Revert "Use []byte byte slices as keys directly avoiding serialing string(s) (#46)" (#50)

This reverts commit 3c1808cad3.

AUTHORS

@@ -0,0 +1,13 @@
+# Entries should be added alphabetically in the form:
+#   Name or Organization <email address>
+# The email address is not required for organizations.
+
+Awn Umar <awn@spacetime.dev>
+Christian Muehlhaeuser <muesli@gmail.com>
+Ignacio Hagopian <jsign.uy@gmail.com>
+James Mills <prologic@shortcircuit.net.au>
+Jesse Donat <donatj@gmail.com>
+Kebert Xela kebertxela
+panyun panyun 
+Whemoon Jang <palindrom615@gmail.com>
+Yury Fedorov orlangure

CONTRIBUTING.md

@@ -1,8 +1,12 @@
 # Contributing
 
-No preference. If you know hot to use Github and contributed to open source projects before then:
+No preference. If you know how to use Github and have contributed to open source projects before then:
 
 * File an issue
 * Submit a pull request
 * File an issue + Submit a pull request
 * Use this project somewhere :)
+
+Be sure to add yourself to the [AUTHORS](/AUTHORS) file when you submit your PR(s). Every contribution counts no how big or small!
+
+Thanks for using Bitcask!

README.md

@@ -4,14 +4,9 @@
 [![CodeCov](https://codecov.io/gh/prologic/bitcask/branch/master/graph/badge.svg)](https://codecov.io/gh/prologic/bitcask)
 [![Go Report Card](https://goreportcard.com/badge/prologic/bitcask)](https://goreportcard.com/report/prologic/bitcask)
 [![GoDoc](https://godoc.org/github.com/prologic/bitcask?status.svg)](https://godoc.org/github.com/prologic/bitcask) 
-[![Sourcegraph](https://sourcegraph.com/github.com/prologic/bitcask/-/badge.svg)](https://sourcegraph.com/github.com/prologic/bitcask?badge)
-[![Github all releases](https://img.shields.io/github/downloads/prologic/bitcask/total.svg)](https://github.com/prologic/bitcask/releases)
 [![GitHub license](https://img.shields.io/github/license/prologic/bitcask.svg)](https://github.com/prologic/bitcask)
 
-[![](https://images.microbadger.com/badges/version/prologic/bitcask.svg)](https://microbadger.com/images/prologic/bitcask)
-[![](https://images.microbadger.com/badges/image/prologic/bitcask.svg)](https://microbadger.com/images/prologic/bitcask)
-
-A high performance Key/Value store written in [Go](https://golang.org) with a predictable read/write performance and high throughput. Uses a [Bitcask](https://en.wikipedia.org/wiki/Bitcask) on-disk layout (LSM+WAL) similar to [Riak](https://riak.com/). 🗃️
+A high performance Key/Value store written in [Go](https://golang.org) with a predictable read/write performance and high throughput. Uses a [Bitcask](https://en.wikipedia.org/wiki/Bitcask) on-disk layout (LSM+WAL) similar to [Riak](https://riak.com/)
 
 For a more feature-complete Redis-compatible server, distributed key/value store have a look at [Bitraft](https://github.com/prologic/bitraft) which uses this library as its backend. Use [Bitcask](https://github.com/prologic/bitcask) as a starting point or if you want to embed in your application, use [Bitraft](https://github.com/prologic/bitraft) if you need a complete server/client solution with high availability with a Redis-compatible API.
 
@@ -21,14 +16,14 @@ For a more feature-complete Redis-compatible server, distributed key/value store
 * Builtin CLI (`bitcask`)
 * Builtin Redis-compatible server (`bitcaskd`)
 * Predictable read/write performance
-* Low latecny
+* Low latency
 * High throughput (See: [Performance](README.md#Performance) )
 
 ## Development
 
 1. Get the source
 
-```#!bash
+```#!sh
 $ git clone https://github.com/prologic/bitcask.git
 ```
 
@@ -37,20 +32,19 @@ $ git clone https://github.com/prologic/bitcask.git
 This library uses [Protobuf](https://github.com/protocolbuffers/protobuf) to serialize data on disk. Please follow the
 instructions for installing `protobuf` on your system. You will also need the
 following Go libraries/tools to generate Go code from Protobuf defs:
+- [protoc-gen-go](https://github.com/golang/protobuf)
 
 3. Build the project
 
-```#!bash
+```#!sh
 $ make
 ```
 
 This will invoke `go generate` and `go build`.
 
-- [protoc-gen-go](https://github.com/golang/protobuf)
-
 ## Install
 
-```#!bash
+```#!sh
 $ go get github.com/prologic/bitcask
 ```
 
@@ -58,7 +52,7 @@ $ go get github.com/prologic/bitcask
 
 Install the package into your project:
 
-```#!bash
+```#!sh
 $ go get github.com/prologic/bitcask
 ```
 
@@ -80,7 +74,7 @@ documentation and other examples.
 
 ## Usage (tool)
 
-```#!bash
+```#!sh
 $ bitcask -p /tmp/db set Hello World
 $ bitcask -p /tmp/db get Hello
 World
@@ -90,14 +84,14 @@ World
 
 There is also a builtin very  simple Redis-compatible server called `bitcaskd`:
 
-```#!bash
+```#!sh
 $ ./bitcaskd ./tmp
 INFO[0000] starting bitcaskd v0.0.7@146f777              bind=":6379" path=./tmp
 ```
 
 Example session:
 
-```
+```#!sh
 $ telnet localhost 6379
 Trying ::1...
 Connected to localhost.
@@ -122,7 +116,7 @@ Connection closed by foreign host.
 
 You can also use the [Bitcask Docker Image](https://cloud.docker.com/u/prologic/repository/docker/prologic/bitcask):
 
-```#!bash
+```#!sh
 $ docker pull prologic/bitcask
 $ docker run -d -p 6379:6379 prologic/bitcask
 ```
@@ -131,39 +125,59 @@ $ docker run -d -p 6379:6379 prologic/bitcask
 
 Benchmarks run on a 11" Macbook with a 1.4Ghz Intel Core i7:
 
-```
+```#!sh
 $ make bench
 ...
-BenchmarkGet/128B-4         	  500000	      2537 ns/op	     672 B/op	       7 allocs/op
-BenchmarkGet/256B-4         	  500000	      2629 ns/op	    1056 B/op	       7 allocs/op
-BenchmarkGet/512B-4         	  500000	      2773 ns/op	    1888 B/op	       7 allocs/op
-BenchmarkGet/1K-4           	  500000	      3202 ns/op	    3552 B/op	       7 allocs/op
-BenchmarkGet/2K-4           	  300000	      3904 ns/op	    6880 B/op	       7 allocs/op
-BenchmarkGet/4K-4           	  300000	      5678 ns/op	   14048 B/op	       7 allocs/op
-BenchmarkGet/8K-4           	  200000	      8948 ns/op	   27360 B/op	       7 allocs/op
-BenchmarkGet/16K-4          	  100000	     14635 ns/op	   53472 B/op	       7 allocs/op
-BenchmarkGet/32K-4          	   50000	     28292 ns/op	  114912 B/op	       7 allocs/op
+goos: darwin
+goarch: amd64
+pkg: github.com/prologic/bitcask
 
