 0;
    server.stat_numconnections = 0;
    server.stat_expiredkeys = 0;
    server.stat_evictedkeys = 0;
    server.stat_starttime = time(NULL);
    server.stat_keyspace_misses = 0;
    server.stat_keyspace_hits = 0;
    server.stat_peak_memory = 0;
    server.stat_fork_time = 0;
    server.stat_rejected_conn = 0;
    memset(server.ops_sec_samples,0,sizeof(server.ops_sec_samples));
    server.ops_sec_idx = 0;
    server.ops_sec_last_sample_time = mstime();
    server.ops_sec_last_sample_ops = 0;
    server.unixtime = time(NULL);
    server.lastbgsave_status = REDIS_OK;
    if(aeCreateTimeEvent(server.el, 1, serverCron, NULL, NULL) == AE_ERR) {
        redisPanic("create time event failed");
        exit(1);
    }
    if (server.ipfd > 0 && aeCreateFileEvent(server.el,server.ipfd,AE_READABLE,
        acceptTcpHandler,NULL) == AE_ERR) redisPanic("Unrecoverable error creating server.ipfd file event.");
    if (server.sofd > 0 && aeCreateFileEvent(server.el,server.sofd,AE_READABLE,
        acceptUnixHandler,NULL) == AE_ERR) redisPanic("Unrecoverable error creating server.sofd file event.");

    if (server.aof_state == REDIS_AOF_ON) {
        server.aof_fd = open(server.aof_filename,
                               O_WRONLY|O_APPEND|O_CREAT,0644);
        if (server.aof_fd == -1) {
            redisLog(REDIS_WARNING, "Can't open the append-only file: %s",
                strerror(errno));
            exit(1);
        }
    }

    /* 32 bit instances are limited to 4GB of address space, so if there is
     * no explicit limit in the user provided configuration we set a limit
     * at 3 GB using maxmemory with 'noeviction' policy'. This avoids
     * useless crashes of the Redis instance for out of memory. */
    if (server.arch_bits == 32 && server.maxmemory == 0) {
        redisLog(REDIS_WARNING,"Warning: 32 bit instance detected but no memory limit set. Setting 3 GB maxmemory limit with 'noeviction' policy now.");
        server.maxmemory = 3072LL*(1024*1024); /* 3 GB */
        server.maxmemory_policy = REDIS_MAXMEMORY_NO_EVICTION;
    }

    scriptingInit();
    slowlogInit();
    bioInit();
}