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elli - Erlang web server for HTTP APIs

Hex.pm Documentation Erlang Common Test Coverage Status MIT License

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

Elli is used in production at Wooga and Game Analytics. Elli requires OTP 18.0 or newer.

Installation

To use elli you will need a working installation of Erlang 18.0 (or later).

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

{deps, [
  %% ...
  {elli, "3.0.0"}
]}.

Afterwards you can run:

$ rebar3 compile

Usage

$ 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 src/elli_example_callback.erl and its generated documentation. There are a bunch of examples used in the tests as well as descriptions of all the events.

A minimal callback module could look like this:

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

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

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

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

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

%% @doc Handle request events, like 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(fancyapi_sup).
-behaviour(supervisor).
-export([start_link/0]).
-export([init/1]).

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

init([]) ->
    ElliOpts = [{callback, fancyapi_callback}, {port, 3000}],
    ElliSpec = {
        fancy_http,
        {elli, start_link, [ElliOpts]},
        permanent,
        5000,
        worker,
        [elli]},

    {ok, { {one_for_one, 5, 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.


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