-BenchmarkPut/128B-4         	  200000	      8173 ns/op	     409 B/op	       6 allocs/op
-BenchmarkPut/256B-4         	  200000	      8404 ns/op	     538 B/op	       6 allocs/op
-BenchmarkPut/512B-4         	  200000	      9741 ns/op	     829 B/op	       6 allocs/op
-BenchmarkPut/1K-4           	  100000	     13118 ns/op	    1411 B/op	       6 allocs/op
-BenchmarkPut/2K-4           	  100000	     17982 ns/op	    2573 B/op	       6 allocs/op
-BenchmarkPut/4K-4           	   50000	     35477 ns/op	    5154 B/op	       6 allocs/op
-BenchmarkPut/8K-4           	   30000	     54021 ns/op	    9804 B/op	       6 allocs/op
-BenchmarkPut/16K-4          	   20000	     96551 ns/op	   18849 B/op	       6 allocs/op
-BenchmarkPut/32K-4          	   10000	    129957 ns/op	   41561 B/op	       7 allocs/op
+BenchmarkGet/128B-4         	  300000	      3913 ns/op	  32.71 MB/s	     387 B/op	       4 allocs/op
+BenchmarkGet/128BWithPool-4 	  300000	      4143 ns/op	  30.89 MB/s	     227 B/op	       3 allocs/op
+BenchmarkGet/256B-4         	  300000	      3919 ns/op	  65.31 MB/s	     643 B/op	       4 allocs/op
+BenchmarkGet/256BWithPool-4 	  300000	      4270 ns/op	  59.95 MB/s	     355 B/op	       3 allocs/op
+BenchmarkGet/512B-4         	  300000	      4248 ns/op	 120.52 MB/s	    1187 B/op	       4 allocs/op
+BenchmarkGet/512BWithPool-4 	  300000	      4676 ns/op	 109.48 MB/s	     611 B/op	       3 allocs/op
+BenchmarkGet/1K-4           	  200000	      5248 ns/op	 195.10 MB/s	    2275 B/op	       4 allocs/op
+BenchmarkGet/1KWithPool-4   	  200000	      5270 ns/op	 194.28 MB/s	    1123 B/op	       3 allocs/op
+BenchmarkGet/2K-4           	  200000	      6229 ns/op	 328.74 MB/s	    4451 B/op	       4 allocs/op
+BenchmarkGet/2KWithPool-4   	  200000	      6282 ns/op	 325.99 MB/s	    2147 B/op	       3 allocs/op
+BenchmarkGet/4K-4           	  200000	      9027 ns/op	 453.74 MB/s	    9059 B/op	       4 allocs/op
+BenchmarkGet/4KWithPool-4   	  200000	      8906 ns/op	 459.87 MB/s	    4195 B/op	       3 allocs/op
+BenchmarkGet/8K-4           	  100000	     12024 ns/op	 681.28 MB/s	   17763 B/op	       4 allocs/op
+BenchmarkGet/8KWithPool-4   	  200000	     11103 ns/op	 737.79 MB/s	    8291 B/op	       3 allocs/op
+BenchmarkGet/16K-4          	  100000	     16844 ns/op	 972.65 MB/s	   34915 B/op	       4 allocs/op
+BenchmarkGet/16KWithPool-4  	  100000	     14575 ns/op	1124.10 MB/s	   16483 B/op	       3 allocs/op
+BenchmarkGet/32K-4          	   50000	     27770 ns/op	1179.97 MB/s	   73827 B/op	       4 allocs/op
+BenchmarkGet/32KWithPool-4  	  100000	     24495 ns/op	1337.74 MB/s	   32867 B/op	       3 allocs/op
 
