Re: [Caml-list] Compressing stream in Async.Tcp.Server

[Yaron Minsky <yminsky@janestreet.com>]

Looping in some folk who work on Async-RPC.

This is a good question. I think there isn't an especially nice
solution for this, but one can write an alternate transport satisfying
this interface:

https://github.com/janestreet/async_rpc_kernel/blob/master/src/transport_intf.ml

that does the compression, which should be enough. But this is not
nicely pre-packaged functionality. It would be nice to have that, and
PRs are certainly welcome...

y

On Thu, Nov 24, 2016 at 12:19 PM, Paolo Donadeo <p.donadeo@gmail.com> wrote:
> Hi all, I'm writing a simple client/server application using Async.Rpc. The
> skeletons of the client and server is essentially derived from the examples
> available on line.
>
> Since the messages are highly compressible, I would like to use ZLib (e.g.
> Cryptokit) but I can't figure out how.
>
> Any ideas?
>
> CLIENT:
>     Tcp.with_connection
>       (Tcp.to_host_and_port host port)
>       ~timeout:(sec 1.)
>       (fun _ r w ->
>         (* COMPRESSION HERE, HOW? *)
>         Rpc.Connection.create r w ~connection_state:Pervasives.ignore
>         >>= function
>         | Error exn -> raise exn
>         | Ok conn   -> begin
>             let msg = {
>               Rpc_protocol.scada_uuid = conf.Config_manager.scada_uuid;
>               measures;
>             } in
>             Rpc.Rpc.dispatch Rpc_protocol.export_data_rpc conn msg >>=
> function
>             | Ok response -> return response
>             | Error e -> begin
>                 error ~tags "SERVER SIDE EXCEPTION";
>                 error ~tags "    %s" (Error.to_string_hum e);
>                 return false
>               end
>           end
>       )
>
>
> SERVER:
>   Tcp.Server.create
>     ~on_handler_error:(`Call (fun _ exn -> Log.Global.sexp (Exn.sexp_of_t
> exn)))
>     (Tcp.on_port port)
>     (fun _addr r w ->
>       (* COMPRESSION HERE, HOW? *)
>       Rpc.Connection.server_with_close r w
>         ~connection_state:(fun c ->
>           {
>             db_thread = db_thread;
>           }
>         )
>         ~on_handshake_error:(
>           `Call (fun exn -> Log.Global.sexp (Exn.sexp_of_t exn); return ()))
>         ~implementations)
>
>
> --
> Paolo