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queue.go
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queue.go
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// Copyright 2016 The etcd Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package etcdqueue
import (
"context"
v3 "github.com/coreos/etcd/clientv3"
)
// Queue implements a multi-reader, multi-writer distributed queue.
type Queue struct {
client *v3.Client
ctx context.Context
cancel context.CancelFunc
keyPrefix string
}
// NewQueue create Queue
func NewQueue(client *v3.Client, keyPrefix string) *Queue {
ctx1, cancel := context.WithCancel(context.Background())
return &Queue{client, ctx1, cancel, keyPrefix}
}
// enqueue
func (q *Queue) Enqueue(val string) error {
_, err := newUniqueKV(q.client, q.keyPrefix, val)
return err
}
// Dequeue returns Enqueue()'d elements in FIFO order. If the
// queue is empty, Dequeue blocks until elements are available.
func (q *Queue) Dequeue() (string, error) {
// TODO: fewer round trips by fetching more than one key
resp, err := q.client.Get(q.ctx, q.keyPrefix, v3.WithFirstRev()...)
if err != nil {
return "", err
}
return q.convertDequeueKey(resp)
}