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# Example sentinel.conf# 定义sentinel 服务端口号port 26379
# 针对 使用端口映射的方式的启动，指定ip:port# sentinel announce-ip <ip># sentinel announce-port <port># 工作目录定义dir /tmp
# 要监视的redis master 定义, 可配置多个 master-name 不同即可# sentinel monitor <master-name> <ip> <redis-port> <quorum>sentinel monitor mymaster 127.0.0.1 6379 2
# 定义master/slave 的密码，要求同一主从服务所有密码必须保持一致# sentinel auth-pass <master-name> <password>
# 定义master 不可达持续多少毫秒后开始定义为节点下线，默认30ssentinel down-after-milliseconds mymaster 30000
# sentinel parallel-syncs <master-name> <numslaves># 在故障转移期间同时与新的master同步的slave数量sentinel parallel-syncs mymaster 1
# 定义进行故障转移的超时时间，默认3分钟sentinel failover-timeout mymaster 180000
# 发生故障转移时调用的通知脚本,被调用时会传递两个参数: eventType, eventDescription# sentinel notification-script mymaster /var/redis/notify.sh
# master 变更时调用脚本配置# 调用时会传递如下参数# <master-name> <role> <state> <from-ip> <from-port> <to-ip> <to-port># sentinel client-reconfig-script mymaster /var/redis/reconfig.sh

 # 使用 redis-sentinel 程序启动, 这个程序不一定会有，需要自己编译 redis-sentinel /path/to/sentinel.conf # 使用 redis-server 程序启动, 一定可用 # 测试时可以加上 --protected-mode no, 在不设置密码情况下访问redis redis-server /path/to/sentinel.conf --sentinel

 通过redis-cli 连接到sentinel 服务内部： redis-cli -p 26379 # 连接到sentinel info sentinel # 查看哨兵信息 SENTINEL slaves mymaster # 查看master下的slave服务器情况 SENTINEL sentinels mymaster # 查看master的哨兵服务器列表 SENTINEL get-master-addr-by-name mymaster # 获取master地址信息

 SENTINEL get-master-addr-by-name mymaster # 获取master地址信息

 <dependency> <groupId>redis.clients</groupId> <artifactId>jedis</artifactId> <version>2.9.0</version> </dependency>

public class RedisSentinelTest {
 @Test public void testSentinel() throws Exception { // 池化基础信息配置 JedisPoolConfig jedisPoolConfig = new JedisPoolConfig(); jedisPoolConfig.setMaxTotal(10); jedisPoolConfig.setMaxIdle(5); jedisPoolConfig.setMinIdle(5); // 哨兵连接信息配置 String masterName = "mymaster"; Set<String> sentinels = new HashSet<>(); sentinels.add("127.0.0.1:26379"); sentinels.add("127.0.0.1:26378"); sentinels.add("127.0.0.1:26377"); // 在redis需要使用密码访问时，传入即可 String password = null; // 使用 JedisSentinelPool 封装哨兵的访问细节 JedisSentinelPool pool = new JedisSentinelPool(masterName, sentinels, jedisPoolConfig, password); Jedis jedis = pool.getResource(); String key = "key1"; String value = "Value1"; jedis.set(key, value); System.out.println("set a value to Redis over. " + key + "->" + value); value = jedis.get("key1"); System.out.println("get a value from Redis over. " + key + "->" + value); pool.close(); }}

