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kvstore.go
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kvstore.go
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// Copyright 2015 CoreOS, Inc.
//
// 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 storage
import (
"errors"
"log"
"math"
"math/rand"
"sync"
"time"
"github.com/coreos/etcd/storage/backend"
"github.com/coreos/etcd/storage/storagepb"
)
var (
batchLimit = 10000
batchInterval = 100 * time.Millisecond
keyBucketName = []byte("key")
metaBucketName = []byte("meta")
scheduledCompactKeyName = []byte("scheduledCompactRev")
finishedCompactKeyName = []byte("finishedCompactRev")
ErrTxnIDMismatch = errors.New("storage: txn id mismatch")
ErrCompacted = errors.New("storage: required revision has been compacted")
ErrFutureRev = errors.New("storage: required revision is a future revision")
ErrCanceled = errors.New("storage: watcher is canceled")
)
type store struct {
mu sync.RWMutex
b backend.Backend
kvindex index
currentRev revision
// the main revision of the last compaction
compactMainRev int64
tx backend.BatchTx
tmu sync.Mutex // protect the txnID field
txnID int64 // tracks the current txnID to verify txn operations
wg sync.WaitGroup
stopc chan struct{}
}
func New(path string) KV {
return newStore(path)
}
func newStore(path string) *store {
s := &store{
b: backend.New(path, batchInterval, batchLimit),
kvindex: newTreeIndex(),
currentRev: revision{},
compactMainRev: -1,
stopc: make(chan struct{}),
}
tx := s.b.BatchTx()
tx.Lock()
tx.UnsafeCreateBucket(keyBucketName)
tx.UnsafeCreateBucket(metaBucketName)
tx.Unlock()
s.b.ForceCommit()
return s
}
func (s *store) Rev() int64 {
s.mu.RLock()
defer s.mu.RUnlock()
return s.currentRev.main
}
func (s *store) Put(key, value []byte) int64 {
id := s.TxnBegin()
s.put(key, value)
s.txnEnd(id)
putCounter.Inc()
return int64(s.currentRev.main)
}
func (s *store) Range(key, end []byte, limit, rangeRev int64) (kvs []storagepb.KeyValue, rev int64, err error) {
id := s.TxnBegin()
kvs, rev, err = s.rangeKeys(key, end, limit, rangeRev)
s.txnEnd(id)
rangeCounter.Inc()
return kvs, rev, err
}
func (s *store) DeleteRange(key, end []byte) (n, rev int64) {
id := s.TxnBegin()
n = s.deleteRange(key, end)
s.txnEnd(id)
deleteCounter.Inc()
return n, int64(s.currentRev.main)
}
func (s *store) TxnBegin() int64 {
s.mu.Lock()
s.currentRev.sub = 0
s.tx = s.b.BatchTx()
s.tx.Lock()
s.tmu.Lock()
defer s.tmu.Unlock()
s.txnID = rand.Int63()
return s.txnID
}
func (s *store) TxnEnd(txnID int64) error {
err := s.txnEnd(txnID)
if err != nil {
return err
}
txnCounter.Inc()
return nil
}
// txnEnd is used for unlocking an internal txn. It does
// not increase the txnCounter.
func (s *store) txnEnd(txnID int64) error {
s.tmu.Lock()
defer s.tmu.Unlock()
if txnID != s.txnID {
return ErrTxnIDMismatch
}
s.tx.Unlock()
if s.currentRev.sub != 0 {
s.currentRev.main += 1
}
s.currentRev.sub = 0
dbTotalSize.Set(float64(s.b.Size()))
s.mu.Unlock()
return nil
}
func (s *store) TxnRange(txnID int64, key, end []byte, limit, rangeRev int64) (kvs []storagepb.KeyValue, rev int64, err error) {
s.tmu.Lock()
defer s.tmu.Unlock()
if txnID != s.txnID {
return nil, 0, ErrTxnIDMismatch
}
return s.rangeKeys(key, end, limit, rangeRev)
}
func (s *store) TxnPut(txnID int64, key, value []byte) (rev int64, err error) {
s.tmu.Lock()
defer s.tmu.Unlock()
if txnID != s.txnID {
return 0, ErrTxnIDMismatch
}
s.put(key, value)
return int64(s.currentRev.main + 1), nil
}
func (s *store) TxnDeleteRange(txnID int64, key, end []byte) (n, rev int64, err error) {
s.tmu.Lock()
defer s.tmu.Unlock()
if txnID != s.txnID {
return 0, 0, ErrTxnIDMismatch
}
n = s.deleteRange(key, end)
if n != 0 || s.currentRev.sub != 0 {
rev = int64(s.currentRev.main + 1)
} else {
rev = int64(s.currentRev.main)
}
return n, rev, nil
}
// RangeEvents gets the events from key to end starting from startRev.
