Zookeeper实现分布式应用的(主节点HA)及客户端动态更新主节点状态

某分布式系统中，主节点可以有多台，可以动态上下线
任意一台客户端都能实时感知到主节点服务器的上下线
服务端逻辑：

服务端启动时在zookeeper集群中 /services节点写入一个临时节点，该临时节点内容为该节点的名称。当服务端下线或者宕机时zookeeper会将该节点删除

客户端逻辑

客户端启动时会查找/services 下所有节点 并将节点名输出，当节点变化时，会重新查找所有节点，并将节点名输出

import org.apache.zookeeper.CreateModeimport org.apache.zookeeper.Watcherimport org.apache.zookeeper.ZooDefsimport org.apache.zookeeper.ZooKeeper/** * 服务端 */object DistributedServer {    //逗号分隔主机：端口对，每个对应一个ZooKeeper 主机名/IP 与配置文件相同    private val CONNECT_STRING: String = "192.168.84.132:2181,192.168.84.133:2181,192.168.84.134:2181"    //会话超时（毫秒）    private val SESSION_TIMEOUT: Int = 2000    //获取zooKeeper客户端连接    private val zooKeeper: ZooKeeper by lazy {        ZooKeeper(CONNECT_STRING, SESSION_TIMEOUT, Watcher { event ->            //Watch回调            println("${event?.type}-->${event?.path}")            //创建监听节点变化，非数据            zooKeeper.getChildren("/", true)        })    }    @JvmStatic    fun main(args: Array<String>) {        val serviceName = args[0]        zooKeeper.create("/services/service", serviceName.toByteArray(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL)        println("serviceName --> $serviceName create")        println("$serviceName start working.....")        Thread.sleep(Long.MAX_VALUE)    }}

import org.apache.zookeeper.Watcherimport org.apache.zookeeper.ZooKeeperimport org.apache.zookeeper.data.Stat/** * 客户端 */object DistributedClient {    //逗号分隔主机：端口对，每个对应一个ZooKeeper 主机名/IP 与配置文件相同    private val CONNECT_STRING: String = "192.168.84.132:2181,192.168.84.133:2181,192.168.84.134:2181"    //会话超时（毫秒）    private val SESSION_TIMEOUT: Int = 2000    private val zooKeeper: ZooKeeper by lazy {        ZooKeeper(CONNECT_STRING, SESSION_TIMEOUT, Watcher { event ->            println("${event?.type}-->${event?.path}")            getServiceList()        })    }    //Volatile    @Volatile private lateinit var services: ArrayList<String>    @JvmStatic    fun main(args: Array<String>) {        getServiceList()        println("client start working.....")        Thread.sleep(Long.MAX_VALUE)    }    private fun getServiceList() {        //每次/services子节点变化都会调用watch        val serviceList = zooKeeper.getChildren("/services", true)        //设置临时集合存储所有service 信息        val tempList = arrayListOf<String>()        serviceList                //取每个service的信息并存入临时集合                .map { zooKeeper.getData("/services/" + it, false, Stat())}                .mapTo(tempList) { String(it) }        services = tempList        println(services)    }}

服务端

客户端

服务端上下线 客户端更新