Redis Sentinel 源码分析
Sentinel
以下是带有完整注释的 Redis Sentinel 功能的实现代码，源文件在这里：
/* Redis Sentinel implementation
*
* Copyright (c) 2009-2012, Salvatore Sanfilippo sent. */
#define SRI_RECONF_INPROG (1<<12) /* Slave synchronization in progress. */
#define SRI_RECONF_DONE (1<<13) /* Slave synchronized with new master. */
#define SRI_FORCE_FAILOVER (1<<14) /* Force failover with master up. */
#define SRI_SCRIPT_KILL_SENT (1<<15) /* SCRIPT KILL already sent on -BUSY */
#define SRI_DEMOTE (1<<16) /* If the instance claims to be a master, demote
it into a slave sending SLAVEOF. */
// 操作的运行时间间隔
#define SENTINEL_INFO_PERIOD 10000
#define SENTINEL_PING_PERIOD 1000
#define SENTINEL_ASK_PERIOD 1000
#define SENTINEL_PUBLISH_PERIOD 5000
#define SENTINEL_DOWN_AFTER_PERIOD 30000
#define SENTINEL_HELLO_CHANNEL "__sentinel__:hello"
#define SENTINEL_TILT_TRIGGER 2000
#define SENTINEL_TILT_PERIOD (SENTINEL_PING_PERIOD*30)
#define SENTINEL_DEFAULT_SLAVE_PRIORITY 100
#define SENTINEL_PROMOTION_RETRY_PERIOD 30000
#define SENTINEL_SLAVE_RECONF_RETRY_PERIOD 10000
#define SENTINEL_DEFAULT_PARALLEL_SYNCS 1
#define SENTINEL_MIN_LINK_RECONNECT_PERIOD 15000
#define SENTINEL_DEFAULT_FAILOVER_TIMEOUT (60*15*1000)
#define SENTINEL_MAX_PENDING_COMMANDS 100
#define SENTINEL_EXTENDED_SDOWN_MULTIPLIER 10
/* How many milliseconds is an information valid? This applies for instance
* to the reply to SENTINEL IS-MASTER-DOWN-BY-ADDR replies. */
// 超时值
#define SENTINEL_INFO_VALIDITY_TIME 5000
#define SENTINEL_FAILOVER_FIXED_DELAY 5000
#define SENTINEL_FAILOVER_MAX_RANDOM_DELAY 10000
/* Failover machine different states. */
// 故障转移时的状态
#define SENTINEL_FAILOVER_STATE_NONE 0 /* No failover in progress. */
#define SENTINEL_FAILOVER_STATE_WAIT_START 1 /* Wait for failover_start_time*/
#define SENTINEL_FAILOVER_STATE_SELECT_SLAVE 2 /* Select slave to promote */
#define SENTINEL_FAILOVER_STATE_SEND_SLAVEOF_NOONE 3 /* Slave -> Master */
#define SENTINEL_FAILOVER_STATE_WAIT_PROMOTION 4 /* Wait slave to change role */
#define SENTINEL_FAILOVER_STATE_RECONF_SLAVES 5 /* SLAVEOF newmaster */
#define SENTINEL_FAILOVER_STATE_WAIT_NEXT_SLAVE 6 /* wait replication */
#define SENTINEL_FAILOVER_STATE_ALERT_CLIENTS 7 /* Run user script. */
#define SENTINEL_FAILOVER_STATE_WAIT_ALERT_SCRIPT 8 /* Wait script exec. */
#define SENTINEL_FAILOVER_STATE_DETECT_END 9 /* Check for failover end. */
#define SENTINEL_FAILOVER_STATE_UPDATE_CONFIG 10 /* Monitor promoted slave. */
// 主从服务器之间的连接状态
#define SENTINEL_MASTER_LINK_STATUS_UP 0
#define SENTINEL_MASTER_LINK_STATUS_DOWN 1
/* Generic flags that can be used with different functions. */
// 通用返回值
#define SENTINEL_NO_FLAGS 0
#define SENTINEL_GENERATE_EVENT 1
#define SENTINEL_LEADER 2
#define SENTINEL_OBSERVER 4
/* Script execution flags and limits. */
// 脚本执行状态和限制
#define SENTINEL_SCRIPT_NONE 0
#define SENTINEL_SCRIPT_RUNNING 1
#define SENTINEL_SCRIPT_MAX_QUEUE 256
#define SENTINEL_SCRIPT_MAX_RUNNING 16
#define SENTINEL_SCRIPT_MAX_RUNTIME 60000 /* 60 seconds max exec time. */
#define SENTINEL_SCRIPT_MAX_RETRY 10
#define SENTINEL_SCRIPT_RETRY_DELAY 30000 /* 30 seconds between retries. */
typedef struct sentinelRedisInstance {
// 实例的类型，以及该实例的当前状态
int flags; /* See SRI_... defines */
// 实例的名字
char *name; /* Master name from the point of view of this sentinel. */
// 实例的运行 ID
char *runid; /* run ID of this instance. */
// 实例的地址
sentinelAddr *addr; /* Master host. */
// 用于发送命令的异步连接
redisAsyncContext *cc; /* Hiredis context for commands. */
// 用于执行 SUBSCRIBE 命令、接收频道信息的异步连接
// 仅在实例为主服务器时使用
redisAsyncContext *pc; /* Hiredis context for Pub / Sub. */
// 已发送但尚未回复的命令数量
int pending_commands; /* Number of commands sent waiting for a reply. */
// cc 连接的创建时间
mstime_t cc_conn_time; /* cc connection time. */
// pc 连接的创建时间
mstime_t pc_conn_time; /* pc connection time. */
// 最后一次从这个实例接收信息的时间
mstime_t pc_last_activity; /* Last time we received any message. */
// 实例最后一次返回正确的 PING 命令回复的时间
mstime_t last_avail_time; /* Last time the instance replied to ping with
a reply we consider valid. */
// 实例最后一次返回 PING 命令的时间，无论内容正确与否
mstime_t last_pong_time; /* Last time the instance replied to ping,
whatever the reply was. That's used to check
if the link is idle and must be reconnected. */
// 最后一次向频道发送问候信息的时间
// 只在当前实例为 sentinel 时使用
mstime_t last_pub_time; /* Last time we sent hello via Pub/Sub. */
// 最后一次接收到这个 sentinel 发来的问候信息的时间
// 只在当前实例为 sentinel 时使用
mstime_t last_hello_time; /* Only used if SRI_SENTINEL is set. Last time
we received an hello from this Sentinel
via Pub/Sub. */
// 最后一次回复 SENTINEL is-master-down-by-addr 命令的时间
// 只在当前实例为 sentinel 时使用
mstime_t last_master_down_reply_time; /* Time of last reply to
SENTINEL is-master-down command. */
// 实例被判断为 SDOWN 状态的时间
mstime_t s_down_since_time; /* Subjectively down since time. */
// 实例被判断为 ODOWN 状态的时间
mstime_t o_down_since_time; /* Objectively down since time. */
// 实例无响应多久才会被判断为下线，
// 也即是 SENTINEL down-after-milliseconds 选项所设定的值
mstime_t down_after_period; /* Consider it down after that period. */
// 从实例获取 INFO 命令的回复的时间
mstime_t info_refresh; /* Time at which we received INFO output from it. */
/* Master specific. */
/* 主服务器实例特有的属性 -------------------------------------------------------------*/
// 其他同样监控这个主服务器的所有 sentinel
dict *sentinels; /* Other sentinels monitoring the same master. */
// 这个主服务器的所有从服务器（仅在实例为主服务器时使用）
dict *slaves; /* Slaves for this master instance. */
// 判断这个主服务器失效所需的 sentinel 数量
// 也即是 SENTINEL monitor 选项中的 quorum 参数
int quorum; /* Number of sentinels that need to agree on failure. */
// 在执行故障转移操作时，可以同时对主服务器进行同步的从服务器数量
// 也即是 SENTINEL parallel-syncs 选项的值
int parallel_syncs; /* How many slaves to reconfigure at same time. */
// 连接主服务器和从服务器所需的密码
char *auth_pass; /* Password to use for AUTH against master & slaves. */
/* Slave specific. */
/* 从服务器实例特有的属性 -------------------------------------------------------------*/
// 主从服务器连接断开的时间
mstime_t master_link_down_time; /* Slave replication link down time. */
// 从服务器优先级
int slave_priority; /* Slave priority according to its INFO output. */
// 执行故障转移操作时，从服务器发送 SLAVEOF 命令的时间
mstime_t slave_reconf_sent_time; /* Time at which we sent SLAVE OF */
// 指向主服务器实例的指针
struct sentinelRedisInstance *master; /* Master instance if SRI_SLAVE is set. */
// INFO 命令的回复中记录的主服务器 hostname
char *slave_master_host; /* Master host as reported by INFO */
// INFO 命令的回复中记录的主服务器端口号
int slave_master_port; /* Master port as reported by INFO */
// INFO 命令的回复中记录的主从服务器连接状态
int slave_master_link_status; /* Master link status as reported by INFO */
/* Failover */
/* 故障转移相关属性 -------------------------------------------------------------------*/
// 如果这是一个主服务器实例，那么 leader 将是负责进行故障转移的 Sentinel 的运行 ID 。
// 如果这是一个 Sentinel 实例，那么 leader 就是被选举出来的领头 Sentinel 。
// 这个域只在 Sentinel 实例的 flags 属性的 SRI_MASTER_DOWN 标志处于打开状态时才有效。
char *leader; /* If this is a master instance, this is the runid of
the Sentinel that should perform the failover. If
this is a Sentinel, this is the runid of the Sentinel
that this other Sentinel is voting as leader.
This field is valid only if SRI_MASTER_DOWN is
set on the Sentinel instance. */
// 故障转移操作的当前状态
int failover_state; /* See SENTINEL_FAILOVER_STATE_* defines. */
// 状态改变的时间
mstime_t failover_state_change_time;
// 故障转移开始的时间
mstime_t failover_start_time; /* When to start to failover if leader. */
// 故障转移状态之间的变幻所能接受的最大时间
// 超过这个时间状态也不改变，表示故障转移操作进度中止，或者过分缓慢
// 也即是 SENTINEL failover-timeout 选项的值
mstime_t failover_timeout; /* Max time to refresh failover state. */
// 指向被提升为新主服务器的从服务器的指针
struct sentinelRedisInstance *promoted_slave; /* Promoted slave instance. */
/* Scripts executed to notify admin or reconfigure clients: when they
* are set to NULL no script is executed. */
// 一个文件路径，保存着 WARNING 级别的事件发生时执行的，
// 用于通知管理员的脚本的地址
char *notification_script;
// 一个文件路径，保存着故障转移执行之前、之后、或者被中止时，
// 需要执行的脚本的地址
char *client_reconfig_script;
} sentinelRedisInstance;
/* Main state. */
// SENTINEL 状态
struct sentinelState {
// 保存了所有被这个 sentinel 监视的主服务器
// 字典的键是主服务器的名字，值则是一个指向 sentinelRedisInstance 结构的指针
dict *masters; /* Dictionary of master sentinelRedisInstances.
