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Sentinel是什么？Redis高可用是什么？参考博文：Redis - 主从复制那些事与高可用sentinel 和深入学习Redis高可用之Sentinel相关概念。
本篇博文分享的是一主二从三哨兵模式。至于为什么用三个哨兵，同第一段。本文是模拟环境，都是一个服务器上面。
【1】POM文件和配置
① pom文件
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.1.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.boot.redis</groupId>
<artifactId>boot-redis</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>boot-redis</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-redis</artifactId>
<exclusions>
<exclusion>
<groupId>redis.clients</groupId>
<artifactId>jedis</artifactId>
</exclusion>
<exclusion>
<groupId>io.lettuce</groupId>
<artifactId>lettuce-core</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>redis.clients</groupId>
<artifactId>jedis</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-pool2</artifactId>
<version>2.5.0</version>
<!--<version>2.4.2</version>-->
</dependency>
</dependencies>
② yml简单配置
spring:
redis:
host: 192.168.2.110 #哨兵模式下不用配置
port: 6379 # 哨兵模式下不用配置
password: admin
jedis:
pool:
#最大连接数
max-active: 1024
#最大阻塞等待时间(负数表示没限制)
max-wait: 20000
#最大空闲
max-idle: 200
#最小空闲
min-idle: 10
sentinel:
master: mymaster
nodes: 192.168.2.110:26379,192.168.2.110:26380,192.168.2.110:26381
server:
port: 8088
至于客户端使用jedis或者lettuce等相关详细配置，这里回头更新。本文重点不在这里。
③ redis服务配置
6379.conf(默认为master)：
port 6379
masterauth admin
requirepass admin
protected-mode yes
# 服务器ip地址
bind 192.168.2.110
6380配置(slave):
port 6380
masterauth admin
requirepass admin
protected-mode yes
# 服务器ip地址
bind 192.168.2.110
slaveof 192.168.2.110 6379
6381同6380，只是端口不一致。若找不到在redis.conf中对应位置，博文末尾GitHub中已经提交相关配置。
④ 哨兵配置
sentinel.conf(默认端口26379)：
port 26379
sentinel monitor mymaster 192.168.2.110 6379 2
sentinel auth-pass mymaster admin
sentinel down-after-milliseconds mymaster 15000
sentinel parallel-syncs mymaster 1
sentinel failover-timeout mymaster 80000
bind 192.168.2.110
protected-mode yes
其他两个哨兵配置文件类似，只是需要修改一下端口分别为26380和26381。
⑤ RedisConfig类
@Configuration
@EnableAutoConfiguration
public class RedisConfig {
private static Logger logger = LoggerFactory.getLogger(RedisConfig.class);
@Value("#{'${spring.redis.sentinel.nodes}'.split(',')}")
private List<String> nodes;
@Bean
@ConfigurationProperties(prefix="spring.redis")
public JedisPoolConfig getRedisConfig(){
JedisPoolConfig config = new JedisPoolConfig();
return config;
}
@Bean
public RedisSentinelConfiguration sentinelConfiguration(){
RedisSentinelConfiguration redisSentinelConfiguration = new RedisSentinelConfiguration();
//配置matser的名称
redisSentinelConfiguration.master("mymaster");
//配置redis的哨兵sentinel
Set<RedisNode> redisNodeSet = new HashSet<>();
nodes.forEach(x->{
redisNodeSet.add(new RedisNode(x.split(":")[0],Integer.parseInt(x.split(":")[1])));
});
logger.info("redisNodeSet -->"+redisNodeSet);
redisSentinelConfiguration.setSentinels(redisNodeSet);
return redisSentinelConfiguration;
}
@Bean
