server.c分析

1. 阅读Redis的Makefile文件。

REDIS_SERVER_NAME=redis-server
REDIS_SENTINEL_NAME=redis-sentinel
REDIS_SERVER_OBJ=adlist.o quicklist.o ae.o anet.o dict.o server.o sds.o zmalloc.o lzf_c.o lzf_d.o pqsort.o zipmap.o sha1.o ziplist.o release.o networking.o util.o object.o db.o replication.o rdb.o t_string.o t_list.o t_set.o t_zset.o t_hash.o config.o aof.o pubsub.o multi.o debug.o sort.o intset.o syncio.o cluster.o crc16.o endianconv.o slowlog.o scripting.o bio.o rio.o rand.o memtest.o crc64.o bitops.o sentinel.o notify.o setproctitle.o blocked.o hyperloglog.o latency.o sparkline.o redis-check-rdb.o redis-check-aof.o geo.o lazyfree.o module.o evict.o expire.o geohash.o geohash_helper.o childinfo.o defrag.o siphash.o rax.o t_stream.o listpack.o localtime.o lolwut.o lolwut5.o
REDIS_CLI_NAME=redis-cli
REDIS_CLI_OBJ=anet.o adlist.o dict.o redis-cli.o zmalloc.o release.o anet.o ae.o crc64.o siphash.o crc16.o
REDIS_BENCHMARK_NAME=redis-benchmark
REDIS_BENCHMARK_OBJ=ae.o anet.o redis-benchmark.o adlist.o zmalloc.o redis-benchmark.o
REDIS_CHECK_RDB_NAME=redis-check-rdb
REDIS_CHECK_AOF_NAME=redis-check-aof
...

# redis-server
$(REDIS_SERVER_NAME): $(REDIS_SERVER_OBJ)
    $(REDIS_LD) -o $@ $^ ../deps/hiredis/libhiredis.a ../deps/lua/src/liblua.a $(FINAL_LIBS)

# redis-sentinel
$(REDIS_SENTINEL_NAME): $(REDIS_SERVER_NAME)
    $(REDIS_INSTALL) $(REDIS_SERVER_NAME) $(REDIS_SENTINEL_NAME)

# redis-check-rdb
$(REDIS_CHECK_RDB_NAME): $(REDIS_SERVER_NAME)
    $(REDIS_INSTALL) $(REDIS_SERVER_NAME) $(REDIS_CHECK_RDB_NAME)

# redis-check-aof
$(REDIS_CHECK_AOF_NAME): $(REDIS_SERVER_NAME)
    $(REDIS_INSTALL) $(REDIS_SERVER_NAME) $(REDIS_CHECK_AOF_NAME)

server.c文件，被编译成redis-server、redis-check-rdb、redis-sentinel、redis-check-aof。

2. server.c的int main(int argc, char **argv)函数，redis-server的主入口

这个main函数的主要逻辑大概就是：各种初始化、加载配置、事件监听。

为了简单，我将这个文件分开来说：

• 初始化部分
• redis-check-rdb部分
• redis-check-aof部分
• redis-sentinel部分
• redis-cluster部分
• redis-server部分
• 其它部分

1. 初始化部分

    //设置时区等信息
    setlocale(LC_COLLATE,"");
    tzset(); /* Populates 'timezone' global. */
    zmalloc_set_oom_handler(redisOutOfMemoryHandler);
    srand(time(NULL)^getpid());
    gettimeofday(&tv,NULL);
    //通过/dev/urandom实现，生成非空随机
    char hashseed[16];
    //标识redis实例的时候用到
    getRandomHexChars(hashseed,sizeof(hashseed));
    dictSetHashFunctionSeed((uint8_t*)hashseed);
    server.sentinel_mode = checkForSentinelMode(argc,argv);
    //初始化默认配置
    initServerConfig();
    moduleInitModulesSystem();

    //保存当前执行文件的绝对路径，执行restartServer的时候用到
    server.executable = getAbsolutePath(argv[0]);
    server.exec_argv = zmalloc(sizeof(char*)*(argc+1));
    server.exec_argv[argc] = NULL;
    for (j = 0; j < argc; j++) server.[exec_argvj] = zstrdup(argv[j]);

2. redis-check-rdb部分

    if (strstr(argv[0],"redis-check-rdb") != NULL)
        redis_check_rdb_main(argc,argv,NULL);

