go.etcd.io/etcd@v3.3.27+incompatible/clientv3/clientv3util/example_key_test.go (about) 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 clientv3util_test 16 17 import ( 18 "context" 19 "log" 20 21 "github.com/coreos/etcd/clientv3" 22 "github.com/coreos/etcd/clientv3/clientv3util" 23 ) 24 25 func ExampleKeyExists_put() { 26 cli, err := clientv3.New(clientv3.Config{ 27 Endpoints: []string{"127.0.0.1:2379"}, 28 }) 29 if err != nil { 30 log.Fatal(err) 31 } 32 defer cli.Close() 33 kvc := clientv3.NewKV(cli) 34 35 // perform a put only if key is missing 36 // It is useful to do the check atomically to avoid overwriting 37 // the existing key which would generate potentially unwanted events, 38 // unless of course you wanted to do an overwrite no matter what. 39 _, err = kvc.Txn(context.Background()). 40 If(clientv3util.KeyMissing("purpleidea")). 41 Then(clientv3.OpPut("purpleidea", "hello world")). 42 Commit() 43 if err != nil { 44 log.Fatal(err) 45 } 46 } 47 48 func ExampleKeyExists_delete() { 49 cli, err := clientv3.New(clientv3.Config{ 50 Endpoints: []string{"127.0.0.1:2379"}, 51 }) 52 if err != nil { 53 log.Fatal(err) 54 } 55 defer cli.Close() 56 kvc := clientv3.NewKV(cli) 57 58 // perform a delete only if key already exists 59 _, err = kvc.Txn(context.Background()). 60 If(clientv3util.KeyExists("purpleidea")). 61 Then(clientv3.OpDelete("purpleidea")). 62 Commit() 63 if err != nil { 64 log.Fatal(err) 65 } 66 }