Sunday, March 17, 2013

[ANN] Riakc 0.0.0

Note, since writing this post, Riakc 1.0.0 has already been released and merged into opam. It fixes the below issue of Links (there is a typo in the release notes, 'not' should be 'now'. The source code can be found here. The 1.0.0 version number does not imply any stability or completeness of the library, just that it is not backwards compatible with 0.0.0.

Riakc is a Riak Protobuf client for Ocaml. Riakc uses Jane St Core/Async for concurrency. Riakc is in early development and so far supports a subset of the Riak API. The supported methods are:

  • ping
  • client_id
  • server_info
  • list_buckets
  • list_keys
  • bucket_props
  • get
  • put
  • delete

A note on GET

Links are currently dropped all together in the implementation, so if you read a value with links and write it back, you will have lost them. This will be fixed in the very near future.

As with anything, please feel free to submit issues and pull requests.

The source code can be found here. Riakc is in opam and you can install it by doing opam install riakc.


There are two API modules in Riakc. Examples of all existing API functions can be found here.


Riakc.Conn provides the API for performing actions on the database. The module interface can be read here.


Riakc.Robj provides the API for objects stored in Riak. The module interface can be read here. Riakc.Conn.get returns a Riakc.Robj.t and Riakc.Conn.put takes one. Robj.t supports representing siblings, however Riakc.Conn.put cannot PUT objects with siblings, this is enforced using phantom types. A value of Riakc.Robj.t that might have siblings is converted to one that doesn't using Riakc.Robj.set_content.

[ANN] Protobuf 0.0.2

Protobuf is an Ocaml library for communicating with Google's protobuf format. It provides a method for writing parsers and builders. There is no protoc support, yet and writing it is not a top goal right now. Protobuf is meant to be fairly lightweight and straight forward to use. The only other Protobuf support for Ocaml I am aware of is through piqi, however that was too heavy for my needs.

Protobuf is meant to be very low level, mostly dealing with representation of values and not semantics. For example, the fixed32 and sfixed32 values are both parsed as Int32.t's. Dealing with being signed or not is left up to the user.

The source code can be viewed here. Protobuf is in opam, to install it opam install protobuf.

The hope is that parsers and builders look reasonably close to the .proto files such that translation is straight forward, at least until protoc support is added. This is an early release and, without a doubt, has bugs in it please submit pull requests and issues.


The best collection of examples right now is the tests. An example from the file:

let simple =
  P.int32 1 >>= P.return

let complex =
  P.int32 1           >>= fun num ->
  P.string 2          >>= fun s ->
  P.embd_msg 3 simple >>= fun emsg ->
  P.return (num, s, emsg)

let run_complex str =
  let open Result.Monad_infix in
  P.State.create (Bitstring.bitstring_of_string str)
  >>= fun s -> complex s

The builder for this message looks like:

let build_simple i =
  let open Result.Monad_infix in
  let b = B.create () in
  B.int32 b 1 i >>= fun () ->
  Ok (B.to_string b)

let build_complex (i1, s, i2) =
  let open Result.Monad_infix in
  let b = B.create () in
  B.int32 b 1 i1                 >>= fun () ->
  B.string b 2 s                 >>= fun () ->
  B.embd_msg b 3 i2 build_simple >>= fun () ->
  Ok (B.to_string b)