Key is the instance name, value is the
sentinelRedisInstance structure pointer. */
// 是否进入了 TILT 模式
int tilt; /* Are we in TILT mode? */
// 现在正在执行的脚本的数量
int running_scripts; /* Number of scripts in execution right now. */
// 进入 TILT 模式的时间
mstime_t tilt_start_time; /* When TITL started. */
// 上一次运行 sentinel 程序的时间
mstime_t previous_time; /* Time last time we ran the time handler. */
// 需要执行的脚本的队列
list *scripts_queue; /* Queue of user scripts to execute. */
} sentinel;
/* A script execution job. */
// 脚本运行状态
typedef struct sentinelScriptJob {
// 标志，记录了脚本是否运行
int flags; /* Script job flags: SENTINEL_SCRIPT_* */
// 该脚本的已尝试执行次数
int retry_num; /* Number of times we tried to execute it. */
// 要传给脚本的参数
char **argv; /* Arguments to call the script. */
// 开始运行脚本的时间
mstime_t start_time; /* Script execution time if the script is running,
otherwise 0 if we are allowed to retry the
execution at any time. If the script is not
running and it's not 0, it means: do not run
before the specified time. */
// 脚本由子进程执行，该属性记录子进程的 pid
pid_t pid; /* Script execution pid. */
} sentinelScriptJob;
/* ======================= hiredis ae.c adapters =============================
* Note: this implementation is taken from hiredis/adapters/ae.h, however
* we have our modified copy for Sentinel in order to use our allocator
* and to have full control over how the adapter works. */
// 客户端适配器（adapter）结构
typedef struct redisAeEvents {
// 客户端连接上下文
redisAsyncContext *context;
// 服务器的事件循环
aeEventLoop *loop;
// 套接字
int fd;
// 记录读事件以及写事件是否就绪
int reading, writing;
} redisAeEvents;
// 读事件处理器
static void redisAeReadEvent(aeEventLoop *el, int fd, void *privdata, int mask) {
((void)el); ((void)fd); ((void)mask);
redisAeEvents *e = (redisAeEvents*)privdata;
// 从连接中进行读取
redisAsyncHandleRead(e->context);
}
// 写事件处理器
static void redisAeWriteEvent(aeEventLoop *el, int fd, void *privdata, int mask) {
((void)el); ((void)fd); ((void)mask);
redisAeEvents *e = (redisAeEvents*)privdata;
// 从连接中进行写入
redisAsyncHandleWrite(e->context);
}
// 将读事件处理器安装到事件循环中
static void redisAeAddRead(void *privdata) {
redisAeEvents *e = (redisAeEvents*)privdata;
aeEventLoop *loop = e->loop;
// 如果读事件处理器未安装，那么进行安装
if (!e->reading) {
e->reading = 1;
aeCreateFileEvent(loop,e->fd,AE_READABLE,redisAeReadEvent,e);
}
}
// 从事件循环中删除读事件处理器
static void redisAeDelRead(void *privdata) {
redisAeEvents *e = (redisAeEvents*)privdata;
aeEventLoop *loop = e->loop;
// 仅在读事件处理器已安装的情况下进行删除
if (e->reading) {
e->reading = 0;
aeDeleteFileEvent(loop,e->fd,AE_READABLE);
}
}
// 将写事件处理器安装到事件循环中
static void redisAeAddWrite(void *privdata) {
redisAeEvents *e = (redisAeEvents*)privdata;
aeEventLoop *loop = e->loop;
if (!e->writing) {
e->writing = 1;
aeCreateFileEvent(loop,e->fd,AE_WRITABLE,redisAeWriteEvent,e);
}
}
// 从事件循环中删除写事件处理器
static void redisAeDelWrite(void *privdata) {
redisAeEvents *e = (redisAeEvents*)privdata;
aeEventLoop *loop = e->loop;
if (e->writing) {
e->writing = 0;
aeDeleteFileEvent(loop,e->fd,AE_WRITABLE);
}
}
// 清理事件
static void redisAeCleanup(void *privdata) {
redisAeEvents *e = (redisAeEvents*)privdata;
redisAeDelRead(privdata);
redisAeDelWrite(privdata);
zfree(e);
}
// 为上下文 ae 和事件循环 loop 创建 hiredis 适配器
// 并设置相关的异步处理函数
static int redisAeAttach(aeEventLoop *loop, redisAsyncContext *ac) {
redisContext *c = &(ac->c);
redisAeEvents *e;
/* Nothing should be attached when something is already attached */
if (ac->ev.data != NULL)
return REDIS_ERR;
/* Create container for context and r/w events */
// 创建适配器
e = (redisAeEvents*)zmalloc(sizeof(*e));
e->context = ac;
e->loop = loop;
e->fd = c->fd;
e->reading = e->writing = 0;
/* Register functions to start/stop listening for events */
// 设置异步调用函数
ac->ev.addRead = redisAeAddRead;
ac->ev.delRead = redisAeDelRead;
ac->ev.addWrite = redisAeAddWrite;
ac->ev.delWrite = redisAeDelWrite;
ac->ev.cleanup = redisAeCleanup;
ac->ev.data = e;
return REDIS_OK;
}
/* ============================= Prototypes ================================= */
void sentinelLinkEstablishedCallback(const redisAsyncContext *c, int status);
void sentinelDisconnectCallback(const redisAsyncContext *c, int status);
void sentinelReceiveHelloMessages(redisAsyncContext *c, void *reply, void *privdata);
sentinelRedisInstance *sentinelGetMasterByName(char *name);
char *sentinelGetSubjectiveLeader(sentinelRedisInstance *master);
char *sentinelGetObjectiveLeader(sentinelRedisInstance *master);
int yesnotoi(char *s);
void sentinelDisconnectInstanceFromContext(const redisAsyncContext *c);
void sentinelKillLink(sentinelRedisInstance *ri, redisAsyncContext *c);
const char *sentinelRedisInstanceTypeStr(sentinelRedisInstance *ri);
void sentinelAbortFailover(sentinelRedisInstance *ri);
void sentinelEvent(int level, char *type, sentinelRedisInstance *ri, const char *fmt, ...);
sentinelRedisInstance *sentinelSelectSlave(sentinelRedisInstance *master);
void sentinelScheduleScriptExecution(char *path, ...);
void sentinelStartFailover(sentinelRedisInstance *master, int state);
void sentinelDiscardReplyCallback(redisAsyncContext *c, void *reply, void *privdata);
/* ========================= Dictionary types =============================== */
unsigned int dictSdsHash(const void *key);
int dictSdsKeyCompare(void *privdata, const void *key1, const void *key2);
void releaseSentinelRedisInstance(sentinelRedisInstance *ri);
void dictInstancesValDestructor (void *privdata, void *obj) {
releaseSentinelRedisInstance(obj);
}
/* Instance name (sds) -> instance (sentinelRedisInstance pointer)
*
* also used for: sentinelRedisInstance->sentinels dictionary that maps
* sentinels ip:port to last seen time in Pub/Sub hello message. */
// 这个字典类型有两个作用：
// 1） 将实例名字映射到一个 sentinelRedisInstance 指针
// 2） 将 sentinelRedisInstance 指针映射到一个字典，
// 字典的键是 Sentinel 的 ip:port 地址，
// 字典的值是该 Sentinel 最后一次向频道发送信息的时间
dictType instancesDictType = {
dictSdsHash, /* hash function */
NULL, /* key dup */
NULL, /* val dup */
dictSdsKeyCompare, /* key compare */
NULL, /* key destructor */
dictInstancesValDestructor /* val destructor */
};
/* Instance runid (sds) -> votes (long casted to void*)
*
* This is useful into sentinelGetObjectiveLeader() function in order to
* count the votes and understand who is the leader. */
// 将一个运行 ID 映射到一个 cast 成 void* 类型的 long 值的投票数量上
// 用于统计客观 leader sentinel
dictType leaderVotesDictType = {
dictSdsHash, /* hash function */
NULL, /* key dup */
NULL, /* val dup */
dictSdsKeyCompare, /* key compare */
NULL, /* key destructor */
NULL /* val destructor */
};
/* =========================== Initialization =============================== */
void sentinelCommand(redisClient *c);
void sentinelInfoCommand(redisClient *c);
// 服务器在 sentinel 模式下可执行的命令
struct redisCommand sentinelcmds[] = {
{"ping",pingCommand,1,"",0,NULL,0,0,0,0,0},
{"sentinel",sentinelCommand,-2,"",0,NULL,0,0,0,0,0},
{"subscribe",subscribeCommand,-2,"",0,NULL,0,0,0,0,0},
{"unsubscribe",unsubscribeCommand,-1,"",0,NULL,0,0,0,0,0},
{"psubscribe",psubscribeCommand,-2,"",0,NULL,0,0,0,0,0},
{"punsubscribe",punsubscribeCommand,-1,"",0,NULL,0,0,0,0,0},
{"info",sentinelInfoCommand,-1,"",0,NULL,0,0,0,0,0}
};
/* This function overwrites a few normal Redis config default with Sentinel
* specific defaults. */
// 这个函数会用 Sentinel 所属的属性覆盖服务器默认的属性
void initSentinelConfig(void) {
server.port = REDIS_SENTINEL_PORT;
}
/* Perform the Sentinel mode initialization. */
// 以 Sentinel 模式初始化服务器
void initSentinel(void) {
int j;
/* Remove usual Redis commands from the command table, then just add
* the SENTINEL command. */
// 清空 Redis 服务器的命令表（该表用于普通模式）
dictEmpty(server.commands);
// 将 SENTINEL 模式所用的命令添加进命令表
for (j = 0; j < sizeof(sentinelcmds)/sizeof(sentinelcmds[0]); j++) {
int retval;
struct redisCommand *cmd = sentinelcmds+j;
retval = dictAdd(server.commands, sdsnew(cmd->name), cmd);
redisAssert(retval == DICT_OK);
}
/* Initialize various data structures. */
// 初始化记录主服务器信息的字典
sentinel.masters = dictCreate(&instancesDictType,NULL);
// 初始化 TILT 模式的相关选项
sentinel.tilt = 0;
sentinel.tilt_start_time = 0;
sentinel.previous_time = mstime();
// 初始化脚本相关选项
sentinel.running_scripts = 0;
sentinel.scripts_queue = listCreate();
}
/* ============================== sentinelAddr ============================== */
/* Create a sentinelAddr object and return it on success.
*
* 创建一个 sentinel 地址对象，并在创建成功时返回该对象。
*
* On error NULL is returned and errno is set to:
*
* 函数在出错时返回 NULL ，并将 errnor 设为以下值：
*
* ENOENT: Can't resolve the hostname.
* 不能解释 hostname
*
* EINVAL: Invalid port number.
* 端口号不正确
*/
sentinelAddr *createSentinelAddr(char *hostname, int port) {
char buf[32];
sentinelAddr *sa;
// 检查端口号
if (port <= 0 || port > 65535) {
errno = EINVAL;
return NULL;
}
// 检查并创建地址
if (anetResolve(NULL,hostname,buf,sizeof(buf)) == ANET_ERR) {
errno = ENOENT;
return NULL;
}
// 创建并返回地址结构
sa = zmalloc(sizeof(*sa));
sa->ip = sdsnew(buf);
sa->port = port;
return sa;
}
/* Free a Sentinel address. Can't fail. */
void releaseSentinelAddr(sentinelAddr *sa) {
sdsfree(sa->ip);
zfree(sa);
}
/* =========================== Events notification ========================== */
/* Send an event to log, pub/sub, user notification script.
*
* 将事件发送到日志、频道，以及用户提醒脚本。
*
* 'level' is the log level for logging. Only REDIS_WARNING events will trigger
* the execution of the user notification script.
*
* level 是日志的级别。只有 REDIS_WARNING 级别的日志会触发用户提醒脚本。
*
* 'type' is the message type, also used as a pub/sub channel name.
*
* type 是信息的类型，也用作频道的名字。
*
* 'ri', is the redis instance target of this event if applicable, and is
* used to obtain the path of the notification script to execute.
*
* ri 是引发事件的 Redis 实例，它可以用来获取可执行的用户脚本。
*
* The remaining arguments are printf-alike.
*
* 剩下的都是类似于传给 printf 函数的参数。
*
* If the format specifier starts with the two characters "%@" then ri is
* not NULL, and the message is prefixed with an instance identifier in the
* following format:
*
* 如果格式指定以 "%@" 两个字符开头，并且 ri 不为空，
* 那么信息将使用以下实例标识符为开头：
*
*
*
* If the instance type is not master, than the additional string is
* added to specify the originating master:
*
* 如果实例的类型不是主服务器，那么以下内容会被追加到信息的后面，
* 用于指定目标主服务器：
*
* @
*
* Any other specifier after "%@" is processed by printf itself.
*
* "%@" 之后的其他指派器（specifier）都和 printf 函数所使用的指派器一样。
*/
void sentinelEvent(int level, char *type, sentinelRedisInstance *ri,
const char *fmt, ...) {
va_list ap;
// 日志字符串
char msg[REDIS_MAX_LOGMSG_LEN];
robj *channel, *payload;
/* Handle %@ */
// 处理 %@
if (fmt[0] == '%' && fmt[1] == '@') {
// 如果 ri 实例是主服务器，那么 master 就是 NULL
// 否则 ri 就是一个从服务器或者 sentinel ，而 master 就是该实例的主服务器
//
// sentinelRedisInstance *master = NULL;
// if (~(ri->flags & SRI_MASTER))
// master = ri->master;
sentinelRedisInstance *master = (ri->flags & SRI_MASTER) ?
NULL : ri->master;
if (master) {
// ri 不是主服务器
snprintf(msg, sizeof(msg), "%s %s %s %d @ %s %s %d",
// 打印 ri 的类型
sentinelRedisInstanceTypeStr(ri),
// 打印 ri 的名字、IP 和端口号
ri->name, ri->addr->ip, ri->addr->port,
// 打印 ri 的主服务器的名字、 IP 和端口号
master->name, master->addr->ip, master->addr->port);
} else {
// ri 是主服务器
snprintf(msg, sizeof(msg), "%s %s %s %d",
// 打印 ri 的类型
sentinelRedisInstanceTypeStr(ri),
// 打印 ri 的名字、IP 和端口号
ri->name, ri->addr->ip, ri->addr->port);
}
// 跳过已处理的 "%@" 字符
fmt += 2;
} else {
msg[0] = '\0';
}
/* Use vsprintf for the rest of the formatting if any. */
// 打印之后的内容，格式和平常的 printf 一样
if (fmt[0] != '\0') {
va_start(ap, fmt);
vsnprintf(msg+strlen(msg), sizeof(msg)-strlen(msg), fmt, ap);
va_end(ap);
}
/* Log the message if the log level allows it to be logged. */
// 如果日志的级别足够高的话，那么记录到日志中
if (level >= server.verbosity)
redisLog(level,"%s %s",type,msg);
/* Publish the message via Pub/Sub if it's not a debugging one. */
// 如果日志不是 DEBUG 日志，那么将它发送到频道中
if (level != REDIS_DEBUG) {
// 频道
channel = createStringObject(type,strlen(type));
// 内容
payload = createStringObject(msg,strlen(msg));
// 发送信息
pubsubPublishMessage(channel,payload);
decrRefCount(channel);
decrRefCount(payload);
}
/* Call the notification script if applicable. */
// 如果有需要的话，调用提醒脚本
if (level == REDIS_WARNING && ri != NULL) {
sentinelRedisInstance *master = (ri->flags & SRI_MASTER) ?
ri : ri->master;
if (master->notification_script) {
sentinelScheduleScriptExecution(master->notification_script,
type,msg,NULL);
}
}
}
/* ============================ script execution ============================ */
/* Release a script job structure and all the associated data. */
void sentinelReleaseScriptJob(sentinelScriptJob *sj) {
int j = 0;
while(sj->argv[j]) sdsfree(sj->argv[j++]);
zfree(sj->argv);
zfree(sj);
}
// 将给定参数和脚本放入队列
#define SENTINEL_SCRIPT_MAX_ARGS 16
void sentinelScheduleScriptExecution(char *path, ...) {
va_list ap;
char *argv[SENTINEL_SCRIPT_MAX_ARGS+1];
int argc = 1;
sentinelScriptJob *sj;
// 生成参数
va_start(ap, path);
while(argc < SENTINEL_SCRIPT_MAX_ARGS) {
argv[argc] = va_arg(ap,char*);
if (!argv[argc]) break;
argv[argc] = sdsnew(argv[argc]); /* Copy the string. */
argc++;
}
va_end(ap);
argv[0] = sdsnew(path);
// 初始化脚本结构
sj = zmalloc(sizeof(*sj));
sj->flags = SENTINEL_SCRIPT_NONE;
sj->retry_num = 0;
sj->argv = zmalloc(sizeof(char*)*(argc+1));
sj->start_time = 0;
sj->pid = 0;
memcpy(sj->argv,argv,sizeof(char*)*(argc+1));
// 添加到等待执行脚本队列的末尾， FIFO
listAddNodeTail(sentinel.scripts_queue,sj);
/* Remove the oldest non running script if we already hit the limit. */
// 如果入队的脚本数量太多，那么移除最旧的未执行脚本
if (listLength(sentinel.scripts_queue) > SENTINEL_SCRIPT_MAX_QUEUE) {
listNode *ln;
listIter li;
listRewind(sentinel.scripts_queue,&li);
while ((ln = listNext(&li)) != NULL) {
sj = ln->value;
// 不删除正在运行的脚本
if (sj->flags & SENTINEL_SCRIPT_RUNNING) continue;
/* The first node is the oldest as we add on tail. */
listDelNode(sentinel.scripts_queue,ln);
sentinelReleaseScriptJob(sj);
break;
}
redisAssert(listLength(sentinel.scripts_queue) <=
SENTINEL_SCRIPT_MAX_QUEUE);
}
}
/* Lookup a script in the scripts queue via pid, and returns the list node
* (so that we can easily remove it from the queue if needed). */
// 根据 pid ，查找正在运行中的脚本
listNode *sentinelGetScriptListNodeByPid(pid_t pid) {
listNode *ln;
listIter li;
listRewind(sentinel.scripts_queue,&li);
while ((ln = listNext(&li)) != NULL) {
sentinelScriptJob *sj = ln->value;
if ((sj->flags & SENTINEL_SCRIPT_RUNNING) && sj->pid == pid)
return ln;
}
return NULL;
}
/* Run pending scripts if we are not already at max number of running
* scripts. */
// 运行等待执行的脚本
void sentinelRunPendingScripts(void) {
listNode *ln;
listIter li;
mstime_t now = mstime();
/* Find jobs that are not running and run them, from the top to the
* tail of the queue, so we run older jobs first. */
// 如果运行的脚本数量未超过最大值，
// 那么从 FIFO 队列中取出未运行的脚本，并运行该脚本
listRewind(sentinel.scripts_queue,&li);
while (sentinel.running_scripts < SENTINEL_SCRIPT_MAX_RUNNING &&
(ln = listNext(&li)) != NULL)
{
sentinelScriptJob *sj = ln->value;
pid_t pid;
/* Skip if already running. */
// 跳过已运行脚本
if (sj->flags & SENTINEL_SCRIPT_RUNNING) continue;
/* Skip if it's a retry, but not enough time has elapsed. */
// 这是一个重试脚本，但它刚刚执行完，稍后再重试
if (sj->start_time && sj->start_time > now) continue;
// 打开运行标记
sj->flags |= SENTINEL_SCRIPT_RUNNING;
// 记录开始时间
sj->start_time = mstime();
// 增加重试计数器
sj->retry_num++;
// 创建子进程
pid = fork();
if (pid == -1) {
// 创建子进程失败
/* Parent (fork error).