// If `end` is nil, the request only observes the events on key.
// If `end` is not nil, it observes the events on key range [key, range_end).
// Limit limits the number of events returned.
// If startRev <=0, rangeEvents returns events from the beginning of uncompacted history.
//
// If the required start rev is compacted, ErrCompacted will be returned.
// If the required start rev has not happened, ErrFutureRev will be returned.
//
// RangeEvents returns events that satisfy the requirement (0 <= n <= limit).
// If events in the revision range have not all happened, it returns immeidately
// what is available.
// It also returns nextRev which indicates the start revision used for the following
// RangeEvents call. The nextRev could be smaller than the given endRev if the store
// has not progressed so far or it hits the event limit.
//
// TODO: return byte slices instead of events to avoid meaningless encode and decode.
func (s *store) RangeEvents(key, end []byte, limit, startRev int64) (evs []storagepb.Event, nextRev int64, err error) {
s.mu.Lock()
defer s.mu.Unlock()
if startRev > 0 && startRev <= s.compactMainRev {
return nil, 0, ErrCompacted
}
if startRev > s.currentRev.main {
return nil, 0, ErrFutureRev
}
revs := s.kvindex.RangeEvents(key, end, startRev)
if len(revs) == 0 {
return nil, s.currentRev.main + 1, nil
}
tx := s.b.BatchTx()
tx.Lock()
defer tx.Unlock()
// fetch events from the backend using revisions
for _, rev := range revs {
revbytes := newRevBytes()
revToBytes(rev, revbytes)
_, vs := tx.UnsafeRange(keyBucketName, revbytes, nil, 0)
if len(vs) != 1 {
log.Fatalf("storage: range cannot find rev (%d,%d)", rev.main, rev.sub)
}
e := storagepb.Event{}
if err := e.Unmarshal(vs[0]); err != nil {
log.Fatalf("storage: cannot unmarshal event: %v", err)
}
evs = append(evs, e)
if limit > 0 && len(evs) >= int(limit) {
return evs, rev.main + 1, nil
}
}
return evs, s.currentRev.main + 1, nil
}
func (s *store) Compact(rev int64) error {
s.mu.Lock()
defer s.mu.Unlock()
if rev <= s.compactMainRev {
return ErrCompacted
}
if rev > s.currentRev.main {
return ErrFutureRev
}
start := time.Now()
s.compactMainRev = rev
rbytes := newRevBytes()
revToBytes(revision{main: rev}, rbytes)
tx := s.b.BatchTx()
tx.Lock()
tx.UnsafePut(metaBucketName, scheduledCompactKeyName, rbytes)
tx.Unlock()
// ensure that desired compaction is persisted
s.b.ForceCommit()
keep := s.kvindex.Compact(rev)
s.wg.Add(1)
go s.scheduleCompaction(rev, keep)
indexCompactionPauseDurations.Observe(float64(time.Now().Sub(start) / time.Millisecond))
return nil
}
func (s *store) Hash() (uint32, error) {
s.b.ForceCommit()
return s.b.Hash()
}
func (s *store) Snapshot() Snapshot {
s.b.ForceCommit()
return s.b.Snapshot()
}
func (s *store) Restore() error {
s.mu.Lock()
defer s.mu.Unlock()
min, max := newRevBytes(), newRevBytes()
revToBytes(revision{}, min)
revToBytes(revision{main: math.MaxInt64, sub: math.MaxInt64}, max)
// restore index
tx := s.b.BatchTx()
tx.Lock()
_, finishedCompactBytes := tx.UnsafeRange(metaBucketName, finishedCompactKeyName, nil, 0)
if len(finishedCompactBytes) != 0 {
s.compactMainRev = bytesToRev(finishedCompactBytes[0]).main
log.Printf("storage: restore compact to %d", s.compactMainRev)
}
// TODO: limit N to reduce max memory usage
keys, vals := tx.UnsafeRange(keyBucketName, min, max, 0)
for i, key := range keys {
e := &storagepb.Event{}
if err := e.Unmarshal(vals[i]); err != nil {
log.Fatalf("storage: cannot unmarshal event: %v", err)
}
rev := bytesToRev(key)
// restore index
switch e.Type {
case storagepb.PUT:
s.kvindex.Restore(e.Kv.Key, revision{e.Kv.CreateRevision, 0}, rev, e.Kv.Version)
case storagepb.DELETE:
s.kvindex.Tombstone(e.Kv.Key, rev)
default:
log.Panicf("storage: unexpected event type %s", e.Type)
}
// update revision
s.currentRev = rev
}
_, scheduledCompactBytes := tx.UnsafeRange(metaBucketName, scheduledCompactKeyName, nil, 0)
if len(scheduledCompactBytes) != 0 {
scheduledCompact := bytesToRev(scheduledCompactBytes[0]).main
if scheduledCompact > s.compactMainRev {
log.Printf("storage: resume scheduled compaction at %d", scheduledCompact)
go s.Compact(scheduledCompact)
}
}
tx.Unlock()
return nil
}
func (s *store) Close() error {
close(s.stopc)
s.wg.Wait()
return s.b.Close()
}
func (a *store) Equal(b *store) bool {
if a.currentRev != b.currentRev {
return false
}
if a.compactMainRev != b.compactMainRev {
return false
}
return a.kvindex.Equal(b.kvindex)
}
// range is a keyword in Go, add Keys suffix.
