1 // Copyright 2017 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 ordering is a clientv3 wrapper that caches response header revisions 16 // to detect ordering violations from stale responses. Users may define a 17 // policy on how to handle the ordering violation, but typically the client 18 // should connect to another endpoint and reissue the request. 19 // 20 // The most common situation where an ordering violation happens is a client 21 // reconnects to a partitioned member and issues a serializable read. Since the 22 // partitioned member is likely behind the last member, it may return a Get 23 // response based on a store revision older than the store revision used to 24 // service a prior Get on the former endpoint. 25 // 26 // First, create a client: 27 // 28 // cli, err := clientv3.New(clientv3.Config{Endpoints: []string{"localhost:2379"}}) 29 // if err != nil { 30 // // handle error! 31 // } 32 // 33 // Next, override the client interface with the ordering wrapper: 34 // 35 // vf := func(op clientv3.Op, resp clientv3.OpResponse, prevRev int64) error { 36 // return fmt.Errorf("ordering: issued %+v, got %+v, expected rev=%v", op, resp, prevRev) 37 // } 38 // cli.KV = ordering.NewKV(cli.KV, vf) 39 // 40 // Now calls using 'cli' will reject order violations with an error. 41 package ordering 42