* We report fork errors as signal 99, in order to unify the
* reporting with other kind of errors. */
sentinelEvent(REDIS_WARNING,"-script-error",NULL,
"%s %d %d", sj->argv[0], 99, 0);
sj->flags &= ~SENTINEL_SCRIPT_RUNNING;
sj->pid = 0;
} else if (pid == 0) {
// 子进程执行脚本
/* Child */
execve(sj->argv[0],sj->argv,environ);
/* If we are here an error occurred. */
_exit(2); /* Don't retry execution. */
} else {
// 父进程
// 增加运行脚本计数器
sentinel.running_scripts++;
// 记录 pid
sj->pid = pid;
// 发送脚本运行信号
sentinelEvent(REDIS_DEBUG,"+script-child",NULL,"%ld",(long)pid);
}
}
}
/* How much to delay the execution of a script that we need to retry after
* an error?
*
* We double the retry delay for every further retry we do. So for instance
* if RETRY_DELAY is set to 30 seconds and the max number of retries is 10
* starting from the second attempt to execute the script the delays are:
* 30 sec, 60 sec, 2 min, 4 min, 8 min, 16 min, 32 min, 64 min, 128 min. */
// 计算重试脚本前的延迟时间
mstime_t sentinelScriptRetryDelay(int retry_num) {
mstime_t delay = SENTINEL_SCRIPT_RETRY_DELAY;
while (retry_num-- > 1) delay *= 2;
return delay;
}
/* Check for scripts that terminated, and remove them from the queue if the
* script terminated successfully. If instead the script was terminated by
* a signal, or returned exit code "1", it is scheduled to run again if
* the max number of retries did not already elapsed. */
// 检查脚本的退出状态，并在脚本成功退出时，将脚本从队列中删除。
// 如果脚本被信号终结，或者返回退出代码 1 ，那么只要该脚本的重试次数未超过限制
// 那么该脚本就会被调度，并等待重试
void sentinelCollectTerminatedScripts(void) {
int statloc;
pid_t pid;
// 获取子进程信号
while ((pid = wait3(&statloc,WNOHANG,NULL)) > 0) {
int exitcode = WEXITSTATUS(statloc);
int bysignal = 0;
listNode *ln;
sentinelScriptJob *sj;
// 发送脚本终结信号
if (WIFSIGNALED(statloc)) bysignal = WTERMSIG(statloc);
sentinelEvent(REDIS_DEBUG,"-script-child",NULL,"%ld %d %d",
(long)pid, exitcode, bysignal);
// 在队列中安 pid 查找脚本
ln = sentinelGetScriptListNodeByPid(pid);
if (ln == NULL) {
redisLog(REDIS_WARNING,"wait3() returned a pid (%ld) we can't find in our scripts execution queue!", (long)pid);
continue;
}
sj = ln->value;
/* If the script was terminated by a signal or returns an
* exit code of "1" (that means: please retry), we reschedule it
* if the max number of retries is not already reached. */
if ((bysignal || exitcode == 1) &&
sj->retry_num != SENTINEL_SCRIPT_MAX_RETRY)
{
// 重试脚本
sj->flags &= ~SENTINEL_SCRIPT_RUNNING;
sj->pid = 0;
sj->start_time = mstime() +
sentinelScriptRetryDelay(sj->retry_num);
} else {
/* Otherwise let's remove the script, but log the event if the
* execution did not terminated in the best of the ways. */
// 发送脚本执行错误事件
if (bysignal || exitcode != 0) {
sentinelEvent(REDIS_WARNING,"-script-error",NULL,
"%s %d %d", sj->argv[0], bysignal, exitcode);
}
// 将脚本从队列中删除
listDelNode(sentinel.scripts_queue,ln);
sentinelReleaseScriptJob(sj);
sentinel.running_scripts--;
}
}
}
/* Kill scripts in timeout, they'll be collected by the
* sentinelCollectTerminatedScripts() function. */
// 杀死超时脚本，这些脚本会被 sentinelCollectTerminatedScripts 函数回收处理
void sentinelKillTimedoutScripts(void) {
listNode *ln;
listIter li;
mstime_t now = mstime();
// 遍历队列中的所有脚本
listRewind(sentinel.scripts_queue,&li);
while ((ln = listNext(&li)) != NULL) {
sentinelScriptJob *sj = ln->value;
// 选出那些正在执行，并且执行时间超过限制的脚本
if (sj->flags & SENTINEL_SCRIPT_RUNNING &&
(now - sj->start_time) > SENTINEL_SCRIPT_MAX_RUNTIME)
{
// 发送脚本超时事件
sentinelEvent(REDIS_WARNING,"-script-timeout",NULL,"%s %ld",
sj->argv[0], (long)sj->pid);
// 杀死脚本进程
kill(sj->pid,SIGKILL);
}
}
}
/* Implements SENTINEL PENDING-SCRIPTS command. */
// 打印脚本队列中所有脚本的状态
void sentinelPendingScriptsCommand(redisClient *c) {
listNode *ln;
listIter li;
addReplyMultiBulkLen(c,listLength(sentinel.scripts_queue));
listRewind(sentinel.scripts_queue,&li);
while ((ln = listNext(&li)) != NULL) {
sentinelScriptJob *sj = ln->value;
int j = 0;
addReplyMultiBulkLen(c,10);
addReplyBulkCString(c,"argv");
while (sj->argv[j]) j++;
addReplyMultiBulkLen(c,j);
j = 0;
while (sj->argv[j]) addReplyBulkCString(c,sj->argv[j++]);
addReplyBulkCString(c,"flags");
addReplyBulkCString(c,
(sj->flags & SENTINEL_SCRIPT_RUNNING) ? "running" : "scheduled");
addReplyBulkCString(c,"pid");
addReplyBulkLongLong(c,sj->pid);
if (sj->flags & SENTINEL_SCRIPT_RUNNING) {
addReplyBulkCString(c,"run-time");
addReplyBulkLongLong(c,mstime() - sj->start_time);
} else {
mstime_t delay = sj->start_time ? (sj->start_time-mstime()) : 0;
if (delay < 0) delay = 0;
addReplyBulkCString(c,"run-delay");
addReplyBulkLongLong(c,delay);
}
addReplyBulkCString(c,"retry-num");
addReplyBulkLongLong(c,sj->retry_num);
}
}
/* This function calls, if any, the client reconfiguration script with the
* following parameters:
*
* 当该函数执行时，使用以下格式的参数调用客户端重配置脚本
*
*
*
* It is called every time a failover starts, ends, or is aborted.
*
* 这个脚本会在故障转移的开始、结束或者中止时执行。
*
* 根据状态的不同，以及实例类型的不同， state 参数和 role 参数有以下选择：
*
* is "start", "end" or "abort".
* is either "leader" or "observer".
*
* from/to fields are respectively master -> promoted slave addresses for
* "start" and "end", or the reverse (promoted slave -> master) in case of
* "abort".
*
* from 和 to 参数表示故障转移开始和结束时的旧 master 到新 master 的转换
* 而当故障转移被中止时，该参数代表新 master 到旧 master 的转换
*/
void sentinelCallClientReconfScript(sentinelRedisInstance *master, int role, char *state, sentinelAddr *from, sentinelAddr *to) {
char fromport[32], toport[32];
if (master->client_reconfig_script == NULL) return;
ll2string(fromport,sizeof(fromport),from->port);
ll2string(toport,sizeof(toport),to->port);
// 将给定参数和脚本放进度列，等待执行
sentinelScheduleScriptExecution(master->client_reconfig_script,
master->name,
(role == SENTINEL_LEADER) ? "leader" : "observer",
state, from->ip, fromport, to->ip, toport, NULL);
}
/* ========================== sentinelRedisInstance ========================= */
/* Create a redis instance, the following fields must be populated by the
* caller if needed:
*
* 创建一个 Redis 实例，在有需要时，以下两个域需要从调用者提取：
*
* runid: set to NULL but will be populated once INFO output is received.
* 设置为 NULL ，并在接收到 INFO 命令的回复时设置
*
* info_refresh: is set to 0 to mean that we never received INFO so far.
* 如果这个值为 0 ，那么表示我们未收到过 INFO 信息。
*
* If SRI_MASTER is set into initial flags the instance is added to
* sentinel.masters table.
*
* 如果 flags 参数为 SRI_MASTER ，
* 那么这个实例会被添加到 sentinel.masters 表。
*
* if SRI_SLAVE or SRI_SENTINEL is set then 'master' must be not NULL and the
* instance is added into master->slaves or master->sentinels table.
*
* 如果 flags 为 SRI_SLAVE 或者 SRI_SENTINEL ，
* 那么 master 参数不能为 NULL ，
* SRI_SLAVE 类型的实例会被添加到 master->slaves 表中，
* 而 SRI_SENTINEL 类型的实例则会被添加到 master->sentinels 表中。
*
* If the instance is a slave or sentinel, the name parameter is ignored and
* is created automatically as hostname:port.
*
* 如果实例是从服务器或者 sentinel ，那么 name 参数会被自动忽略，
* 实例的名字会被自动设置为 hostname:port 。
*
* The function fails if hostname can't be resolved or port is out of range.
* When this happens NULL is returned and errno is set accordingly to the
* createSentinelAddr() function.
*
* 当 hostname 不能被解释，或者超出范围时，函数将失败。
* 函数将返回 NULL ，并设置 errno 变量，
* 具体的出错值请参考 createSentinelAddr() 函数。
*
* The function may also fail and return NULL with errno set to EBUSY if
* a master or slave with the same name already exists.
*
* 当相同名字的主服务器或者从服务器已经存在时，函数返回 NULL ，
* 并将 errno 设为 EBUSY 。
*/
sentinelRedisInstance *createSentinelRedisInstance(char *name, int flags, char *hostname, int port, int quorum, sentinelRedisInstance *master) {
sentinelRedisInstance *ri;
sentinelAddr *addr;
dict *table = NULL;
char slavename[128], *sdsname;
redisAssert(flags & (SRI_MASTER|SRI_SLAVE|SRI_SENTINEL));
redisAssert((flags & SRI_MASTER) || master != NULL);
/* Check address validity. */
// 保存 IP 地址和端口号到 addr
addr = createSentinelAddr(hostname,port);
if (addr == NULL) return NULL;
/* For slaves and sentinel we use ip:port as name. */
// 如果实例是从服务器或者 sentinel ，那么使用 ip:port 格式为实例设置名字
if (flags & (SRI_SLAVE|SRI_SENTINEL)) {
snprintf(slavename,sizeof(slavename),
strchr(hostname,':') ? "[%s]:%d" : "%s:%d",
hostname,port);
name = slavename;
}
/* Make sure the entry is not duplicated. This may happen when the same
* name for a master is used multiple times inside the configuration or
* if we try to add multiple times a slave or sentinel with same ip/port
* to a master. */
// 配置文件中添加了重复的主服务器配置
// 或者尝试添加一个相同 ip 或者端口号的从服务器或者 sentinel 时
// 就可能出现重复添加同一个实例的情况
// 为了避免这种现象，程序在添加新实例之前，需要先检查实例是否已存在
// 只有不存在的实例会被添加
// 选择要添加的表
// 注意主服务会被添加到 sentinel.masters 表
// 而从服务器和 sentinel 则会被添加到 master 所属的 slaves 表和 sentinels 表中
if (flags & SRI_MASTER) table = sentinel.masters;
else if (flags & SRI_SLAVE) table = master->slaves;
else if (flags & SRI_SENTINEL) table = master->sentinels;
sdsname = sdsnew(name);
if (dictFind(table,sdsname)) {
// 实例已存在，函数直接返回
sdsfree(sdsname);
errno = EBUSY;
return NULL;
}
/* Create the instance object. */
// 创建实例对象
ri = zmalloc(sizeof(*ri));
/* Note that all the instances are started in the disconnected state,
* the event loop will take care of connecting them. */
// 所有连接都已断线为起始状态，sentinel 会在需要时自动为它创建连接
ri->flags = flags | SRI_DISCONNECTED;
ri->name = sdsname;
ri->runid = NULL;
ri->addr = addr;
ri->cc = NULL;
ri->pc = NULL;
ri->pending_commands = 0;
ri->cc_conn_time = 0;
ri->pc_conn_time = 0;
ri->pc_last_activity = 0;
ri->last_avail_time = mstime();
ri->last_pong_time = mstime();
ri->last_pub_time = mstime();
ri->last_hello_time = mstime();
ri->last_master_down_reply_time = mstime();
ri->s_down_since_time = 0;
ri->o_down_since_time = 0;
ri->down_after_period = master ? master->down_after_period :
SENTINEL_DOWN_AFTER_PERIOD;
ri->master_link_down_time = 0;
ri->auth_pass = NULL;
ri->slave_priority = SENTINEL_DEFAULT_SLAVE_PRIORITY;
ri->slave_reconf_sent_time = 0;
ri->slave_master_host = NULL;
ri->slave_master_port = 0;
ri->slave_master_link_status = SENTINEL_MASTER_LINK_STATUS_DOWN;
ri->sentinels = dictCreate(&instancesDictType,NULL);
ri->quorum = quorum;
ri->parallel_syncs = SENTINEL_DEFAULT_PARALLEL_SYNCS;
ri->master = master;
ri->slaves = dictCreate(&instancesDictType,NULL);
ri->info_refresh = 0;
/* Failover state. */
ri->leader = NULL;
ri->failover_state = SENTINEL_FAILOVER_STATE_NONE;
ri->failover_state_change_time = 0;
ri->failover_start_time = 0;
ri->failover_timeout = SENTINEL_DEFAULT_FAILOVER_TIMEOUT;
ri->promoted_slave = NULL;
ri->notification_script = NULL;
ri->client_reconfig_script = NULL;
/* Add into the right table. */
// 将实例添加到适当的表中
dictAdd(table, ri->name, ri);
// 返回实例
return ri;
}
/* Release this instance and all its slaves, sentinels, hiredis connections.
*
* 释放一个实例，以及它的所有从服务器、sentinel ，以及 hiredis 连接。
*
* This function also takes care of unlinking the instance from the main
* masters table (if it is a master) or from its master sentinels/slaves table
* if it is a slave or sentinel.
*
* 如果这个实例是一个从服务器或者 sentinel ，
* 那么这个函数也会从该实例所属的主服务器表中删除这个从服务器/sentinel 。
*/
void releaseSentinelRedisInstance(sentinelRedisInstance *ri) {
/* Release all its slaves or sentinels if any. */
// 释放（可能有的）sentinel 和 slave
dictRelease(ri->sentinels);
dictRelease(ri->slaves);
/* Release hiredis connections. */
// 释放连接
if (ri->cc) sentinelKillLink(ri,ri->cc);
if (ri->pc) sentinelKillLink(ri,ri->pc);
/* Free other resources. */
// 释放其他资源
sdsfree(ri->name);
sdsfree(ri->runid);
sdsfree(ri->notification_script);
sdsfree(ri->client_reconfig_script);
sdsfree(ri->slave_master_host);
sdsfree(ri->leader);
sdsfree(ri->auth_pass);
releaseSentinelAddr(ri->addr);
/* Clear state into the master if needed. */
// 清除故障转移带来的状态
if ((ri->flags & SRI_SLAVE) && (ri->flags & SRI_PROMOTED) && ri->master)
ri->master->promoted_slave = NULL;
zfree(ri);
}
/* Lookup a slave in a master Redis instance, by ip and port. */
// 根据 IP 和端口号，查找主服务器实例的从服务器
sentinelRedisInstance *sentinelRedisInstanceLookupSlave(
sentinelRedisInstance *ri, char *ip, int port)
{
sds key;
sentinelRedisInstance *slave;
redisAssert(ri->flags & SRI_MASTER);
key = sdscatprintf(sdsempty(),
strchr(ip,':') ? "[%s]:%d" : "%s:%d",
ip,port);
slave = dictFetchValue(ri->slaves,key);
sdsfree(key);
return slave;
}
/* Return the name of the type of the instance as a string. */
// 以字符串形式返回实例的类型
const char *sentinelRedisInstanceTypeStr(sentinelRedisInstance *ri) {
if (ri->flags & SRI_MASTER) return "master";
else if (ri->flags & SRI_SLAVE) return "slave";
else if (ri->flags & SRI_SENTINEL) return "sentinel";
else return "unknown";
}
/* This function removes all the instances found in the dictionary of instances
* 'd', having either:
*
* 从实例字典中移除满足以下条件的实例：
*
* 1) The same ip/port as specified.