-BenchmarkScan-4             	 1000000	      2011 ns/op	     493 B/op	      25 allocs/op
+BenchmarkPut/128B-4         	  100000	     17492 ns/op	   7.32 MB/s	     441 B/op	       6 allocs/op
+BenchmarkPut/256B-4         	  100000	     17234 ns/op	  14.85 MB/s	     571 B/op	       6 allocs/op
+BenchmarkPut/512B-4         	  100000	     22837 ns/op	  22.42 MB/s	     861 B/op	       6 allocs/op
+BenchmarkPut/1K-4           	   50000	     30333 ns/op	  33.76 MB/s	    1443 B/op	       6 allocs/op
+BenchmarkPut/2K-4           	   30000	     45304 ns/op	  45.21 MB/s	    2606 B/op	       6 allocs/op
+BenchmarkPut/4K-4           	   20000	     83953 ns/op	  48.79 MB/s	    5187 B/op	       6 allocs/op
+BenchmarkPut/8K-4           	   10000	    142142 ns/op	  57.63 MB/s	    9845 B/op	       6 allocs/op
+BenchmarkPut/16K-4          	    5000	    206722 ns/op	  79.26 MB/s	   18884 B/op	       6 allocs/op
+BenchmarkPut/32K-4          	    5000	    361108 ns/op	  90.74 MB/s	   41582 B/op	       7 allocs/op
+
+BenchmarkScan-4             	 1000000	      1679 ns/op	     408 B/op	      16 allocs/op
+PASS
 ```
 
 For 128B values:
 
-* ~400,000 reads/sec
-* ~130,000 writes/sec
+* ~200,000 reads/sec
+* ~50,000 writes/sec
 
-The full benchmark above shows linear performance as you increase key/value sizes.
+The full benchmark above shows linear performance as you increase key/value sizes. Memory pooling starts to become advantageous for larger values.
+
+## Contributors
+
+Thank you to all those that have contributed to this project, battle-tested it, used it in their own projects or pdocuts, fixed bugs, improved performance and even fix tiny tpyos in documentation! Thank you and keep contirbuting!
+
+You can find an [AUTHORS](/AUTHORS) file where we keep a list of contributors to the project. If you contriibute a PR please consider adding your name there. There is also Github's own [Contributors](https://github.com/prologic/bitcask/graphs/contributors) statistics.
 
 ## License
 
-bitcask is licensed under the [MIT License](https://github.com/prologic/bitcask/blob/master/LICENSE)
+bitcask is licensed under the term of the [MIT License](https://github.com/prologic/bitcask/blob/master/LICENSE)

bitcask.go

@@ -1,17 +1,18 @@
 package bitcask
 
 import (
+	"encoding/json"
 	"errors"
 	"hash/crc32"
 	"io"
 	"io/ioutil"
 	"os"
+	"path"
 	"path/filepath"
-	"strings"
 	"sync"
 
+	"github.com/derekparker/trie"
 	"github.com/gofrs/flock"
-	"github.com/prologic/trie"
 
 	"github.com/prologic/bitcask/internal"
 )
@@ -35,6 +36,10 @@ var (
 	// ErrDatabaseLocked is the error returned if the database is locked
 	// (typically opened by another process)
 	ErrDatabaseLocked = errors.New("error: database locked")
+
+	// ErrCreatingMemPool is the error returned when trying to configurate
+	// the mempool fails
+	ErrCreatingMemPool = errors.New("error: creating the mempool failed")
 )
 
 // Bitcask is a struct that represents a on-disk LSM and WAL data structure
@@ -46,13 +51,38 @@ type Bitcask struct {
 	*flock.Flock
 
 	config    *config
+	options   []Option
 	path      string
 	curr      *internal.Datafile
 	keydir    *internal.Keydir
-	datafiles []*internal.Datafile
+	datafiles map[int]*internal.Datafile
 	trie      *trie.Trie
 }
 
+// Stats is a struct returned by Stats() on an open Bitcask instance
+type Stats struct {
+	Datafiles int
+	Keys      int
+	Size      int64
+}
+
+// Stats returns statistics about the database including the number of
+// data files, keys and overall size on disk of the data
+func (b *Bitcask) Stats() (stats Stats, err error) {
+	var size int64
+
+	size, err = internal.DirSize(b.path)
+	if err != nil {
+		return
+	}
+
+	stats.Datafiles = len(b.datafiles)
+	stats.Keys = b.keydir.Len()
+	stats.Size = size
+
+	return
+}
+
 // Close closes the database and removes the lock. It is important to call
 // Close() as this is the only way to cleanup the lock held by the open
 // database.
@@ -62,9 +92,16 @@ func (b *Bitcask) Close() error {
 		os.Remove(b.Flock.Path())
 	}()
 
-	for _, df := range b.datafiles {
-		df.Close()
+	if err := b.keydir.Save(path.Join(b.path, "index")); err != nil {
+		return err
 	}
+
+	for _, df := range b.datafiles {
+		if err := df.Close(); err != nil {
+			return err
+		}
+	}
+
 	return b.curr.Close()
 }
 
@@ -188,14 +225,16 @@ func (b *Bitcask) put(key string, value []byte) (int64, int64, error) {
 			return -1, 0, err
 		}
 
-		df, err := internal.NewDatafile(b.path, b.curr.FileID(), true)
+		id := b.curr.FileID()
+
+		df, err := internal.NewDatafile(b.path, id, true)
 		if err != nil {
 			return -1, 0, err
 		}
 
-		b.datafiles = append(b.datafiles, df)
+		b.datafiles[id] = df
 
-		id := b.curr.FileID() + 1
+		id = b.curr.FileID() + 1
 		curr, err := internal.NewDatafile(b.path, id, false)
 		if err != nil {
 			return -1, 0, err
@@ -207,176 +246,72 @@ func (b *Bitcask) put(key string, value []byte) (int64, int64, error) {
 	return b.curr.Write(e)
 }
 
-// Merge merges all datafiles in the database creating hint files for faster
-// startup. Old keys are squashed and deleted keys removes. Call this function
-// periodically to reclaim disk space.
-func Merge(path string, force bool) error {
-	fns, err := internal.GetDatafiles(path)
-	if err != nil {
-		return err
-	}
-
-	ids, err := internal.ParseIds(fns)
-	if err != nil {
-		return err
-	}
-
-	// Do not merge if we only have 1 Datafile
-	if len(ids) <= 1 {
-		return nil
-	}
-
-	// Don't merge the Active Datafile (the last one)
-	fns = fns[:len(fns)-1]
-	ids = ids[:len(ids)-1]
-
-	temp, err := ioutil.TempDir(path, "merge")
-	if err != nil {
-		return err
-	}
-	defer os.RemoveAll(temp)
-
-	for i, fn := range fns {
-		// Don't merge Datafiles whose .hint files we've already generated
-		// (they are already merged); unless we set the force flag to true
-		// (forcing a re-merge).
-		if filepath.Ext(fn) == ".hint" && !force {
-			// Already merged
-			continue
-		}
-
-		id := ids[i]
-
-		keydir := internal.NewKeydir()
-
-		df, err := internal.NewDatafile(path, id, true)
-		if err != nil {
-			return err
-		}
-		defer df.Close()
-
-		for {
-			e, n, err := df.Read()
-			if err != nil {
-				if err == io.EOF {
-					break
-				}
-				return err
-			}
-
-			// Tombstone value  (deleted key)
-			if len(e.Value) == 0 {
-				keydir.Delete(e.Key)
-				continue
-			}
-
-			keydir.Add(e.Key, ids[i], e.Offset, n)
-		}
-
-		tempdf, err := internal.NewDatafile(temp, id, false)
-		if err != nil {
-			return err
-		}
-		defer tempdf.Close()
-
-		for key := range keydir.Keys() {
-			item, _ := keydir.Get(key)