 // redis.clients.jedis.JedisSentinelPool#JedisSentinelPool public JedisSentinelPool(String masterName, Set<String> sentinels) { this(masterName, sentinels, new GenericObjectPoolConfig(), Protocol.DEFAULT_TIMEOUT, null, Protocol.DEFAULT_DATABASE); } public JedisSentinelPool(String masterName, Set<String> sentinels, final GenericObjectPoolConfig poolConfig, int timeout, final String password, final int database) { this(masterName, sentinels, poolConfig, timeout, timeout, password, database); } public JedisSentinelPool(String masterName, Set<String> sentinels, final GenericObjectPoolConfig poolConfig, final int timeout, final int soTimeout, final String password, final int database) { this(masterName, sentinels, poolConfig, timeout, soTimeout, password, database, null); } 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; // 从sentinel中获取master信息，关键 HostAndPort master = initSentinels(sentinels, masterName); // 初始化连接池，非本文重点 initPool(master); }
 private HostAndPort initSentinels(Set<String> sentinels, final String masterName) {
 HostAndPort master = null; boolean sentinelAvailable = false;
 log.info("Trying to find master from available Sentinels..."); // 依次遍历 sentinels, 直到找到一个可用的sentinel 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()); // 向sentinel发送命令请求: SENTINEL get-master-addr-by-name mymaster, 获取master地址信息 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; }
 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..."); // 为每个 sentinel, 建立一个监听线程, 监听 sentinel 的 +switch-master 信息 // 当master发生变化时，重新初始化连接池 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; } // 每个 sentinel 监听线程事务处理流程如下 // redis.clients.jedis.JedisSentinelPool.MasterListener#run @Override public void run() {
 running.set(true);
 while (running.get()) {
 j = new Jedis(host, port);
 try { // double check that it is not being shutdown if (!running.get()) { break; } // SUBSCRIBE +switch-master j.subscribe(new JedisPubSub() { @Override public void onMessage(String channel, String message) { log.fine("Sentinel " + host + ":" + port + " published: " + message + ".");
 String[] switchMasterMsg = message.split(" "); // 格式为: masterName xx xx masterHost masterPort if (switchMasterMsg.length > 3) {
 if (masterName.equals(switchMasterMsg[0])) { 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(); } } }

 // redis.clients.jedis.JedisSentinelPool#initPool private void initPool(HostAndPort master) { if (!master.equals(currentHostMaster)) { currentHostMaster = master; 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); } } // redis.clients.util.Pool#initPool public void initPool(final GenericObjectPoolConfig poolConfig, PooledObjectFactory<T> factory) {
 if (this.internalPool != null) { try { closeInternalPool(); } catch (Exception e) { } }
 this.internalPool = new GenericObjectPool<T>(factory, poolConfig); }