* 实例给定的 IP 和端口号和字典中已有的实例相同
*
* 2) The same runid.
* 实例给定的运行 ID 和字典中已有的实例相同
*
* "1" and "2" don't need to verify at the same time, just one is enough.
*
* 以上条件任意满足一个，移除操作就会被执行。
*
* If "runid" is NULL it is not checked.
* Similarly if "ip" is NULL it is not checked.
*
* 如果 runid 参数为 NULL ，那么不检查该参数。
* 如果 ip 参数为 NULL ，那么不检查该参数。
*
* This function is useful because every time we add a new Sentinel into
* a master's Sentinels dictionary, we want to be very sure about not
* having duplicated instances for any reason. This is so important because
* we use those other sentinels in order to run our quorum protocol to
* understand if it's time to proceed with the fail over.
*
* Making sure no duplication is possible we greatly improve the robustness
* of the quorum (otherwise we may end counting the same instance multiple
* times for some reason).
*
* 因为 sentinel 的操作比如故障转移，需要多个 sentinel 投票才能进行。
* 所以我们必须保证所添加的各个 sentinel 都是不相同、独一无二的，
* 这样才能确保投票的合法性。
*
* The function returns the number of Sentinels removed.
*
* 函数的返回值为被移除 sentinel 的数量
*/
int removeMatchingSentinelsFromMaster(sentinelRedisInstance *master, char *ip, int port, char *runid) {
dictIterator *di;
dictEntry *de;
int removed = 0;
di = dictGetSafeIterator(master->sentinels);
while((de = dictNext(di)) != NULL) {
sentinelRedisInstance *ri = dictGetVal(de);
// 运行 ID 相同，或者 IP 和端口号相同，那么移除该实例
if ((ri->runid && runid && strcmp(ri->runid,runid) == 0) ||
(ip && strcmp(ri->addr->ip,ip) == 0 && port == ri->addr->port))
{
dictDelete(master->sentinels,ri->name);
removed++;
}
}
dictReleaseIterator(di);
return removed;
}
/* Search an instance with the same runid, ip and port into a dictionary
* of instances. Return NULL if not found, otherwise return the instance
* pointer.
*
* 在给定的实例中查找具有相同 runid 、ip 、port 的实例，
* 没找到则返回 NULL 。
*
* runid or ip can be NULL. In such a case the search is performed only
* by the non-NULL field.
*
* runid 或者 ip 都可以为 NULL ，在这种情况下，函数只检查非空域。
*/
sentinelRedisInstance *getSentinelRedisInstanceByAddrAndRunID(dict *instances, char *ip, int port, char *runid) {
dictIterator *di;
dictEntry *de;
sentinelRedisInstance *instance = NULL;
redisAssert(ip || runid); /* User must pass at least one search param. */
// 遍历所有输入实例
di = dictGetIterator(instances);
while((de = dictNext(di)) != NULL) {
sentinelRedisInstance *ri = dictGetVal(de);
// runid 不相同，忽略该实例
if (runid && !ri->runid) continue;
// 检查 ip 和端口号是否相同
if ((runid == NULL || strcmp(ri->runid, runid) == 0) &&
(ip == NULL || (strcmp(ri->addr->ip, ip) == 0 &&
ri->addr->port == port)))
{
instance = ri;
break;
}
}
dictReleaseIterator(di);
return instance;
}
/* Simple master lookup by name */
// 根据名字查找主服务器
sentinelRedisInstance *sentinelGetMasterByName(char *name) {
sentinelRedisInstance *ri;
sds sdsname = sdsnew(name);
ri = dictFetchValue(sentinel.masters,sdsname);
sdsfree(sdsname);
return ri;
}
/* Add the specified flags to all the instances in the specified dictionary. */
// 为输入的所有实例打开指定的 flags
void sentinelAddFlagsToDictOfRedisInstances(dict *instances, int flags) {
dictIterator *di;
dictEntry *de;
di = dictGetIterator(instances);
while((de = dictNext(di)) != NULL) {
sentinelRedisInstance *ri = dictGetVal(de);
ri->flags |= flags;
}
dictReleaseIterator(di);
}
/* Remove the specified flags to all the instances in the specified
* dictionary. */
// 从字典中移除所有实例的给定 flags
void sentinelDelFlagsToDictOfRedisInstances(dict *instances, int flags) {
dictIterator *di;
dictEntry *de;
// 遍历所有实例
di = dictGetIterator(instances);
while((de = dictNext(di)) != NULL) {
sentinelRedisInstance *ri = dictGetVal(de);
// 移除 flags
ri->flags &= ~flags;
}
dictReleaseIterator(di);
}
/* Reset the state of a monitored master:
*
* 重置主服务区的监控状态
*
* 1) Remove all slaves.
* 移除主服务器的所有从服务器
* 2) Remove all sentinels.
* 移除主服务器的所有 sentinel
* 3) Remove most of the flags resulting from runtime operations.
* 移除大部分运行时操作标志
* 4) Reset timers to their default value.
* 重置计时器为默认值
* 5) In the process of doing this undo the failover if in progress.
* 如果故障转移正在执行的话，那么取消该它
* 6) Disconnect the connections with the master (will reconnect automatically).
* 断开 sentinel 与主服务器的连接（之后会自动重连）
*/
void sentinelResetMaster(sentinelRedisInstance *ri, int flags) {
redisAssert(ri->flags & SRI_MASTER);
// 清空并重新创建字典
dictRelease(ri->slaves);
dictRelease(ri->sentinels);
ri->slaves = dictCreate(&instancesDictType,NULL);
ri->sentinels = dictCreate(&instancesDictType,NULL);
// 断开连接
if (ri->cc) sentinelKillLink(ri,ri->cc);
if (ri->pc) sentinelKillLink(ri,ri->pc);
// 重置状态和标志
ri->flags &= SRI_MASTER|SRI_CAN_FAILOVER|SRI_DISCONNECTED;
if (ri->leader) {
sdsfree(ri->leader);
ri->leader = NULL;
}
ri->failover_state = SENTINEL_FAILOVER_STATE_NONE;
ri->failover_state_change_time = 0;
ri->failover_start_time = 0;
ri->promoted_slave = NULL;
sdsfree(ri->runid);
sdsfree(ri->slave_master_host);
ri->runid = NULL;
ri->slave_master_host = NULL;
ri->last_avail_time = mstime();
ri->last_pong_time = mstime();
// 发送主服务器重置事件
if (flags & SENTINEL_GENERATE_EVENT)
sentinelEvent(REDIS_WARNING,"+reset-master",ri,"%@");
}
/* Call sentinelResetMaster() on every master with a name matching the specified
* pattern. */
// 重置所有符合给定模式的主服务器
int sentinelResetMastersByPattern(char *pattern, int flags) {
dictIterator *di;
dictEntry *de;
int reset = 0;
di = dictGetIterator(sentinel.masters);
while((de = dictNext(di)) != NULL) {
sentinelRedisInstance *ri = dictGetVal(de);
if (ri->name) {
if (stringmatch(pattern,ri->name,0)) {
sentinelResetMaster(ri,flags);
reset++;
}
}
}
dictReleaseIterator(di);
return reset;
}
/* Reset the specified master with sentinelResetMaster(), and also change
* the ip:port address, but take the name of the instance unmodified.
*
* 重置给定的主服务器，修改它的 ip 和端口号，但保持实例名不边
*
* This is used to handle the +switch-master and +redirect-to-master events.
*
* 这个函数用于处理 +switch-master 和 +redirect-to-master 事件
*
* The function returns REDIS_ERR if the address can't be resolved for some
* reason. Otherwise REDIS_OK is returned.
*
* 如果函数因为不能解释给定地址而失败，那么返回 REDIS_ERR ，一切正常则返回 REDIS_OK 。
*
* TODO: make this reset so that original sentinels are re-added with
* same ip / port / runid.
*/
int sentinelResetMasterAndChangeAddress(sentinelRedisInstance *master, char *ip, int port) {
sentinelAddr *oldaddr, *newaddr;
// 根据 ip 和端口，创建地址结构
newaddr = createSentinelAddr(ip,port);
if (newaddr == NULL) return REDIS_ERR;
// 重置主服务器实例
sentinelResetMaster(master,SENTINEL_NO_FLAGS);
// 更新实例的地址，以及下线状态
oldaddr = master->addr;
master->addr = newaddr;
master->o_down_since_time = 0;
master->s_down_since_time = 0;
/* Release the old address at the end so we are safe even if the function
* gets the master->addr->ip and master->addr->port as arguments. */
// 释放旧地址
releaseSentinelAddr(oldaddr);
return REDIS_OK;
}
/* Return non-zero if there was no SDOWN or ODOWN error associated to this
* instance in the latest 'ms' milliseconds. */
// 如果实例在给定 ms 中没有出现过 SDOWN 或者 ODOWN 状态
// 那么函数返回一个非零值
int sentinelRedisInstanceNoDownFor(sentinelRedisInstance *ri, mstime_t ms) {
mstime_t most_recent;
most_recent = ri->s_down_since_time;
if (ri->o_down_since_time > most_recent)
most_recent = ri->o_down_since_time;
return most_recent == 0 || (mstime() - most_recent) > ms;
}
/* ============================ Config handling ============================= */
char *sentinelHandleConfiguration(char **argv, int argc) {
sentinelRedisInstance *ri;
// SENTINEL monitor 选项
if (!strcasecmp(argv[0],"monitor") && argc == 5) {
/* monitor */
// 读入 quorum 参数
int quorum = atoi(argv[4]);
// 检查 quorum 参数必须大于 0
if (quorum <= 0) return "Quorum must be 1 or greater.";
// 创建主服务器实例
if (createSentinelRedisInstance(argv[1],SRI_MASTER,argv[2],
atoi(argv[3]),quorum,NULL) == NULL)
{
switch(errno) {
case EBUSY: return "Duplicated master name.";
case ENOENT: return "Can't resolve master instance hostname.";
case EINVAL: return "Invalid port number";
}
}
// SENTINEL down-after-milliseconds 选项
} else if (!strcasecmp(argv[0],"down-after-milliseconds") && argc == 3) {
/* down-after-milliseconds */
// 查找主服务器
ri = sentinelGetMasterByName(argv[1]);
if (!ri) return "No such master with specified name.";
// 设置选项
ri->down_after_period = atoi(argv[2]);
if (ri->down_after_period <= 0)
return "negative or zero time parameter.";
// SENTINEL failover-timeout 选项
} else if (!strcasecmp(argv[0],"failover-timeout") && argc == 3) {
/* failover-timeout */
// 查找主服务器
ri = sentinelGetMasterByName(argv[1]);
if (!ri) return "No such master with specified name.";
// 设置选项
ri->failover_timeout = atoi(argv[2]);
if (ri->failover_timeout <= 0)
return "negative or zero time parameter.";
// SENTINEL can-failover 选项
} else if (!strcasecmp(argv[0],"can-failover") && argc == 3) {
/* can-failover */
int yesno = yesnotoi(argv[2]);
// 查找主服务器
ri = sentinelGetMasterByName(argv[1]);
if (!ri) return "No such master with specified name.";
// 参数不是 "yes" 或者 "no" ，出错
if (yesno == -1) return "Argument must be either yes or no.";
// 设置选项
if (yesno)
ri->flags |= SRI_CAN_FAILOVER;
else
ri->flags &= ~SRI_CAN_FAILOVER;
// SENTINEL parallel-syncs 选项
} else if (!strcasecmp(argv[0],"parallel-syncs") && argc == 3) {
/* parallel-syncs */
// 查找主服务器
ri = sentinelGetMasterByName(argv[1]);
if (!ri) return "No such master with specified name.";
// 设置选项
ri->parallel_syncs = atoi(argv[2]);
// SENTINEL notification-script 选项
} else if (!strcasecmp(argv[0],"notification-script") && argc == 3) {
/* notification-script */
// 查找主服务器
ri = sentinelGetMasterByName(argv[1]);
if (!ri) return "No such master with specified name.";
// 检查给定路径所指向的文件是否存在，以及是否可执行
if (access(argv[2],X_OK) == -1)
return "Notification script seems non existing or non executable.";
// 设置选项
ri->notification_script = sdsnew(argv[2]);
// SENTINEL client-reconfig-script 选项
} else if (!strcasecmp(argv[0],"client-reconfig-script") && argc == 3) {
/* client-reconfig-script */
// 查找主服务器
ri = sentinelGetMasterByName(argv[1]);
if (!ri) return "No such master with specified name.";
// 检查给定路径所指向的文件是否存在，以及是否可执行
if (access(argv[2],X_OK) == -1)
return "Client reconfiguration script seems non existing or "
"non executable.";
// 设置选项
ri->client_reconfig_script = sdsnew(argv[2]);
// 设置 SENTINEL auth-pass 选项
} else if (!strcasecmp(argv[0],"auth-pass") && argc == 3) {
/* auth-pass */
// 查找主服务器
ri = sentinelGetMasterByName(argv[1]);
if (!ri) return "No such master with specified name.";
// 设置选项
ri->auth_pass = sdsnew(argv[2]);
// 未识别的选项
} else {
return "Unrecognized sentinel configuration statement.";
}
return NULL;
}
/* ====================== hiredis connection handling ======================= */
/* Completely disconnect an hiredis link from an instance. */
// 断开实例的连接
void sentinelKillLink(sentinelRedisInstance *ri, redisAsyncContext *c) {
if (ri->cc == c) {
ri->cc = NULL;
ri->pending_commands = 0;
}
if (ri->pc == c) ri->pc = NULL;
c->data = NULL;
// 打开断线标志
ri->flags |= SRI_DISCONNECTED;
// 断开连接
redisAsyncFree(c);
}
/* This function takes an hiredis context that is in an error condition
* and make sure to mark the instance as disconnected performing the
* cleanup needed.
*
* 函数将一个出错连接设置正确的断线标志，并执行清理操作
*
* Note: we don't free the hiredis context as hiredis will do it for us
* for async connections.
