OCaml Weekly News

Previous Week Up Next Week


Here is the latest OCaml Weekly News, for the week of October 08 to 15, 2019.

Table of Contents

capnp-rpc 0.4.0

Thomas Leonard announced

I'm pleased to announce the release of capnp-rpc 0.4.0, an OCaml implementation of the Cap'n Proto RPC specification.

If you haven't used the library before, please see the documentation and tutorial. Cap'n Proto RPC aims to provide secure, efficient, typed communications between multiple parties.

This library is now being used to build ocaml-ci, where it is used for all communication between the web frontend and backend services, and to provide a command-line client.

Main changes since v0.3

Breaking changes:

  • Wrap errors with the `Capnp tag to make it easier to compose with other types of error.
  • Prefix all command-line options with capnp-. e.g. --listen-address is now --capnp-listen-address. The old names were confusing for applications that supported other protocols too (e.g. a web server).

New features:

  • Add Capability.with_ref convenience function. This automatically calls dec_ref when done.
  • Add Unix Cap_file module to load and save Sturdy_refs. In particular, this ensures that saved cap files get a mode of 0o600, since they contain secrets.
  • Export cmdliner network address parsing. This is useful if you don't want to use the default option parsing. For example, if you want to make Cap'n Proto an optional feature of your program.
  • Upgrade from uint (which is deprecated) to the newer stdint. The latest version of uint is just a wrapper around stdint, so this shouldn't break anything if you are using the latest version.
  • Put cmdliner options in their own man-page section. Use Capnp_rpc_unix.manpage_capnp_options to control where in your man-page they appear.
  • Enable SO_KEEPALIVE for TCP connections. For use with Docker's libnetwork, try something like this in your stack.yml:

      - 'net.ipv4.tcp_keepalive_time=60'


Anders Fugmann announced

I'm happy to announce the second release of ocaml-protoc-plugin.

Ocaml-protoc-plugin is a plugin to googles protoc compiler which generates type idiomatic to ocaml from .proto files including full compliant serialization and deserialization functions.

Most noteworthy changes in this release:

  • Full proto2 support.
  • The list of dependencies has been slimmed way down, and now only depends on conf-protoc (the protoc compiler and googles well known types).
  • Buckescript support.
  • Added options to change the ocaml (type for scalar types (int, int64 or int32).

Many thanks to Wojtek Czekalski for helping trimming dependencies and for Buclescript support.

Full changelog:

  • Support enum aliasing
  • Avoid name clash with on 'name'
  • Fix code generation when argument contains a path
  • Refactor internal types to make serialization and deserialization type spec symmetrical.
  • Optimize deserialization for messages with max_id < 1024
  • Don't depend on Base in runtime
  • Slim runtime dependencies: Remove need for base, ocplib-endian and ppx_let
  • Honor [packed=…] flag.
  • Make fixed scalar types default to int32 and int64
  • Support proto2 specification
  • Add options to switch between int64|int32 and int
  • Fix name clash problem with special enum names
  • Refactor serialization and deserialization to simplify emitted code
  • Eagerly evaluate serialization (for speed).


If you happen to miss a CWN, you can send me a message and I'll mail it to you, or go take a look at the archive or the RSS feed of the archives.

If you also wish to receive it every week by mail, you may subscribe online.