syncthing/lib/db/transactions.go

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// Copyright (C) 2014 The Syncthing Authors.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at https://mozilla.org/MPL/2.0/.
package db
import (
"github.com/syncthing/syncthing/lib/protocol"
"github.com/syndtr/goleveldb/leveldb"
"github.com/syndtr/goleveldb/leveldb/util"
)
// Flush batches to disk when they contain this many records.
const batchFlushSize = 64
// A readOnlyTransaction represents a database snapshot.
type readOnlyTransaction struct {
*leveldb.Snapshot
db *instance
}
func (db *instance) newReadOnlyTransaction() readOnlyTransaction {
snap, err := db.GetSnapshot()
if err != nil {
panic(err)
}
return readOnlyTransaction{
Snapshot: snap,
db: db,
}
}
func (t readOnlyTransaction) close() {
t.Release()
}
func (t readOnlyTransaction) getFile(folder, device, file []byte) (protocol.FileInfo, bool) {
return t.getFileByKey(t.db.keyer.GenerateDeviceFileKey(nil, folder, device, file))
}
func (t readOnlyTransaction) getFileByKey(key []byte) (protocol.FileInfo, bool) {
if f, ok := t.getFileTrunc(key, false); ok {
return f.(protocol.FileInfo), true
}
return protocol.FileInfo{}, false
}
func (t readOnlyTransaction) getFileTrunc(key []byte, trunc bool) (FileIntf, bool) {
bs, err := t.Get(key, nil)
if err == leveldb.ErrNotFound {
return nil, false
}
if err != nil {
l.Debugln("surprise error:", err)
return nil, false
}
f, err := unmarshalTrunc(bs, trunc)
if err != nil {
l.Debugln("unmarshal error:", err)
return nil, false
}
return f, true
}
func (t readOnlyTransaction) getGlobalInto(gk, dk, folder, file []byte, truncate bool) ([]byte, []byte, FileIntf, bool) {
gk = t.db.keyer.GenerateGlobalVersionKey(gk, folder, file)
bs, err := t.Get(gk, nil)
if err != nil {
return gk, dk, nil, false
}
vl, ok := unmarshalVersionList(bs)
if !ok {
return gk, dk, nil, false
}
dk = t.db.keyer.GenerateDeviceFileKey(dk, folder, vl.Versions[0].Device, file)
if fi, ok := t.getFileTrunc(dk, truncate); ok {
return gk, dk, fi, true
}
return gk, dk, nil, false
}
// A readWriteTransaction is a readOnlyTransaction plus a batch for writes.
// The batch will be committed on close() or by checkFlush() if it exceeds the
// batch size.
type readWriteTransaction struct {
readOnlyTransaction
*leveldb.Batch
}
func (db *instance) newReadWriteTransaction() readWriteTransaction {
t := db.newReadOnlyTransaction()
return readWriteTransaction{
readOnlyTransaction: t,
Batch: new(leveldb.Batch),
}
}
func (t readWriteTransaction) close() {
t.flush()
t.readOnlyTransaction.close()
}
func (t readWriteTransaction) checkFlush() {
if t.Batch.Len() > batchFlushSize {
t.flush()
t.Batch.Reset()
}
}
func (t readWriteTransaction) flush() {
if err := t.db.Write(t.Batch, nil); err != nil {
panic(err)
}
}
func (t readWriteTransaction) insertFile(fk, folder, device []byte, file protocol.FileInfo) {
l.Debugf("insert; folder=%q device=%v %v", folder, protocol.DeviceIDFromBytes(device), file)
t.Put(fk, mustMarshal(&file))
}
// updateGlobal adds this device+version to the version list for the given
// file. If the device is already present in the list, the version is updated.
// If the file does not have an entry in the global list, it is created.
func (t readWriteTransaction) updateGlobal(gk, folder, device []byte, file protocol.FileInfo, meta *metadataTracker) bool {
l.Debugf("update global; folder=%q device=%v file=%q version=%v invalid=%v", folder, protocol.DeviceIDFromBytes(device), file.Name, file.Version, file.IsInvalid())
var fl VersionList
if svl, err := t.Get(gk, nil); err == nil {
fl.Unmarshal(svl) // Ignore error, continue with empty fl
}
fl, removedFV, removedAt, insertedAt := fl.update(folder, device, file, t.readOnlyTransaction)
if insertedAt == -1 {
l.Debugln("update global; same version, global unchanged")
return false
}
name := []byte(file.Name)
var global protocol.FileInfo
if insertedAt == 0 {
// Inserted a new newest version
global = file
} else if new, ok := t.getFile(folder, fl.Versions[0].Device, name); ok {
global = new
} else {
panic("This file must exist in the db")
}
// Fixup the list of files we need.