*
* 这个函数没有手动释放连接，因为异步连接会自动释放
*/
void sentinelDisconnectInstanceFromContext(const redisAsyncContext *c) {
sentinelRedisInstance *ri = c->data;
int pubsub;
if (ri == NULL) return; /* The instance no longer exists. */
// 发送断线事件
pubsub = (ri->pc == c);
sentinelEvent(REDIS_DEBUG, pubsub ? "-pubsub-link" : "-cmd-link", ri,
"%@ #%s", c->errstr);
if (pubsub)
ri->pc = NULL;
else
ri->cc = NULL;
// 打开标志
ri->flags |= SRI_DISCONNECTED;
}
// 异步连接的连接回调函数
void sentinelLinkEstablishedCallback(const redisAsyncContext *c, int status) {
if (status != REDIS_OK) {
sentinelDisconnectInstanceFromContext(c);
} else {
sentinelRedisInstance *ri = c->data;
int pubsub = (ri->pc == c);
// 发送连接事件
sentinelEvent(REDIS_DEBUG, pubsub ? "+pubsub-link" : "+cmd-link", ri,
"%@");
}
}
// 异步连接的断线回调函数
void sentinelDisconnectCallback(const redisAsyncContext *c, int status) {
sentinelDisconnectInstanceFromContext(c);
}
/* Send the AUTH command with the specified master password if needed.
* Note that for slaves the password set for the master is used.
*
* 如果 sentinel 设置了 auth-pass 选项，那么向主服务器或者从服务器发送验证密码。
* 注意从服务器使用的是主服务器的密码。
*
* We don't check at all if the command was successfully transmitted
* to the instance as if it fails Sentinel will detect the instance down,
* will disconnect and reconnect the link and so forth.
*
* 函数不检查命令是否被成功发送，因为如果目标服务器掉线了的话， sentinel 会识别到，
* 并对它进行重连接，然后又重新发送 AUTH 命令。
*/
void sentinelSendAuthIfNeeded(sentinelRedisInstance *ri, redisAsyncContext *c) {
// 如果 ri 是主服务器，那么使用实例自己的密码
// 如果 ri 是从服务器，那么使用主服务器的密码
char *auth_pass = (ri->flags & SRI_MASTER) ? ri->auth_pass :
ri->master->auth_pass;
// 发送 AUTH 命令
if (auth_pass)
redisAsyncCommand(c, sentinelDiscardReplyCallback, NULL, "AUTH %s",
auth_pass);
}
/* Create the async connections for the specified instance if the instance
* is disconnected. Note that the SRI_DISCONNECTED flag is set even if just
* one of the two links (commands and pub/sub) is missing. */
// 如果 sentinel 与实例处于断线（未连接）状态，那么创建连向实例的异步连接。
void sentinelReconnectInstance(sentinelRedisInstance *ri) {
// 示例未断线（已连接），返回
if (!(ri->flags & SRI_DISCONNECTED)) return;
/* Commands connection. */
// 创建一个连向实例的连接，用于向实例发送 Redis 命令
if (ri->cc == NULL) {
// 连接实例
ri->cc = redisAsyncConnect(ri->addr->ip,ri->addr->port);
// 连接出错
if (ri->cc->err) {
sentinelEvent(REDIS_DEBUG,"-cmd-link-reconnection",ri,"%@ #%s",
ri->cc->errstr);
sentinelKillLink(ri,ri->cc);
// 连接成功
} else {
// 设置连接属性
ri->cc_conn_time = mstime();
ri->cc->data = ri;
redisAeAttach(server.el,ri->cc);
// 设置连线 callback
redisAsyncSetConnectCallback(ri->cc,
sentinelLinkEstablishedCallback);
// 设置断线 callback
redisAsyncSetDisconnectCallback(ri->cc,
sentinelDisconnectCallback);
// 发送 AUTH 命令，验证身份
sentinelSendAuthIfNeeded(ri,ri->cc);
}
}
/* Pub / Sub */
// 如果实例是服务器，那么 sentinel 还要创建一个连接
// 用于发送和接收频道的命令
if ((ri->flags & SRI_MASTER) && ri->pc == NULL) {
// 连接实例
ri->pc = redisAsyncConnect(ri->addr->ip,ri->addr->port);
// 连接出错
if (ri->pc->err) {
sentinelEvent(REDIS_DEBUG,"-pubsub-link-reconnection",ri,"%@ #%s",
ri->pc->errstr);
sentinelKillLink(ri,ri->pc);
// 连接成功
} else {
int retval;
// 设置连接属性
ri->pc_conn_time = mstime();
ri->pc->data = ri;
redisAeAttach(server.el,ri->pc);
// 设置连接 callback
redisAsyncSetConnectCallback(ri->pc,
sentinelLinkEstablishedCallback);
// 设置断线 callback
redisAsyncSetDisconnectCallback(ri->pc,
sentinelDisconnectCallback);
// 发送 AUTH 命令，验证身份
sentinelSendAuthIfNeeded(ri,ri->pc);
/* Now we subscribe to the Sentinels "Hello" channel. */
// 发送 SUBSCRIBE __sentinel__:hello 命令，订阅频道
retval = redisAsyncCommand(ri->pc,
sentinelReceiveHelloMessages, NULL, "SUBSCRIBE %s",
SENTINEL_HELLO_CHANNEL);
// 订阅出错，断开连接
if (retval != REDIS_OK) {
/* If we can't subscribe, the Pub/Sub connection is useless
* and we can simply disconnect it and try again. */
sentinelKillLink(ri,ri->pc);
return;
}
}
}
/* Clear the DISCONNECTED flags only if we have both the connections
* (or just the commands connection if this is a slave or a
* sentinel instance). */
// 如果实例是主服务器，并且 cc 和 pc 两个连接都创建成功，那么关闭 DISCONNECTED 标志
// 如果实例是从服务器，或者 SENTINEL ，那么只要 cc 连接创建成功，那么关闭 DISCONNECTED 标志
if (ri->cc && (ri->flags & (SRI_SLAVE|SRI_SENTINEL) || ri->pc))
ri->flags &= ~SRI_DISCONNECTED;
}
/* ======================== Redis instances pinging ======================== */
/* Process the INFO output from masters. */
// 从主服务器或者从服务器所返回的 INFO 命令的回复中分析相关信息
// （上面的英文注释错了，这个函数不仅处理主服务器的 INFO 回复，还处理从服务器的 INFO 回复）
void sentinelRefreshInstanceInfo(sentinelRedisInstance *ri, const char *info) {
sds *lines;
int numlines, j;
int role = 0;
int runid_changed = 0; /* true if runid changed. */
int first_runid = 0; /* true if this is the first runid we receive. */
/* The following fields must be reset to a given value in the case they
* are not found at all in the INFO output. */
// 将该变量重置为 0 ，避免 INFO 回复中无该值的情况
ri->master_link_down_time = 0;
/* Process line by line. */
// 对 INFO 命令的回复进行逐行分析
lines = sdssplitlen(info,strlen(info),"\r\n",2,&numlines);
for (j = 0; j < numlines; j++) {
sentinelRedisInstance *slave;
sds l = lines[j];
/* run_id:<40 hex chars>*/
// 读取并分析 runid
if (sdslen(l) >= 47 && !memcmp(l,"run_id:",7)) {
// 新设置 runid
if (ri->runid == NULL) {
ri->runid = sdsnewlen(l+7,40);
// 标记这是新设置的 runid
first_runid = 1;
// 更新 runid
} else {
if (strncmp(ri->runid,l+7,40) != 0) {
// 标记 runid 已改变
runid_changed = 1;
// 发送重启事件
sentinelEvent(REDIS_NOTICE,"+reboot",ri,"%@");
// 释放旧 ID ，设置新 ID
sdsfree(ri->runid);
ri->runid = sdsnewlen(l+7,40);
}
}
}
// 读取从服务器的 ip 和端口号
/* old versions: slave0:,,
* new versions: slave0:ip=127.0.0.1,port=9999,... */
if ((ri->flags & SRI_MASTER) &&
sdslen(l) >= 7 &&
!memcmp(l,"slave",5) && isdigit(l[5]))
{
char *ip, *port, *end;
if (strstr(l,"ip=") == NULL) {
/* Old format. */
ip = strchr(l,':'); if (!ip) continue;
ip++; /* Now ip points to start of ip address. */
port = strchr(ip,','); if (!port) continue;
*port = '\0'; /* nul term for easy access. */
port++; /* Now port points to start of port number. */
end = strchr(port,','); if (!end) continue;
*end = '\0'; /* nul term for easy access. */
} else {
/* New format. */
ip = strstr(l,"ip="); if (!ip) continue;
ip += 3; /* Now ip points to start of ip address. */
port = strstr(l,"port="); if (!port) continue;
port += 5; /* Now port points to start of port number. */
/* Nul term both fields for easy access. */
end = strchr(ip,','); if (end) *end = '\0';
end = strchr(port,','); if (end) *end = '\0';
}
/* Check if we already have this slave into our table,
* otherwise add it. */
if (sentinelRedisInstanceLookupSlave(ri,ip,atoi(port)) == NULL) {
if ((slave = createSentinelRedisInstance(NULL,SRI_SLAVE,ip,
atoi(port), ri->quorum, ri)) != NULL)
{
sentinelEvent(REDIS_NOTICE,"+slave",slave,"%@");
}
}
}
/* master_link_down_since_seconds: */
// 读取主从服务器的断线时长
if (sdslen(l) >= 32 &&
!memcmp(l,"master_link_down_since_seconds",30))
{
ri->master_link_down_time = strtoll(l+31,NULL,10)*1000;
}
/* role: */
// 读取实例的角色
if (!memcmp(l,"role:master",11)) role = SRI_MASTER;
else if (!memcmp(l,"role:slave",10)) role = SRI_SLAVE;
// 处理从服务器
if (role == SRI_SLAVE) {
/* master_host: */
// 读入主服务器的 IP
if (sdslen(l) >= 12 && !memcmp(l,"master_host:",12)) {
sdsfree(ri->slave_master_host);
ri->slave_master_host = sdsnew(l+12);
}
/* master_port: */
// 读入主服务器的端口号
if (sdslen(l) >= 12 && !memcmp(l,"master_port:",12))
ri->slave_master_port = atoi(l+12);
/* master_link_status: */
// 读入主服务器的状态
if (sdslen(l) >= 19 && !memcmp(l,"master_link_status:",19)) {
ri->slave_master_link_status =
(strcasecmp(l+19,"up") == 0) ?
SENTINEL_MASTER_LINK_STATUS_UP :
SENTINEL_MASTER_LINK_STATUS_DOWN;
}
/* slave_priority: */
// 读入从服务器的优先级
if (sdslen(l) >= 15 && !memcmp(l,"slave_priority:",15))
ri->slave_priority = atoi(l+15);
}
}
// 更新刷新 INFO 命令回复的时间
ri->info_refresh = mstime();
sdsfreesplitres(lines,numlines);
/* ---------------------------- Acting half -----------------------------
* Some things will not happen if sentinel.tilt is true, but some will
* still be processed.
*
* 如果 sentinel 进入了 TILT 模式，那么可能只有一部分动作会被执行
*/
/* When what we believe is our master, turned into a slave, the wiser
* thing we can do is to follow the events and redirect to the new
* master, always. */
// 如果服务器原来是主服务器，但现在变成了从服务器
// 那么发送一个 +redirect-to-master 事件，并更新主服务器的 IP 和地址
if ((ri->flags & SRI_MASTER) && role == SRI_SLAVE && ri->slave_master_host)
{
// 发送事件
sentinelEvent(REDIS_WARNING,"+redirect-to-master",ri,
"%s %s %d %s %d",
ri->name, ri->addr->ip, ri->addr->port,
ri->slave_master_host, ri->slave_master_port);
// 修改主服务器实例的 IP 和端口
sentinelResetMasterAndChangeAddress(ri,ri->slave_master_host,
ri->slave_master_port);
return; /* Don't process anything after this event. */
}
/* Handle slave -> master role switch. */
// 处理从服务器转变为主服务器的情况
if ((ri->flags & SRI_SLAVE) && role == SRI_MASTER) {
// sentinel 未处于 TILT 状态，并且这个实例被标记为 DEMOTE
if (!sentinel.tilt && ri->flags & SRI_DEMOTE) {
/* If this sentinel was partitioned from the slave's master,
* or tilted recently, wait some time before to act,
* so that DOWN and roles INFO will be refreshed. */
// 如果实例刚断线重连不久，或者 sentinel 刚进入 TILT 模式不久
// 那么等待一阵子再执行操作
mstime_t wait_time = SENTINEL_INFO_PERIOD*2 +
ri->master->down_after_period*2;
if (!sentinelRedisInstanceNoDownFor(ri->master,wait_time) ||
(mstime()-sentinel.tilt_start_time) < wait_time)
return;
/* Old master returned back? Turn it into a slave ASAP if
* we can reach what we believe is the new master now, and
* have a recent role information for it.
*
* 这是一个旧主服务器，将它设置为从服务器。
*
* Note: we'll clear the DEMOTE flag only when we have the
* acknowledge that it's a slave again. */
if (ri->master->flags & SRI_MASTER &&
(ri->master->flags & (SRI_S_DOWN|SRI_O_DOWN)) == 0 &&
(mstime() - ri->master->info_refresh) < SENTINEL_INFO_PERIOD*2)
{
// 实例处于活跃状态，并且仍然认为自己是主服务器
int retval;
// 发送 SLAVEOF 命令，让它成为从服务器，并复制新主服务器
retval = redisAsyncCommand(ri->cc,
sentinelDiscardReplyCallback, NULL, "SLAVEOF %s %d",
ri->master->addr->ip,
ri->master->addr->port);
// 发送 demote 事件
if (retval == REDIS_OK)
sentinelEvent(REDIS_NOTICE,"+demote-old-slave",ri,"%@");
} else {
/* Otherwise if there are not the conditions to demote, we
* no longer trust the DEMOTE flag and remove it. */
// 关闭 demote 标志
ri->flags &= ~SRI_DEMOTE;
// 发送清除 demote 标志事件
sentinelEvent(REDIS_NOTICE,"-demote-flag-cleared",ri,"%@");
}
// 实例的主服务器正在执行故障转移，并且实例已重启
} else if (!(ri->master->flags & SRI_FAILOVER_IN_PROGRESS) &&
(runid_changed || first_runid))
{
/* If a slave turned into master but:
*
* 1) Failover not in progress.
* 2) RunID has changed or its the first time we see an INFO output.
*
* We assume this is a reboot with a wrong configuration.
* Log the event and remove the slave. Note that this is processed
* in tilt mode as well, otherwise we lose the information that the
* runid changed (reboot?) and when the tilt mode ends a fake
* failover will be detected. */
int retval;
sentinelEvent(REDIS_WARNING,"-slave-restart-as-master",ri,"%@ #removing it from the attached slaves");
retval = dictDelete(ri->master->slaves,ri->name);
redisAssert(retval == REDIS_OK);
return;
// sentinel 未处于 TILT 模式，并且实例被提升为新主服务器
} else if (!sentinel.tilt && ri->flags & SRI_PROMOTED) {
/* If this is a promoted slave we can change state to the
* failover state machine. */
if ((ri->master->flags & SRI_FAILOVER_IN_PROGRESS) &&
(ri->master->flags & SRI_I_AM_THE_LEADER) &&
(ri->master->failover_state ==
SENTINEL_FAILOVER_STATE_WAIT_PROMOTION))
{
// 更新故障转移的状态
ri->master->failover_state = SENTINEL_FAILOVER_STATE_RECONF_SLAVES;
ri->master->failover_state_change_time = mstime();
// 发送事件
sentinelEvent(REDIS_WARNING,"+promoted-slave",ri,"%@");
sentinelEvent(REDIS_WARNING,"+failover-state-reconf-slaves",
ri->master,"%@");
// 执行用户脚本
sentinelCallClientReconfScript(ri->master,SENTINEL_LEADER,
"start",ri->master->addr,ri->addr);
}
// sentinel 未处于 TILT 模式，并且
// 故障转移操作未开始，或者
// 故障转移已开始、当前 sentinel 为 LEADER ，并且 sentinel 处于等待故障转移执行
// （这表示已经有一个故障转移操作抢先执行了）
} else if (!sentinel.tilt && (
!(ri->master->flags & SRI_FAILOVER_IN_PROGRESS) ||
((ri->master->flags & SRI_FAILOVER_IN_PROGRESS) &&
(ri->master->flags & SRI_I_AM_THE_LEADER) &&
ri->master->failover_state ==
SENTINEL_FAILOVER_STATE_WAIT_START)))
{
/* No failover in progress? Then it is the start of a failover
* and we are an observer.
