kvstore_txn.go
// 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 mvcc
import (
"github.com/coreos/etcd/lease"
"github.com/coreos/etcd/mvcc/backend"
"github.com/coreos/etcd/mvcc/mvccpb"
)
type storeTxnRead struct {
s *store
tx backend.ReadTx
firstRev int64
rev int64
}
func (s *store) Read() TxnRead {
s.mu.RLock()
tx := s.b.ReadTx()
s.revMu.RLock()
tx.Lock()
firstRev, rev := s.compactMainRev, s.currentRev
s.revMu.RUnlock()
return newMetricsTxnRead(&storeTxnRead{s, tx, firstRev, rev})
}
func (tr *storeTxnRead) FirstRev() int64 { return tr.firstRev }
func (tr *storeTxnRead) Rev() int64 { return tr.rev }
func (tr *storeTxnRead) Range(key, end []byte, ro RangeOptions) (r *RangeResult, err error) {
return tr.rangeKeys(key, end, tr.Rev(), ro)
}
func (tr *storeTxnRead) End() {
tr.tx.Unlock()
tr.s.mu.RUnlock()
}
type storeTxnWrite struct {
storeTxnRead
tx backend.BatchTx
// beginRev is the revision where the txn begins; it will write to the next revision.
beginRev int64
changes []mvccpb.KeyValue
}
func (s *store) Write() TxnWrite {
s.mu.RLock()
tx := s.b.BatchTx()
tx.Lock()
tw := &storeTxnWrite{
storeTxnRead: storeTxnRead{s, tx, 0, 0},
tx: tx,
beginRev: s.currentRev,
changes: make([]mvccpb.KeyValue, 0, 4),
}
return newMetricsTxnWrite(tw)
}
func (tw *storeTxnWrite) Rev() int64 { return tw.beginRev }
func (tw *storeTxnWrite) Range(key, end []byte, ro RangeOptions) (r *RangeResult, err error) {
rev := tw.beginRev
if len(tw.changes) > 0 {
rev++
}
return tw.rangeKeys(key, end, rev, ro)
}
func (tw *storeTxnWrite) DeleteRange(key, end []byte) (int64, int64) {
if n := tw.deleteRange(key, end); n != 0 || len(tw.changes) > 0 {
return n, int64(tw.beginRev + 1)
}
return 0, int64(tw.beginRev)
}
func (tw *storeTxnWrite) Put(key, value []byte, lease lease.LeaseID) int64 {
tw.put(key, value, lease)
return int64(tw.beginRev + 1)
}
func (tw *storeTxnWrite) End() {
// only update index if the txn modifies the mvcc state.
if len(tw.changes) != 0 {
tw.s.saveIndex(tw.tx)
// hold revMu lock to prevent new read txns from opening until writeback.
