141 lines
4.3 KiB
Go
141 lines
4.3 KiB
Go
// Copyright 2015 CoreOS, Inc.
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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 storage
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import (
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"encoding/binary"
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"log"
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"github.com/coreos/etcd/storage/storagepb"
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)
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var (
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consistentIndexKeyName = []byte("consistent_index")
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)
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// ConsistentIndexGetter is an interface that wraps the Get method.
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// Consistent index is the offset of an entry in a consistent replicated log.
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type ConsistentIndexGetter interface {
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// ConsistentIndex returns the consistent index of current executing entry.
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ConsistentIndex() uint64
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}
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type consistentWatchableStore struct {
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*watchableStore
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// The field is used to get the consistent index of current
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// executing entry.
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// When the store finishes executing current entry, it will
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// put the index got from ConsistentIndexGetter into the
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// underlying backend. This helps to recover consistent index
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// when restoring.
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ig ConsistentIndexGetter
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skip bool // indicate whether or not to skip an operation
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}
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func New(path string, ig ConsistentIndexGetter) ConsistentWatchableKV {
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return newConsistentWatchableStore(path, ig)
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}
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// newConsistentWatchableStore creates a new consistentWatchableStore
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// using the file at the given path.
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// If the file at the given path does not exist then it will be created automatically.
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func newConsistentWatchableStore(path string, ig ConsistentIndexGetter) *consistentWatchableStore {
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return &consistentWatchableStore{
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watchableStore: newWatchableStore(path),
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ig: ig,
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}
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}
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func (s *consistentWatchableStore) Put(key, value []byte) (rev int64) {
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id := s.TxnBegin()
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rev, err := s.TxnPut(id, key, value)
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if err != nil {
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log.Panicf("unexpected TxnPut error (%v)", err)
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}
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if err := s.TxnEnd(id); err != nil {
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log.Panicf("unexpected TxnEnd error (%v)", err)
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}
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return rev
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}
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func (s *consistentWatchableStore) DeleteRange(key, end []byte) (n, rev int64) {
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id := s.TxnBegin()
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n, rev, err := s.TxnDeleteRange(id, key, end)
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if err != nil {
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log.Panicf("unexpected TxnDeleteRange error (%v)", err)
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}
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if err := s.TxnEnd(id); err != nil {
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log.Panicf("unexpected TxnEnd error (%v)", err)
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}
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return n, rev
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}
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func (s *consistentWatchableStore) TxnBegin() int64 {
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id := s.watchableStore.TxnBegin()
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// If the consistent index of executing entry is not larger than store
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// consistent index, skip all operations in this txn.
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s.skip = s.ig.ConsistentIndex() <= s.consistentIndex()
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if !s.skip {
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// TODO: avoid this unnecessary allocation
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bs := make([]byte, 8)
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binary.BigEndian.PutUint64(bs, s.ig.ConsistentIndex())
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// put the index into the underlying backend
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// tx has been locked in TxnBegin, so there is no need to lock it again
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s.watchableStore.store.tx.UnsafePut(metaBucketName, consistentIndexKeyName, bs)
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}
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return id
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}
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func (s *consistentWatchableStore) TxnRange(txnID int64, key, end []byte, limit, rangeRev int64) (kvs []storagepb.KeyValue, rev int64, err error) {
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if s.skip {
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return nil, 0, nil
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}
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return s.watchableStore.TxnRange(txnID, key, end, limit, rangeRev)
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}
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func (s *consistentWatchableStore) TxnPut(txnID int64, key, value []byte) (rev int64, err error) {
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if s.skip {
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return 0, nil
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}
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return s.watchableStore.TxnPut(txnID, key, value)
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}
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func (s *consistentWatchableStore) TxnDeleteRange(txnID int64, key, end []byte) (n, rev int64, err error) {
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if s.skip {
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return 0, 0, nil
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}
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return s.watchableStore.TxnDeleteRange(txnID, key, end)
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}
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func (s *consistentWatchableStore) TxnEnd(txnID int64) error {
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// reset skip var
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s.skip = false
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return s.watchableStore.TxnEnd(txnID)
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}
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func (s *consistentWatchableStore) consistentIndex() uint64 {
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// get the index
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// tx has been locked in TxnBegin, so there is no need to lock it again
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_, vs := s.watchableStore.store.tx.UnsafeRange(metaBucketName, consistentIndexKeyName, nil, 0)
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if len(vs) == 0 {
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return 0
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}
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return binary.BigEndian.Uint64(vs[0])
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}
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