t.updateLocalNeed(folder, name, fl, global)
if removedAt != 0 && insertedAt != 0 {
l.Debugf(`new global for "%v" after update: %v`, file.Name, fl)
t.Put(gk, mustMarshal(&fl))
return true
}
// Remove the old global from the global size counter
var oldGlobalFV FileVersion
if removedAt == 0 {
oldGlobalFV = removedFV
} else if len(fl.Versions) > 1 {
// The previous newest version is now at index 1
oldGlobalFV = fl.Versions[1]
}
if oldFile, ok := t.getFile(folder, oldGlobalFV.Device, name); ok {
// A failure to get the file here is surprising and our
// global size data will be incorrect until a restart...
meta.removeFile(protocol.GlobalDeviceID, oldFile)
}
// Add the new global to the global size counter
meta.addFile(protocol.GlobalDeviceID, global)
l.Debugf(`new global for "%v" after update: %v`, file.Name, fl)
t.Put(gk, mustMarshal(&fl))
return true
}
// updateLocalNeeds checks whether the given file is still needed on the local
// device according to the version list and global FileInfo given and updates
// the db accordingly.
func (t readWriteTransaction) updateLocalNeed(folder, name []byte, fl VersionList, global protocol.FileInfo) {
nk := t.db.keyer.GenerateNeedFileKey(nil, folder, name)
hasNeeded, _ := t.db.Has(nk, nil)
if localFV, haveLocalFV := fl.Get(protocol.LocalDeviceID[:]); need(global, haveLocalFV, localFV.Version) {
if !hasNeeded {
l.Debugf("local need insert; folder=%q, name=%q", folder, name)
t.Put(nk, nil)
}
} else if hasNeeded {
l.Debugf("local need delete; folder=%q, name=%q", folder, name)
t.Delete(nk)
}
}
func need(global FileIntf, haveLocal bool, localVersion protocol.Vector) bool {
// We never need an invalid file.
if global.IsInvalid() {
return false
}
// We don't need a deleted file if we don't have it.
if global.IsDeleted() && !haveLocal {
return false
}
// We don't need the global file if we already have the same version.
if haveLocal && localVersion.GreaterEqual(global.FileVersion()) {
return false
}
return true
}
// removeFromGlobal removes the device from the global version list for the
// given file. If the version list is empty after this, the file entry is
// removed entirely.
func (t readWriteTransaction) removeFromGlobal(gk, folder, device, file []byte, meta *metadataTracker) {
l.Debugf("remove from global; folder=%q device=%v file=%q", folder, protocol.DeviceIDFromBytes(device), file)
svl, err := t.Get(gk, nil)
if err != nil {
// We might be called to "remove" a global version that doesn't exist
// if the first update for the file is already marked invalid.
return
}
var fl VersionList
err = fl.Unmarshal(svl)
if err != nil {
l.Debugln("unmarshal error:", err)
return
}
fl, _, removedAt := fl.pop(device)
if removedAt == -1 {
// There is no version for the given device
return
}
if removedAt == 0 {
// A failure to get the file here is surprising and our
// global size data will be incorrect until a restart...
if f, ok := t.getFile(folder, device, file); ok {
meta.removeFile(protocol.GlobalDeviceID, f)
}
}
if len(fl.Versions) == 0 {
t.Delete(t.db.keyer.GenerateNeedFileKey(nil, folder, file))
t.Delete(gk)
return
}
if removedAt == 0 {
global, ok := t.getFile(folder, fl.Versions[0].Device, file)
if !ok {
panic("This file must exist in the db")
}
t.updateLocalNeed(folder, file, fl, global)
meta.addFile(protocol.GlobalDeviceID, global)
}
l.Debugf("new global after remove: %v", fl)
t.Put(gk, mustMarshal(&fl))
}
func (t readWriteTransaction) deleteKeyPrefix(prefix []byte) {
dbi := t.NewIterator(util.BytesPrefix(prefix), nil)
for dbi.Next() {
t.Delete(dbi.Key())
t.checkFlush()
}
dbi.Release()
}
type marshaller interface {
Marshal() ([]byte, error)
}
func mustMarshal(f marshaller) []byte {
bs, err := f.Marshal()
if err != nil {
panic(err)
}
return bs
}