6be3ad36be
fix the unexpected blocking when using Barrier.Wait(), e.g. NewBarrier(client, "a").Wait() will block if key "a" is not existed but "a0" is existed, but it should return immediately. Signed-off-by: zhangwenkang <zwenkang@vmware.com>
67 lines
1.7 KiB
Go
67 lines
1.7 KiB
Go
// Copyright 2016 The etcd Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package recipe
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import (
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"context"
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"go.etcd.io/etcd/api/v3/mvccpb"
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v3 "go.etcd.io/etcd/client/v3"
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)
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// Barrier creates a key in etcd to block processes, then deletes the key to
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// release all blocked processes.
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type Barrier struct {
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client *v3.Client
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ctx context.Context
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key string
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}
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func NewBarrier(client *v3.Client, key string) *Barrier {
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return &Barrier{client, context.TODO(), key}
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}
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// Hold creates the barrier key causing processes to block on Wait.
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func (b *Barrier) Hold() error {
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_, err := newKey(b.client, b.key, v3.NoLease)
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return err
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}
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// Release deletes the barrier key to unblock all waiting processes.
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func (b *Barrier) Release() error {
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_, err := b.client.Delete(b.ctx, b.key)
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return err
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}
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// Wait blocks on the barrier key until it is deleted. If there is no key, Wait
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// assumes Release has already been called and returns immediately.
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func (b *Barrier) Wait() error {
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resp, err := b.client.Get(b.ctx, b.key)
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if err != nil {
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return err
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}
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if len(resp.Kvs) == 0 {
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// key already removed
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return nil
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}
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_, err = WaitEvents(
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b.client,
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b.key,
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resp.Header.Revision,
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[]mvccpb.Event_EventType{mvccpb.PUT, mvccpb.DELETE})
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return err
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}
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