Abstracted backend as an interface and implemented the LevelDB stuff as such.

backend.go

@@ -0,0 +1,10 @@
+package main
+
+type Backend interface {
+	Fetch(hash, key []byte) ([]byte, error)
+	InTransaction() bool
+	Store(hash, key, value []byte) (bool, error)
+	BeginTransaction() error
+	CommitTransAction() error
+	Shutdown() error
+}

connection.go

@@ -5,13 +5,11 @@ import (
 	"fmt"
 	"log"
 	"net"
-
-	leveldb "github.com/jmhodges/levigo"
 )
 
 var (
 	redisOk          = []byte("+OK\r\n")
-	redisDbError     = []byte("-FAIL\r\n")
+	redisError       = []byte("-ERR\r\n")
 	redisNoSuchBlock = []byte("$-1\r\n")
 	redisCrnl        = []byte("\r\n")
 	redisEmptyArray  = []byte("*0\r\n")
@@ -19,18 +17,16 @@ var (
 )
 
 type Connection struct {
-	conn     net.Conn
+	conn      net.Conn
-	db       *leveldb.DB
+	backend   Backend
-	tx       *leveldb.WriteBatch
+	boolArray []bool
-	intArray []int
 }
 
-func NewConnection(conn net.Conn, db *leveldb.DB) *Connection {
+func NewConnection(conn net.Conn, backend Backend) *Connection {
 	return &Connection{
-		conn,
+		conn:      conn,
-		db,
+		backend:   backend,
-		nil,
+		boolArray: []bool{}}
-		[]int{}}
 }
 
 func (c *Connection) Run() {
@@ -46,90 +42,58 @@ func logError(err error) {
 }
 
 func (c *Connection) Hget(hash, key []byte) bool {
-	log.Printf("client requested block: %q", key)
+
 	var err error
 	var data []byte
-	ro := leveldb.NewReadOptions()
+	if data, err = c.backend.Fetch(hash, key); err != nil {
-	defer ro.Close()
+		return c.writeError(err)
-	if data, err = c.db.Get(ro, key); err != nil {
-		logError(err)
-		return c.writeError()
 	}
+
 	return c.writeBlock(data)
 }
 
-func (c *Connection) Hset(hash, key, block []byte) bool {
+func (c *Connection) Hset(hash, key, data []byte) bool {
-	log.Printf("client wants to store block: %q", key)
 
 	var err error
-	var exists int
+	var exists bool
-
+	if exists, err = c.backend.Store(hash, key, data); err != nil {
-	if exists, err = c.keyExists(key); err != nil {
+		return c.writeError(err)
-		logError(err)
-		return c.writeError()
 	}
 
-	if c.tx != nil {
+	if c.backend.InTransaction() {
-		c.tx.Put(key, block)
+		c.boolArray = append(c.boolArray, exists)
-		c.intArray = append(c.intArray, exists)
 		return c.writeQueued()
 	}
 
-	wo := leveldb.NewWriteOptions()
+	return c.writeBool(exists)
-	defer wo.Close()
-	if err = c.db.Put(wo, key, block); err != nil {
-		logError(err)
-		return c.writeError()
-	}
-
-	return c.writeInteger(exists)
-}
-
-func (c *Connection) keyExists(key []byte) (exists int, err error) {
-	ro := leveldb.NewReadOptions()
-	defer ro.Close()
-	var data []byte
-	if data, err = c.db.Get(ro, key); err != nil {
-		return
-	}
-	if data != nil {
-		exists = 1
-	} else {
-		exists = 0
-	}
-	return
 }
 
 func (c *Connection) Multi() bool {
-	if c.tx != nil {
+	if c.backend.InTransaction() {
 		log.Println("WARN: Already running transaction.")
 	} else {
-		c.tx = leveldb.NewWriteBatch()
+		if err := c.backend.BeginTransaction(); err != nil {
+			return c.writeError(err)
+		}
 	}
 	return c.writeOk()
 }
 
 func (c *Connection) Exec() bool {
-	var err error
+	if !c.backend.InTransaction() {
-	if c.tx == nil {
 		return c.writeEmptyArray()
 	}
-	tx := c.tx
+	arr := c.boolArray
-	c.tx = nil
+	c.boolArray = []bool{}
-	defer tx.Close()
+	if err := c.backend.CommitTransAction(); err != nil {
-	arr := c.intArray
+		return c.writeError(err)
-	c.intArray = []int{}
-	wo := leveldb.NewWriteOptions()
-	defer wo.Close()
-	if err = c.db.Write(wo, tx); err != nil {
-		logError(err)
-		return c.writeError()
 	}
-	return c.writeIntegerArray(arr)
+	return c.writeBoolArray(arr)
 }
 
-func (c *Connection) writeError() bool {
+func (c *Connection) writeError(err error) bool {
-	if _, err := c.conn.Write(redisDbError); err != nil {
+	logError(err)
+	if _, err = c.conn.Write(redisError); err != nil {
 		logError(err)
 		return false
 	}
@@ -137,28 +101,35 @@ func (c *Connection) writeError() bool {
 }
 
 func (c *Connection) writeEmptyArray() bool {
-	if _, err := c.conn.Write(redisDbError); err != nil {
+	if _, err := c.conn.Write(redisEmptyArray); err != nil {
 		logError(err)
 		return false
 	}
 	return true
 }
 