如果当前执行的文件是redis-check-rdb，则执行redis-check-rdb.c文件中的int redis_check_rdb_main(int argc, char **argv, FILE *fp) 方法。

int redis_check_rdb_main(int argc, char **argv, FILE *fp) {
    //如果没传入 rdb文件路径的话，就会报错
    if (argc != 2 && fp == NULL) {
        fprintf(stderr, "Usage: %s <rdb-file-name>\n", argv[0]);
        exit(1);
    }
    /* In order to call the loading functions we need to create the shared
     * integer objects, however since this function may be called from
     * an already initialized Redis instance, check if we really need to. */
    if (shared.integers[0] == NULL)
        createSharedObjects();
    server.loading_process_events_interval_bytes = 0;
    rdbCheckMode = 1;
    rdbCheckInfo("Checking RDB file %s", argv[1]);
    rdbCheckSetupSignals();
    int retval = redis_check_rdb(argv[1],fp);
    if (retval == 0) {
        rdbCheckInfo("\\o/ RDB looks OK! \\o/");
        rdbShowGenericInfo();
    }
    if (fp) return (retval == 0) ? C_OK : C_ERR;
    exit(retval);
}

效果如图：

image.png

3. redis-check-aof部分

    else if (strstr(argv[0],"redis-check-aof") != NULL)
        redis_check_aof_main(argc,argv);

如果当前执行的文件是redis-check-aof，则执行redis-check-aof.c文件中的int redis_check_aof_main(int argc, char **argv) 方法。

int redis_check_aof_main(int argc, char **argv) {
    char *filename;
    int fix = 0;
    //如果没传aof文件路径，则会报错
    if (argc < 2) {
        printf("Usage: %s [--fix] <file.aof>\n", argv[0]);
        exit(1);
    } else if (argc == 2) {
        filename = argv[1];
    } else if (argc == 3) {
        //传入--fix可以对aof文件进行修复
        if (strcmp(argv[1],"--fix") != 0) {
            printf("Invalid argument: %s\n", argv[1]);
            exit(1);
        }
        filename = argv[2];
        fix = 1;
    } else {
        printf("Invalid arguments\n");
        exit(1);
    }

    //打开aof文件
    FILE *fp = fopen(filename,"r+");
    if (fp == NULL) {
        printf("Cannot open file: %s\n", filename);
        exit(1);
    }

    struct redis_stat sb;
    if (redis_fstat(fileno(fp),&sb) == -1) {
        printf("Cannot stat file: %s\n", filename);
        exit(1);
    }

    off_t size = sb.st_size;
    //如果aof文件为空，则直接退出
    if (size == 0) {
        printf("Empty file: %s\n", filename);
        exit(1);
    }

    /* This AOF file may have an RDB preamble. Check this to start, and if this
     * is the case, start processing the RDB part. */
    //这里做个测试，将rdb文件改为aof文件 cp ./dump.rdb ./dump.aof
    if (size >= 8) {    /* There must be at least room for the RDB header. */
        char sig[5];
        int has_preamble = fread(sig,sizeof(sig),1,fp) == 1 &&
                            memcmp(sig,"REDIS",sizeof(sig)) == 0;
        rewind(fp);
        //如果该aof文件内容包含了rdb格式的文件内容，则以RDB方式加载
        if (has_preamble) {
            printf("The AOF appears to start with an RDB preamble.\n"
                   "Checking the RDB preamble to start:\n");
            if (redis_check_rdb_main(argc,argv,fp) == C_ERR) {
                printf("RDB preamble of AOF file is not sane, aborting.\n");
                exit(1);
            } else {
                printf("RDB preamble is OK, proceeding with AOF tail...\n");
            }
        }
    }

    //开始解析AOF文件
    off_t pos = process(fp);
    off_t diff = size-pos;
    printf("AOF analyzed: size=%lld, ok_up_to=%lld, diff=%lld\n",
        (long long) size, (long long) pos, (long long) diff);
    if (diff > 0) {
        if (fix) {
            char buf[2];
            printf("This will shrink the AOF from %lld bytes, with %lld bytes, to %lld bytes\n",(long long)size,(long long)diff,(long long)pos);
            printf("Continue? [y/N]: ");
            if (fgets(buf,sizeof(buf),stdin) == NULL ||
                strncasecmp(buf,"y",1) != 0) {
                    printf("Aborting...\n");
                    exit(1);
            }
            if (ftruncate(fileno(fp), pos) == -1) {
                printf("Failed to truncate AOF\n");
                exit(1);
            } else {
                printf("Successfully truncated AOF\n");
            }
        } else {
            printf("AOF is not valid. "
                   "Use the --fix option to try fixing it.\n");
            exit(1);
        }
    } else {
        printf("AOF is valid\n");
    }

    fclose(fp);
    exit(0);
}

效果如图：

非正常aof文件.png

正常aof文件.png

4. redis-sentinel部分
我们启动redis-sentinel有两种方式。
一种是redis-sentinel /path/to/sentinel.conf
一种是redis-server --sentinel /path/to/sentinel.conf
因此，在server.c中，会去判断这两种方式。

server.sentinel_mode = checkForSentinelMode(argc,argv);
    