public JedisConnectionFactory jedisConnectionFactory(JedisPoolConfig jedisPoolConfig,RedisSentinelConfiguration sentinelConfig) {
JedisConnectionFactory jedisConnectionFactory = new JedisConnectionFactory(sentinelConfig,jedisPoolConfig);
return jedisConnectionFactory;
}
}
然后在服务器依次启动redis服务6379、6380、6381和哨兵服务26379/26380以及26381。
此时可以通过命令窗口查看主从以及哨兵状况，可以使用命令进行主从切换，查看哨兵选举。
另外将项目打包放到服务器运行，查看当master挂掉时，SpringBoot所获取到的信息与转变。
【2】几点说明
① 哨兵之间通信
哨兵启动后，相互之间是保持通信的：
如下所示，一个哨兵挂掉重启后将会从其他哨兵获取最新信息：
② 当master挂掉之后，三个哨兵需要选举出来一个leader进行主从转移
③ 如果哨兵挂掉，则MasterListener将会隔5秒重试
④ 如果master挂掉，MasterListener将会通过Sentinel获取最新的master信息并重置JedisSentinelPool
所以不用担心master挂掉，SpringBoot会怎么办。有MasterListener在，一切OK。
⑤ 哨兵配置动态修改
哨兵启动后，配置文件是会被动态改变的，如下所示：
port 26379
sentinel myid 8ac857af0b63edc73e07cce9c11462eef047704d
sentinel monitor mymaster 127.0.0.1 6380 2
sentinel down-after-milliseconds mymaster 15000
sentinel failover-timeout mymaster 80000
sentinel auth-pass mymaster admin
bind 192.168.2.110
protected-mode yes
# Generated by CONFIG REWRITE
dir "/root"
sentinel config-epoch mymaster 1
sentinel leader-epoch mymaster 1
sentinel known-slave mymaster 192.168.2.110 6379
sentinel known-slave mymaster 127.0.0.1 6381
sentinel known-sentinel mymaster 192.168.2.110 26381 b3d9ee9efae47556349a733ed668385d8083b5cc
sentinel known-sentinel mymaster 192.168.2.110 26380 e7a100d97d70834ea3b117cf23a4b08f7a46b425
sentinel current-epoch 1
【3】几个类
这里面有几个类十分重要 ，建议查看源码跟踪一番。
① JedisConnectionFactory
时序图如下：
重点在步骤12中，MasterListener继承了Thread，它是个单独的线程，通过Jedis监听Redis的哨兵，如果收到master改变的消息，那么会修改JedisFactory。
如下图所示是MasterListener收到master节点变化的消息：
想要debug跟踪源码的同学可以在下图处打上断点：
② JedisSentinelPool
其构造方法如下：
public JedisSentinelPool(String masterName, Set<String> sentinels,
final GenericObjectPoolConfig poolConfig, final int connectionTimeout, final int soTimeout,
final String password, final int database, final String clientName) {
this.poolConfig = poolConfig;
this.connectionTimeout = connectionTimeout;
this.soTimeout = soTimeout;
this.password = password;
this.database = database;
this.clientName = clientName;
HostAndPort master = initSentinels(sentinels, masterName);
initPool(master);
}
其中initSentinels(sentinels, masterName)就是根据哨兵和master名字来获取master的信息–host和port。然后根据获取的maser来初始化pool(所以yml中不用配置spring.redis.host和spring.redis.port)。
从应用启动也可以看到这一点：
获取HostAndPort master方法如下所示：
private HostAndPort initSentinels(Set<String> sentinels, final String masterName) {
HostAndPort master = null;
boolean sentinelAvailable = false;
log.info("Trying to find master from available Sentinels...");
//遍历sentinels，获取master，然后基于该master创建pool
for (String sentinel : sentinels) {
final HostAndPort hap = HostAndPort.parseString(sentinel);
log.fine("Connecting to Sentinel " + hap);
Jedis jedis = null;
try {
jedis = new Jedis(hap.getHost(), hap.getPort());
//根据哨兵的host port 以及masterName获取masterAddr
List<String> masterAddr = jedis.sentinelGetMasterAddrByName(masterName);
// connected to sentinel...
