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42 lines
1.7 KiB
Go
42 lines
1.7 KiB
Go
// Copyright 2017 The etcd Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package ordering is a clientv3 wrapper that caches response header revisions
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// to detect ordering violations from stale responses. Users may define a
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// policy on how to handle the ordering violation, but typically the client
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// should connect to another endpoint and reissue the request.
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//
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// The most common situation where an ordering violation happens is a client
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// reconnects to a partitioned member and issues a serializable read. Since the
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// partitioned member is likely behind the last member, it may return a Get
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// response based on a store revision older than the store revision used to
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// service a prior Get on the former endpoint.
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//
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// First, create a client:
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//
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// cli, err := clientv3.New(clientv3.Config{Endpoints: []string{"localhost:2379"}})
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// if err != nil {
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// // handle error!
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// }
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//
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// Next, override the client interface with the ordering wrapper:
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//
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// vf := func(op clientv3.Op, resp clientv3.OpResponse, prevRev int64) error {
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// return fmt.Errorf("ordering: issued %+v, got %+v, expected rev=%v", op, resp, prevRev)
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// }
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// cli.KV = ordering.NewKV(cli.KV, vf)
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//
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// Now calls using 'cli' will reject order violations with an error.
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package ordering
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