-			e, err := df.ReadAt(item.Offset, item.Size)
-			if err != nil {
-				return err
-			}
-
-			_, _, err = tempdf.Write(e)
-			if err != nil {
-				return err
-			}
-		}
-
-		err = tempdf.Close()
+func (b *Bitcask) readConfig() error {
+	if internal.Exists(filepath.Join(b.path, "config.json")) {
+		data, err := ioutil.ReadFile(filepath.Join(b.path, "config.json"))
 		if err != nil {
 			return err
 		}
 
-		err = df.Close()
-		if err != nil {
-			return err
-		}
-
-		err = os.Rename(tempdf.Name(), df.Name())
-		if err != nil {
-			return err
-		}
-
-		hint := strings.TrimSuffix(df.Name(), ".data") + ".hint"
-		err = keydir.Save(hint)
-		if err != nil {
+		if err := json.Unmarshal(data, &b.config); err != nil {
 			return err
 		}
 	}
-
 	return nil
 }
 
-// Open opens the database at the given path with optional options.
-// Options can be provided with the `WithXXX` functions that provide
-// configuration options as functions.
-func Open(path string, options ...Option) (*Bitcask, error) {
-	if err := os.MkdirAll(path, 0755); err != nil {
-		return nil, err
-	}
-
-	err := Merge(path, false)
+func (b *Bitcask) writeConfig() error {
+	data, err := json.Marshal(b.config)
 	if err != nil {
-		return nil, err
+		return err
 	}
+	return ioutil.WriteFile(filepath.Join(b.path, "config.json"), data, 0600)
+}
 
-	fns, err := internal.GetDatafiles(path)
+func (b *Bitcask) reopen() error {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	fns, err := internal.GetDatafiles(b.path)
 	if err != nil {
-		return nil, err
+		return err
 	}
 
 	ids, err := internal.ParseIds(fns)
 	if err != nil {
-		return nil, err
+		return err
 	}
 
-	var datafiles []*internal.Datafile
+	datafiles := make(map[int]*internal.Datafile, len(ids))
+
+	for _, id := range ids {
+		df, err := internal.NewDatafile(b.path, id, true)
+		if err != nil {
+			return err
+		}
+		datafiles[id] = df
+	}
 
 	keydir := internal.NewKeydir()
 	trie := trie.New()
 
-	for i, fn := range fns {
-		df, err := internal.NewDatafile(path, ids[i], true)
-		if err != nil {
-			return nil, err
+	if internal.Exists(path.Join(b.path, "index")) {
+		if err := keydir.Load(path.Join(b.path, "index")); err != nil {
+			return err
 		}
-		datafiles = append(datafiles, df)
-
-		if filepath.Ext(fn) == ".hint" {
-			f, err := os.Open(filepath.Join(path, fn))
-			if err != nil {
-				return nil, err
-			}
-			defer f.Close()
-
-			hint, err := internal.NewKeydirFromBytes(f)
-			if err != nil {
-				return nil, err
-			}
-
-			for key := range hint.Keys() {
-				item, _ := hint.Get(key)
-				_ = keydir.Add(key, item.FileID, item.Offset, item.Size)
-				trie.Add(key, item)
-			}
-		} else {
+		for key := range keydir.Keys() {
+			item, _ := keydir.Get(key)
+			trie.Add(key, item)
+		}
+	} else {
+		for i, df := range datafiles {
 			for {
 				e, n, err := df.Read()
 				if err != nil {
 					if err == io.EOF {
 						break
 					}
-					return nil, err
+					return err
 				}
 
 				// Tombstone value  (deleted key)
@@ -396,28 +331,134 @@ func Open(path string, options ...Option) (*Bitcask, error) {
 		id = ids[(len(ids) - 1)]
 	}
 
-	curr, err := internal.NewDatafile(path, id, false)
+	curr, err := internal.NewDatafile(b.path, id, false)
 	if err != nil {
+		return err
+	}
+
+	b.curr = curr
+	b.datafiles = datafiles
+
+	b.keydir = keydir
+
+	b.trie = trie
+
+	return nil
+}
+
+// Merge merges all datafiles in the database. Old keys are squashed
+// and deleted keys removes. Duplicate key/value pairs are also removed.
+// Call this function periodically to reclaim disk space.
+func (b *Bitcask) Merge() error {
+	// Temporary merged database path
+	temp, err := ioutil.TempDir(b.path, "merge")
+	if err != nil {
+		return err
+	}
+	defer os.RemoveAll(temp)
+
+	// Create a merged database
+	mdb, err := Open(temp, b.options...)
+	if err != nil {
+		return err
+	}
+
+	// Rewrite all key/value pairs into merged database
+	// Doing this automatically strips deleted keys and
+	// old key/value pairs
+	err = b.Fold(func(key string) error {
+		value, err := b.Get(key)
+		if err != nil {
+			return err
+		}
+
+		if err := mdb.Put(key, value); err != nil {
+			return err
+		}
+
+		return nil
+	})
+	if err != nil {
+		return err
+	}
+
+	err = mdb.Close()
+	if err != nil {
+		return err
+	}
+
+	// Close the database
+	err = b.Close()
+	if err != nil {
+		return err
+	}
+
+	// Remove all data files
+	files, err := ioutil.ReadDir(b.path)
+	if err != nil {
+		return err
+	}
+	for _, file := range files {
+		if !file.IsDir() {
+			err := os.RemoveAll(path.Join([]string{b.path, file.Name()}...))
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	// Rename all merged data files
+	files, err = ioutil.ReadDir(mdb.path)
+	if err != nil {
+		return err
+	}
+	for _, file := range files {
+		err := os.Rename(
+			path.Join([]string{mdb.path, file.Name()}...),
+			path.Join([]string{b.path, file.Name()}...),
+		)
+		if err != nil {
+			return err
+		}
+	}
+
+	// And finally reopen the database
+	return b.reopen()
+}
+
+// Open opens the database at the given path with optional options.
+// Options can be provided with the `WithXXX` functions that provide
+// configuration options as functions.
+func Open(path string, options ...Option) (*Bitcask, error) {
+	var (
+		cfg *config
+		err error
+	)
+
+	if err := os.MkdirAll(path, 0755); err != nil {
 		return nil, err
 	}
 
+	cfg, err = getConfig(path)
+	if err != nil {
+		cfg = newDefaultConfig()
+	}
+
 	bitcask := &Bitcask{
-		Flock:     flock.New(filepath.Join(path, "lock")),
-		config:    newDefaultConfig(),
-		path:      path,
-		curr:      curr,
-		keydir:    keydir,
-		datafiles: datafiles,
-		trie:      trie,
+		Flock:   flock.New(filepath.Join(path, "lock")),
+		config:  cfg,
+		options: options,
+		path:    path,
 	}
 
 	for _, opt := range options {
-		err = opt(bitcask.config)
-		if err != nil {
+		if err := opt(bitcask.config); err != nil {
 			return nil, err
 		}
 	}
 
+	internal.ConfigureMemPool(bitcask.config.maxConcurrency)
+
 	locked, err := bitcask.Flock.TryLock()
 	if err != nil {
 		return nil, err
@@ -427,5 +468,26 @@ func Open(path string, options ...Option) (*Bitcask, error) {
 		return nil, ErrDatabaseLocked
 	}
 
+	if err := bitcask.writeConfig(); err != nil {
+		return nil, err
+	}
+
+	if err := bitcask.reopen(); err != nil {
+		return nil, err
+	}
+
 	return bitcask, nil
 }
+
+// Merge calls Bitcask.Merge()
+// XXX: Deprecated; Please use the `.Merge()` method
+// XXX: This is only kept here for backwards compatibility
+//      it will be removed in future releases at some point
+func Merge(path string, force bool) error {
