（四）Redis主从复制和sentinel

主从复制

数据副本

扩展读性能

• 一个master可以有多个slave
• 一个slave只能有一个master
• 数据流只能从mater流向slave

slaveof命令式复制：

redis-8380> slaveof 127.0.0.1:6379

配置复制：

slaveof ip port
# 具体看版本
slaveof/replicaof ip port
slave-read-only yes

1、主从复制demo

拷贝配置文件：

mkdir config
cp redis.conf config/
cd config
cp redis.conf redis-6379.conf   # (主)
cp redis-6379.conf redis-6380.conf  # (从)

配置从节点：

# 具体看版本
slaveof/replicaof ip port
slave-read-only yes

启动服务：

redis-server redis-6379.conf
redis-server redis-6380.conf

测试：

• 主节点

[root@localhost ~]# redis-cli
127.0.0.1:6379> info replication
# Replication
role:master
connected_slaves:1
slave0:ip=127.0.0.1,port=6380,state=online,offset=2322,lag=0
master_replid:998f21abddaadcf5cb8b6595659b76ded9b2c603
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:2322
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:2322
127.0.0.1:6379> set kkk fffffffff
OK
127.0.0.1:6379> get kkk
"fffffffff"

• 从节点

[root@localhost config]# redis-cli -p 6380
127.0.0.1:6380> info replication
# Replication
role:slave
master_host:127.0.0.1
master_port:6379
master_link_status:up
master_last_io_seconds_ago:3
master_sync_in_progress:0
slave_repl_offset:2364
slave_priority:100
slave_read_only:1
connected_slaves:0
master_replid:998f21abddaadcf5cb8b6595659b76ded9b2c603
master_replid2:0000000000000000000000000000000000000000
master_repl_offset:2364
second_repl_offset:-1
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1
repl_backlog_histlen:2364
127.0.0.1:6380> get kkk
"fffffffff"
127.0.0.1:6380> set kkk
(error) ERR wrong number of arguments for 'set' command

Redis Sentinel

1、服务端高可用

主从复制高可用的问题

1、手动故障转移

2、写能力和存储能力受到限制

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Redis Sentinel

• 客户端从redis sentinel获取redis信息
• Redis Sentinel管理redis集群
• Redis Sentinel本身是多节点

安装配置：

1、配置开启主从节点

主节点：默认配置
从节点：replicaof 127.0.0.1 7000    # 主节点的ip port

2、配置开启sentinel监控主节点

port ${port}
dir ./
logfile ${port}.log
sentinel monitor mymaster 127.0.0.1 7000            # 监控的主节点 name ip port
sentinel down-after-milliseconds mymaster 30000     # 30秒认定为down
sentinel parallel-syncs mymaster 1                  # 并发还是串行
sentinel failover-timeout mymaster 180000           # 故障转移时间

3、实际应用多机器

[root@localhost config]# redis-server redis-7000.conf 
[root@localhost config]# redis-server redis-7001.conf 
[root@localhost config]# redis-server redis-7002.conf 
[root@localhost config]# ps -ef | grep 700
root      29701      1  0 12:53 ?        00:00:00 redis-server *:7000
root      29708      1  0 12:53 ?        00:00:00 redis-server *:7001
root      29714      1  0 12:53 ?        00:00:00 redis-server *:7002
root      29719  29651  0 12:53 pts/0    00:00:00 grep --color=auto 700

4、启动redid-sentinel

redis-sentinel sentinel-26379.conf

port 26381
daemonize yes
pidfile /var/run/redis-sentinel.pid
logfile "/usr/local/redis-5.0.4/logs/sentinel-26381.log"
dir /tmp
sentinel monitor mymaster 192.168.0.109 6379 2
sentinel down-after-milliseconds mymaster 30000
sentinel parallel-syncs mymaster 1
sentinel failover-timeout mymaster 180000
sentinel deny-scripts-reconfig yes      

5、启动后发现配置文件改变

# sentinel找到了监控的主节点的从节点，并写入了配置文件
protected-mode no
sentinel leader-epoch mymaster 0
sentinel known-replica mymaster 192.168.0.109 7002
sentinel known-replica mymaster 192.168.0.109 7001
sentinel current-epoch 0

6、启动多个redis-sentinel

sed "s/26379/26380/g" sentinel-26379.conf > sentinel-26380.conf
sed "s/26379/26381/g" sentinel-26379.conf > sentinel-26381.conf
redis-sentinel sentinel-26380.conf
redis-sentinel sentinel-26381.conf
ps -ef | grep 263 | grep -v col
root      29763      1  0 03:50 ?        00:02:19 redis-sentinel *:26379 [sentinel]
root      30868      1  0 17:02 ?        00:00:00 redis-sentinel *:26380 [sentinel]
root      30873      1  0 17:02 ?        00:00:00 redis-sentinel *:26381 [sentinel]

