Redis源碼閱讀筆記-服務器啓動和初始化
服務器的啓動
Redis服務器的main函數是在server.c中。node
// server.c
int main(int argc, char **argv) {
struct timeval tv;
int j;
/* 對服務器一些常量等進行設置 */
/* We need to initialize our libraries, and the server configuration. */
#ifdef INIT_SETPROCTITLE_REPLACEMENT
spt_init(argc, argv);
#endif
setlocale(LC_COLLATE,"");
tzset(); /* Populates 'timezone' global. */
// OutOfMemory時的處理，主要是打印到日誌中
zmalloc_set_oom_handler(redisOutOfMemoryHandler);
srand(time(NULL)^getpid());
gettimeofday(&tv,NULL);
char hashseed[16];
getRandomHexChars(hashseed,sizeof(hashseed));
dictSetHashFunctionSeed((uint8_t*)hashseed);
// 判斷是不是sentinel模式（哨兵模式）
server.sentinel_mode = checkForSentinelMode(argc,argv);
// 初始化Redis server的常量配置
initServerConfig();
moduleInitModulesSystem();
/* Store the executable path and arguments in a safe place in order
* to be able to restart the server later. */
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_argv[j] = zstrdup(argv[j]);
/* We need to init sentinel right now as parsing the configuration file
* in sentinel mode will have the effect of populating the sentinel
* data structures with master nodes to monitor. */
if (server.sentinel_mode) {
// 若是是sentinel模式，則進行sentinel的配置初始化
initSentinelConfig();
initSentinel();
}
// 下面是對命令和參數進行處理，判斷是不是執行server啓動的命令，或者其餘命令
/* Check if we need to start in redis-check-rdb/aof mode. We just execute
* the program main. However the program is part of the Redis executable
* so that we can easily execute an RDB check on loading errors. */
// argv[0] 爲執行的程序名稱
// 執行的是否爲redis-check-rdb RDB文件檢查工具
if (strstr(argv[0],"redis-check-rdb") != NULL)
redis_check_rdb_main(argc,argv,NULL);
// 執行的是否爲redis-check-aof AOF文件修復工具
else if (strstr(argv[0],"redis-check-aof") != NULL)
redis_check_aof_main(argc,argv);
// 判斷是否只是輸出提示的的命令操做
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);
}
}
// 獲取指定配置文件的路徑
/* 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();
loadServerConfig(configfile,options);
sdsfree(options);
}
serverLog(LL_WARNING, "oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo");
serverLog(LL_WARNING,
"Redis version=%s, bits=%d, commit=%s, modified=%d, pid=%d, just started",
REDIS_VERSION,
(sizeof(long) == 8) ? 64 : 32,
redisGitSHA1(),
strtol(redisGitDirty(),NULL,10) > 0,
(int)getpid());
if (argc == 1) {
serverLog(LL_WARNING, "Warning: no config file specified, using the default config. In order to specify a config file use %s /path/to/%s.conf", argv[0], server.sentinel_mode ? "sentinel" : "redis");
} else {
serverLog(LL_WARNING, "Configuration loaded");
}
// 定義是upstart仍是systemd接管redis進程
server.supervised = redisIsSupervised(server.supervised_mode);
int background = server.daemonize && !server.supervised;
// 是否在後臺執行
if (background) daemonize();
// 初始化服務
initServer();
if (background || server.pidfile) createPidFile();
redisSetProcTitle(argv[0]);
redisAsciiArt();
checkTcpBacklogSettings();
// 打印部分警告或者提示
if (!server.sentinel_mode) {
/* Things not needed when running in Sentinel mode. */
serverLog(LL_WARNING,"Server initialized");
#ifdef __linux__
linuxMemoryWarnings();
#endif
moduleLoadFromQueue();
loadDataFromDisk();
if (server.cluster_enabled) {
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);
}
}
if (server.ipfd_count > 0)
