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 leasing serves linearizable reads from a local cache by acquiring 16 // exclusive write access to keys through a client-side leasing protocol. This 17 // leasing layer can either directly wrap the etcd client or it can be exposed 18 // through the etcd grpc proxy server, granting multiple clients write access. 19 // 20 // First, create a leasing KV from a clientv3.Client 'cli': 21 // 22 // lkv, err := leasing.NewKV(cli, "leasing-prefix") 23 // if err != nil { 24 // // handle error 25 // } 26 // 27 // A range request for a key "abc" tries to acquire a leasing key so it can cache the range's 28 // key locally. On the server, the leasing key is stored to "leasing-prefix/abc": 29 // 30 // resp, err := lkv.Get(context.TODO(), "abc") 31 // 32 // Future linearized read requests using 'lkv' will be served locally for the lease's lifetime: 33 // 34 // resp, err = lkv.Get(context.TODO(), "abc") 35 // 36 // If another leasing client writes to a leased key, then the owner relinquishes its exclusive 37 // access, permitting the writer to modify the key: 38 // 39 // lkv2, err := leasing.NewKV(cli, "leasing-prefix") 40 // if err != nil { 41 // // handle error 42 // } 43 // lkv2.Put(context.TODO(), "abc", "456") 44 // resp, err = lkv.Get("abc") 45 package leasing 46