2.0

CHANGES:

capnp-rpc 2.0 switches from using Lwt to Eio.
The capnp-rpc-lwt package is now just Lwt wrappers around the Eio functions in capnp-rpc.
This allows libraries using the old Lwt API to be used with applications and libraries using the new Eio one,
in the same binary.
Because Lwt libraries (using capnp-rpc-lwt) can be used with Eio applications (using capnp-rpc-unix),
you should first upgrade your application and then upgrade the libraries afterwards.

It is recommended to upgrade in stages, checking your application still works after each step:

1. Upgrade to the latest Lwt version (opam install capnp-rpc-unix.1.2.4).
   This uses the new version of mirage-crypto, tls, etc,
   which may be incompatible with other libraries you are using.
   Get that sorted out before switching to capnp-rpc 2.0.

2. Use lwt_eio to allow using Eio and Lwt together in your application.
   This means replacing your call to Lwt_main.run with code to run Eio and Lwt together,
   as explained at the start of the lwt_eio README.

3. Upgrade your main application to capnp-rpc-unix 2.0.
   Calls to functions in the Capnp_rpc_unix and Capnp_rpc_net modules will need minor updates.
   They were previously called from Lwt context, so you'll need to wrap them with Lwt_eio.run_eio
   (or remove a Lwt_eio.run_lwt if you already updated the surrounding code).
   You should also use mirage-crypto-rng-eio to ensure randomness is available
   (capnp-rpc-unix no longer does this, although some other library might).

4. Upgrade code and libraries using Capnp_rpc_lwt:

   1. Replace open Capnp_rpc_lwt with open Capnp_rpc.Std.
   2. Replace all other uses of Capnp_rpc_lwt with just Capnp_rpc.
   3. In dune and opam files, replace capnp-rpc-lwt with capnp-rpc.
   4. Some modules are in Capnp_rpc but not the Capnp_rpc.Std subset.
      Those should now be fully qualified (e.g. replace Persistence with
      Capnp_rpc.Persistence).
   5. Replace Service.return_lwt with Lwt_eio.run_lwt.
      Replace Lwt.return (Ok x) with Service.return x.

Once all Lwt code is gone, you can remove the dependencies on lwt and lwt_eio.

New features:

• Allow numeric IPv6 listen addresses (@talex5 #296, requested by @BChabanne).

API changes:

• Eio port (@talex5 #280 #284 #298 #292 #297 #300 #304).

  This switches capnp-rpc from Lwt to Eio.
  One particularly nice side effect of this is that Service.return_lwt has gone,
  as there is no distinction now between concurrent and non-concurrent service methods.

  Uses of Capnp_rpc_lwt should be replaced by uses of Capnp_rpc
  (and the old Capnp_rpc is now an internal module, Capnp_rpc_proto).
  The new Capnp_rpc now provides Error, Exception and Debug aliases to the same modules in Capnp_rpc_proto,
  so that Capnp_rpc_proto doesn't need to be used directly.

  Capnp_rpc_lwt now provides (deprecated) compatibility wrappers, using lwt_eio.

  This also adds Capnp_rpc.Std with some common module aliases,
  to reduce the need to open Capnp_rpc (which is rather large).

• Deprecate Debug.failf (@talex5 #291).

Performance and bug fixes:

• Add buffering of outgoing messages (@talex5 #287 #303).
  Sending each message in its own TCP packet isn't very efficient, and also interacts very badly with Nagle's algorithm.
  See https://roscidus.com/blog/blog/2024/07/22/performance/ for details.

• Only disconnect socket when sending is done (@talex5 #295).
  Allows sending the reason for the disconnection in some cases.

• Fix type of Capability.call (@talex5 #293).
  It was previously unusable.

• Work around FreeBSD close problem (@talex5 #302).

Build:

• Update to capnp 3.6.0 (@talex5 #285).

• Update to dune 3.16 and fix warnings (@talex5 #282).

• Use String.starts_with instead of Astring (@talex5 #290).

• Remove unused tls-mirage dependency (@talex5 #289).

• Remove asetmap dependency (@talex5 #288).

1.2.4

CHANGES:

• Update dependencies and remove capnp-rpc-mirage (@talex5 #276).

  • Update for breaking changes in tls, mirage-crypto and mirage-flow.
  • capnp-rpc-mirage isn't used much, and won't be needed after switching to Eio.

• Update tests to Cap'n Proto 1.0.1 (@MisterDA #274).

• Update links to ocaml-ci and capnp-ocaml (@tmcgilchrist #271).

• Opam doesn't allow with-test in conflicts (@talex5 #269).

• Disable opam tests on macos (@talex5 #268).

• Update CI (@MisterDA #272, @talex5 #277).

1.2.3

CHANGES:

• Update to cmdliner 1.1.0 (@MisterDA #249).

• Fix tests on Windows, avoid using Unix domain sockets (@talex5 #251).

• Fix warning on Unix.ENOTCONN under macos (@talex5 #252).

• Add Capnp_rpc_unix.Cap_file.save_uri (@talex5 #253).

• Update README to use MDX (@talex5 #254).