/* Returns 1 if there is --sentinel among the arguments or if
 * argv[0] contains "redis-sentinel". */
int checkForSentinelMode(int argc, char **argv) {
    int j;
    //当前执行文件为redis-sentinel
    if (strstr(argv[0],"redis-sentinel") != NULL) return 1;
    //启动参数列表中包含 --sentinel
    for (j = 1; j < argc; j++)
        if (!strcmp(argv[j],"--sentinel")) return 1;
    return 0;
}

如果确定了是sentinel模式的话，将会去初始化sentinel及其配置。

 if (server.sentinel_mode) {
        initSentinelConfig();
        initSentinel();
 }
 
void initSentinelConfig(void) {
    //默认端口26379
    server.port = REDIS_SENTINEL_PORT;
    server.protected_mode = 0; /* Sentinel must be exposed. */
}
/* Perform the Sentinel mode initialization. */
void initSentinel(void) {
   //省略，一些初始值
}

完成上述操作之后，会去刷新sentinel的配置信息(rewriteConfig)

 sentinelIsRunning();

  /* This function gets called when the server is in Sentinel mode, started,
 * loaded the configuration, and is ready for normal operations. */
void sentinelIsRunning(void) {
    int j;
    //sentinel配置文件没有指定则会报错
    if (server.configfile == NULL) {
        serverLog(LL_WARNING,
            "Sentinel started without a config file. Exiting...");
        exit(1);
    } else if (access(server.configfile,W_OK) == -1) {
        serverLog(LL_WARNING,
            "Sentinel config file %s is not writable: %s. Exiting...",
            server.configfile,strerror(errno));
        exit(1);
    }

    /* If this Sentinel has yet no ID set in the configuration file, we
     * pick a random one and persist the config on disk. From now on this
     * will be this Sentinel ID across restarts. */
    for (j = 0; j < CONFIG_RUN_ID_SIZE; j++)
        if (sentinel.myid[j] != 0) break;

    if (j == CONFIG_RUN_ID_SIZE) {
        /* Pick ID and persist the config. */
        getRandomHexChars(sentinel.myid,CONFIG_RUN_ID_SIZE);
        sentinelFlushConfig();
    }

    /* Log its ID to make debugging of issues simpler. */
    serverLog(LL_WARNING,"Sentinel ID is %s", sentinel.myid);

    /* We want to generate a +monitor event for every configured master
     * at startup. */
    sentinelGenerateInitialMonitorEvents();
}

void sentinelFlushConfig(void) {
    int fd = -1;
    int saved_hz = server.hz;
    int rewrite_status;

    server.hz = CONFIG_DEFAULT_HZ;
    // 刷新配置信息
    rewrite_status = rewriteConfig(server.configfile);
    server.hz = saved_hz;

    if (rewrite_status == -1) goto werr;
    if ((fd = open(server.configfile,O_RDONLY)) == -1) goto werr;
    if (fsync(fd) == -1) goto werr;
    if (close(fd) == EOF) goto werr;
    return;

werr:
    if (fd != -1) close(fd);
    serverLog(LL_WARNING,"WARNING: Sentinel was not able to save the new configuration on disk!!!: %s", strerror(errno));
}

5. redis-cluster部分

        moduleLoadFromQueue();
        //从本地磁盘加载RDB、AOF
        loadDataFromDisk();
        if (server.cluster_enabled) {
            //验证及加载配置、创建slot
            if (verifyClusterConfigWithData() == C_ERR) {
                serverLog(LL_WARNING,
                    "You can't have keys in a DB different than DB 0 when in "
                    "Cluster mode. Exiting.");
                exit(1);
            }
        }

6. redis-server部分
除了以上的其它模式，剩下这个正常使用的模式。./redis-server
包含了三种功能：

• 带-的
• 带--的
• 什么也不带

效果如图：

image.png

 if (argc >= 2) {
        j = 1; /* First option to parse in argv[] */
        sds options = sdsempty();
        char *configfile = NULL;

