blob: dc9926ec6c2b530e85952cbe8ce4f9afabc73dc4 [file] [log] [blame]
// 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
}
}
}