+	db, err := Open(path)
+	if err != nil {
+		return err
+	}
+
+	return db.Merge()
+}

bitcask_test.go

@@ -211,38 +211,39 @@ func TestMaxValueSize(t *testing.T) {
 	})
 }
 
-func TestOpenMerge(t *testing.T) {
+func TestStats(t *testing.T) {
+	var (
+		db  *Bitcask
+		err error
+	)
+
 	assert := assert.New(t)
 
 	testdir, err := ioutil.TempDir("", "bitcask")
 	assert.NoError(err)
 
 	t.Run("Setup", func(t *testing.T) {
-		var (
-			db  *Bitcask
-			err error
-		)
-
 		t.Run("Open", func(t *testing.T) {
-			db, err = Open(testdir, WithMaxDatafileSize(32))
+			db, err = Open(testdir)
 			assert.NoError(err)
 		})
 
 		t.Run("Put", func(t *testing.T) {
-			for i := 0; i < 1024; i++ {
-				err = db.Put(string(i), []byte(strings.Repeat(" ", 1024)))
-				assert.NoError(err)
-			}
+			err := db.Put("foo", []byte("bar"))
+			assert.NoError(err)
 		})
 
 		t.Run("Get", func(t *testing.T) {
-			for i := 0; i < 32; i++ {
-				err = db.Put(string(i), []byte(strings.Repeat(" ", 1024)))
-				assert.NoError(err)
-				val, err := db.Get(string(i))
-				assert.NoError(err)
-				assert.Equal([]byte(strings.Repeat(" ", 1024)), val)
-			}
+			val, err := db.Get("foo")
+			assert.NoError(err)
+			assert.Equal([]byte("bar"), val)
+		})
+
+		t.Run("Stats", func(t *testing.T) {
+			stats, err := db.Stats()
+			assert.NoError(err)
+			assert.Equal(stats.Datafiles, 0)
+			assert.Equal(stats.Keys, 1)
 		})
 
 		t.Run("Sync", func(t *testing.T) {
@@ -255,34 +256,9 @@ func TestOpenMerge(t *testing.T) {
 			assert.NoError(err)
 		})
 	})
-
-	t.Run("Merge", func(t *testing.T) {
-		var (
-			db  *Bitcask
-			err error
-		)
-
-		t.Run("Open", func(t *testing.T) {
-			db, err = Open(testdir)
-			assert.NoError(err)
-		})
-
-		t.Run("Get", func(t *testing.T) {
-			for i := 0; i < 32; i++ {
-				val, err := db.Get(string(i))
-				assert.NoError(err)
-				assert.Equal([]byte(strings.Repeat(" ", 1024)), val)
-			}
-		})
-
-		t.Run("Close", func(t *testing.T) {
-			err = db.Close()
-			assert.NoError(err)
-		})
-	})
 }
 
-func TestMergeOpen(t *testing.T) {
+func TestMerge(t *testing.T) {
 	var (
 		db  *Bitcask
 		err error
@@ -300,22 +276,40 @@ func TestMergeOpen(t *testing.T) {
 		})
 
 		t.Run("Put", func(t *testing.T) {
-			for i := 0; i < 1024; i++ {
-				err = db.Put(string(i), []byte(strings.Repeat(" ", 1024)))
+			err := db.Put("foo", []byte("bar"))
+			assert.NoError(err)
+		})
+
+		s1, err := db.Stats()
+		assert.NoError(err)
+		assert.Equal(0, s1.Datafiles)
+		assert.Equal(1, s1.Keys)
+
+		t.Run("Put", func(t *testing.T) {
+			for i := 0; i < 10; i++ {
+				err := db.Put("foo", []byte("bar"))
 				assert.NoError(err)
 			}
 		})
 
-		t.Run("Get", func(t *testing.T) {
-			for i := 0; i < 32; i++ {
-				err = db.Put(string(i), []byte(strings.Repeat(" ", 1024)))
-				assert.NoError(err)
-				val, err := db.Get(string(i))
-				assert.NoError(err)
-				assert.Equal([]byte(strings.Repeat(" ", 1024)), val)
-			}
+		s2, err := db.Stats()
+		assert.NoError(err)
+		assert.Equal(5, s2.Datafiles)
+		assert.Equal(1, s2.Keys)
+		assert.True(s2.Size > s1.Size)
+
+		t.Run("Merge", func(t *testing.T) {
+			err := db.Merge()
+			assert.NoError(err)
 		})
 
+		s3, err := db.Stats()
+		assert.NoError(err)
+		assert.Equal(1, s3.Datafiles)
+		assert.Equal(1, s3.Keys)
+		assert.True(s3.Size > s1.Size)
+		assert.True(s3.Size < s2.Size)
+
 		t.Run("Sync", func(t *testing.T) {
 			err = db.Sync()
 			assert.NoError(err)
@@ -326,31 +320,6 @@ func TestMergeOpen(t *testing.T) {
 			assert.NoError(err)
 		})
 	})
-
-	t.Run("Merge", func(t *testing.T) {
-		t.Run("Merge", func(t *testing.T) {
-			err = Merge(testdir, true)
-			assert.NoError(err)
-		})
-
-		t.Run("Open", func(t *testing.T) {
-			db, err = Open(testdir)
-			assert.NoError(err)
-		})
-
-		t.Run("Get", func(t *testing.T) {
-			for i := 0; i < 32; i++ {
-				val, err := db.Get(string(i))
-				assert.NoError(err)
-				assert.Equal([]byte(strings.Repeat(" ", 1024)), val)
-			}
-		})
-
-		t.Run("Close", func(t *testing.T) {
-			err = db.Close()
-			assert.NoError(err)
-		})
-	})
 }
 
 func TestConcurrent(t *testing.T) {
@@ -499,8 +468,9 @@ func TestLocking(t *testing.T) {
 }
 
 type benchmarkTestCase struct {
-	name string
-	size int
+	name     string
+	size     int
+	withPool bool
 }
 
 func BenchmarkGet(b *testing.B) {
@@ -515,22 +485,25 @@ func BenchmarkGet(b *testing.B) {
 	}
 	defer os.RemoveAll(testdir)
 
-	db, err := Open(testdir)
-	if err != nil {
-		b.Fatal(err)
-	}
-	defer db.Close()
-
 	tests := []benchmarkTestCase{
-		{"128B", 128},
-		{"256B", 256},
-		{"512B", 512},
-		{"1K", 1024},
-		{"2K", 2048},
-		{"4K", 4096},
-		{"8K", 8192},
-		{"16K", 16384},
-		{"32K", 32768},
+		{"128B", 128, false},
+		{"128BWithPool", 128, true},
+		{"256B", 256, false},
+		{"256BWithPool", 256, true},
+		{"512B", 512, false},
+		{"512BWithPool", 512, true},
+		{"1K", 1024, false},
+		{"1KWithPool", 1024, true},
+		{"2K", 2048, false},
+		{"2KWithPool", 2048, true},
+		{"4K", 4096, false},
+		{"4KWithPool", 4096, true},
+		{"8K", 8192, false},
+		{"8KWithPool", 8192, true},
+		{"16K", 16384, false},
+		{"16KWithPool", 16384, true},
+		{"32K", 32768, false},
+		{"32KWithPool", 32768, true},
 	}
 
 	for _, tt := range tests {
@@ -540,6 +513,18 @@ func BenchmarkGet(b *testing.B) {
 			key := "foo"
 			value := []byte(strings.Repeat(" ", tt.size))
 
+			options := []Option{
+				WithMaxKeySize(len(key)),
+				WithMaxValueSize(tt.size),
+			}
+			if tt.withPool {
+				options = append(options, WithMemPool(1))
+			}
+			db, err := Open(testdir, options...)
+			if err != nil {
+				b.Fatal(err)
+			}
+
 			err = db.Put(key, value)
 			if err != nil {
 				b.Fatal(err)
@@ -555,6 +540,8 @@ func BenchmarkGet(b *testing.B) {
 					b.Errorf("unexpected value")
 				}
 			}
+			b.StopTimer()
+			db.Close()
 		})
 	}
 }
@@ -578,15 +565,15 @@ func BenchmarkPut(b *testing.B) {
 	defer db.Close()
 
 	tests := []benchmarkTestCase{
-		{"128B", 128},
-		{"256B", 256},
-		{"512B", 512},
-		{"1K", 1024},
-		{"2K", 2048},
-		{"4K", 4096},
-		{"8K", 8192},
-		{"16K", 16384},
-		{"32K", 32768},
+		{"128B", 128, false},
+		{"256B", 256, false},
+		{"512B", 512, false},
+		{"1K", 1024, false},
+		{"2K", 2048, false},
+		{"4K", 4096, false},
+		{"8K", 8192, false},
+		{"16K", 16384, false},
+		{"32K", 32768, false},
 	}
 
 	for _, tt := range tests {

cmd/bitcask/export.go

@@ -0,0 +1,142 @@
+package main
+
+import (
+	"encoding/base64"
+	"encoding/json"
+	"errors"
+	"io"
+	"os"
+
+	log "github.com/sirupsen/logrus"
+	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
+
+	"github.com/prologic/bitcask"
+)
