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Spring Boot(十三):整合Redis哨兵,集群模式实践

程序员文章站 2022-11-22 10:24:47
前面的两篇文章( "Redis的持久化方案" , "一文掌握Redis的三种集群方案" )分别介绍了Redis的持久化与集群方案 —— 包括主从复制模式、哨兵模式、Cluster模式,其中主从复制模式由于不能自动做故障转移,当节点出现故障时需要人为干预,不满足生产环境的高可用需求,所以在生产环境一般 ......

前面的两篇文章(redis的持久化方案一文掌握redis的三种集群方案)分别介绍了redis的持久化与集群方案 —— 包括主从复制模式、哨兵模式、cluster模式,其中主从复制模式由于不能自动做故障转移,当节点出现故障时需要人为干预,不满足生产环境的高可用需求,所以在生产环境一般使用哨兵模式或cluster模式。那么在spring boot项目中,如何访问这两种模式的redis集群,可能遇到哪些问题,是本文即将介绍的内容。

spring boot 2 整合redis

spring boot中整合redis非常简单,在pom.xml中添加依赖

<dependency>
    <groupid>org.springframework.boot</groupid>
    <artifactid>spring-boot-starter-data-redis</artifactid>
</dependency>

spring boot 2的spring-boot-starter-data-redis中,默认使用的是lettuce作为redis客户端,它与jedis的主要区别如下:

  1. jedis是同步的,不支持异步,jedis客户端实例不是线程安全的,需要每个线程一个jedis实例,所以一般通过连接池来使用jedis
  2. lettuce是基于netty框架的事件驱动的redis客户端,其方法调用是异步的,lettuce的api也是线程安全的,所以多个线程可以操作单个lettuce连接来完成各种操作,同时lettuce也支持连接池

如果不使用默认的lettuce,使用jedis的话,可以排除lettuce的依赖,手动加入jedis依赖,配置如下

<dependency>
    <groupid>org.springframework.boot</groupid>
    <artifactid>spring-boot-starter-data-redis</artifactid>
    <exclusions>
        <exclusion>
            <groupid>io.lettuce</groupid>
            <artifactid>lettuce-core</artifactid>
        </exclusion>
    </exclusions>
</dependency>
<dependency>
    <groupid>redis.clients</groupid>
    <artifactid>jedis</artifactid>
    <version>2.9.0</version>
</dependency>

在配置文件application.yml中添加配置(针对单实例)

spring:
  redis:
    host: 192.168.40.201
    port: 6379
    password: passw0rd
    database: 0 # 数据库索引,默认0
    timeout: 5000  # 连接超时,单位ms
    jedis:  # 或lettuce, 连接池配置,springboot2.0中使用jedis或者lettuce配置连接池,默认为lettuce连接池
      pool:
        max-active: 8 # 连接池最大连接数(使用负值表示没有限制)
        max-wait: -1 # 连接池分配连接最大阻塞等待时间(阻塞时间到,抛出异常。使用负值表示无限期阻塞)
        max-idle: 8 # 连接池中的最大空闲连接数
        min-idle: 0 # 连接池中的最小空闲连接数

然后添加配置类。其中@enablecaching注解是为了使@cacheable、@cacheevict、@cacheput、@caching注解生效

@configuration
@enablecaching
public class redisconfig {

    @bean
    public redistemplate<string, object> redistemplate(redisconnectionfactory factory) {
        redistemplate<string, object> template = new redistemplate<>();
        template.setconnectionfactory(factory);

        // 使用jackson2jsonredisserialize 替换默认的jdkserializeable序列化
        jackson2jsonredisserializer jackson2jsonredisserializer = new jackson2jsonredisserializer(object.class);
        objectmapper om = new objectmapper();
        om.setvisibility(propertyaccessor.all, jsonautodetect.visibility.any);
        om.enabledefaulttyping(objectmapper.defaulttyping.non_final);
        jackson2jsonredisserializer.setobjectmapper(om);

        stringredisserializer stringredisserializer = new stringredisserializer();

        // key采用string的序列化方式
        template.setkeyserializer(stringredisserializer);
        // hash的key也采用string的序列化方式
        template.sethashkeyserializer(stringredisserializer);
        // value序列化方式采用jackson
        template.setvalueserializer(jackson2jsonredisserializer);
        // hash的value序列化方式采用jackson
        template.sethashvalueserializer(jackson2jsonredisserializer);
        template.afterpropertiesset();
        return template;
    }
}

