// Copyright 2018 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package localstore
import (
"github.com/ethereum/go-ethereum/log"
"github.com/ethereum/go-ethereum/swarm/chunk"
"github.com/ethereum/go-ethereum/swarm/shed"
"github.com/syndtr/goleveldb/leveldb"
)
// ModeGet enumerates different Getter modes.
type ModeGet int
// Getter modes.
const (
// ModeGetRequest: when accessed for retrieval
ModeGetRequest ModeGet = iota
// ModeGetSync: when accessed for syncing or proof of custody request
ModeGetSync
)
// Getter provides Get method to retrieve Chunks
// from database.
type Getter struct {
db *DB
mode ModeGet
}
// NewGetter returns a new Getter on database
// with a specific Mode.
func (db *DB) NewGetter(mode ModeGet) *Getter {
return &Getter{
mode: mode,
db: db,
}
}
// Get returns a chunk from the database. If the chunk is
// not found chunk.ErrChunkNotFound will be returned.
// All required indexes will be updated required by the
// Getter Mode.
func (g *Getter) Get(addr chunk.Address) (ch chunk.Chunk, err error) {
out, err := g.db.get(g.mode, addr)
if err != nil {
if err == leveldb.ErrNotFound {
return nil, chunk.ErrChunkNotFound
}
return nil, err
}
return chunk.NewChunk(out.Address, out.Data), nil
}
// get returns Item from the retrieval index
// and updates other indexes.
func (db *DB) get(mode ModeGet, addr chunk.Address) (out shed.Item, err error) {
item := addressToItem(addr)
out, err = db.retrievalDataIndex.Get(item)
if err != nil {
return out, err
}
switch mode {
// update the access timestamp and gc index
case ModeGetRequest:
if db.updateGCSem != nil {
// wait before creating new goroutines
// if updateGCSem buffer id full
db.updateGCSem <- struct{}{}
}
db.updateGCWG.Add(1)
go func() {
defer db.updateGCWG.Done()
if db.updateGCSem != nil {
// free a spot in updateGCSem buffer
// for a new goroutine
defer func() { <-db.updateGCSem }()
}
err := db.updateGC(out)
if err != nil {
log.Error("localstore update gc", "err", err)
}
// if gc update hook is defined, call it
if testHookUpdateGC != nil {
testHookUpdateGC()
}
}()
// no updates to indexes
case ModeGetSync:
default:
return out, ErrInvalidMode
}
return out, nil
}
// updateGC updates garbage collection index for
// a single item. Provided item is expected to have
// only Address and Data fields with non zero values,
// which is ensured by the get function.
func (db *DB) updateGC(item shed.Item) (err error) {
db.batchMu.Lock()
defer db.batchMu.Unlock()
batch := new(leveldb.Batch)
// update accessTimeStamp in retrieve, gc
i, err := db.retrievalAccessIndex.Get(item)
switch err {
case nil:
item.AccessTimestamp = i.AccessTimestamp
case leveldb.ErrNotFound:
// no chunk accesses
default:
return err
}
if item.AccessTimestamp == 0 {
// chunk is not yet synced
// do not add it to the gc index
return nil
}
// delete current entry from the gc index
db.gcIndex.DeleteInBatch(batch, item)
// update access timestamp
item.AccessTimestamp = now()
// update retrieve access index
db.retrievalAccessIndex.PutInBatch(batch, item)
// add new entry to gc index
db.gcIndex.PutInBatch(batch, item)
return db.shed.WriteBatch(batch)
}
// testHookUpdateGC is a hook that can provide
// information when a garbage collection index is updated.
var testHookUpdateGC func()