+
+var errNotAllDataWritten = errors.New("error: not all data written")
+
+var exportCmd = &cobra.Command{
+	Use:     "export",
+	Aliases: []string{"backup", "dump"},
+	Short:   "Export a database",
+	Long: `This command allows you to export or dump/backup a database's
+key/values into a long-term portable archival format suitable for backup and
+restore purposes or migrating from older on-disk formats of Bitcask.
+
+All key/value pairs are base64 encoded and serialized as JSON one pair per
+line to form an output stream to either standard output or a file. You can
+optionally compress the output with standard compression tools such as gzip.`,
+	Args: cobra.RangeArgs(0, 1),
+	Run: func(cmd *cobra.Command, args []string) {
+		var output string
+
+		path := viper.GetString("path")
+
+		if len(args) == 1 {
+			output = args[0]
+		} else {
+			output = "-"
+		}
+
+		os.Exit(export(path, output))
+	},
+}
+
+func init() {
+	RootCmd.AddCommand(exportCmd)
+
+	exportCmd.PersistentFlags().IntP(
+		"with-max-datafile-size", "", bitcask.DefaultMaxDatafileSize,
+		"Maximum size of each datafile",
+	)
+	exportCmd.PersistentFlags().IntP(
+		"with-max-key-size", "", bitcask.DefaultMaxKeySize,
+		"Maximum size of each key",
+	)
+	exportCmd.PersistentFlags().IntP(
+		"with-max-value-size", "", bitcask.DefaultMaxValueSize,
+		"Maximum size of each value",
+	)
+}
+
+type kvPair struct {
+	Key   string `json:"key"`
+	Value string `json:"value"`
+}
+
+func export(path, output string) int {
+	var (
+		err error
+		w   io.WriteCloser
+	)
+
+	db, err := bitcask.Open(path)
+	if err != nil {
+		log.WithError(err).Error("error opening database")
+		return 1
+	}
+	defer db.Close()
+
+	if output == "-" {
+		w = os.Stdout
+	} else {
+		w, err = os.OpenFile(output, os.O_WRONLY|os.O_CREATE|os.O_EXCL|os.O_TRUNC, 0755)
+		if err != nil {
+			log.WithError(err).
+				WithField("output", output).
+				Error("error opening output for writing")
+			return 1
+		}
+	}
+
+	err = db.Fold(func(key string) error {
+		value, err := db.Get(key)
+		if err != nil {
+			log.WithError(err).
+				WithField("key", key).
+				Error("error reading key")
+			return err
+		}
+
+		kv := kvPair{
+			Key:   base64.StdEncoding.EncodeToString([]byte(key)),
+			Value: base64.StdEncoding.EncodeToString(value),
+		}
+
+		data, err := json.Marshal(&kv)
+		if err != nil {
+			log.WithError(err).
+				WithField("key", key).
+				Error("error serialzing key")
+			return err
+		}
+
+		if n, err := w.Write(data); err != nil || n != len(data) {
+			if err == nil && n != len(data) {
+				err = errNotAllDataWritten
+			}
+			log.WithError(err).
+				WithField("key", key).
+				WithField("n", n).
+				Error("error writing key")
+			return err
+		}
+
+		if _, err := w.Write([]byte("\n")); err != nil {
+			log.WithError(err).Error("error writing newline")
+			return err
+		}
+
+		return nil
+	})
+	if err != nil {
+		log.WithError(err).
+			WithField("path", path).
+			WithField("output", output).
+			Error("error exporting keys")
+		return 2
+	}
+
+	return 0
+}

cmd/bitcask/import.go

@@ -0,0 +1,106 @@
+package main
+
+import (
+	"bufio"
+	"encoding/base64"
+	"encoding/json"
+	"io"
+	"os"
+
+	log "github.com/sirupsen/logrus"
+	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
+
+	"github.com/prologic/bitcask"
+)
+
+var importCmd = &cobra.Command{
+	Use:     "import",
+	Aliases: []string{"restore", "read"},
+	Short:   "Import a database",
+	Long: `This command allows you to import or restore a database from a
+previous export/dump using the export command either creating a new database
+or adding additional key/value pairs to an existing one.`,
+	Args: cobra.RangeArgs(0, 1),
+	Run: func(cmd *cobra.Command, args []string) {
+		var input string
+
+		path := viper.GetString("path")
+
+		if len(args) == 1 {
+			input = args[0]
+		} else {
+			input = "-"
+		}
+
+		os.Exit(_import(path, input))
+	},
+}
+
+func init() {
+	RootCmd.AddCommand(importCmd)
+}
+
+func _import(path, input string) int {
+	var (
+		err error
+		r   io.ReadCloser
+	)
+
+	db, err := bitcask.Open(path)
+	if err != nil {
+		log.WithError(err).Error("error opening database")
+		return 1
+	}
+	defer db.Close()
+
+	if input == "-" {
+		r = os.Stdin
+	} else {
+		r, err = os.Open(input)
+		if err != nil {
+			log.WithError(err).
+				WithField("input", input).
+				Error("error opening input for reading")
+			return 1
+		}
+	}
+
+	var kv kvPair
+
+	scanner := bufio.NewScanner(r)
+	for scanner.Scan() {
+		if err := json.Unmarshal(scanner.Bytes(), &kv); err != nil {
+			log.WithError(err).
+				WithField("input", input).
+				Error("error reading input")
+			return 2
+		}
+
+		key, err := base64.StdEncoding.DecodeString(kv.Key)
+		if err != nil {
+			log.WithError(err).Error("error decoding key")
+			return 2
+		}
+
+		value, err := base64.StdEncoding.DecodeString(kv.Value)
+		if err != nil {
+			log.WithError(err).Error("error decoding value")
+			return 2
+		}
+
+		if err := db.Put(string(key), value); err != nil {
+			log.WithError(err).Error("error writing key/value")
+			return 2
+		}
+	}
+	if err := scanner.Err(); err != nil {
+		log.WithError(err).
+			WithField("input", input).
+			Error("error reading input")
+		return 2
+
+	}
+
+	return 0
+}

cmd/bitcask/initdb.go

@@ -0,0 +1,67 @@
+package main
+
+import (
+	"os"
+
+	log "github.com/sirupsen/logrus"
+	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
+
+	"github.com/prologic/bitcask"
+)
+
+var initdbCmd = &cobra.Command{
+	Use:     "initdb",
+	Aliases: []string{"create", "init"},
+	Short:   "Initialize a new database",
+	Long:    `This initializes a new database with persisted options`,
+	Args:    cobra.ExactArgs(0),
+	PreRun: func(cmd *cobra.Command, args []string) {
+		viper.BindPFlag("with-max-datafile-size", cmd.Flags().Lookup("with-max-datafile-size"))
+		viper.SetDefault("with-max-datafile-size", bitcask.DefaultMaxDatafileSize)
+
+		viper.BindPFlag("with-max-key-size", cmd.Flags().Lookup("with-max-key-size"))
+		viper.SetDefault("with-max-key-size", bitcask.DefaultMaxKeySize)
+
+		viper.BindPFlag("with-max-value-size", cmd.Flags().Lookup("with-max-value-size"))
+		viper.SetDefault("with-max-value-size", bitcask.DefaultMaxValueSize)
+	},
+	Run: func(cmd *cobra.Command, args []string) {
+		path := viper.GetString("path")
+
+		maxDatafileSize := viper.GetInt("with-max-datafile-size")
+		maxKeySize := viper.GetInt("with-max-key-size")
+		maxValueSize := viper.GetInt("with-max-value-size")
+
+		db, err := bitcask.Open(
+			path,
+			bitcask.WithMaxDatafileSize(maxDatafileSize),
+			bitcask.WithMaxKeySize(maxKeySize),