上述配置类注入了自定义的redistemplate<string, object>, 替换redisautoconfiguration中自动配置的redistemplate<object, object>类(redisautoconfiguration另外还自动配置了stringredistemplate)。

此时,我们可以通过定义一个基于redistemplate的工具类,或通过在service层添加@cacheable、@cacheevict、@cacheput、@caching注解来使用缓存。比如定义一个redisservice类,封装常用的redis操作方法,

@component
@slf4j
public class redisservice {

    @autowired
    private redistemplate<string, object> redistemplate;

    /**
     * 指定缓存失效时间
     *
     * @param key 键
     * @param time 时间(秒)
     * @return
     */
    public boolean expire(string key, long time) {
        try {
            if (time > 0) {
                redistemplate.expire(key, time, timeunit.seconds);
            }
            return true;
        } catch (exception e) {
            log.error("exception when expire key {}. ", key, e);
            return false;
        }
    }

    /**
     * 根据key获取过期时间
     *
     * @param key 键 不能为null
     * @return 时间(秒) 返回0代表为永久有效
     */
    public long getexpire(string key) {
        return redistemplate.getexpire(key, timeunit.seconds);
    }

    /**
     * 判断key是否存在
     *
     * @param key  键
     * @return true 存在 false不存在
     */
    public boolean haskey(string key) {
        try {
            return redistemplate.haskey(key);
        } catch (exception e) {
            log.error("exception when check key {}. ", key, e);
            return false;
        }
    }

   ...
}

出于篇幅,完整代码请查阅本文示例源码:

或在service层使用注解,如

@service
@cacheconfig(cachenames = "users")
public class userservice {

    private static map<string, user> usermap = new hashmap<>();

    @cacheput(key = "#user.username")
    public user adduser(user user){
        user.setuid(uuid.randomuuid().tostring());
        system.out.println("add user: " + user);
        usermap.put(user.getusername(), user);
        return user;
    }

    @caching(put = {
            @cacheput( key = "#user.username"),
            @cacheput( key = "#user.uid")
    })
    public user adduser2(user user) {
        user.setuid(uuid.randomuuid().tostring());
        system.out.println("add user2: " + user);
        usermap.put(user.getusername(), user);
        return user;
    }
    ...
}

spring boot 2 整合redis哨兵模式

spring boot 2 整合redis哨兵模式除了配置稍有差异,其它与整合单实例模式类似,配置示例为

spring:
  redis:
    password: passw0rd
    timeout: 5000
    sentinel:
      master: mymaster
      nodes: 192.168.40.201:26379,192.168.40.201:36379,192.168.40.201:46379 # 哨兵的ip:port列表
    jedis: # 或lettuce
      pool:
        max-active: 8
        max-wait: -1
        max-idle: 8
        min-idle: 0

完整示例可查阅源码:

上述配置只指定了哨兵节点的地址与master的名称,但redis客户端最终访问操作的是master节点,那么redis客户端是如何获取master节点的地址,并在发生故障转移时,如何自动切换master地址的呢?我们以jedis连接池为例,通过源码来揭开其内部实现的神秘面纱。

在 jedissentinelpool 类的构造函数中,对连接池做了初始化,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);
 }

private hostandport initsentinels(set<string> sentinels, final string mastername) {

    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());

        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();
        }
      }
    }
    //省略了非关键代码

    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;
  }

initsentinels 方法中主要干了两件事:

  1. 遍历哨兵节点,通过get-master-addr-by-name命令获取master节点的地址信息,找到了就退出循环。get-master-addr-by-name命令执行结果如下所示
[root@dev-server-1 master-slave]# redis-cli -p 26379
127.0.0.1:26379> sentinel get-master-addr-by-name mymaster
1) "192.168.40.201"
2) "7001"
127.0.0.1:26379>
  1. 对每一个哨兵节点通过一个 masterlistener 进行监听(redis的发布订阅功能),订阅哨兵节点+switch-master频道,当发生故障转移时,客户端能收到哨兵的通知,通过重新初始化连接池,完成主节点的切换。
    masterlistener.run方法中监听哨兵部分代码如下
 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])) {
                  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");

initpool 方法如下:如果发现新的master节点与当前的master不同,则重新初始化。

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);
    }
  }

通过以上两步,jedis客户端在只知道哨兵地址的情况下便能获得master节点的地址信息,并且当发生故障转移时能自动切换到新的master节点地址。

spring boot 2 整合redis cluster模式

spring boot 2 整合redis cluster模式除了配置稍有差异,其它与整合单实例模式也类似,配置示例为

spring:
  redis:
    password: passw0rd
    timeout: 5000
    database: 0
    cluster:
      nodes: 192.168.40.201:7100,192.168.40.201:7200,192.168.40.201:7300,192.168.40.201:7400,192.168.40.201:7500,192.168.40.201:7600
      max-redirects: 3  # 重定向的最大次数
    jedis:
      pool:
        max-active: 8
        max-wait: -1
        max-idle: 8
        min-idle: 0

