By Ugorji Nwoke   11 Apr 2012   /blog   golang technology

Announcing go-msgpack

Announcing go-msgpack, a rich msgpack codec for Go. Supports encoding/decoding to msgpack binary format, and use for net/rpc communication.

It provides features similar to encoding packages in the standard library (ie json, xml, gob, etc).


  1. Standard Marshal/Unmarshal interface.
  2. Standard field renaming via tags
  3. Encoding from any value
    (struct, slice, map, primitives, pointers, interface{}, etc)
  4. Decoding into a pointer to any non-nil value
    (struct, slice, map, int, float32, bool, string, etc)
  5. Decoding into a nil interface{} (big)
  6. Handles time.Time transparently.
  7. Provides a Server and Client Codec so msgpack can be used as communication protocol for net/rpc.


// v can be interface{}, int32, bool, map[string]bool, etc
dec = msgpack.NewDecoder(r, nil)
err = dec.Decode(&v)

enc = msgpack.NewEncoder(w, nil)
err = enc.Encode(v)

//methods below are convenience methods over functions above.
data, err = msgpack.Marshal(v, nil)
err = msgpack.Unmarshal(data, &v, nil)
//RPC Communication
conn, err = net.Dial("tcp", "localhost:5555")
rpcCodec := msgpack.NewRPCCodec(conn)
client := rpc.NewClientWithCodec(rpcCodec)


I was initially looking at different binary serialization formats for an application I’m developing. I looked at Thrift, Protocol Buffers, BSON, Msgpack, etc.

I finally decided on msgpack:

  1. compact
  2. supports basic types (just like JSON. Numbers, Bool, Null, Bytes/String, Map, List) from which other data structures else can be assembled
  3. raw bytes support (which can represent binary data or strings)
  4. no schema needed (just like JSON)
  5. cross-language support
  6. has pretty good mindshare

Unfortunately, the Go library on the site is old, does not build, and is not “smart” like the encoding/json package. Specifically, it doesn’t allow me decode into a typed object (e.g. struct, bool, etc).

I wrote go-msgpack to give the same conveniences we’ve gotten used to (spoiled by using the encoding/json package), while being really performant.

Summary of my testing:

  1. Decodes significantly faster (120% faster) and encodes only slightly slower (20% slower) than encoding/json
  2. Uses less disk space (40% less)
  3. May not require compression (compression only gave a 10% reduction in size).
    Since compression/decompression time may be significant, this may be an important win.

Hope folks use it and enjoy using it. I know I will. Please feel free to send me feedback.

Tags: golang technology

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© Ugorji Nwoke