*
* We also do that if we are a leader doing a failover, in wait
* start, but well, somebody else started before us. */
// 已经有别的 sentinel 抢先开始了故障转移
if (ri->master->flags & SRI_FAILOVER_IN_PROGRESS) {
sentinelEvent(REDIS_WARNING,"-failover-abort-race",
ri->master, "%@");
sentinelAbortFailover(ri->master);
}
// 故障转移正在执行
ri->master->flags |= SRI_FAILOVER_IN_PROGRESS;
sentinelEvent(REDIS_WARNING,"+failover-detected",ri->master,"%@");
// 标记当前 sentinel 发起的故障转移为 END 状态，让已有的故障转移继续执行
ri->master->failover_state = SENTINEL_FAILOVER_STATE_DETECT_END;
ri->master->failover_state_change_time = mstime();
// 设置标志
ri->master->promoted_slave = ri;
ri->flags |= SRI_PROMOTED;
ri->flags &= ~SRI_DEMOTE;
// 调用脚本
sentinelCallClientReconfScript(ri->master,SENTINEL_OBSERVER,
"start", ri->master->addr,ri->addr);
/* We are an observer, so we can only assume that the leader
* is reconfiguring the slave instances. For this reason we
* set all the instances as RECONF_SENT waiting for progresses
* on this side. */
sentinelAddFlagsToDictOfRedisInstances(ri->master->slaves,
SRI_RECONF_SENT);
}
}
/* None of the following conditions are processed when in tilt mode, so
* return asap. */
// 以下动作都不能在 TILT 模式下执行
if (sentinel.tilt) return;
/* Detect if the slave that is in the process of being reconfigured
* changed state. */
// sentinel 监视的实例为从服务器，并且已经向它发送 SLAVEOF 命令
if ((ri->flags & SRI_SLAVE) && role == SRI_SLAVE &&
(ri->flags & (SRI_RECONF_SENT|SRI_RECONF_INPROG)))
{
/* SRI_RECONF_SENT -> SRI_RECONF_INPROG. */
// 将 SENT 状态改为 INPROG 状态，表示同步正在进行
if ((ri->flags & SRI_RECONF_SENT) &&
ri->slave_master_host &&
strcmp(ri->slave_master_host,
ri->master->promoted_slave->addr->ip) == 0 &&
ri->slave_master_port == ri->master->promoted_slave->addr->port)
{
ri->flags &= ~SRI_RECONF_SENT;
ri->flags |= SRI_RECONF_INPROG;
sentinelEvent(REDIS_NOTICE,"+slave-reconf-inprog",ri,"%@");
}
/* SRI_RECONF_INPROG -> SRI_RECONF_DONE */
// 将 INPROG 状态改为 DONE 状态，表示同步已完成
if ((ri->flags & SRI_RECONF_INPROG) &&
ri->slave_master_link_status == SENTINEL_MASTER_LINK_STATUS_UP)
{
ri->flags &= ~SRI_RECONF_INPROG;
ri->flags |= SRI_RECONF_DONE;
sentinelEvent(REDIS_NOTICE,"+slave-reconf-done",ri,"%@");
/* If we are moving forward (a new slave is now configured)
* we update the change_time as we are conceptually passing
* to the next slave. */
ri->failover_state_change_time = mstime();
}
}
/* Detect if the old master was demoted as slave and generate the
* +slave event. */
// 给旧主服务器加上 DEMOTE 状态
if (role == SRI_SLAVE && ri->flags & SRI_DEMOTE) {
sentinelEvent(REDIS_NOTICE,"+slave",ri,"%@");
ri->flags &= ~SRI_DEMOTE;
}
}
// 处理 INFO 命令的回复
void sentinelInfoReplyCallback(redisAsyncContext *c, void *reply, void *privdata) {
sentinelRedisInstance *ri = c->data;
redisReply *r;
if (ri) ri->pending_commands--;
if (!reply || !ri) return;
r = reply;
if (r->type == REDIS_REPLY_STRING) {
sentinelRefreshInstanceInfo(ri,r->str);
}
}
/* Just discard the reply. We use this when we are not monitoring the return
* value of the command but its effects directly. */
// 这个回调函数用于处理不需要检查回复的命令（只使用命令的副作用）
void sentinelDiscardReplyCallback(redisAsyncContext *c, void *reply, void *privdata) {
sentinelRedisInstance *ri = c->data;
if (ri) ri->pending_commands--;
}
// 处理 PING 命令的回复
void sentinelPingReplyCallback(redisAsyncContext *c, void *reply, void *privdata) {
sentinelRedisInstance *ri = c->data;
redisReply *r;
if (ri) ri->pending_commands--;
if (!reply || !ri) return;
r = reply;
if (r->type == REDIS_REPLY_STATUS ||
r->type == REDIS_REPLY_ERROR) {
/* Update the "instance available" field only if this is an
* acceptable reply. */
// 只在实例返回 acceptable 回复时更新 last_avail_time
if (strncmp(r->str,"PONG",4) == 0 ||
strncmp(r->str,"LOADING",7) == 0 ||
strncmp(r->str,"MASTERDOWN",10) == 0)
{
// 实例运作正常
ri->last_avail_time = mstime();
} else {
// 实例运作不正常
/* Send a SCRIPT KILL command if the instance appears to be
* down because of a busy script. */
// 如果服务器因为执行脚本而进入 BUSY 状态，
// 那么尝试通过发送 SCRIPT KILL 来恢复服务器
if (strncmp(r->str,"BUSY",4) == 0 &&
(ri->flags & SRI_S_DOWN) &&
!(ri->flags & SRI_SCRIPT_KILL_SENT))
{
redisAsyncCommand(ri->cc,
sentinelDiscardReplyCallback, NULL, "SCRIPT KILL");
ri->flags |= SRI_SCRIPT_KILL_SENT;
}
}
}
// 更新实例最后一次回复 PING 命令的时间
ri->last_pong_time = mstime();
}
/* This is called when we get the reply about the PUBLISH command we send
* to the master to advertise this sentinel. */
// 处理 PUBLISH 命令的回复
void sentinelPublishReplyCallback(redisAsyncContext *c, void *reply, void *privdata) {
sentinelRedisInstance *ri = c->data;
redisReply *r;
if (ri) ri->pending_commands--;
if (!reply || !ri) return;
r = reply;
/* Only update pub_time if we actually published our message. Otherwise
* we'll retry against in 100 milliseconds. */
// 如果命令发送成功，那么更新 last_pub_time
if (r->type != REDIS_REPLY_ERROR)
ri->last_pub_time = mstime();
}
/* This is our Pub/Sub callback for the Hello channel. It's useful in order
* to discover other sentinels attached at the same master. */
// 此回调函数用于处理 Hello 频道的返回值，它可以发现其他正在订阅统一主服务器的 sentinel
void sentinelReceiveHelloMessages(redisAsyncContext *c, void *reply, void *privdata) {
sentinelRedisInstance *ri = c->data;
redisReply *r;
if (!reply || !ri) return;
r = reply;
/* Update the last activity in the pubsub channel. Note that since we
* receive our messages as well this timestamp can be used to detect
* if the link is probably disconnected even if it seems otherwise. */
// 更新最后一次接收频道命令的时间
ri->pc_last_activity = mstime();
/* Sanity check in the reply we expect, so that the code that follows
* can avoid to check for details. */
// 只处理频道发来的信息，不处理订阅时和退订时产生的信息
if (r->type != REDIS_REPLY_ARRAY ||
r->elements != 3 ||
r->element[0]->type != REDIS_REPLY_STRING ||
r->element[1]->type != REDIS_REPLY_STRING ||
r->element[2]->type != REDIS_REPLY_STRING ||
strcmp(r->element[0]->str,"message") != 0) return;
/* We are not interested in meeting ourselves */
// 只处理非自己发送的信息
if (strstr(r->element[2]->str,server.runid) != NULL) return;
{
// 分析信息，内容为
int numtokens, port, removed, canfailover;
/* Separator changed from ":" to "," in recent versions in order to
* play well with IPv6 addresses. For now we make sure to parse both
* correctly detecting if there is "," inside the string. */
char *sep = strchr(r->element[2]->str,',') ? "," : ":";
char **token = sdssplitlen(r->element[2]->str,
r->element[2]->len,
sep,1,&numtokens);
sentinelRedisInstance *sentinel;
if (numtokens == 4) {
/* First, try to see if we already have this sentinel. */
// 端口号
port = atoi(token[1]);
// sentinel 是否可以执行故障转移
canfailover = atoi(token[3]);
// 根据 runid ，获取 sentinel
sentinel = getSentinelRedisInstanceByAddrAndRunID(
ri->sentinels,token[0],port,token[2]);
// sentinel 不存在
if (!sentinel) {
/* If not, remove all the sentinels that have the same runid
* OR the same ip/port, because it's either a restart or a
* network topology change. */
// 移除所有和这个 sentinel 的地址（IP和端口）或者 runid 相同的已存在实例
removed = removeMatchingSentinelsFromMaster(ri,token[0],port,
token[2]);
// 发送移除 sentinel 实例事件
if (removed) {
sentinelEvent(REDIS_NOTICE,"-dup-sentinel",ri,
"%@ #duplicate of %s:%d or %s",
token[0],port,token[2]);
}
/* Add the new sentinel. */
// 添加新 sentinel
sentinel = createSentinelRedisInstance(NULL,SRI_SENTINEL,
token[0],port,ri->quorum,ri);
// 发送添加新 sentinel 事件
if (sentinel) {
sentinelEvent(REDIS_NOTICE,"+sentinel",sentinel,"%@");
/* The runid is NULL after a new instance creation and
* for Sentinels we don't have a later chance to fill it,
* so do it now. */
sentinel->runid = sdsnew(token[2]);
}
}
/* Update the state of the Sentinel. */
// 如果 sentinel 已存在，那么更新该 sentinel 的状态
if (sentinel) {
// 最后一次发送信息的时间
sentinel->last_hello_time = mstime();
// 是否可以执行故障转移
if (canfailover)
sentinel->flags |= SRI_CAN_FAILOVER;
else
sentinel->flags &= ~SRI_CAN_FAILOVER;
}
}
sdsfreesplitres(token,numtokens);
}
}
// 根据时间和实例类型等情况，向实例发送命令，比如 INFO 、PING 和 PUBLISH
// 虽然函数的名字包含 Ping ，但命令并不只发送 PING 命令
void sentinelPingInstance(sentinelRedisInstance *ri) {
mstime_t now = mstime();
mstime_t info_period;
int retval;
/* Return ASAP if we have already a PING or INFO already pending, or
* in the case the instance is not properly connected. */
// 函数不能在网络连接未创建时执行
if (ri->flags & SRI_DISCONNECTED) return;
/* For INFO, PING, PUBLISH that are not critical commands to send we
* also have a limit of SENTINEL_MAX_PENDING_COMMANDS. We don't
* want to use a lot of memory just because a link is not working
* properly (note that anyway there is a redundant protection about this,
* that is, the link will be disconnected and reconnected if a long
* timeout condition is detected. */
// 为了避免 sentinel 在实例处于不正常状态时，发送过多命令
// sentinel 只在待发送命令的数量未超过 SENTINEL_MAX_PENDING_COMMANDS 常量时
// 才进行命令发送
if (ri->pending_commands >= SENTINEL_MAX_PENDING_COMMANDS) return;
/* If this is a slave of a master in O_DOWN condition we start sending
* it INFO every second, instead of the usual SENTINEL_INFO_PERIOD
* period. In this state we want to closely monitor slaves in case they
* are turned into masters by another Sentinel, or by the sysadmin. */
// 对于从服务器来说， sentinel 默认每 SENTINEL_INFO_PERIOD 秒向它发送一次 INFO 命令
// 但是，当从服务器的主服务器处于 SDOWN 状态，或者正在执行故障转移时
// 为了更快速地捕捉从服务器的变动， sentinel 会将发送 INFO 命令的频率该为每秒一次
if ((ri->flags & SRI_SLAVE) &&
(ri->master->flags & (SRI_O_DOWN|SRI_FAILOVER_IN_PROGRESS))) {
info_period = 1000;
} else {
info_period = SENTINEL_INFO_PERIOD;
}
// 实例不是 SENTINEL （主服务器或者从服务器）
// 并且 SENTINEL 未收到过这个服务器的 INFO 命令回复
// 或者距离上一次该实例回复 INFO 命令已经超过 info_period 间隔
if ((ri->flags & SRI_SENTINEL) == 0 &&
(ri->info_refresh == 0 ||
(now - ri->info_refresh) > info_period))
{
/* Send INFO to masters and slaves, not sentinels. */
retval = redisAsyncCommand(ri->cc,
sentinelInfoReplyCallback, NULL, "INFO");
if (retval != REDIS_OK) return;
ri->pending_commands++;
// 如果距离上次向实例发送 PING 命令已经过了 SENTINEL_PING_PERIOD 毫秒
// 那么再次发送 PING 命令
// 实例可以是任意类型：sentinel 、主服务器或者从服务器
} else if ((now - ri->last_pong_time) > SENTINEL_PING_PERIOD) {
/* Send PING to all the three kinds of instances. */
retval = redisAsyncCommand(ri->cc,
sentinelPingReplyCallback, NULL, "PING");
if (retval != REDIS_OK) return;
ri->pending_commands++;
// 如果实例是主服务器
// 并且最后一次向主服务器的频道发送命令的时间查过 SENTINEL_PUBLISH_PERIOD
// 那么再次发送 PUBLISH 命令
// SENTINEL 通过这个 PUBLISH 命令，于其他监视相同主服务器的 SENTINEL 交流
} else if ((ri->flags & SRI_MASTER) &&
(now - ri->last_pub_time) > SENTINEL_PUBLISH_PERIOD)
{
/* PUBLISH hello messages only to masters. */
char ip[REDIS_IP_STR_LEN];
if (anetSockName(ri->cc->c.fd,ip,sizeof(ip),NULL) != -1) {
char myaddr[REDIS_IP_STR_LEN+128];
// 内容为 ", , , "
snprintf(myaddr,sizeof(myaddr),"%s,%d,%s,%d",
ip, server.port, server.runid,
(ri->flags & SRI_CAN_FAILOVER) != 0);
// 发送命令 PUBLISH __sentinel__:hello */
sentinelRedisInstance *ri;
if (c->argc != 3) goto numargserr;
if ((ri = sentinelGetMasterByNameOrReplyError(c,c->argv[2])) == NULL)
return;
addReplyDictOfRedisInstances(c,ri->slaves);
} else if (!strcasecmp(c->argv[1]->ptr,"sentinels")) {
/* SENTINEL SENTINELS */
sentinelRedisInstance *ri;
if (c->argc != 3) goto numargserr;
if ((ri = sentinelGetMasterByNameOrReplyError(c,c->argv[2])) == NULL)
return;
addReplyDictOfRedisInstances(c,ri->sentinels);
} else if (!strcasecmp(c->argv[1]->ptr,"is-master-down-by-addr")) {
/* SENTINEL IS-MASTER-DOWN-BY-ADDR */
sentinelRedisInstance *ri;
char *leader = NULL;
long port;
int isdown = 0;
if (c->argc != 4) goto numargserr;
if (getLongFromObjectOrReply(c,c->argv[3],&port,NULL) != REDIS_OK)
return;
ri = getSentinelRedisInstanceByAddrAndRunID(sentinel.masters,
c->argv[2]->ptr,port,NULL);
/* It exists? Is actually a master? Is subjectively down? It's down.