 // redis.clients.jedis.JedisSentinelPool#getResource @Override public Jedis getResource() { while (true) { // 调用父类方法获取实例 Jedis jedis = super.getResource(); jedis.setDataSource(this);
 // get a reference because it can change concurrently final HostAndPort master = currentHostMaster; final HostAndPort connection = new HostAndPort(jedis.getClient().getHost(), jedis.getClient() .getPort()); // host:port 比对，如果master未变化，说明获取到了正确的连接，返回 if (master.equals(connection)) { // connected to the correct master return jedis; }  // 如果master 发生了切换，则将当前连接释放，继续尝试获取master连接 else { returnBrokenResource(jedis); } } } // redis.clients.util.Pool#getResource public T getResource() { try { return internalPool.borrowObject(); } catch (NoSuchElementException nse) { throw new JedisException("Could not get a resource from the pool", nse); } catch (Exception e) { throw new JedisConnectionException("Could not get a resource from the pool", e); } } // org.apache.commons.pool2.impl.GenericObjectPool#borrowObject() @Override public T borrowObject() throws Exception { return borrowObject(getMaxWaitMillis()); } // org.apache.commons.pool2.impl.GenericObjectPool#borrowObject(long) public T borrowObject(final long borrowMaxWaitMillis) throws Exception { assertOpen();
 final AbandonedConfig ac = this.abandonedConfig; if (ac != null && ac.getRemoveAbandonedOnBorrow() && (getNumIdle() < 2) && (getNumActive() > getMaxTotal() - 3) ) { removeAbandoned(ac); }
 PooledObject<T> p = null;
 // Get local copy of current config so it is consistent for entire // method execution final boolean blockWhenExhausted = getBlockWhenExhausted();
 boolean create; final long waitTime = System.currentTimeMillis();
 while (p == null) { create = false; p = idleObjects.pollFirst(); if (p == null) { // 没有获取到连接时，主动创建一个 p = create(); if (p != null) { create = true; } } if (blockWhenExhausted) { if (p == null) { if (borrowMaxWaitMillis < 0) { p = idleObjects.takeFirst(); } else { p = idleObjects.pollFirst(borrowMaxWaitMillis, TimeUnit.MILLISECONDS); } } if (p == null) { throw new NoSuchElementException( "Timeout waiting for idle object"); } } else { if (p == null) { throw new NoSuchElementException("Pool exhausted"); } } if (!p.allocate()) { p = null; }
 if (p != null) { try { // 确保激活当前数据库 factory.activateObject(p); } catch (final Exception e) { try { destroy(p); } catch (final Exception e1) { // Ignore - activation failure is more important } p = null; if (create) { final NoSuchElementException nsee = new NoSuchElementException( "Unable to activate object"); nsee.initCause(e); throw nsee; } } if (p != null && (getTestOnBorrow() || create && getTestOnCreate())) { boolean validate = false; Throwable validationThrowable = null; try { validate = factory.validateObject(p); } catch (final Throwable t) { PoolUtils.checkRethrow(t); validationThrowable = t; } if (!validate) { try { destroy(p); destroyedByBorrowValidationCount.incrementAndGet(); } catch (final Exception e) { // Ignore - validation failure is more important } p = null; if (create) { final NoSuchElementException nsee = new NoSuchElementException( "Unable to validate object"); nsee.initCause(validationThrowable); throw nsee; } } } } }
 updateStatsBorrow(p, System.currentTimeMillis() - waitTime);
 return p.getObject(); }
 /** * Attempts to create a new wrapped pooled object. * <p> * If there are {@link #getMaxTotal()} objects already in circulation * or in process of being created, this method returns null. * * @return The new wrapped pooled object * * @throws Exception if the object factory's {@code makeObject} fails */ private PooledObject<T> create() throws Exception { int localMaxTotal = getMaxTotal(); // This simplifies the code later in this method if (localMaxTotal < 0) { localMaxTotal = Integer.MAX_VALUE; }
 // Flag that indicates if create should: // - TRUE: call the factory to create an object // - FALSE: return null // - null: loop and re-test the condition that determines whether to // call the factory Boolean create = null; while (create == null) { synchronized (makeObjectCountLock) { final long newCreateCount = createCount.incrementAndGet(); if (newCreateCount > localMaxTotal) { // The pool is currently at capacity or in the process of // making enough new objects to take it to capacity. createCount.decrementAndGet(); if (makeObjectCount == 0) { // There are no makeObject() calls in progress so the // pool is at capacity. Do not attempt to create a new // object. Return and wait for an object to be returned create = Boolean.FALSE; } else { // There are makeObject() calls in progress that might // bring the pool to capacity. Those calls might also // fail so wait until they complete and then re-test if // the pool is at capacity or not. makeObjectCountLock.wait(); } } else { // The pool is not at capacity. Create a new object. makeObjectCount++; create = Boolean.TRUE; } } }
 if (!create.booleanValue()) { return null; }
 final PooledObject<T> p; try { // 调用指定factory的 makeObject() 方法 p = factory.makeObject(); } catch (final Exception e) { createCount.decrementAndGet(); throw e; } finally { synchronized (makeObjectCountLock) { makeObjectCount--; makeObjectCountLock.notifyAll(); } }
 final AbandonedConfig ac = this.abandonedConfig; if (ac != null && ac.getLogAbandoned()) { p.setLogAbandoned(true); }
 createdCount.incrementAndGet(); allObjects.put(new IdentityWrapper<T>(p.getObject()), p); return p; } // 使用 JedisFactory 创建一个连接到 master // redis.clients.jedis.JedisFactory#makeObject @Override public PooledObject<Jedis> makeObject() throws Exception { final HostAndPort hostAndPort = this.hostAndPort.get(); final Jedis jedis = new Jedis(hostAndPort.getHost(), hostAndPort.getPort(), connectionTimeout, soTimeout, ssl, sslSocketFactory, sslParameters, hostnameVerifier);
 try { jedis.connect(); // 如果存在密码设置，则进行 auth xxx 操作 // redis 配置: requirepass xxx if (null != this.password) { jedis.auth(this.password); } if (database != 0) { jedis.select(database); } if (clientName != null) { jedis.clientSetname(clientName); } } catch (JedisException je) { jedis.close(); throw je; }
 return new DefaultPooledObject<Jedis>(jedis);
 } // redis.clients.jedis.JedisFactory#activateObject @Override public void activateObject(PooledObject<Jedis> pooledJedis) throws Exception { final BinaryJedis jedis = pooledJedis.getObject(); if (jedis.getDB() != database) { jedis.select(database); }
 }