swarm: add database abstractions (shed package) (#18183)

Author: janos

swarm/shed/db.go

@@ -0,0 +1,130 @@
+// 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 shed provides a simple abstraction components to compose
+// more complex operations on storage data organized in fields and indexes.
+//
+// Only type which holds logical information about swarm storage chunks data
+// and metadata is IndexItem. This part is not generalized mostly for
+// performance reasons.
+package shed
+
+import (
+	"github.com/ethereum/go-ethereum/metrics"
+	"github.com/syndtr/goleveldb/leveldb"
+	"github.com/syndtr/goleveldb/leveldb/iterator"
+	"github.com/syndtr/goleveldb/leveldb/opt"
+)
+
+// The limit for LevelDB OpenFilesCacheCapacity.
+const openFileLimit = 128
+
+// DB provides abstractions over LevelDB in order to
+// implement complex structures using fields and ordered indexes.
+// It provides a schema functionality to store fields and indexes
+// information about naming and types.
+type DB struct {
+	ldb *leveldb.DB
+}
+
+// NewDB constructs a new DB and validates the schema
+// if it exists in database on the given path.
+func NewDB(path string) (db *DB, err error) {
+	ldb, err := leveldb.OpenFile(path, &opt.Options{
+		OpenFilesCacheCapacity: openFileLimit,
+	})
+	if err != nil {
+		return nil, err
+	}
+	db = &DB{
+		ldb: ldb,
+	}
+
+	if _, err = db.getSchema(); err != nil {
+		if err == leveldb.ErrNotFound {
+			// save schema with initialized default fields
+			if err = db.putSchema(schema{
+				Fields:  make(map[string]fieldSpec),
+				Indexes: make(map[byte]indexSpec),
+			}); err != nil {
+				return nil, err
+			}
+		} else {
+			return nil, err
+		}
+	}
+	return db, nil
+}
+
+// Put wraps LevelDB Put method to increment metrics counter.
+func (db *DB) Put(key []byte, value []byte) (err error) {
+	err = db.ldb.Put(key, value, nil)
+	if err != nil {
+		metrics.GetOrRegisterCounter("DB.putFail", nil).Inc(1)
+		return err
+	}
+	metrics.GetOrRegisterCounter("DB.put", nil).Inc(1)
+	return nil
+}
+
+// Get wraps LevelDB Get method to increment metrics counter.
+func (db *DB) Get(key []byte) (value []byte, err error) {
+	value, err = db.ldb.Get(key, nil)
+	if err != nil {
+		if err == leveldb.ErrNotFound {
+			metrics.GetOrRegisterCounter("DB.getNotFound", nil).Inc(1)
+		} else {
+			metrics.GetOrRegisterCounter("DB.getFail", nil).Inc(1)
+		}
+		return nil, err
+	}
+	metrics.GetOrRegisterCounter("DB.get", nil).Inc(1)
+	return value, nil
+}
+
+// Delete wraps LevelDB Delete method to increment metrics counter.
+func (db *DB) Delete(key []byte) (err error) {
+	err = db.ldb.Delete(key, nil)
+	if err != nil {
+		metrics.GetOrRegisterCounter("DB.deleteFail", nil).Inc(1)
+		return err
+	}
+	metrics.GetOrRegisterCounter("DB.delete", nil).Inc(1)
+	return nil
+}
+
+// NewIterator wraps LevelDB NewIterator method to increment metrics counter.
+func (db *DB) NewIterator() iterator.Iterator {
+	metrics.GetOrRegisterCounter("DB.newiterator", nil).Inc(1)
+
+	return db.ldb.NewIterator(nil, nil)
+}
+
+// WriteBatch wraps LevelDB Write method to increment metrics counter.
+func (db *DB) WriteBatch(batch *leveldb.Batch) (err error) {
+	err = db.ldb.Write(batch, nil)
+	if err != nil {
+		metrics.GetOrRegisterCounter("DB.writebatchFail", nil).Inc(1)
+		return err
+	}
+	metrics.GetOrRegisterCounter("DB.writebatch", nil).Inc(1)
+	return nil
+}
+
+// Close closes LevelDB database.
+func (db *DB) Close() (err error) {
+	return db.ldb.Close()
+}

swarm/shed/db_test.go

@@ -0,0 +1,110 @@
+// 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 shed
+
+import (
+	"io/ioutil"
+	"os"
+	"testing"
+)
+
+// TestNewDB constructs a new DB
+// and validates if the schema is initialized properly.
+func TestNewDB(t *testing.T) {
+	db, cleanupFunc := newTestDB(t)
+	defer cleanupFunc()
+
+	s, err := db.getSchema()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if s.Fields == nil {
+		t.Error("schema fields are empty")
+	}
+	if len(s.Fields) != 0 {
+		t.Errorf("got schema fields length %v, want %v", len(s.Fields), 0)
+	}
+	if s.Indexes == nil {
+		t.Error("schema indexes are empty")
+	}
+	if len(s.Indexes) != 0 {
+		t.Errorf("got schema indexes length %v, want %v", len(s.Indexes), 0)
+	}
+}
+
+// TestDB_persistence creates one DB, saves a field and closes that DB.
+// Then, it constructs another DB and trues to retrieve the saved value.
+func TestDB_persistence(t *testing.T) {
+	dir, err := ioutil.TempDir("", "shed-test-persistence")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(dir)
+
+	db, err := NewDB(dir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	stringField, err := db.NewStringField("preserve-me")
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := "persistent value"
+	err = stringField.Put(want)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = db.Close()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	db2, err := NewDB(dir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	stringField2, err := db2.NewStringField("preserve-me")
+	if err != nil {
+		t.Fatal(err)
+	}
+	got, err := stringField2.Get()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != want {
+		t.Errorf("got string %q, want %q", got, want)
+	}
+}
+
+// newTestDB is a helper function that constructs a
+// temporary database and returns a cleanup function that must
+// be called to remove the data.
+func newTestDB(t *testing.T) (db *DB, cleanupFunc func()) {
+	t.Helper()
+
+	dir, err := ioutil.TempDir("", "shed-test")
+	if err != nil {
+		t.Fatal(err)
+	}
+	cleanupFunc = func() { os.RemoveAll(dir) }
+	db, err = NewDB(dir)
+	if err != nil {
+		cleanupFunc()
+		t.Fatal(err)
+	}
+	return db, cleanupFunc
+}