func (s *store) rangeKeys(key, end []byte, limit, rangeRev int64) (kvs []storagepb.KeyValue, rev int64, err error) {
curRev := int64(s.currentRev.main)
if s.currentRev.sub > 0 {
curRev += 1
}
if rangeRev > curRev {
return nil, s.currentRev.main, ErrFutureRev
}
if rangeRev <= 0 {
rev = curRev
} else {
rev = rangeRev
}
if rev <= s.compactMainRev {
return nil, 0, ErrCompacted
}
_, revpairs := s.kvindex.Range(key, end, int64(rev))
if len(revpairs) == 0 {
return nil, rev, nil
}
for _, revpair := range revpairs {
revbytes := newRevBytes()
revToBytes(revpair, revbytes)
_, vs := s.tx.UnsafeRange(keyBucketName, revbytes, nil, 0)
if len(vs) != 1 {
log.Fatalf("storage: range cannot find rev (%d,%d)", revpair.main, revpair.sub)
}
e := &storagepb.Event{}
if err := e.Unmarshal(vs[0]); err != nil {
log.Fatalf("storage: cannot unmarshal event: %v", err)
}
kvs = append(kvs, *e.Kv)
if limit > 0 && len(kvs) >= int(limit) {
break
}
}
return kvs, rev, nil
}
func (s *store) put(key, value []byte) {
rev := s.currentRev.main + 1
c := rev
// if the key exists before, use its previous created
_, created, ver, err := s.kvindex.Get(key, rev)
if err == nil {
c = created.main
}
ibytes := newRevBytes()
revToBytes(revision{main: rev, sub: s.currentRev.sub}, ibytes)
ver = ver + 1
event := storagepb.Event{
Type: storagepb.PUT,
Kv: &storagepb.KeyValue{
Key: key,
Value: value,
CreateRevision: c,
ModRevision: rev,
Version: ver,
},
}
d, err := event.Marshal()
if err != nil {
log.Fatalf("storage: cannot marshal event: %v", err)
}
s.tx.UnsafePut(keyBucketName, ibytes, d)
s.kvindex.Put(key, revision{main: rev, sub: s.currentRev.sub})
s.currentRev.sub += 1
}
func (s *store) deleteRange(key, end []byte) int64 {
rrev := s.currentRev.main
if s.currentRev.sub > 0 {
rrev += 1
}
keys, _ := s.kvindex.Range(key, end, rrev)
if len(keys) == 0 {
return 0
}
for _, key := range keys {
s.delete(key)
}
return int64(len(keys))
}
func (s *store) delete(key []byte) {
mainrev := s.currentRev.main + 1
ibytes := newRevBytes()
revToBytes(revision{main: mainrev, sub: s.currentRev.sub}, ibytes)
event := storagepb.Event{
Type: storagepb.DELETE,
Kv: &storagepb.KeyValue{
Key: key,
},
}
d, err := event.Marshal()
if err != nil {
log.Fatalf("storage: cannot marshal event: %v", err)
}
s.tx.UnsafePut(keyBucketName, ibytes, d)
err = s.kvindex.Tombstone(key, revision{main: mainrev, sub: s.currentRev.sub})
if err != nil {
log.Fatalf("storage: cannot tombstone an existing key (%s): %v", string(key), err)
}
s.currentRev.sub += 1
}