zshipko/resp-server

An OCaml library for building servers that speak RESP

resp-server — Servers that communicate using the Redis serialization protocol

%%VERSION%%

resp-server is an OCaml library for building servers that communicate using the Redis serialization protocol.

resp-server is distributed under the ISC license.

Homepage: https://github.com/zshipko/resp-server

Installation

resp-server can be installed with opam:

opam install resp-server

If you don't use opam consult the opam file for build instructions.

Documentation

Documentation is available online.

To generate documentation locally run odig odoc resp-server - then to view run odig doc in the root of the project.

See src/resp_server.mli for the commented interface description.

Getting started

To create a new server using resp-server you need to define a few modules.

As an example we can create a simple counter server that has keys with integer values that can be incremented and decremented:

1. BACKEND - defines the request context and client types

module Backend = struct
    (** This is the global request context type *)
    type t = (string, int) Hashtbl.t

    (** The client type is the per-client request context type *)
    type client = unit

    let new_client _ctx = ()
end

2. AUTH - defines authentication types

module Auth = struct
    type t = string
    let check t cmd =
        Array.length cmd > 0 && cmd.(0) = t
end

3. Use Make to create the new server

module Server = Make(Auth)(Backend)

4. Define some commands

let modify_value db args f =
    match args with
    | [| String key |] ->
        let () =
            match Hashtbl.find_opt srv key with
            | Some i -> Hashtbl.replace srv key (f i)
            | None -> Hashtbl.replace srv key (f 0)
        in
        Server.ok
    | _ -> Server.error "Invalid arguments"

let _incr db _cli _cmd args =
    modify_value db args (fun a -> a + 1)

let _decr db _cli _cmd args =
    modify_value db args (fun a -> a - 1)

let commands = [
    "incr", _incr;
    "decr", _decr;
]

4. Create and run the server

let main =
    let db = Hashtbl.create 16 in
    let auth = "password" in
    let srv = Server.create ~auth ~commands (`TCP (`Port 1234)) db in
    Server.run srv

let () = Lwt_main.run main

Tests

In the distribution sample programs and tests are located in the test directory. They can be built and run with:

jbuilder runtest