swarm/storage/localstore: new localstore package (#19015)

swarm/storage/localstore/mode_get.go

@@ -0,0 +1,154 @@
+// 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/shed"
+	"github.com/ethereum/go-ethereum/swarm/storage"
+	"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 storage.ErrChunkNotFound will be returned.
+// All required indexes will be updated required by the
+// Getter Mode.
+func (g *Getter) Get(addr storage.Address) (chunk storage.Chunk, err error) {
+	out, err := g.db.get(g.mode, addr)
+	if err != nil {
+		if err == leveldb.ErrNotFound {
+			return nil, storage.ErrChunkNotFound
+		}
+		return nil, err
+	}
+	return storage.NewChunk(out.Address, out.Data), nil
+}
+
+// get returns Item from the retrieval index
+// and updates other indexes.
+func (db *DB) get(mode ModeGet, addr storage.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) {
+	unlock, err := db.lockAddr(item.Address)
+	if err != nil {
+		return err
+	}
+	defer 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()