-func (c *Connection) writeInteger(v int) bool {
+func asInt(b bool) int {
-	if _, err := c.conn.Write([]byte(fmt.Sprintf(":%d\r\n", v))); err != nil {
+	if b {
+		return 1
+	}
+	return 0
+}
+
+func (c *Connection) writeBool(b bool) bool {
+	if _, err := c.conn.Write([]byte(fmt.Sprintf(":%d\r\n", asInt(b)))); err != nil {
 		logError(err)
 		return false
 	}
 	return true
 }
 
-func (c *Connection) writeIntegerArray(arr []int) bool {
+func (c *Connection) writeBoolArray(arr []bool) bool {
 	if _, err := c.conn.Write([]byte(fmt.Sprintf("*%d\r\n", len(arr)))); err != nil {
 		logError(err)
 		return false
 	}
-	for x := range arr {
+	for _, b := range arr {
-		if !c.writeInteger(x) {
+		if !c.writeBool(b) {
 			return false
 		}
 	}

leveldb.go

@@ -0,0 +1,87 @@
+package main
+
+import (
+	leveldb "github.com/jmhodges/levigo"
+)
+
+type LevelDBBackend struct {
+	cache *leveldb.Cache
+	db    *leveldb.DB
+	tx    *leveldb.WriteBatch
+}
+
+func NewLeveDBBackend(path string, cacheSize int) (ldb *LevelDBBackend, err error) {
+	cache := leveldb.NewLRUCache(cacheSize * 1024 * 1024)
+	opts := leveldb.NewOptions()
+	opts.SetCache(cache)
+	opts.SetCreateIfMissing(true)
+	var db *leveldb.DB
+	if db, err = leveldb.Open(path, opts); err != nil {
+		cache.Close()
+		return
+	}
+	ldb = &LevelDBBackend{
+		cache: cache,
+		db:    db}
+	return
+}
+
+func (ldb *LevelDBBackend) Shutdown() error {
+	ldb.db.Close()
+	ldb.cache.Close()
+	return nil
+}
+
+func (ldb *LevelDBBackend) Fetch(hash, key []byte) ([]byte, error) {
+	ro := leveldb.NewReadOptions()
+	defer ro.Close()
+	return ldb.db.Get(ro, key)
+}
+
+func (ldb *LevelDBBackend) InTransaction() bool {
+	return ldb.tx != nil
+}
+
+func (ldb *LevelDBBackend) keyExists(key []byte) (exists bool, err error) {
+	ro := leveldb.NewReadOptions()
+	defer ro.Close()
+	var data []byte
+	if data, err = ldb.db.Get(ro, key); err != nil {
+		return
+	}
+	exists = data != nil
+	return
+}
+
+func (ldb *LevelDBBackend) Store(hash, key, value []byte) (exists bool, err error) {
+
+	if exists, err = ldb.keyExists(key); err != nil {
+		return
+	}
+
+	if ldb.tx != nil {
+		ldb.tx.Put(key, value)
+		return
+	}
+
+	wo := leveldb.NewWriteOptions()
+	defer wo.Close()
+	if err = ldb.db.Put(wo, key, value); err != nil {
+		return
+	}
+
+	return
+}
+
+func (ldb *LevelDBBackend) BeginTransaction() error {
+	ldb.tx = leveldb.NewWriteBatch()
+	return nil
+}
+
+func (ldb *LevelDBBackend) CommitTransAction() error {
+	tx := ldb.tx
+	ldb.tx = nil
+	wo := leveldb.NewWriteOptions()
+	defer wo.Close()
+	return ldb.db.Write(wo, tx)
+}

main.go

@@ -7,8 +7,6 @@ import (
 	"net"
 	"os"
 	"os/signal"
-
-	leveldb "github.com/jmhodges/levigo"
 )
 
 func main() {
@@ -28,20 +26,13 @@ func main() {
 		log.Fatal("Missing path to world")
 	}
 
-	cache := leveldb.NewLRUCache(cacheSize * 1024 * 1024)
-	defer cache.Close()
-
-	opts := leveldb.NewOptions()
-	opts.SetCache(cache)
-	opts.SetCreateIfMissing(true)
-
 	var err error
-	var db *leveldb.DB
+	var backend Backend
 
-	if db, err = leveldb.Open(args[0], opts); err != nil {
+	if backend, err = NewLeveDBBackend(args[0], cacheSize); err != nil {
 		log.Fatal(err)
 	}
-	defer db.Close()
+	defer backend.Shutdown()
 
 	var listener net.Listener
 
@@ -71,7 +62,7 @@ func main() {
 	for {
 		select {
 		case conn := <-connChan:
-			go NewConnection(conn, db).Run()
+			go NewConnection(conn, backend).Run()
 		case <-sigChan:
 			log.Println("Shutting down")
 			return