client.go

Documentation: go.etcd.io/etcd/client/v3/experimental/recipes

     1  // Copyright 2016 The etcd Authors
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package recipe
    16  
    17  import (
    18  	"context"
    19  	"errors"
    20  
    21  	spb "go.etcd.io/etcd/api/v3/mvccpb"
    22  	v3 "go.etcd.io/etcd/client/v3"
    23  )
    24  
    25  var (
    26  	ErrKeyExists      = errors.New("key already exists")
    27  	ErrWaitMismatch   = errors.New("unexpected wait result")
    28  	ErrTooManyClients = errors.New("too many clients")
    29  	ErrNoWatcher      = errors.New("no watcher channel")
    30  )
    31  
    32  // deleteRevKey deletes a key by revision, returning false if key is missing
    33  func deleteRevKey(kv v3.KV, key string, rev int64) (bool, error) {
    34  	cmp := v3.Compare(v3.ModRevision(key), "=", rev)
    35  	req := v3.OpDelete(key)
    36  	txnresp, err := kv.Txn(context.TODO()).If(cmp).Then(req).Commit()
    37  	if err != nil {
    38  		return false, err
    39  	} else if !txnresp.Succeeded {
    40  		return false, nil
    41  	}
    42  	return true, nil
    43  }
    44  
    45  func claimFirstKey(kv v3.KV, kvs []*spb.KeyValue) (*spb.KeyValue, error) {
    46  	for _, k := range kvs {
    47  		ok, err := deleteRevKey(kv, string(k.Key), k.ModRevision)
    48  		if err != nil {
    49  			return nil, err
    50  		} else if ok {
    51  			return k, nil
    52  		}
    53  	}
    54  	return nil, nil
    55  }
    56
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