* Note: if we are in tilt mode we always reply with "0". */
if (!sentinel.tilt && ri && (ri->flags & SRI_S_DOWN) &&
(ri->flags & SRI_MASTER))
isdown = 1;
if (ri) leader = sentinelGetSubjectiveLeader(ri);
/* Reply with a two-elements multi-bulk reply: down state, leader. */
addReplyMultiBulkLen(c,2);
addReply(c, isdown ? shared.cone : shared.czero);
addReplyBulkCString(c, leader ? leader : "?");
if (leader) sdsfree(leader);
} else if (!strcasecmp(c->argv[1]->ptr,"reset")) {
/* SENTINEL RESET */
if (c->argc != 3) goto numargserr;
addReplyLongLong(c,sentinelResetMastersByPattern(c->argv[2]->ptr,SENTINEL_GENERATE_EVENT));
} else if (!strcasecmp(c->argv[1]->ptr,"get-master-addr-by-name")) {
/* SENTINEL GET-MASTER-ADDR-BY-NAME */
sentinelRedisInstance *ri;
if (c->argc != 3) goto numargserr;
ri = sentinelGetMasterByName(c->argv[2]->ptr);
if (ri == NULL) {
addReply(c,shared.nullmultibulk);
} else if (ri->info_refresh == 0) {
addReplySds(c,sdsnew("-IDONTKNOW I have not enough information to reply. Please ask another Sentinel.\r\n"));
} else {
sentinelAddr *addr = ri->addr;
/* If we are in the middle of a failover, and the slave was
* already successfully switched to master role, we can advertise
* the new address as slave in order to allow clients to talk
* with the new master ASAP. */
if ((ri->flags & SRI_FAILOVER_IN_PROGRESS) &&
ri->promoted_slave &&
ri->failover_state >= SENTINEL_FAILOVER_STATE_RECONF_SLAVES)
{
addr = ri->promoted_slave->addr;
}
addReplyMultiBulkLen(c,2);
addReplyBulkCString(c,addr->ip);
addReplyBulkLongLong(c,addr->port);
}
} else if (!strcasecmp(c->argv[1]->ptr,"failover")) {
/* SENTINEL FAILOVER */
sentinelRedisInstance *ri;
if (c->argc != 3) goto numargserr;
if ((ri = sentinelGetMasterByNameOrReplyError(c,c->argv[2])) == NULL)
return;
if (ri->flags & SRI_FAILOVER_IN_PROGRESS) {
addReplySds(c,sdsnew("-INPROG Failover already in progress\r\n"));
return;
}
if (sentinelSelectSlave(ri) == NULL) {
addReplySds(c,sdsnew("-NOGOODSLAVE No suitable slave to promote\r\n"));
return;
}
sentinelStartFailover(ri,SENTINEL_FAILOVER_STATE_WAIT_START);
ri->flags |= SRI_FORCE_FAILOVER;
addReply(c,shared.ok);
} else if (!strcasecmp(c->argv[1]->ptr,"pending-scripts")) {
/* SENTINEL PENDING-SCRIPTS */
if (c->argc != 2) goto numargserr;
sentinelPendingScriptsCommand(c);
} else {
addReplyErrorFormat(c,"Unknown sentinel subcommand '%s'",
(char*)c->argv[1]->ptr);
}
return;
numargserr:
addReplyErrorFormat(c,"Wrong number of commands for 'sentinel %s'",
(char*)c->argv[1]->ptr);
}
// sentinel 模式下的 INFO 命令
void sentinelInfoCommand(redisClient *c) {
char *section = c->argc == 2 ? c->argv[1]->ptr : "default";
sds info = sdsempty();
int defsections = !strcasecmp(section,"default");
int sections = 0;
if (c->argc > 2) {
addReply(c,shared.syntaxerr);
return;
}
if (!strcasecmp(section,"server") || defsections) {
if (sections++) info = sdscat(info,"\r\n");
sds serversection = genRedisInfoString("server");
info = sdscatlen(info,serversection,sdslen(serversection));
sdsfree(serversection);
}
if (!strcasecmp(section,"sentinel") || defsections) {
dictIterator *di;
dictEntry *de;
int master_id = 0;
if (sections++) info = sdscat(info,"\r\n");
info = sdscatprintf(info,
"# Sentinel\r\n"
"sentinel_masters:%lu\r\n"
"sentinel_tilt:%d\r\n"
"sentinel_running_scripts:%d\r\n"
"sentinel_scripts_queue_length:%ld\r\n",
dictSize(sentinel.masters),
sentinel.tilt,
sentinel.running_scripts,
listLength(sentinel.scripts_queue));
di = dictGetIterator(sentinel.masters);
while((de = dictNext(di)) != NULL) {
sentinelRedisInstance *ri = dictGetVal(de);
char *status = "ok";
if (ri->flags & SRI_O_DOWN) status = "odown";
else if (ri->flags & SRI_S_DOWN) status = "sdown";
info = sdscatprintf(info,
"master%d:name=%s,status=%s,address=%s:%d,"
"slaves=%lu,sentinels=%lu\r\n",
master_id++, ri->name, status,
ri->addr->ip, ri->addr->port,
dictSize(ri->slaves),
dictSize(ri->sentinels)+1);
}
dictReleaseIterator(di);
}
addReplySds(c,sdscatprintf(sdsempty(),"$%lu\r\n",
(unsigned long)sdslen(info)));
addReplySds(c,info);
addReply(c,shared.crlf);
}
/* ===================== SENTINEL availability checks ======================= */
/* Is this instance down from our point of view? */
void sentinelCheckSubjectivelyDown(sentinelRedisInstance *ri) {
// 实例上次正确回复 PING 命令距离现在有多久
mstime_t elapsed = mstime() - ri->last_avail_time;
/* Check if we are in need for a reconnection of one of the
* links, because we are detecting low activity.
*
* 如果检测到连接的活跃度（activity）很低，那么考虑重断开连接，并进行重连
*
* 1) Check if the command link seems connected, was connected not less
* than SENTINEL_MIN_LINK_RECONNECT_PERIOD, but still we have an
* idle time that is greater than down_after_period / 2 seconds. */
// 考虑断开实例的 cc 连接
if (ri->cc &&
(mstime() - ri->cc_conn_time) > SENTINEL_MIN_LINK_RECONNECT_PERIOD &&
(mstime() - ri->last_pong_time) > (ri->down_after_period/2))
{
sentinelKillLink(ri,ri->cc);
}
/* 2) Check if the pubsub link seems connected, was connected not less
* than SENTINEL_MIN_LINK_RECONNECT_PERIOD, but still we have no
* activity in the Pub/Sub channel for more than
* SENTINEL_PUBLISH_PERIOD * 3.
*/
// 考虑断开实例的 pc 连接
if (ri->pc &&
(mstime() - ri->pc_conn_time) > SENTINEL_MIN_LINK_RECONNECT_PERIOD &&
(mstime() - ri->pc_last_activity) > (SENTINEL_PUBLISH_PERIOD*3))
{
sentinelKillLink(ri,ri->pc);
}
/* Update the subjectively down flag. */
if (elapsed > ri->down_after_period) {
// 进入 SDOWN 状态
/* Is subjectively down */
if ((ri->flags & SRI_S_DOWN) == 0) {
// 发送事件
sentinelEvent(REDIS_WARNING,"+sdown",ri,"%@");
// 记录进入 SDOWN 状态的时间
ri->s_down_since_time = mstime();
// 打开 SDOWN 标志
ri->flags |= SRI_S_DOWN;
}
} else {
// 移除（可能有的） SDOWN 状态
/* Is subjectively up */
if (ri->flags & SRI_S_DOWN) {
// 发送事件
sentinelEvent(REDIS_WARNING,"-sdown",ri,"%@");
// 移除相关标志
ri->flags &= ~(SRI_S_DOWN|SRI_SCRIPT_KILL_SENT);
}
}
}
/* Is this instance down accordingly to the configured quorum? */
// 判断 master 是否进入 ODOWN 状态
void sentinelCheckObjectivelyDown(sentinelRedisInstance *master) {
dictIterator *di;
dictEntry *de;
int quorum = 0, odown = 0;
// 统计所有 SENTINEL 的意见，判断 master 是否进入 ODWN
if (master->flags & SRI_S_DOWN) {
/* Is down for enough sentinels? */
quorum = 1; /* the current sentinel. */
/* Count all the other sentinels. */
// 统计其他认为 master 进入 SDOWN 状态的 SENTINEL 的数量
di = dictGetIterator(master->sentinels);
while((de = dictNext(di)) != NULL) {
sentinelRedisInstance *ri = dictGetVal(de);
// 该 SENTINEL 也认为 master 已下线
if (ri->flags & SRI_MASTER_DOWN) quorum++;
}
dictReleaseIterator(di);
// 如果投票得出的支持数目大于等于判断 ODOWN 所需的票数
// 那么进入 ODOWN 状态
if (quorum >= master->quorum) odown = 1;
}
/* Set the flag accordingly to the outcome. */
if (odown) {
// master 已 ODOWN
if ((master->flags & SRI_O_DOWN) == 0) {
// 发送事件
sentinelEvent(REDIS_WARNING,"+odown",master,"%@ #quorum %d/%d",
quorum, master->quorum);
// 打开 ODOWN 标志
master->flags |= SRI_O_DOWN;
// 记录进入 ODOWN 的时间
master->o_down_since_time = mstime();
}
} else {
// 未进入 ODOWN
if (master->flags & SRI_O_DOWN) {
// 如果 master 曾经进入过 ODOWN 状态，那么移除该状态
// 发送事件
sentinelEvent(REDIS_WARNING,"-odown",master,"%@");
// 移除 ODOWN 标志
master->flags &= ~SRI_O_DOWN;
}
}
}
/* Receive the SENTINEL is-master-down-by-addr reply, see the
* sentinelAskMasterStateToOtherSentinels() function for more information. */
// 本回调函数用于处理SENTINEL 接收到其他 SENTINEL
// 发回的 SENTINEL is-master-down-by-addr 命令的回复
void sentinelReceiveIsMasterDownReply(redisAsyncContext *c, void *reply, void *privdata) {
sentinelRedisInstance *ri = c->data;
redisReply *r;
if (ri) ri->pending_commands--;
if (!reply || !ri) return;
r = reply;
/* Ignore every error or unexpected reply.
* 忽略错误回复
* Note that if the command returns an error for any reason we'll
* end clearing the SRI_MASTER_DOWN flag for timeout anyway.
*/
// 命令的回复是以下格式： to all the remaining slaves that
* still don't appear to have the configuration updated. */
// 向所有尚未同步新主服务器的从服务器发送 SLAVEOF 命令
void sentinelFailoverReconfNextSlave(sentinelRedisInstance *master) {
dictIterator *di;
dictEntry *de;
int in_progress = 0;
// 计算正在同步新主服务器的从服务器数量
di = dictGetIterator(master->slaves);
while((de = dictNext(di)) != NULL) {
sentinelRedisInstance *slave = dictGetVal(de);
// SLAVEOF 命令已发送，或者同步正在进行
if (slave->flags & (SRI_RECONF_SENT|SRI_RECONF_INPROG))
in_progress++;
}
dictReleaseIterator(di);
// 如果正在同步的从服务器的数量少于 parallel-syncs 选项的值
// 那么继续遍历从服务器，并让从服务器对新主服务器进行同步
di = dictGetIterator(master->slaves);
while(in_progress < master->parallel_syncs &&
(de = dictNext(di)) != NULL)
{
sentinelRedisInstance *slave = dictGetVal(de);
int retval;
char master_port[32];
/* Skip the promoted slave, and already configured slaves. */
// 跳过新主服务器，以及已经完成了同步的从服务器
if (slave->flags & (SRI_PROMOTED|SRI_RECONF_DONE)) continue;
/* Clear the SRI_RECONF_SENT flag if too much time elapsed without
* the slave moving forward to the next state. */
// 如果 SLAVEOF 命令已经发送了很久，但从服务器仍未完成同步
// 那么尝试重新发送命令
if ((slave->flags & SRI_RECONF_SENT) &&
(mstime() - slave->slave_reconf_sent_time) >
SENTINEL_SLAVE_RECONF_RETRY_PERIOD)
{
// 发送重拾同步事件
sentinelEvent(REDIS_NOTICE,"-slave-reconf-sent-timeout",slave,"%@");
// 清除已发送 SLAVEOF 命令的标记
slave->flags &= ~SRI_RECONF_SENT;
}
/* Nothing to do for instances that are disconnected or already
* in RECONF_SENT state. */
// 如果已向从服务器发送 SLAVEOF 命令，或者同步正在进行
// 又或者从服务器已断线，那么略过该服务器
if (slave->flags & (SRI_DISCONNECTED|SRI_RECONF_SENT|SRI_RECONF_INPROG))
continue;
/* Send SLAVEOF . */
// 向从服务器发送 SLAVEOF 命令，让它同步新主服务器
ll2string(master_port,sizeof(master_port),
master->promoted_slave->addr->port);
retval = redisAsyncCommand(slave->cc,
sentinelDiscardReplyCallback, NULL, "SLAVEOF %s %s",
master->promoted_slave->addr->ip,
master_port);
if (retval == REDIS_OK) {
// 将状态改为 SLAVEOF 命令已发送
slave->flags |= SRI_RECONF_SENT;
slave->pending_commands++;
// 更新发送 SLAVEOF 命令的时间
slave->slave_reconf_sent_time = mstime();
sentinelEvent(REDIS_NOTICE,"+slave-reconf-sent",slave,"%@");
// 增加当前正在同步的从服务器的数量
in_progress++;
}
}
dictReleaseIterator(di);
// 检查故障转移引起的同步操作是否已经结束
sentinelFailoverDetectEnd(master);
}
/* This function is called when the slave is in
* SENTINEL_FAILOVER_STATE_UPDATE_CONFIG state. In this state we need
* to remove it from the master table and add the promoted slave instead.
*
* 这个函数在 SENTINEL_FAILOVER_STATE_UPDATE_CONFIG 状态时执行。
* 它从 sentinel.masters 表中移除当前 master ，并被升级的从服务器（新主服务器）
* 添加到 sentinel.masters 表中
*
* If there are no promoted slaves as this instance is unique, we remove
* and re-add it with the same address to trigger a complete state
* refresh.