tw.s.revMu.Lock()
tw.s.currentRev++
}
tw.tx.Unlock()
if len(tw.changes) != 0 {
tw.s.revMu.Unlock()
}
tw.s.mu.RUnlock()
}
func (tr *storeTxnRead) rangeKeys(key, end []byte, curRev int64, ro RangeOptions) (*RangeResult, error) {
rev := ro.Rev
if rev > curRev {
return &RangeResult{KVs: nil, Count: -1, Rev: curRev}, ErrFutureRev
}
if rev <= 0 {
rev = curRev
}
if rev < tr.s.compactMainRev {
return &RangeResult{KVs: nil, Count: -1, Rev: 0}, ErrCompacted
}
revpairs := tr.s.kvindex.Revisions(key, end, int64(rev))
if len(revpairs) == 0 {
return &RangeResult{KVs: nil, Count: 0, Rev: curRev}, nil
}
if ro.Count {
return &RangeResult{KVs: nil, Count: len(revpairs), Rev: curRev}, nil
}
limit := int(ro.Limit)
if limit <= 0 || limit > len(revpairs) {
limit = len(revpairs)
}
kvs := make([]mvccpb.KeyValue, limit)
revBytes := newRevBytes()
for i, revpair := range revpairs[:len(kvs)] {
revToBytes(revpair, revBytes)
_, vs := tr.tx.UnsafeRange(keyBucketName, revBytes, nil, 0)
if len(vs) != 1 {
plog.Fatalf("range cannot find rev (%d,%d)", revpair.main, revpair.sub)
}
if err := kvs[i].Unmarshal(vs[0]); err != nil {
plog.Fatalf("cannot unmarshal event: %v", err)
}
}
return &RangeResult{KVs: kvs, Count: len(revpairs), Rev: curRev}, nil
}
func (tw *storeTxnWrite) put(key, value []byte, leaseID lease.LeaseID) {
rev := tw.beginRev + 1
c := rev
oldLease := lease.NoLease
// if the key exists before, use its previous created and
// get its previous leaseID
_, created, ver, err := tw.s.kvindex.Get(key, rev)
if err == nil {
c = created.main
oldLease = tw.s.le.GetLease(lease.LeaseItem{Key: string(key)})
}
ibytes := newRevBytes()
idxRev := revision{main: rev, sub: int64(len(tw.changes))}
revToBytes(idxRev, ibytes)
ver = ver + 1
kv := mvccpb.KeyValue{
Key: key,
Value: value,
CreateRevision: c,
ModRevision: rev,
Version: ver,
Lease: int64(leaseID),
}
d, err := kv.Marshal()
if err != nil {
plog.Fatalf("cannot marshal event: %v", err)
}
tw.tx.UnsafeSeqPut(keyBucketName, ibytes, d)
tw.s.kvindex.Put(key, idxRev)
tw.changes = append(tw.changes, kv)
if oldLease != lease.NoLease {
if tw.s.le == nil {
panic("no lessor to detach lease")
}
err = tw.s.le.Detach(oldLease, []lease.LeaseItem{{Key: string(key)}})
if err != nil {
plog.Errorf("unexpected error from lease detach: %v", err)
}
}
if leaseID != lease.NoLease {
if tw.s.le == nil {
panic("no lessor to attach lease")
}
err = tw.s.le.Attach(leaseID, []lease.LeaseItem{{Key: string(key)}})
if err != nil {
panic("unexpected error from lease Attach")
}
}
}
func (tw *storeTxnWrite) deleteRange(key, end []byte) int64 {
rrev := tw.beginRev
if len(tw.changes) > 0 {
rrev += 1
}
keys, revs := tw.s.kvindex.Range(key, end, rrev)
if len(keys) == 0 {
return 0
}
for i, key := range keys {
tw.delete(key, revs[i])
}
return int64(len(keys))
}
func (tw *storeTxnWrite) delete(key []byte, rev revision) {
ibytes := newRevBytes()
idxRev := revision{main: tw.beginRev + 1, sub: int64(len(tw.changes))}
revToBytes(idxRev, ibytes)
ibytes = appendMarkTombstone(ibytes)
kv := mvccpb.KeyValue{Key: key}
d, err := kv.Marshal()
if err != nil {
plog.Fatalf("cannot marshal event: %v", err)
}
tw.tx.UnsafeSeqPut(keyBucketName, ibytes, d)
err = tw.s.kvindex.Tombstone(key, idxRev)
if err != nil {
plog.Fatalf("cannot tombstone an existing key (%s): %v", string(key), err)
}
tw.changes = append(tw.changes, kv)
item := lease.LeaseItem{Key: string(key)}
leaseID := tw.s.le.GetLease(item)
if leaseID != lease.NoLease {
err = tw.s.le.Detach(leaseID, []lease.LeaseItem{item})
if err != nil {
plog.Errorf("cannot detach %v", err)
}
}
}
func (tw *storeTxnWrite) Changes() []mvccpb.KeyValue { return tw.changes }