clientv3/ordering: kv order caching

clientv3/kv.go

@@ -74,6 +74,19 @@ func (op OpResponse) Get() *GetResponse    { return op.get }
 func (op OpResponse) Del() *DeleteResponse { return op.del }
 func (op OpResponse) Txn() *TxnResponse    { return op.txn }
 
+func (resp *PutResponse) ToOpResponse() OpResponse {
+	return OpResponse{put: resp}
+}
+func (resp *GetResponse) ToOpResponse() OpResponse {
+	return OpResponse{get: resp}
+}
+func (resp *DeleteResponse) ToOpResponse() OpResponse {
+	return OpResponse{del: resp}
+}
+func (resp *TxnResponse) ToOpResponse() OpResponse {
+	return OpResponse{txn: resp}
+}
+
 type kv struct {
 	remote pb.KVClient
 }

clientv3/ordering/kv.go

@@ -0,0 +1,148 @@
+// 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) {
+	prevRev := kv.getPrevRev()
+	kv.revMu.Lock()
+	defer kv.revMu.Unlock()
+	if currRev > 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 {
+			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
+		}
+	}
+}