完整示例可查阅源码:

一文掌握redis的三种集群方案 中已经介绍了cluster模式访问的基本原理,可以通过任意节点跳转到目标节点执行命令,上面配置中 max-redirects 控制在集群中跳转的最大次数。

查看jedisclusterconnection的execute方法,

public object execute(string command, byte[]... args) {

    assert.notnull(command, "command must not be null!");
    assert.notnull(args, "args must not be null!");

    return clustercommandexecutor
            .executecommandonarbitrarynode((jedisclustercommandcallback<object>) client -> jedisclientutils.execute(command,
                    empty_2d_byte_array, args, () -> client))
            .getvalue();
}

集群命令的执行是通过clustercommandexecutor.executecommandonarbitrarynode来实现的,

public <t> noderesult<t> executecommandonarbitrarynode(clustercommandcallback<?, t> cmd) {

    assert.notnull(cmd, "clustercommandcallback must not be null!");
    list<redisclusternode> nodes = new arraylist<>(getclustertopology().getactivenodes());
    return executecommandonsinglenode(cmd, nodes.get(new random().nextint(nodes.size())));
}

private <s, t> noderesult<t> executecommandonsinglenode(clustercommandcallback<s, t> cmd, redisclusternode node,
        int redirectcount) {

    assert.notnull(cmd, "clustercommandcallback must not be null!");
    assert.notnull(node, "redisclusternode must not be null!");

    if (redirectcount > maxredirects) {
        throw new toomanyclusterredirectionsexception(string.format(
                "cannot follow cluster redirects over more than %s legs. please consider increasing the number of redirects to follow. current value is: %s.",
                redirectcount, maxredirects));
    }

    redisclusternode nodetouse = lookupnode(node);

    s client = this.resourceprovider.getresourceforspecificnode(nodetouse);
    assert.notnull(client, "could not acquire resource for node. is your cluster info up to date?");

    try {
        return new noderesult<>(node, cmd.doincluster(client));
    } catch (runtimeexception ex) {

        runtimeexception translatedexception = converttodataaccessexception(ex);
        if (translatedexception instanceof clusterredirectexception) {
            clusterredirectexception cre = (clusterredirectexception) translatedexception;
            return executecommandonsinglenode(cmd,
                    topologyprovider.gettopology().lookup(cre.gettargethost(), cre.gettargetport()), redirectcount + 1);
        } else {
            throw translatedexception != null ? translatedexception : ex;
        }
    } finally {
        this.resourceprovider.returnresourceforspecificnode(nodetouse, client);
    }
}

上述代码逻辑如下

  1. 从集群节点列表中随机选择一个节点
  2. 从该节点获取一个客户端连接(如果配置了连接池,从连接池中获取),执行命令
  3. 如果抛出clusterredirectexception异常,则跳转到返回的目标节点上执行
  4. 如果跳转次数大于配置的值 max-redirects, 则抛出toomanyclusterredirectionsexception异常

可能遇到的问题

  1. redis连接超时

检查服务是否正常启动(比如 ps -ef|grep redis查看进程,netstat -ano|grep 6379查看端口是否起来,以及日志文件),如果正常启动,则查看redis服务器是否开启防火墙,关闭防火墙或配置通行端口。

  1. cluster模式下,报连接到127.0.0.1被拒绝错误,如 connection refused: no further information: /127.0.0.1:7600

这是因为在redis.conf中配置 bind 0.0.0.0bind 127.0.0.1导致,需要改为具体在外部可访问的ip,如 bind 192.168.40.201。如果之前已经起了集群,并产生了数据,则修改redis.conf文件后,还需要修改cluster-config-file文件,将127.0.0.1替换为bind 的具体ip,然后重启。

  1. master挂了,slave升级成为master,重启master,不能正常同步新的master数据

如果设置了密码,需要在master, slave的配置文件中都配置masterauth password

相关阅读:

  1. redis的持久化方案
  2. 一文掌握redis的三种集群方案

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Spring Boot(十三):整合Redis哨兵,集群模式实践