feature:ETCD key value mvcc

_posts/2024-11-11-test-markdown.md

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+---
+layout: post
+title: ETCD 实现键值的 MVCC，并与 etcd 进行同步
+subtitle: 
+tags: [Go]
+comments: true
+---  
+
+
+### 完整代码
+
+```go
+package main
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	clientv3 "go.etcd.io/etcd/client/v3"
+)
+
+// 创建客户端
+func createEtcdClient() (*clientv3.Client, error) {
+	cli, err := clientv3.New(clientv3.Config{
+		Endpoints:   []string{"127.0.0.1:2379"}, // etcd 的地址
+		DialTimeout: 5 * time.Second,
+		Username:    "root", // 用户名
+		Password:    "root", // 密码
+	})
+	if err != nil {
+		return nil, err
+	}
+	return cli, nil
+}
+
+// 获取键值
+func getKeyValue(cli *clientv3.Client, key string) (string, int64, error) {
+	resp, err := cli.Get(context.Background(), key)
+	if err != nil {
+		return "", 0, err
+	}
+	if len(resp.Kvs) == 0 {
+		return "", 0, fmt.Errorf("key not found")
+	}
+	kv := resp.Kvs[0]
+	return string(kv.Value), kv.ModRevision, nil
+}
+
+// 存储的键值结构体
+type LocalKeyValue struct {
+	Key      string
+	Value    string
+	Revision int64
+}
+
+func NewLocalKeyValue(key string, value string, revision int64) *LocalKeyValue {
+	return &LocalKeyValue{
+		Key:      key,
+		Value:    value,
+		Revision: revision,
+	}
+}
+
+
+func watchKey(cli *clientv3.Client, lkv *LocalKeyValue) {
+	rch := cli.Watch(context.Background(), lkv.Key, clientv3.WithRev(lkv.Revision+1))
+	go func() {
+		for wresp := range rch {
+			for _, ev := range wresp.Events {
+				switch ev.Type {
+				case clientv3.EventTypePut:
+					lkv.Value = string(ev.Kv.Value)
+					lkv.Revision = ev.Kv.ModRevision
+					fmt.Printf("Key updated: %s, New Value: %s, Revision: %d\n", lkv.Key, lkv.Value, lkv.Revision)
+				case clientv3.EventTypeDelete:
+					lkv.Value = ""
+					lkv.Revision = ev.Kv.ModRevision
+					fmt.Printf("Key deleted: %s, Revision: %d\n", lkv.Key, lkv.Revision)
+				}
+			}
+		}
+	}()
+}
+
+// 读取键值
+func (lkv *LocalKeyValue) Read() (string, int64) {
+	return lkv.Value, lkv.Revision
+}
+
+// 写入键值
+func (lkv *LocalKeyValue) Write(cli *clientv3.Client, newValue string) error {
+	txn := cli.Txn(context.Background())
+	cmp := clientv3.Compare(clientv3.ModRevision(lkv.Key), "=", lkv.Revision)
+	put := clientv3.OpPut(lkv.Key, newValue)
+	resp, err := txn.If(cmp).Then(put).Commit()
+	if err != nil {
+		return err
+	}
+	if resp.Succeeded {
+		// 更新本地的值和版本
+		lkv.Value = newValue
+		lkv.Revision = resp.Header.Revision
+		fmt.Printf("Key updated successfully: %s, New Value: %s, Revision: %d\n", lkv.Key, lkv.Value, lkv.Revision)
+		return nil
+	} else {
+		// 版本冲突，获取最新的值和版本
+		value, revision, err := getKeyValue(cli, lkv.Key)
+		if err != nil {
+			return err
+		}
+		lkv.Value = value
+		lkv.Revision = revision
+		return fmt.Errorf("write conflict: key has been updated by another client")
+	}
+}
+
+func main() {
+	cli, err := createEtcdClient()
+	if err != nil {
+		fmt.Println("Error creating etcd client:", err)
+		return
+	}
+	defer cli.Close()
+
+	key := "/my/key"
+
+	// 获取初始的键值和版本
+	value, revision, err := getKeyValue(cli, key)
+	if err != nil {
+		if err.Error() == "key not found" {
+			// 如果键不存在，初始化值和版本
+			value = ""
+			revision = 0
+		} else {
+			fmt.Println("Error getting key:", err)
+			return
+		}
+	}
+
+	// 创建本地键值对象
+	lkv := NewLocalKeyValue(key, value, revision)
+	fmt.Printf("Local key-value initialized: %s, Value: %s, Revision: %d\n", lkv.Key, lkv.Value, lkv.Revision)
+
+	// 模拟读取操作
+	localValue, localRevision := lkv.Read()
+	fmt.Printf("Local read: Value: %s, Revision: %d\n", localValue, localRevision)
+
+	// 模拟写入操作
+	err = lkv.Write(cli, "new value")
+	if err != nil {
+		fmt.Println("Error writing key:", err)
+	}
+
+}
+
+```