serverLog(LL_NOTICE,"Ready to accept connections");
if (server.sofd > 0)
serverLog(LL_NOTICE,"The server is now ready to accept connections at %s", server.unixsocket);
} else {
sentinelIsRunning();
}
/* Warning the user about suspicious maxmemory setting. */
if (server.maxmemory > 0 && server.maxmemory < 1024*1024) {
serverLog(LL_WARNING,"WARNING: You specified a maxmemory value that is less than 1MB (current value is %llu bytes). Are you sure this is what you really want?", server.maxmemory);
}
// 設置每次事件循環等待前的事件處理
aeSetBeforeSleepProc(server.el,beforeSleep);
// 設置每次事件循環等待後的事件處理
aeSetAfterSleepProc(server.el,afterSleep);
// 進入事件循環
aeMain(server.el);
aeDeleteEventLoop(server.el);
return 0;
}
整個啓動的順序大概是：linux
- 設置部分全局變量，好比hash種子等。
- 解析命令和命令行參數，若是執行的不是
redis-server或者是redis-server的其餘(好比--version等)命令，則指定對應命令後退出。 - 準備啓動服務，調用
initServer()初始化服務，會開始監聽對應的端口，和把要監控的時間/文件事件添加到EventLoop中。 - 設置EventLoop的 事件循環等待前的事件處理 和 事件循環等待後的事件處理，而後進入
aeMain()事件的監聽和循環，默認的IO多路複用是epoll。
其中ae.c是封裝好的事件循環調用，而ae_epoll.c和ae_select.c等則是封裝epoll和select等的代碼，使它們都由一個統一的接口。redis
服務器初始化initServer()
// server.c
// 初始化服務器，監聽端口，設置事件回調，申請須要的內存等
void initServer(void) {
int j;
// 設置信號的處理
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);
}
// 爲server變量的部分值設置和初始化變量
server.hz = server.config_hz;
server.pid = getpid();// 進程id
server.current_client = NULL;
server.clients = listCreate();
server.clients_index = raxNew();
server.clients_to_close = listCreate();
server.slaves = listCreate();
server.monitors = listCreate();
server.clients_pending_write = listCreate();
server.slaveseldb = -1; /* Force to emit the first SELECT command. */
server.unblocked_clients = listCreate();
server.ready_keys = listCreate();
server.clients_waiting_acks = listCreate();
server.get_ack_from_slaves = 0;
server.clients_paused = 0;
server.system_memory_size = zmalloc_get_memory_size();
// 建立一個能夠共享的對象，主要是SDS結構的對象
createSharedObjects();
// 根據最大客戶端數等，設置文件(socket, pipe等)打開數量限制
adjustOpenFilesLimit();
// 建立EventLoop
server.el = aeCreateEventLoop(server.maxclients+CONFIG_FDSET_INCR);
if (server.el == NULL) {
serverLog(LL_WARNING,
"Failed creating the event loop. Error message: '%s'",
strerror(errno));
exit(1);
}
server.db = zmalloc(sizeof(redisDb)*server.dbnum);
// 監聽TCP端口
/* Open the TCP listening socket for the user commands. */
if (server.port != 0 &&
listenToPort(server.port,server.ipfd,&server.ipfd_count) == C_ERR)
exit(1);
// 監聽Unix scoket
/* Open the listening Unix domain socket. */
if (server.unixsocket != NULL) {
unlink(server.unixsocket); /* don't care if this fails */
server.sofd = anetUnixServer(server.neterr,server.unixsocket,
server.unixsocketperm, server.tcp_backlog);
if (server.sofd == ANET_ERR) {
serverLog(LL_WARNING, "Opening Unix socket: %s", server.neterr);
exit(1);
}
anetNonBlock(NULL,server.sofd);
}
// 判斷是否監聽端口成功
/* Abort if there are no listening sockets at all. */
if (server.ipfd_count == 0 && server.sofd < 0) {
serverLog(LL_WARNING, "Configured to not listen anywhere, exiting.");
exit(1);
}
/* Create the Redis databases, and initialize other internal state. */
// 初始化默認的數據庫，默認爲16個
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(&objectKeyPointerValueDictType,NULL);
server.db[j].watched_keys = dictCreate(&keylistDictType,NULL);
