140 lines
4.0 KiB
Go
140 lines
4.0 KiB
Go
package zk
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import (
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"errors"
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"fmt"
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"github.com/samuel/go-zookeeper/zk"
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"time"
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)
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type ZookeeperConfig struct {
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Servers []string
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RootPath string
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MasterPath string
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}
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type ElectionManager struct {
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ZKClientConn *zk.Conn
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ZKConfig *ZookeeperConfig
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IsMasterQ chan bool
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}
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func NewElectionManager(zkConfig *ZookeeperConfig, isMasterQ chan bool) *ElectionManager {
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electionManager := &ElectionManager{
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nil,
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zkConfig,
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isMasterQ,
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}
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electionManager.initConnection()
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return electionManager
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}
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func (electionManager *ElectionManager) Run() {
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err := electionManager.electMaster()
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if err != nil {
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fmt.Println("elect master error, ", err)
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}
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electionManager.watchMaster()
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}
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// 判断是否成功连接到zookeeper
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func (electionManager *ElectionManager) isConnected() bool {
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if electionManager.ZKClientConn == nil {
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return false
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} else if electionManager.ZKClientConn.State() != zk.StateConnected {
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return false
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}
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return true
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}
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// 初始化zookeeper连接
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func (electionManager *ElectionManager) initConnection() error {
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// 连接为空，或连接不成功，获取zookeeper服务器的连接
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if !electionManager.isConnected() {
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conn, connChan, err := zk.Connect(electionManager.ZKConfig.Servers, time.Second)
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if err != nil {
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return err
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}
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// 等待连接成功
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for {
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isConnected := false
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select {
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case connEvent := <-connChan:
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if connEvent.State == zk.StateConnected {
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isConnected = true
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fmt.Println("connect to zookeeper server success!")
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}
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case _ = <-time.After(time.Second * 3): // 3秒仍未连接成功则返回连接超时
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return errors.New("connect to zookeeper server timeout!")
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}
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if isConnected {
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break
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}
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}
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electionManager.ZKClientConn = conn
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}
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return nil
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}
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// 选举master
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func (electionManager *ElectionManager) electMaster() error {
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err := electionManager.initConnection()
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if err != nil {
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return err
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}
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// 判断zookeeper中是否存在root目录，不存在则创建该目录
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isExist, _, err := electionManager.ZKClientConn.Exists(electionManager.ZKConfig.RootPath)
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if err != nil {
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return err
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}
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if !isExist {
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path, err := electionManager.ZKClientConn.Create(electionManager.ZKConfig.RootPath, nil, 0, zk.WorldACL(zk.PermAll))
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if err != nil {
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return err
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}
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if electionManager.ZKConfig.RootPath != path {
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return errors.New("Create returned different path " + electionManager.ZKConfig.RootPath + " != " + path)
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}
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}
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// 创建用于选举master的ZNode，该节点为Ephemeral类型，表示客户端连接断开后，其创建的节点也会被销毁
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masterPath := electionManager.ZKConfig.RootPath + electionManager.ZKConfig.MasterPath
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path, err := electionManager.ZKClientConn.Create(masterPath, nil, zk.FlagEphemeral, zk.WorldACL(zk.PermAll))
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if err == nil { // 创建成功表示选举master成功
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if path == masterPath {
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fmt.Println("elect master success!")
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electionManager.IsMasterQ <- true
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} else {
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return errors.New("Create returned different path " + masterPath + " != " + path)
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}
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} else { // 创建失败表示选举master失败
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fmt.Printf("elect master failure, ", err)
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electionManager.IsMasterQ <- false
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}
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return nil
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}
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// 监听zookeeper中master znode，若被删除，表示master故障或网络迟缓，重新选举
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func (electionManager *ElectionManager) watchMaster() {
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// watch zk根znode下面的子znode，当有连接断开时，对应znode被删除，触发事件后重新选举
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children, state, childCh, err := electionManager.ZKClientConn.ChildrenW(electionManager.ZKConfig.RootPath + electionManager.ZKConfig.MasterPath)
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if err != nil {
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fmt.Println("watch children error, ", err)
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}
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fmt.Println("watch children result, ", children, state)
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for {
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select {
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case childEvent := <-childCh:
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if childEvent.Type == zk.EventNodeDeleted {
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fmt.Println("receive znode delete event, ", childEvent)
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// 重新选举
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fmt.Println("start elect new master ...")
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err = electionManager.electMaster()
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if err != nil {
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fmt.Println("elect new master error, ", err)
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}
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}
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}
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}
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}
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