README.md

Elli - Erlang web server for HTTP APIs

Elli is a webserver you can run inside your Erlang application to expose an HTTP API. It is aimed exclusively at building high-throughput, low-latency HTTP APIs. If robustness and performance is more important to you than general purpose features, then Elli might be for you. If you find yourself digging into the implementation of a webserver, then Elli might be for you. If you're building web services, not web sites, then Elli might be for you.

Elli requires OTP 22.0 or newer.

Installation

Add elli to your application as a dependency to your rebar.config:

{deps, [
  {elli, "3.3.0"}
]}.

Afterwards, to compile it, you can run:

rebar3 compile

Usage

To boot Elli inside an Erlang shell, run:

rebar3 shell

%% starting elli
1> {ok, Pid} = elli:start_link([{callback, elli_example_callback}, {port, 3000}]).

Examples

Callback Module

The best source to learn how to write a callback module is elli_example_callback. There are also a bunch of examples used in the tests as well as descriptions of all the events.

A minimal callback module looks something like this:

-module(elli_minimal_callback).
-behaviour(elli_handler).

-include_lib("elli/include/elli.hrl").

-export([handle/2, handle_event/3]).

handle(Req, _Args) ->
    %% Delegate to our handler function
    Method = Req#req.method,
    Path = elli_request:path(Req),
    handle(Method, Path, Req).

handle('GET' = _Method, [<<"hello">>, <<"world">>] = _Path, _Req) ->
    %% Reply with a normal response. `ok' can be used instead of `200'
    %% to signal success.
    StatusCode = ok,
    Headers = [],
    Body = <<"Hello World!">>,
    {StatusCode, Headers, Body};

handle(_Method, _Path, _Req) ->
    {404, [], <<"Not Found">>}.

%% @doc Handle request events: request completed, exception
%% thrown, client timeout, etc. Must return `ok'.
handle_event(_Event, _Data, _Args) ->
    ok.

Supervisor ChildSpec

To add elli to a supervisor you can use the following example and adapt it to your needs.

-module(elli_minimal_sup).
-behaviour(supervisor).

-export([start_link/0, init/1]).

start_link() ->
    SupName = {local, ?MODULE},
    Module = ?MODULE,
    Args = [],
    supervisor:start_link(SupName, Module, Args).

init([] = _Args) ->
    ElliOpts = [
        {callback, elli_minimal_callback},
        {port, 3000}
    ],
    ElliSpec = {
        _Id = elli_minimal_http,
        _Start = {elli, start_link, [ElliOpts]},
        _Restart = permanent,
        _Shutdown = 5000,
        _Worker = worker,
        _Modules = [elli]},

    {ok, {{_Strategy = one_for_one, _Intensity = 5, _Period = 10}, [ElliSpec]} }.

Further reading

For more information about the features and design philosophy of Elli check out the overview.

License

Elli is licensed under The MIT License.