*
* 如果没有新主服务器，那么我们先移除这个 master ，然后重新将它添加到表中，
* 以此来引发一次完整的状态刷新。
*/
void sentinelFailoverSwitchToPromotedSlave(sentinelRedisInstance *master) {
/// 选出要添加的 master
sentinelRedisInstance *ref = master->promoted_slave ?
master->promoted_slave : master;
sds old_master_ip;
int old_master_port;
// 发送更新 master 事件
sentinelEvent(REDIS_WARNING,"+switch-master",master,"%s %s %d %s %d",
// 原 master 信息
master->name, master->addr->ip, master->addr->port,
// 新 master 信息
ref->addr->ip, ref->addr->port);
// 记录原 master 信息
old_master_ip = sdsdup(master->addr->ip);
old_master_port = master->addr->port;
// 用新主服务器的信息代替原 master 的信息
sentinelResetMasterAndChangeAddress(master,ref->addr->ip,ref->addr->port);
/* If this is a real switch, that is, we have master->promoted_slave not
* NULL, then we want to add the old master as a slave of the new master,
* but flagging it with SRI_DEMOTE so that we know we'll need to send
* SLAVEOF once the old master is reachable again. */
// 如果这是一次实际的 switch 操作，
// 那么我们将原 master 切换成新主服务器的从服务器实例，
// 并为该实例添加 DEMOTE 标志，让它可以在重新上线时，自动对新主服务器进行同步
if (master != ref) {
/* Add the new slave, but don't generate a Sentinel event as it will
* happen later when finally the instance will claim to be a slave
* in the INFO output. */
// 添加实例，但不发送事件，因为后面对 INFO 命令的检查会发送事件
createSentinelRedisInstance(NULL,SRI_SLAVE|SRI_DEMOTE,
old_master_ip, old_master_port, master->quorum, master);
}
sdsfree(old_master_ip);
}
// 执行故障转移
void sentinelFailoverStateMachine(sentinelRedisInstance *ri) {
redisAssert(ri->flags & SRI_MASTER);
// 实例未进行故障转移，直接返回
if (!(ri->flags & SRI_FAILOVER_IN_PROGRESS)) return;
switch(ri->failover_state) {
// 等待故障转移开始
case SENTINEL_FAILOVER_STATE_WAIT_START:
sentinelFailoverWaitStart(ri);
break;
// 选择新主服务器
case SENTINEL_FAILOVER_STATE_SELECT_SLAVE:
sentinelFailoverSelectSlave(ri);
break;
// 升级被选中的从服务器为新主服务器
case SENTINEL_FAILOVER_STATE_SEND_SLAVEOF_NOONE:
sentinelFailoverSendSlaveOfNoOne(ri);
break;
// 等待升级生效，如果升级超时，那么重新选择新主服务器
case SENTINEL_FAILOVER_STATE_WAIT_PROMOTION:
sentinelFailoverWaitPromotion(ri);
break;
// 向从服务器发送 SLAVEOF 命令，让它们同步新主服务器
case SENTINEL_FAILOVER_STATE_RECONF_SLAVES:
sentinelFailoverReconfNextSlave(ri);
break;
// 检查故障转移引起的同步操作是否已经完成
case SENTINEL_FAILOVER_STATE_DETECT_END:
sentinelFailoverDetectEnd(ri);
break;
}
}
/* Abort a failover in progress with the following steps:
*
* 执行以下步骤，取消故障转移：
*
* 1) If this instance is the leaer send a SLAVEOF command to all the already
* reconfigured slaves if any to configure them to replicate with the
* original master.
* 通过发送 SLAVEOF 命令，让从服务器将复制目标指向原来的主服务器，
* 而不是新主服务器。
*
* 2) For both leaders and observers: clear the failover flags and state in
* the master instance.
* 清除所有 sentinel 中（包括 leader 和 observer）关于实例的故障转移状态
*
* 3) If there is already a promoted slave and we are the leader, and this
* slave is not DISCONNECTED, try to reconfigure it to replicate
* back to the master as well, sending a best effort SLAVEOF command.
* 如果已经有了新主服务器，并且该服务器状态正常，
* 那么向它发送一个 SLAVEOF 命令，让它重新变成从服务器，并复制原主服务器
*/
void sentinelAbortFailover(sentinelRedisInstance *ri) {
char master_port[32];
dictIterator *di;
dictEntry *de;
int sentinel_role;
redisAssert(ri->flags & SRI_FAILOVER_IN_PROGRESS);
ll2string(master_port,sizeof(master_port),ri->addr->port);
/* Clear failover related flags from slaves.
* Also if we are the leader make sure to send SLAVEOF commands to all the
* already reconfigured slaves in order to turn them back into slaves of
* the original master. */
// 遍历所有从服务器
di = dictGetIterator(ri->slaves);
while((de = dictNext(di)) != NULL) {
sentinelRedisInstance *slave = dictGetVal(de);
// 当前 sentinel 为 leader sentinel
// 并且该从服务器为新主服务器
if ((ri->flags & SRI_I_AM_THE_LEADER) &&
!(slave->flags & SRI_DISCONNECTED) &&
(slave->flags & (SRI_PROMOTED|SRI_RECONF_SENT|SRI_RECONF_INPROG|
SRI_RECONF_DONE)))
{
int retval;
// 发送 SLAVEOF 命令，让它重新开始复制旧主服务器
retval = redisAsyncCommand(slave->cc,
sentinelDiscardReplyCallback, NULL, "SLAVEOF %s %s",
ri->addr->ip,
master_port);
if (retval == REDIS_OK)
sentinelEvent(REDIS_NOTICE,"-slave-reconf-undo",slave,"%@");
}
// 清除故障迁移所产生的标志
slave->flags &= ~(SRI_RECONF_SENT|SRI_RECONF_INPROG|SRI_RECONF_DONE);
}
dictReleaseIterator(di);
// 清除状态
sentinel_role = (ri->flags & SRI_I_AM_THE_LEADER) ? SENTINEL_LEADER :
SENTINEL_OBSERVER;
ri->flags &= ~(SRI_FAILOVER_IN_PROGRESS|SRI_I_AM_THE_LEADER|SRI_FORCE_FAILOVER);
ri->failover_state = SENTINEL_FAILOVER_STATE_NONE;
ri->failover_state_change_time = mstime();
if (ri->promoted_slave) {
// 停止重配置，调用用户脚本
sentinelCallClientReconfScript(ri,sentinel_role,"abort",
ri->promoted_slave->addr,ri->addr);
// 取消新服务器的升级标志
ri->promoted_slave->flags &= ~SRI_PROMOTED;
// 清空新服务器
ri->promoted_slave = NULL;
}
}
/* The following is called only for master instances and will abort the
* failover process if:
*
* 当满足以下条件时 sentinel 停止执行故障转移
*
* 1) The failover is in progress.
* 故障转移正在执行中
*
* 2) We already promoted a slave.
* sentinel 已经选出了新主服务器
*
* 3) The promoted slave is in extended SDOWN condition.
* 新主服务器进入了 extended SDOWN 状态
*/
void sentinelAbortFailoverIfNeeded(sentinelRedisInstance *ri) {
/* Failover is in progress? Do we have a promoted slave? */
// 没有在进行故障转移，直接返回
if (!(ri->flags & SRI_FAILOVER_IN_PROGRESS) || !ri->promoted_slave) return;
/* Is the promoted slave into an extended SDOWN state? */
// 如果新主服务器进入 SDOWN 状态，但是断线的时长在给定范围之内
// 那么不断线
if (!(ri->promoted_slave->flags & SRI_S_DOWN) ||
(mstime() - ri->promoted_slave->s_down_since_time) <
(ri->down_after_period * SENTINEL_EXTENDED_SDOWN_MULTIPLIER)) return;
// 服务器进入 SDOWN 状态，并且断线的时长超出了给定范围。。。
// 发送故障转移取消事件
sentinelEvent(REDIS_WARNING,"-failover-abort-x-sdown",ri->promoted_slave,"%@");
// 取消故障转移的执行
sentinelAbortFailover(ri);
}
/* ======================== SENTINEL timer handler ==========================
* This is the "main" our Sentinel, being sentinel completely non blocking
* in design. The function is called every second.
* -------------------------------------------------------------------------- */
/* Perform scheduled operations for the specified Redis instance. */
// 对给定的实例执行定期操作
void sentinelHandleRedisInstance(sentinelRedisInstance *ri) {
/* ========== MONITORING HALF ============ */
/* ========== 监控操作 =========*/
/* Every kind of instance */
/* 对所有类型实例进行处理 */
// 如果有需要的话，创建连向实例的网络连接
sentinelReconnectInstance(ri);
// 根据情况，向实例发送 PING、 INFO 或者 PUBLISH 命令
sentinelPingInstance(ri);
/* Masters and slaves */
/* 对主服务器和从服务器进行处理*/
if (ri->flags & (SRI_MASTER|SRI_SLAVE)) {
/* Nothing so far. */
}
/* Only masters */
/* 对主服务器进行处理 */
if (ri->flags & SRI_MASTER) {
// 如果本 SENTINEL 认为主服务器已经下线（主观下线）
// 那么向其他监视相同主服务器的 SENTINEL 询问意见
// 看是否能满足客观下线状态
sentinelAskMasterStateToOtherSentinels(ri);
}
/* ============== ACTING HALF ============= */
/* We don't proceed with the acting half if we are in TILT mode.
* TILT happens when we find something odd with the time, like a
* sudden change in the clock. */
if (sentinel.tilt) {
// 如果 TILI 模式未解除，那么不执行动作
if (mstime()-sentinel.tilt_start_time < SENTINEL_TILT_PERIOD) return;
// 时间已过，退出 TILT 模式
sentinel.tilt = 0;
sentinelEvent(REDIS_WARNING,"-tilt",NULL,"#tilt mode exited");
}
/* Every kind of instance */
// 检查所有实例是否进入 SDOWN 状态
sentinelCheckSubjectivelyDown(ri);
/* Masters and slaves */
if (ri->flags & (SRI_MASTER|SRI_SLAVE)) {
/* Nothing so far. */
}
/* Only masters */
/* 对主服务器进行处理 */
if (ri->flags & SRI_MASTER) {
// 判断 master 是否进入 ODOWN 状态
sentinelCheckObjectivelyDown(ri);
// 检查是否需要对主服务器进行故障转移
sentinelStartFailoverIfNeeded(ri);
// 执行故障转移操作
sentinelFailoverStateMachine(ri);
// 对新主服务器进行断线检查
// 并在必要时取消故障转移的执行
sentinelAbortFailoverIfNeeded(ri);
}
}
/* Perform scheduled operations for all the instances in the dictionary.
* Recursively call the function against dictionaries of slaves. */
// 对主服务器、主服务的所有从服务器、以及主服务器的所有 sentinel
// 执行定期操作
//
// sentinelHandleRedisInstance
// |
// |
// v
// master
// / \
// / \
// v v
// slaves sentinels
void sentinelHandleDictOfRedisInstances(dict *instances) {
dictIterator *di;
dictEntry *de;
sentinelRedisInstance *switch_to_promoted = NULL;
/* There are a number of things we need to perform against every master. */
// 遍历多个实例，这些实例可以是多个主服务器、多个从服务器或者多个 sentinel
di = dictGetIterator(instances);
while((de = dictNext(di)) != NULL) {
sentinelRedisInstance *ri = dictGetVal(de);
// 执行调度操作
sentinelHandleRedisInstance(ri);
// 如果被遍历的是主服务器，那么递归地遍历该主服务器的所有从服务器
// 以及所有 sentinel
if (ri->flags & SRI_MASTER) {
// 所有从服务器
sentinelHandleDictOfRedisInstances(ri->slaves);
// 所有 sentinel
sentinelHandleDictOfRedisInstances(ri->sentinels);
// 进行新旧主服务器切换
if (ri->failover_state == SENTINEL_FAILOVER_STATE_UPDATE_CONFIG) {
switch_to_promoted = ri;
}
}
}
// 切换到新主服务器
if (switch_to_promoted)
sentinelFailoverSwitchToPromotedSlave(switch_to_promoted);
dictReleaseIterator(di);
}
/* This function checks if we need to enter the TITL mode.
*
* 这个函数检查 sentinel 是否需要进入 TITL 模式。
*
* The TILT mode is entered if we detect that between two invocations of the
* timer interrupt, a negative amount of time, or too much time has passed.
*
* 当程序发现两次执行 sentinel 之间的时间差为负值，或者过大时，
* 就会进入 TILT 模式。
*
* Note that we expect that more or less just 100 milliseconds will pass
* if everything is fine. However we'll see a negative number or a
* difference bigger than SENTINEL_TILT_TRIGGER milliseconds if one of the
* following conditions happen:
*
* 通常来说，两次执行 sentinel 之间的差会在 100 毫秒左右，
* 但当出现以下内容时，这个差就可能会出现异常：
*
* 1) The Sentiel process for some time is blocked, for every kind of
* random reason: the load is huge, the computer was frozen for some time
* in I/O or alike, the process was stopped by a signal. Everything.
*
* sentinel 进程因为某些原因而被阻塞，比如载入的数据太大，计算机 I/O 任务繁重，
* 进程被信号停止，诸如此类。
*
* 2) The system clock was altered significantly.
* 系统的时钟产生了非常明显的变化。
*
* Under both this conditions we'll see everything as timed out and failing
* without good reasons. Instead we enter the TILT mode and wait
* for SENTINEL_TILT_PERIOD to elapse before starting to act again.
*
* 当出现以上两种情况时， sentinel 可能会将任何实例都视为掉线，并无原因地判断实例为失效。
* 为了避免这种情况，我们让 sentinel 进入 TILT 模式，
* 停止进行任何动作，并等待 SENTINEL_TILT_PERIOD 秒钟。
*
* During TILT time we still collect information, we just do not act.
*
* TILT 模式下的 sentinel 仍然会进行监控并收集信息，
* 它只是不执行诸如故障转移、下线判断之类的操作而已。
*/
void sentinelCheckTiltCondition(void) {
// 计算当前时间
mstime_t now = mstime();
// 计算上次运行 sentinel 和当前时间的差
mstime_t delta = now - sentinel.previous_time;
// 如果差为负数，或者大于 2 秒钟，那么进入 TILT 模式
if (delta < 0 || delta > SENTINEL_TILT_TRIGGER) {
// 打开标记
sentinel.tilt = 1;
// 记录进入 TILT 模式的开始时间
sentinel.tilt_start_time = mstime();
// 打印事件
sentinelEvent(REDIS_WARNING,"+tilt",NULL,"#tilt mode entered");
}
// 更新最后一次 sentinel 运行时间
sentinel.previous_time = mstime();
}
// sentinel 模式的主函数，由 redis.c/serverCron 函数调用
void sentinelTimer(void) {
// 记录本次 sentinel 调用的事件，
// 并判断是否需要进入 TITL 模式
sentinelCheckTiltCondition();
// 执行定期操作
// 比如 PING 实例、分析主服务器和从服务器的 INFO 命令
// 向其他监视相同主服务器的 sentinel 发送问候信息
// 并接收其他 sentinel 发来的问候信息
// 执行故障转移操作，等等
sentinelHandleDictOfRedisInstances(sentinel.masters);
// 运行等待执行的脚本
sentinelRunPendingScripts();
// 清理已执行完毕的脚本，并重试出错的脚本
sentinelCollectTerminatedScripts();
// 杀死运行超时的脚本
sentinelKillTimedoutScripts();