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client.go
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client.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 recipe
import (
"context"
"errors"
v3 "github.com/coreos/etcd/clientv3"
spb "github.com/coreos/etcd/mvcc/mvccpb"
)
var (
ErrKeyExists = errors.New("key already exists")
ErrWaitMismatch = errors.New("unexpected wait result")
ErrTooManyClients = errors.New("too many clients")
ErrNoWatcher = errors.New("no watcher channel")
)
// deleteRevKey deletes a key by revision, returning false if key is missing
func deleteRevKey(kv v3.KV, key string, rev int64) (bool, error) {
cmp := v3.Compare(v3.ModRevision(key), "=", rev)
req := v3.OpDelete(key)
txnresp, err := kv.Txn(context.TODO()).If(cmp).Then(req).Commit()
if err != nil {
return false, err
} else if !txnresp.Succeeded {
return false, nil
}
return true, nil
}
func claimFirstKey(kv v3.KV, kvs []*spb.KeyValue) (*spb.KeyValue, error) {
for _, k := range kvs {
ok, err := deleteRevKey(kv, string(k.Key), k.ModRevision)
if err != nil {
return nil, err
} else if ok {
return k, nil
}
}
return nil, nil
}