sentinelAvailable = true;
if (masterAddr == null || masterAddr.size() != 2) {
log.warning("Can not get master addr, master name: " + masterName + ". Sentinel: " + hap
+ ".");
continue;
}
//转换格式
master = toHostAndPort(masterAddr);
log.fine("Found Redis master at " + master);
break;
} catch (JedisException e) {
// resolves #1036, it should handle JedisException there's another chance
// of raising JedisDataException
log.warning("Cannot get master address from sentinel running @ " + hap + ". Reason: " + e
+ ". Trying next one.");
} finally {
if (jedis != null) {
jedis.close();
}
}
}
if (master == null) {
if (sentinelAvailable) {
// can connect to sentinel, but master name seems to not
// monitored
throw new JedisException("Can connect to sentinel, but " + masterName
+ " seems to be not monitored...");
} else {
throw new JedisConnectionException("All sentinels down, cannot determine where is "
+ masterName + " master is running...");
}
}
log.info("Redis master running at " + master + ", starting Sentinel listeners...");
//如下，启动每个哨兵的监听
for (String sentinel : sentinels) {
final HostAndPort hap = HostAndPort.parseString(sentinel);
MasterListener masterListener = new MasterListener(masterName, hap.getHost(), hap.getPort());
// whether MasterListener threads are alive or not, process can be stopped
masterListener.setDaemon(true);
masterListeners.add(masterListener);
masterListener.start();
}
return master;
}
初始化pool的方法如下所示：
private void initPool(HostAndPort master) {
if (!master.equals(currentHostMaster)) {
currentHostMaster = master;
//判断JedisFactory是否为null，为null则使用master创建
if (factory == null) {
factory = new JedisFactory(master.getHost(), master.getPort(), connectionTimeout,
soTimeout, password, database, clientName, false, null, null, null);
initPool(poolConfig, factory);
} else {
factory.setHostAndPort(currentHostMaster);
// although we clear the pool, we still have to check the
// returned object
// in getResource, this call only clears idle instances, not
// borrowed instances
internalPool.clear();
}
log.info("Created JedisPool to master at " + master);
}
}
③ MasterListener
MasterListener 是一个继承自Thread 的线程类，用来监听哨兵的master改变信息。 收到master改变的消息后，调用initPool方法修改JedisFactory，进而会影响connection的获取。
protected class MasterListener extends Thread {
protected String masterName;
protected String host;
protected int port;
protected long subscribeRetryWaitTimeMillis = 5000;
protected volatile Jedis j;
protected AtomicBoolean running = new AtomicBoolean(false);
protected MasterListener() {
}
public MasterListener(String masterName, String host, int port) {
super(String.format("MasterListener-%s-[%s:%d]", masterName, host, port));
this.masterName = masterName;
this.host = host;
this.port = port;
}
public MasterListener(String masterName, String host, int port,
long subscribeRetryWaitTimeMillis) {
this(masterName, host, port);
this.subscribeRetryWaitTimeMillis = subscribeRetryWaitTimeMillis;
}
//主要功能如下
@Override
public void run() {
running.set(true);
while (running.get()) {
//拿到一个Jedis
j = new Jedis(host, port);
try {
// double check that it is not being shutdown
if (!running.get()) {
break;
}
//发布订阅模式
j.subscribe(new JedisPubSub() {
@Override
public void onMessage(String channel, String message) {
log.fine("Sentinel " + host + ":" + port + " published: " + message + ".");
String[] switchMasterMsg = message.split(" ");
if (switchMasterMsg.length > 3) {
if (masterName.equals(switchMasterMsg[0])) {
//这里，重置initPool
initPool(toHostAndPort(Arrays.asList(switchMasterMsg[3], switchMasterMsg[4])));
} else {
log.fine("Ignoring message on +switch-master for master name "
+ switchMasterMsg[0] + ", our master name is " + masterName);
}
} else {
log.severe("Invalid message received on Sentinel " + host + ":" + port
+ " on channel +switch-master: " + message);
}
}
}, "+switch-master");
} catch (JedisConnectionException e) {
if (running.get()) {
log.log(Level.SEVERE, "Lost connection to Sentinel at " + host + ":" + port
+ ". Sleeping 5000ms and retrying.", e);
try {
Thread.sleep(subscribeRetryWaitTimeMillis);
} catch (InterruptedException e1) {
log.log(Level.SEVERE, "Sleep interrupted: ", e1);
}
} else {
log.fine("Unsubscribing from Sentinel at " + host + ":" + port);
}
} finally {
j.close();
}
}
}
public void shutdown() {
try {
log.fine("Shutting down listener on " + host + ":" + port);
running.set(false);
// This isn't good, the Jedis object is not thread safe
if (j != null) {
j.disconnect();
}
} catch (Exception e) {
log.log(Level.SEVERE, "Caught exception while shutting down: ", e);
}
}
}
参考博文：
Redis - 主从复制那些事与高可用sentinel
深入学习Redis高可用之Sentinel相关概念
SpringBoot2.0整合Redis
Redis - 发布订阅机制详解
GitHub地址：https://github.com/JanusJ/SpringBoot