| // Copyright 2017 The etcd Authors |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| package ordering |
| |
| import ( |
| "context" |
| "sync" |
| |
| "github.com/coreos/etcd/clientv3" |
| ) |
| |
| // kvOrdering ensures that serialized requests do not return |
| // get with revisions less than the previous |
| // returned revision. |
| type kvOrdering struct { |
| clientv3.KV |
| orderViolationFunc OrderViolationFunc |
| prevRev int64 |
| revMu sync.RWMutex |
| } |
| |
| func NewKV(kv clientv3.KV, orderViolationFunc OrderViolationFunc) *kvOrdering { |
| return &kvOrdering{kv, orderViolationFunc, 0, sync.RWMutex{}} |
| } |
| |
| func (kv *kvOrdering) getPrevRev() int64 { |
| kv.revMu.RLock() |
| defer kv.revMu.RUnlock() |
| return kv.prevRev |
| } |
| |
| func (kv *kvOrdering) setPrevRev(currRev int64) { |
| kv.revMu.Lock() |
| defer kv.revMu.Unlock() |
| if currRev > kv.prevRev { |
| kv.prevRev = currRev |
| } |
| } |
| |
| func (kv *kvOrdering) Get(ctx context.Context, key string, opts ...clientv3.OpOption) (*clientv3.GetResponse, error) { |
| // prevRev is stored in a local variable in order to record the prevRev |
| // at the beginning of the Get operation, because concurrent |
| // access to kvOrdering could change the prevRev field in the |
| // middle of the Get operation. |
| prevRev := kv.getPrevRev() |
| op := clientv3.OpGet(key, opts...) |
| for { |
| r, err := kv.KV.Do(ctx, op) |
| if err != nil { |
| return nil, err |
| } |
| resp := r.Get() |
| if resp.Header.Revision == prevRev { |
| return resp, nil |
| } else if resp.Header.Revision > prevRev { |
| kv.setPrevRev(resp.Header.Revision) |
| return resp, nil |
| } |
| err = kv.orderViolationFunc(op, r, prevRev) |
| if err != nil { |
| return nil, err |
| } |
| } |
| } |
| |
| func (kv *kvOrdering) Txn(ctx context.Context) clientv3.Txn { |
| return &txnOrdering{ |
| kv.KV.Txn(ctx), |
| kv, |
| ctx, |
| sync.Mutex{}, |
| []clientv3.Cmp{}, |
| []clientv3.Op{}, |
| []clientv3.Op{}, |
| } |
| } |
| |
| // txnOrdering ensures that serialized requests do not return |
| // txn responses with revisions less than the previous |
| // returned revision. |
| type txnOrdering struct { |
| clientv3.Txn |
| *kvOrdering |
| ctx context.Context |
| mu sync.Mutex |
| cmps []clientv3.Cmp |
| thenOps []clientv3.Op |
| elseOps []clientv3.Op |
| } |
| |
| func (txn *txnOrdering) If(cs ...clientv3.Cmp) clientv3.Txn { |
| txn.mu.Lock() |
| defer txn.mu.Unlock() |
| txn.cmps = cs |
| txn.Txn.If(cs...) |
| return txn |
| } |
| |
| func (txn *txnOrdering) Then(ops ...clientv3.Op) clientv3.Txn { |
| txn.mu.Lock() |
| defer txn.mu.Unlock() |
| txn.thenOps = ops |
| txn.Txn.Then(ops...) |
| return txn |
| } |
| |
| func (txn *txnOrdering) Else(ops ...clientv3.Op) clientv3.Txn { |
| txn.mu.Lock() |
| defer txn.mu.Unlock() |
| txn.elseOps = ops |
| txn.Txn.Else(ops...) |
| return txn |
| } |
| |
| func (txn *txnOrdering) Commit() (*clientv3.TxnResponse, error) { |
| // prevRev is stored in a local variable in order to record the prevRev |
| // at the beginning of the Commit operation, because concurrent |
| // access to txnOrdering could change the prevRev field in the |
| // middle of the Commit operation. |
| prevRev := txn.getPrevRev() |
| opTxn := clientv3.OpTxn(txn.cmps, txn.thenOps, txn.elseOps) |
| for { |
| opResp, err := txn.KV.Do(txn.ctx, opTxn) |
| if err != nil { |
| return nil, err |
| } |
| txnResp := opResp.Txn() |
| if txnResp.Header.Revision >= prevRev { |
| txn.setPrevRev(txnResp.Header.Revision) |
| return txnResp, nil |
| } |
| err = txn.orderViolationFunc(opTxn, opResp, prevRev) |
| if err != nil { |
| return nil, err |
| } |
| } |
| } |