        /* Handle special options --help and --version */
        if (strcmp(argv[1], "-v") == 0 ||
            strcmp(argv[1], "--version") == 0) version();
        if (strcmp(argv[1], "--help") == 0 ||
            strcmp(argv[1], "-h") == 0) usage();
        if (strcmp(argv[1], "--test-memory") == 0) {
            if (argc == 3) {
                memtest(atoi(argv[2]),50);
                exit(0);
            } else {
                fprintf(stderr,"Please specify the amount of memory to test in megabytes.\n");
                fprintf(stderr,"Example: ./redis-server --test-memory 4096\n\n");
                exit(1);
            }
        }

        /* First argument is the config file name? */
        if (argv[j][0] != '-' || argv[j][1] != '-') {
            configfile = argv[j];
            server.configfile = getAbsolutePath(configfile);
            /* Replace the config file in server.exec_argv with
             * its absolute path. */
            zfree(server.exec_argv[j]);
            server.exec_argv[j] = zstrdup(server.configfile);
            j++;
        }

        /* All the other options are parsed and conceptually appended to the
         * configuration file. For instance --port 6380 will generate the
         * string "port 6380\n" to be parsed after the actual file name
         * is parsed, if any. */
        while(j != argc) {
            if (argv[j][0] == '-' && argv[j][1] == '-') {
                /* Option name */
                if (!strcmp(argv[j], "--check-rdb")) {
                    /* Argument has no options, need to skip for parsing. */
                    j++;
                    continue;
                }
                if (sdslen(options)) options = sdscat(options,"\n");
                options = sdscat(options,argv[j]+2);
                options = sdscat(options," ");
            } else {
                /* Option argument */
                options = sdscatrepr(options,argv[j],strlen(argv[j]));
                options = sdscat(options," ");
            }
            j++;
        }
        if (server.sentinel_mode && configfile && *configfile == '-') {
            serverLog(LL_WARNING,
                "Sentinel config from STDIN not allowed.");
            serverLog(LL_WARNING,
                "Sentinel needs config file on disk to save state.  Exiting...");
            exit(1);
        }
        resetServerSaveParams();
        //加载redis.conf配置
        loadServerConfig(configfile,options);
        sdsfree(options);
    }

7. 其它部分
监控

server.supervised = redisIsSupervised(server.supervised_mode);

int redisIsSupervised(int mode) {
    if (mode == SUPERVISED_AUTODETECT) {
        const char *upstart_job = getenv("UPSTART_JOB");
        const char *notify_socket = getenv("NOTIFY_SOCKET");
        if (upstart_job) {
           //通过up_start方式来异步启动redis
            redisSupervisedUpstart();
        } else if (notify_socket) {
            //通过systemd方式启动redis
            redisSupervisedSystemd();
        }
    } else if (mode == SUPERVISED_UPSTART) {
        return redisSupervisedUpstart();
    } else if (mode == SUPERVISED_SYSTEMD) {
        return redisSupervisedSystemd();
    }
    return 0;
}

守护进程，supervised模式下不可以使用，否则失效。

 int background = server.daemonize && !server.supervised;
 if (background) daemonize();

void daemonize(void) {
    int fd;
    //fork出子进程，exit 父进程
    if (fork() != 0) exit(0); /* parent exits */
    setsid(); /* create a new session */

    if ((fd = open("/dev/null", O_RDWR, 0)) != -1) {
        dup2(fd, STDIN_FILENO);
        dup2(fd, STDOUT_FILENO);
        dup2(fd, STDERR_FILENO);
        if (fd > STDERR_FILENO) close(fd);
    }
}

image.png

image.png

可以看到，启动时显示的pid和启动后进程的pid不一致。

初始化Server

    //初始化server
    initServer();
   //daemonize模式下，在/var/run目录下创建redis.pid文件
    if (background || server.pidfile) createPidFile(); 
    //设置进程名称
    redisSetProcTitle(argv[0]);
    //显示logo
    redisAsciiArt();
    //检查tcp的半连接队列配置
    //查看/proc/sys/net/core/somaxconn中配置的值
    checkTcpBacklogSettings();

事件驱动

    aeSetBeforeSleepProc(server.el,beforeSleep);
    aeSetAfterSleepProc(server.el,afterSleep);
    //包括 select、epoll、kqueue，Redis高性能的原因
    aeMain(server.el);
    aeDeleteEventLoop(server.el);

执行aeMain，进入一个死循环，处理可被处理的文件事件、时间事件。

void aeMain(aeEventLoop *eventLoop) {
    eventLoop->stop = 0;
    while (!eventLoop->stop) {
        if (eventLoop->beforesleep != NULL)
            eventLoop->beforesleep(eventLoop);
        aeProcessEvents(eventLoop, AE_ALL_EVENTS|AE_CALL_AFTER_SLEEP);
    }
}

Redis.png

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