2、客户端高可用

需要的信息：

1、Sentinel地址集合

2、masterName

注意：Sentinel不是代理模式

jedis：

JedisSentinelPool sentinelPool = new JedisSentinelPool(masterName, sentinelSet, poolConfig, timeout);
Jedis jedis = null;
try {
    jedis = redisSentinelPool.getResource();
    callback(jedis);
} catch (Exception e) {
    log.error(e.getMessage(), e);
} finally {
    if (jedis != null) {
        jedis.close();
    }
}

example：

@Test
public void testRedisSentinel() throws InterruptedException {
    String masterName = "mymaster";
    Set<String> sentinelSet = new HashSet<>();
    sentinelSet.add("192.168.0.109:26379");
    sentinelSet.add("192.168.0.109:26380");
    sentinelSet.add("192.168.0.109:26381");
    JedisSentinelPool pool = new JedisSentinelPool(masterName, sentinelSet);
    int count = 0;
    while (true) {
        try (Jedis resource = pool.getResource()) {
            HostAndPort currentHostMaster = pool.getCurrentHostMaster();
            String host = currentHostMaster.getHost();
            int port = currentHostMaster.getPort();
            resource.set("host" + count, host);
            resource.set("port" + count, String.valueOf(port));
            List<String> valueList = resource.mget("host" + count, "port" + count);
            log.info("host" + count + " {}, port" + count + " {};", valueList.get(0), valueList.get(1));
        } catch (Exception e) {
            e.printStackTrace();
        }
        Thread.sleep(1000);
        count++;
        if (count == 10000) {
            break;
        }
        log.info("count = {}", count);
    }
}

3、故障转移模拟

启动java程序：

[INFO ] 2019-03-29 17:09:47,130 method:com.zuizui.connect.redis.JedisTest.testRedisSentinel(JedisTest.java:49)
host9 192.168.0.109, port9 6379;
[INFO ] 2019-03-29 17:09:48,130 method:com.zuizui.connect.redis.JedisTest.testRedisSentinel(JedisTest.java:58)
count = 10
[INFO ] 2019-03-29 17:09:48,132 method:com.zuizui.connect.redis.JedisTest.testRedisSentinel(JedisTest.java:49)
host10 192.168.0.109, port10 6379;

# 6379 shutdown后
count = 11redis.clients.jedis.exceptions.JedisConnectionException: Unexpected end of stream.
    at redis.clients.jedis.util.RedisInputStream.ensureFill(RedisInputStream.java:202)
    at redis.clients.jedis.util.RedisInputStream.readByte(RedisInputStream.java:43)
    at redis.clients.jedis.Protocol.process(Protocol.java:154)
    at redis.clients.jedis.Protocol.read(Protocol.java:219)
    at redis.clients.jedis.Connection.readProtocolWithCheckingBroken(Connection.java:309)
    at redis.clients.jedis.Connection.getStatusCodeReply(Connection.java:236)
    at redis.clients.jedis.Jedis.set(Jedis.java:149)
    at com.zuizui.connect.redis.JedisTest.testRedisSentinel(JedisTest.java:46)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:69)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:48)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:292)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:157)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
redis.clients.jedis.exceptions.JedisConnectionException: Could not get a resource from the pool
[INFO ] 2019-03-29 17:09:50,141 method:com.zuizui.connect.redis.JedisTest.testRedisSentinel(JedisTest.java:58)
count = 12
    at redis.clients.jedis.util.Pool.getResource(Pool.java:59)
    at redis.clients.jedis.JedisSentinelPool.getResource(JedisSentinelPool.java:213)
    at com.zuizui.connect.redis.JedisTest.testRedisSentinel(JedisTest.java:42)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:69)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:48)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:292)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:157)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
Caused by: redis.clients.jedis.exceptions.JedisConnectionException: Failed connecting to host 192.168.0.109:6379
    at redis.clients.jedis.Connection.connect(Connection.java:204)
    at redis.clients.jedis.BinaryClient.connect(BinaryClient.java:100)
    at redis.clients.jedis.BinaryJedis.connect(BinaryJedis.java:1862)
    at redis.clients.jedis.JedisFactory.makeObject(JedisFactory.java:117)
    at org.apache.commons.pool2.impl.GenericObjectPool.create(GenericObjectPool.java:888)
    at org.apache.commons.pool2.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:432)
    at org.apache.commons.pool2.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:361)
    at redis.clients.jedis.util.Pool.getResource(Pool.java:50)
    ... 24 more

# 新选举master后
[INFO ] 2019-03-29 17:10:19,301 method:com.zuizui.connect.redis.JedisTest.testRedisSentinel(JedisTest.java:49)
host41 192.168.0.109, port41 6381;
[INFO ] 2019-03-29 17:10:20,301 method:com.zuizui.connect.redis.JedisTest.testRedisSentinel(JedisTest.java:58)
count = 42
[INFO ] 2019-03-29 17:10:20,303 method:com.zuizui.connect.redis.JedisTest.testRedisSentinel(JedisTest.java:49)
host42 192.168.0.109, port42 6381;

4、三个定时任务

每10秒：每个sentinel对master和slave执行info

• 发现slave节点
• 确定主从关系

每2秒：每个sentinel通过master节点的channel交换信息（pub/sub）

• 通过_sentinel_:hello 频道交互
• 交互对节点和自身信息

每1秒：每个sentinel对其他sentinel和redis执行ping

• 心跳检查

5、主观下线和客观下线

sentinel monitor <masterName> <ip> <port> <quorunm>
quorunm:配置几个sentinel节点主观认定redis下线时，认定为客观下线

6、领导者选举

• 只有一个sentinel节点完成故障转移

通过sentinel is master-down-by-addr命令都希望成为leader

1. 每个做主观下线的sentinel节点向其他sentinel节点发送命令，要求将它设置为领导者
2. 收到命令的sentinel节点如果没有同意通过其他Sentinel节点发送的命令，则同意该请求，否则拒绝
3. 如果该Sentinel节点发现自己的票数已经超过Sentinel集合半数且超过quorum，将成为领导者

7、节点运维

节点下线：

1、主节点下线：手动故障转移 sentinel failover <masterName>

2、从节点下线：清理一些数据文件，但是要考虑读写分离的情况

3、sentinel下线：清理一些数据文件

节点上线：

1、主节点：sentinel failover进行替换

2、从节点：配置slaveof即可

3、sentinel节点：配置启动