server.db[j].id = j;
server.db[j].avg_ttl = 0;
server.db[j].defrag_later = listCreate();
}
evictionPoolAlloc(); /* Initialize the LRU keys pool. */
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;
server.rdb_child_type = RDB_CHILD_TYPE_NONE;
server.rdb_bgsave_scheduled = 0;
server.child_info_pipe[0] = -1;
server.child_info_pipe[1] = -1;
server.child_info_data.magic = 0;
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;
resetServerStats();
/* A few stats we don't want to reset: server startup time, and peak mem. */
server.stat_starttime = time(NULL);
server.stat_peak_memory = 0;
server.stat_rdb_cow_bytes = 0;
server.stat_aof_cow_bytes = 0;
server.cron_malloc_stats.zmalloc_used = 0;
server.cron_malloc_stats.process_rss = 0;
server.cron_malloc_stats.allocator_allocated = 0;
server.cron_malloc_stats.allocator_active = 0;
server.cron_malloc_stats.allocator_resident = 0;
server.lastbgsave_status = C_OK;
server.aof_last_write_status = C_OK;
server.aof_last_write_errno = 0;
server.repl_good_slaves_count = 0;
/* Create the timer callback, this is our way to process many background
* operations incrementally, like clients timeout, eviction of unaccessed
* expired keys and so forth. */
// 時間事件，雖然這裏設置了1毫秒，可是是爲了保證每一個EventLoop有時間或者timeout後，都能執行
if (aeCreateTimeEvent(server.el, 1, serverCron, NULL, NULL) == AE_ERR) {
serverPanic("Can't create event loop timers.");
exit(1);
}
// 爲監聽的端口的fd設置epoll事件和回調， 針對TCP socket
/* Create an event handler for accepting new connections in TCP and Unix
* domain sockets. */
for (j = 0; j < server.ipfd_count; j++) {
if (aeCreateFileEvent(server.el, server.ipfd[j], AE_READABLE,
acceptTcpHandler,NULL) == AE_ERR)
{
serverPanic(
"Unrecoverable error creating server.ipfd file event.");
}
}
// 爲Unix socket的fd設置epoll事件和回調， 針對Unix socket
if (server.sofd > 0 && aeCreateFileEvent(server.el,server.sofd,AE_READABLE,
acceptUnixHandler,NULL) == AE_ERR) serverPanic("Unrecoverable error creating server.sofd file event.");
// 針對管道的事件回調
/* Register a readable event for the pipe used to awake the event loop
* when a blocked client in a module needs attention. */
if (aeCreateFileEvent(server.el, server.module_blocked_pipe[0], AE_READABLE,
moduleBlockedClientPipeReadable,NULL) == AE_ERR) {
serverPanic(
"Error registering the readable event for the module "
"blocked clients subsystem.");
}
// 是否打開AOF
/* Open the AOF file if needed. */
if (server.aof_state == AOF_ON) {
server.aof_fd = open(server.aof_filename,
O_WRONLY|O_APPEND|O_CREAT,0644);
if (server.aof_fd == -1) {
serverLog(LL_WARNING, "Can't open the append-only file: %s",
strerror(errno));
exit(1);
}
}
// 針對32位系統的內存限制，限制爲3G
/* 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) {
serverLog(LL_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 = MAXMEMORY_NO_EVICTION;
}
// 是否打開redis集羣
if (server.cluster_enabled) clusterInit();
replicationScriptCacheInit();
scriptingInit(1);
slowlogInit();
latencyMonitorInit();
bioInit();
server.initial_memory_usage = zmalloc_used_memory();
}
initServer()主要作了：數據庫
- 獲取系統部分限制，好比文件最大打開數和32位系統下限制最大3G內存使用。
- 開始監聽對應的TCP socket、Unix socket等，並將它們加入到EventLoop中監聽讀事件。
- 將
ServerCron函數加加入到時間事件中。 - 初始化其餘各類功能。
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