+			bitcask.WithMaxValueSize(maxValueSize),
+		)
+		if err != nil {
+			log.WithError(err).Error("error opening database")
+			os.Exit(1)
+		}
+		defer db.Close()
+
+		os.Exit(0)
+	},
+}
+
+func init() {
+	RootCmd.AddCommand(initdbCmd)
+
+	initdbCmd.PersistentFlags().IntP(
+		"with-max-datafile-size", "", bitcask.DefaultMaxDatafileSize,
+		"Maximum size of each datafile",
+	)
+	initdbCmd.PersistentFlags().IntP(
+		"with-max-key-size", "", bitcask.DefaultMaxKeySize,
+		"Maximum size of each key",
+	)
+	initdbCmd.PersistentFlags().IntP(
+		"with-max-value-size", "", bitcask.DefaultMaxValueSize,
+		"Maximum size of each value",
+	)
+}

cmd/bitcask/merge.go

@@ -20,28 +20,23 @@ keys.`,
 	Args: cobra.ExactArgs(0),
 	Run: func(cmd *cobra.Command, args []string) {
 		path := viper.GetString("path")
-		force, err := cmd.Flags().GetBool("force")
-		if err != nil {
-			log.WithError(err).Error("error parsing force flag")
-			os.Exit(1)
-		}
 
-		os.Exit(merge(path, force))
+		os.Exit(merge(path))
 	},
 }
 
 func init() {
 	RootCmd.AddCommand(mergeCmd)
-
-	mergeCmd.Flags().BoolP(
-		"force", "f", false,
-		"Force a re-merge even if .hint files exist",
-	)
 }
 
-func merge(path string, force bool) int {
-	err := bitcask.Merge(path, force)
+func merge(path string) int {
+	db, err := bitcask.Open(path)
 	if err != nil {
+		log.WithError(err).Error("error opening database")
+		return 1
+	}
+
+	if err = db.Merge(); err != nil {
 		log.WithError(err).Error("error merging database")
 		return 1
 	}

cmd/bitcask/put.go

@@ -13,11 +13,11 @@ import (
 	"github.com/prologic/bitcask"
 )
 
-var setCmd = &cobra.Command{
-	Use:     "set <key> [<value>]",
-	Aliases: []string{"add"},
-	Short:   "Add/Set a new Key/Value pair",
-	Long: `This adds or sets a new key/value pair.
+var putCmd = &cobra.Command{
+	Use:     "put <key> [<value>]",
+	Aliases: []string{"add", "set", "store"},
+	Short:   "Adds a new Key/Value pair",
+	Long: `This adds a new key/value pair or modifies an existing one.
 
 If the value is not specified as an argument it is read from standard input.`,
 	Args: cobra.MinimumNArgs(1),
@@ -33,15 +33,15 @@ If the value is not specified as an argument it is read from standard input.`,
 			value = os.Stdin
 		}
 
-		os.Exit(set(path, key, value))
+		os.Exit(put(path, key, value))
 	},
 }
 
 func init() {
-	RootCmd.AddCommand(setCmd)
+	RootCmd.AddCommand(putCmd)
 }
 
-func set(path, key string, value io.Reader) int {
+func put(path, key string, value io.Reader) int {
 	db, err := bitcask.Open(path)
 	if err != nil {
 		log.WithError(err).Error("error opening database")

cmd/bitcask/stats.go

@@ -0,0 +1,55 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+
+	log "github.com/sirupsen/logrus"
+	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
+
+	"github.com/prologic/bitcask"
+)
+
+var statsCmd = &cobra.Command{
+	Use:     "stats",
+	Aliases: []string{},
+	Short:   "Display statis about the Database",
+	Long:    `This displays statistics about the Database"`,
+	Args:    cobra.ExactArgs(0),
+	Run: func(cmd *cobra.Command, args []string) {
+		path := viper.GetString("path")
+
+		os.Exit(stats(path))
+	},
+}
+
+func init() {
+	RootCmd.AddCommand(statsCmd)
+}
+
+func stats(path string) int {
+	db, err := bitcask.Open(path)
+	if err != nil {
+		log.WithError(err).Error("error opening database")
+		return 1
+	}
+	defer db.Close()
+
+	stats, err := db.Stats()
+	if err != nil {
+		log.WithError(err).Error("error getting stats")
+		return 1
+	}
+
+	data, err := json.MarshalIndent(stats, "", "  ")
+	if err != nil {
+		log.WithError(err).Error("error marshalling stats")
+		return 1
+	}
+
+	fmt.Println(string(data))
+
+	return 0
+}

doc.go

@@ -0,0 +1,13 @@
+// Package bitcask implements a high-performance key-value store based on a
+// WAL and LSM.
+//
+// By default, the client assumes a default configuration regarding maximum key size,
+// maximum value size, maximum datafile size, and memory pools to avoid allocations.
+// Refer to Constants section to know default values.
+//
+// For extra performance, configure the memory pool option properly. This option
+// requires to specify the maximum number of concurrent use of the package. Failing to
+// set a high-enough value would impact latency and throughput. Likewise, overestimating
+// would yield in an unnecessary big memory footprint.
+// The default configuration doesn't use a memory pool.
+package bitcask

doc_test.go

@@ -0,0 +1,14 @@
+package bitcask
+
+func Example() {
+	_, _ = Open("path/to/db")
+}
+
+func Example_withOptions() {
+	opts := []Option{
+		WithMaxKeySize(1024),
+		WithMaxValueSize(4096),
+		WithMemPool(10),
+	}
+	_, _ = Open("path/to/db", opts...)
+}

go.mod

@@ -1,14 +1,15 @@
 module github.com/prologic/bitcask
 
 require (
+	github.com/derekparker/trie v0.0.0-20190805173922-4e1a77fb815d
 	github.com/gofrs/flock v0.7.1
 	github.com/gogo/protobuf v1.2.1
 	github.com/golang/protobuf v1.3.2
 	github.com/konsorten/go-windows-terminal-sequences v1.0.2 // indirect
 	github.com/magiconair/properties v1.8.1 // indirect
+	github.com/oxtoacart/bpool v0.0.0-20190530202638-03653db5a59c
 	github.com/pelletier/go-toml v1.4.0 // indirect
 	github.com/pkg/errors v0.8.1
-	github.com/prologic/trie v0.0.0-20190322091023-3972df81f9b5
 	github.com/sirupsen/logrus v1.4.2
 	github.com/spf13/afero v1.2.2 // indirect
 	github.com/spf13/cobra v0.0.5

go.sum

@@ -21,6 +21,8 @@ github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/derekparker/trie v0.0.0-20190805173922-4e1a77fb815d h1:TocZO8frNoxkwqFPePHFldSw8vLu+gBrlvFZYWqxiF4=
+github.com/derekparker/trie v0.0.0-20190805173922-4e1a77fb815d/go.mod h1:D6ICZm05D9VN1n/8iOtBxLpXtoGp6HDFUJ1RNVieOSE=
 github.com/dgrijalva/jwt-go v3.2.0+incompatible/go.mod h1:E3ru+11k8xSBh+hMPgOLZmtrrCbhqsmaPHjLKYnJCaQ=
 github.com/dgryski/go-sip13 v0.0.0-20181026042036-e10d5fee7954/go.mod h1:vAd38F8PWV+bWy6jNmig1y/TA+kYO4g3RSRF0IAv0no=
 github.com/fsnotify/fsnotify v1.4.7 h1:IXs+QLmnXW2CcXuY+8Mzv/fWEsPGWxqefPtCP5CnV9I=
@@ -77,6 +79,8 @@ github.com/mitchellh/mapstructure v1.1.2 h1:fmNYVwqnSfB9mZU6OS2O6GsXM+wcskZDuKQz
 github.com/mitchellh/mapstructure v1.1.2/go.mod h1:FVVH3fgwuzCH5S8UJGiWEs2h04kUh9fWfEaFds41c1Y=
 github.com/mwitkow/go-conntrack v0.0.0-20161129095857-cc309e4a2223/go.mod h1:qRWi+5nqEBWmkhHvq77mSJWrCKwh8bxhgT7d/eI7P4U=
 github.com/oklog/ulid v1.3.1/go.mod h1:CirwcVhetQ6Lv90oh/F+FBtV6XMibvdAFo93nm5qn4U=
+github.com/oxtoacart/bpool v0.0.0-20190530202638-03653db5a59c h1:rp5dCmg/yLR3mgFuSOe4oEnDDmGLROTvMragMUXpTQw=
+github.com/oxtoacart/bpool v0.0.0-20190530202638-03653db5a59c/go.mod h1:X07ZCGwUbLaax7L0S3Tw4hpejzu63ZrrQiUe6W0hcy0=