• Update tests to Cap'n Proto 0.10.3 (@MisterDA #257 #260).

• Update to mirage-crypto-rng 0.11 and dns 7.0.0 API changes (@hannesm #261).

• Update for opam 2.1+ installations (@frumioj #259).

• Install Cap'n Proto binaries in Windows GHA (@MisterDA #248).

1.2.2

CHANGES:

• Switch from mirage-{stack,protocols} to tcpip (@MisterDA #246).

• Remove deprecated tcpip.unix dependency (@hannesm #245).

• Add OCaml 4.14 support (@kit-ty-kate #244).

1.2.1

CHANGES:

• Fix Fmt deprecation warnings (@tmcgilchrist #239).

• Update to latest X509 and DNS APIs (@tmcgilchrist #240).

v1.2

CHANGES:

• Don't crash if the peer disconnects before the bootstrap reply is ready (@talex5 #234).
  When replying to a normal question we checked that the answer was still needed before trying to reply, but didn't for bootstrap requests.

• Replace wait_until_settled with safer await_settled (@talex5 #233).
  wait_until_settled makes it too easy to ignore errors.

• Require fmt >= 0.8.7 for kstr and set OCaml 4.08 as the minimum version everywhere (@talex5 #232).
  Older versions aren't tested in CI because the unix and mirage packages require at least OCaml 4.08.

v1.1

CHANGES:

• Update to latest X509, TCP and TLS APIs (@talex5 @hannesm #228).

• Add Service.fail_lwt convenience function (@talex5 #229).

• Remove confusing debug details from call_for_value_exn errors (@talex5 #230).
  The hidden information is now logged (at debug level) instead.

• Configure TCP keep-alives for incoming connections, not just outgoing ones (@talex5 #227).
  This is needed when the client machine crashes without resetting the connection.

• Include version number in opam license field (@talex5 #226).

v1.0

CHANGES:

• Skip the setting of object_id if it is empty (@LasseBlaauwbroek #224).
  This improves interoperability with the C++ implementation.

• Use open_in_bin instead of open_in for Windows compatibility (@MisterDA #222).

v0.9.0

CHANGES:

• Add connection progress indicator (@talex5 #220).
  Clients can now use Capnp_rpc_unix.with_cap_exn to show a progress indicator while waiting to connect.
  It will use the log if enabled.
  If not, but stderr is a tty, it shows a message while connecting and then erases it (if connecting takes longer than 0.5s).
  If stderr is not a tty, it just prints a message there.

• Use Mirage_crypto_rng_lwt.initialize instead of Mirage_crypto_rng_unix.initialize (@hannesm #217).
  The former periodically feeds entropy to the RNG, while the latter seeds the RNG only once.

• Set TCP_KEEPIDLE=60 if possible (@talex5 #214).
  Cap'n Proto connections tend to be long lived and we therefore turn on the SO_KEEPALIVE option.
  However, the default keepalive timeout of 2 hours is much too long for some networks.
  In particular, Docker's libnetwork silently drops idle connections after about 10 minutes.

Windows support:

• Prevent crash if ExtUnix wasn't built with sockopt (@MisterDA #218).
  If ExtUnix isn't built with sockopt then the symbol have_sockopt_int isn't available and an exception is raised.
  This may be the case on some environments (e.g., ExtUnix built with mingw-w64).
  It is a workaround until support for TCP_KEEPIDLE is added for these environments (e.g., using Winsock instead).

• There is no SIGPIPE on Windows (@dra27 #212).

• Switch from "capnpc" to "capnp compile" (@talex5 #213).
  capnpc seems to be the old name, and isn't present on Windows.

Build changes:

• Remove Travis and Dockerfile (@talex5 #220).
  Travis is very slow and error-prone now, and ocaml-ci generates a working Dockerfile automatically for people who want it.

• Include transitive dependencies in opam files (@talex5 #219).
  Patch generated by https://github.com/ocurrent/opam-dune-lint/

• Require tcpip.unix specifically to get the checksum stubs linked (@hannesm #216).

v0.8.0

CHANGES:

Bug fixes and diagnostics:

• Don't GC imports with callbacks (@talex5, #210).

• Improve "Already resolved!" error message (@talex5, #209).
  Show the state of the promise we were trying to set, and what we tried to set it to.

• Reject attempts to send after disconnecting (@talex5, #208).

• Unix: don't leak FDs if Network.connect fails (@talex5, #206).
  Also, use Lwt to open connections so we don't block the whole process.

New functions:

• Add Sturdy_ref.with_cap and with_cap_exn convenience functions (@talex5, #207).
  Using the plain connect functions, it's easy to forget to release the live-ref at the end.

Build changes:

• capnp-rpc-mirage: adapt test to tcpip 5.0.0 API (@hannesm, #205).

• Upgrade to dune 2 (@talex5, #204).

• Switch tests to build in native code and use the test stanza (@avsm, #203).

Documentation:

• Show how to make a connection directly (@talex5, #202).
  The new test-bin/calc_direct.ml example shows how a parent process can
  spawn a child and communicate with it directly over a socketpair.