增加监听一次key变化的处理

middleware/etcd/define.go

@@ -41,3 +41,6 @@ type WatcherHandler func(event *clientv3.Event)
 
 // CancelWatcherHandler 取消监听后的处理函数
 type CancelWatcherHandler func(key string, data interface{})
+
+// TimeoutWatcherHandler 超时之后的回调函数
+type TimeoutWatcherHandler func(key string, timeout time.Duration)

middleware/etcd/string_test.go

@@ -114,3 +114,48 @@ func TestWatchKeyWithCancelByChangeCallback(t *testing.T) {
 	}()
 	WatchKeyWithCancel(nil, key, dealFunc, cancelChan, cancelFunc)
 }
+
+// TestWatchKeyOnce ...
+//
+// Author : go_developer@163.com<白茶清欢>
+//
+// Date : 4:50 下午 2021/11/23
+func TestWatchKeyOnce(t *testing.T) {
+	key := "name"
+	dealFunc := func(data *clientv3.Event) {
+		fmt.Println(string(data.Kv.Key), string(data.Kv.Value), data.Kv.Version, data.Kv.CreateRevision, data.Kv.ModRevision)
+	}
+
+	timeoutFunc := func(key string, timeout time.Duration) {
+		fmt.Println("监听超时", key, timeout)
+	}
+
+	timeout := 10 * time.Second
+	go func() {
+		for i := 0; i < 30; i++ {
+			_ = Put(nil, key, fmt.Sprintf("test-%d", i), 0)
+			time.Sleep(time.Second)
+		}
+	}()
+	WatchKeyOnce(nil, key, dealFunc, timeout, timeoutFunc)
+}
+
+// TestWatchKeyOnceForTimeout ...
+//
+// Author : go_developer@163.com<白茶清欢>
+//
+// Date : 4:53 下午 2021/11/23
+func TestWatchKeyOnceForTimeout(t *testing.T) {
+	key := "name"
+	dealFunc := func(data *clientv3.Event) {
+		fmt.Println(string(data.Kv.Key), string(data.Kv.Value), data.Kv.Version, data.Kv.CreateRevision, data.Kv.ModRevision)
+	}
+
+	timeoutFunc := func(key string, timeout time.Duration) {
+		fmt.Println("监听超时", key, timeout)
+	}
+
+	timeout := time.Second
+
+	WatchKeyOnce(nil, key, dealFunc, timeout, timeoutFunc)
+}

middleware/etcd/watch.go

@@ -9,6 +9,8 @@ package etcd
 
 import (
 	"context"
+	"math"
+	"time"
 )
 
 // WatchKey 监听key的变化
@@ -66,3 +68,39 @@ func WatchKeyWithCancel(ctx context.Context, watchKey string, callbackFunc Watch
 		}
 	}
 }
+
+// WatchKeyOnce 监听一次key
+//
+// timeout 若 <= 0 , 则会一直等待当前key发生变化为止
+//
+// timeout 若 > 0 , 则在制定时间内为监听到变化, 立即自动取消,
+//
+// Author : go_developer@163.com<白茶清欢>
+//
+// Date : 4:35 下午 2021/11/23
+func WatchKeyOnce(ctx context.Context, watchKey string, callbackFunc WatcherHandler, timeout time.Duration, timeoutHandler TimeoutWatcherHandler) {
+	if nil == callbackFunc {
+		// 变化之后,没有任何逻辑处理,视为不需要监听变化
+		return
+	}
+
+	if timeout == 0 {
+		// 不指定超时时间，默认设置成int64最大值
+		timeout = math.MaxInt16 * time.Second
+	}
+
+	if nil == ctx {
+		ctx = context.Background()
+	}
+	rch := Client.Watch(ctx, watchKey) // <-chan WatchResponse
+	select {
+	case <-time.After(timeout):
+		if nil != timeoutHandler {
+			timeoutHandler(watchKey, timeout)
+		}
+	case watchResp := <-rch:
+		for _, ev := range watchResp.Events {
+			callbackFunc(ev)
+		}
+	}
+}