 github.com/pelletier/go-toml v1.2.0 h1:T5zMGML61Wp+FlcbWjRDT7yAxhJNAiPPLOFECq181zc=
 github.com/pelletier/go-toml v1.2.0/go.mod h1:5z9KED0ma1S8pY6P1sdut58dfprrGBbd/94hg7ilaic=
 github.com/pelletier/go-toml v1.4.0 h1:u3Z1r+oOXJIkxqw34zVhyPgjBsm6X2wn21NWs/HfSeg=
@@ -86,8 +90,6 @@ github.com/pkg/errors v0.8.1 h1:iURUrRGxPUNPdy5/HRSm+Yj6okJ6UtLINN0Q9M4+h3I=
 github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/prologic/trie v0.0.0-20190322091023-3972df81f9b5 h1:H8dTZzU3aWNQnuRyiT45J9szv7EFakAhFzsFq27t3Uo=
-github.com/prologic/trie v0.0.0-20190322091023-3972df81f9b5/go.mod h1:LFuDmpHJGmciXd8Rl5YMhVlLMps9gz2GtYLzwxrFhzs=
 github.com/prometheus/client_golang v0.9.1/go.mod h1:7SWBe2y4D6OKWSNQJUaRYU/AaXPKyh/dDVn+NZz0KFw=
 github.com/prometheus/client_golang v0.9.3/go.mod h1:/TN21ttK/J9q6uSwhBd54HahCDft0ttaMvbicHlPoso=
 github.com/prometheus/client_model v0.0.0-20180712105110-5c3871d89910/go.mod h1:MbSGuTsp3dbXC40dX6PRTWyKYBIrTGTE9sqQNg2J8bo=

internal/datafile.go

@@ -1,26 +1,31 @@
 package internal
 
 import (
-	"bytes"
 	"fmt"
 	"os"
 	"path/filepath"
 	"sync"
 
+	"github.com/oxtoacart/bpool"
 	"github.com/pkg/errors"
 	"golang.org/x/exp/mmap"
 
+	"github.com/gogo/protobuf/proto"
 	pb "github.com/prologic/bitcask/internal/proto"
 	"github.com/prologic/bitcask/internal/streampb"
 )
 
 const (
 	DefaultDatafileFilename = "%09d.data"
+	prefixSize              = 8
 )
 
 var (
 	ErrReadonly  = errors.New("error: read only datafile")
 	ErrReadError = errors.New("error: read error")
+
+	memPool   *bpool.BufferPool
+	mxMemPool sync.RWMutex
 )
 
 type Datafile struct {
@@ -136,7 +141,17 @@ func (df *Datafile) Read() (e pb.Entry, n int64, err error) {
 func (df *Datafile) ReadAt(index, size int64) (e pb.Entry, err error) {
 	var n int
 
-	b := make([]byte, size)
+	var b []byte
+	if memPool == nil {
+		b = make([]byte, size)
+	} else {
+		poolSlice := memPool.Get()
+		if poolSlice.Cap() < int(size) {
+			poolSlice.Grow(int(size) - poolSlice.Cap())
+		}
+		defer memPool.Put(poolSlice)
+		b = poolSlice.Bytes()[:size]
+	}
 
 	if df.w == nil {
 		n, err = df.ra.ReadAt(b, index)
@@ -151,9 +166,10 @@ func (df *Datafile) ReadAt(index, size int64) (e pb.Entry, err error) {
 		return
 	}
 
-	buf := bytes.NewBuffer(b)
-	dec := streampb.NewDecoder(buf)
-	_, err = dec.Decode(&e)
+	err = proto.Unmarshal(b[prefixSize:], &e)
+	if err != nil {
+		return
+	}
 	return
 }
 
@@ -175,3 +191,15 @@ func (df *Datafile) Write(e pb.Entry) (int64, int64, error) {
 
 	return e.Offset, n, nil
 }
+
+// ConfigureMemPool configurate the mempool accordingly
+func ConfigureMemPool(maxConcurrency *int) {
+	mxMemPool.Lock()
+	defer mxMemPool.Unlock()
+	if maxConcurrency == nil {
+		memPool = nil
+	} else {
+		memPool = bpool.NewBufferPool(*maxConcurrency)
+	}
+	return
+}

internal/keydir.go

@@ -5,6 +5,7 @@ import (
 	"encoding/gob"
 	"io"
 	"io/ioutil"
+	"os"
 	"sync"
 )
 
@@ -41,17 +42,15 @@ func (k *Keydir) Add(key string, fileid int, offset, size int64) Item {
 
 func (k *Keydir) Get(key string) (Item, bool) {
 	k.RLock()
-	defer k.RUnlock()
-
 	item, ok := k.kv[key]
+	k.RUnlock()
 	return item, ok
 }
 
 func (k *Keydir) Delete(key string) {
 	k.Lock()
-	defer k.Unlock()
-
 	delete(k.kv, key)
+	k.Unlock()
 }
 
 func (k *Keydir) Len() int {
@@ -62,11 +61,11 @@ func (k *Keydir) Keys() chan string {
 	ch := make(chan string)
 	go func() {
 		k.RLock()
-		defer k.RUnlock()
 		for key := range k.kv {
 			ch <- key
 		}
 		close(ch)
+		k.RUnlock()
 	}()
 	return ch
 }
@@ -81,6 +80,21 @@ func (k *Keydir) Bytes() ([]byte, error) {
 	return buf.Bytes(), nil
 }
 
+func (k *Keydir) Load(fn string) error {
+	f, err := os.Open(fn)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	dec := gob.NewDecoder(f)
+	if err := dec.Decode(&k.kv); err != nil {
+		return err
+	}
+
+	return nil
+}
+
 func (k *Keydir) Save(fn string) error {
 	data, err := k.Bytes()
 	if err != nil {

internal/utils.go

@@ -2,12 +2,32 @@ package internal
 
 import (
 	"fmt"
+	"os"
 	"path/filepath"
 	"sort"
 	"strconv"
 	"strings"
 )
 
+func Exists(path string) bool {
+	_, err := os.Stat(path)
+	return err == nil
+}
+
+func DirSize(path string) (int64, error) {
+	var size int64
+	err := filepath.Walk(path, func(_ string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+		if !info.IsDir() {
+			size += info.Size()
+		}
+		return err
+	})
+	return size, err
+}
+
 func GetDatafiles(path string) ([]string, error) {
 	fns, err := filepath.Glob(fmt.Sprintf("%s/*.data", path))
 	if err != nil {

options.go

@@ -1,5 +1,12 @@
 package bitcask
 
+import (
+	"encoding/json"
+	"errors"
+	"io/ioutil"
+	"path/filepath"
+)
+
 const (
 	// DefaultMaxDatafileSize is the default maximum datafile size in bytes
 	DefaultMaxDatafileSize = 1 << 20 // 1MB
@@ -11,6 +18,12 @@ const (
 	DefaultMaxValueSize = 1 << 16 // 65KB
 )
 
+var (
+	// ErrMaxConcurrencyLowerEqZero is the error returned for
+	// maxConcurrency option not greater than zero
+	ErrMaxConcurrencyLowerEqZero = errors.New("error: maxConcurrency must be greater than zero")
+)
+
 // Option is a function that takes a config struct and modifies it
 type Option func(*config) error
 
@@ -18,6 +31,44 @@ type config struct {
 	maxDatafileSize int
 	maxKeySize      int
 	maxValueSize    int
+	maxConcurrency  *int
+}
+
+func (c *config) MarshalJSON() ([]byte, error) {
+	return json.Marshal(struct {
+		MaxDatafileSize int `json:"max_datafile_size"`
+		MaxKeySize      int `json:"max_key_size"`
+		MaxValueSize    int `json:"max_value_size"`
+	}{
+		MaxDatafileSize: c.maxDatafileSize,
+		MaxKeySize:      c.maxKeySize,
+		MaxValueSize:    c.maxValueSize,
+	})
+}
+
+func getConfig(path string) (*config, error) {
+	type Config struct {
+		MaxDatafileSize int `json:"max_datafile_size"`
+		MaxKeySize      int `json:"max_key_size"`
+		MaxValueSize    int `json:"max_value_size"`
+	}
+
+	var cfg Config
+
+	data, err := ioutil.ReadFile(filepath.Join(path, "config.json"))
+	if err != nil {
+		return nil, err
+	}
+
+	if err := json.Unmarshal(data, &cfg); err != nil {
+		return nil, err
+	}
+
+	return &config{
+		maxDatafileSize: cfg.MaxDatafileSize,
+		maxKeySize:      cfg.MaxKeySize,
+		maxValueSize:    cfg.MaxValueSize,
+	}, nil
 }
 
 func newDefaultConfig() *config {
@@ -51,3 +102,14 @@ func WithMaxValueSize(size int) Option {
 		return nil
 	}
 }
+
+// WithMemPool configures usage of a memory pool to avoid allocations
+func WithMemPool(maxConcurrency int) Option {
+	return func(cfg *config) error {
+		if maxConcurrency <= 0 {
+			return ErrMaxConcurrencyLowerEqZero
+		}
+		cfg.maxConcurrency = &maxConcurrency
+		return nil
+	}
+}