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hackney - simple HTTP client in Erlang

Copyright (c) 2012 Benoît Chesneau.

Version: 0.1


hackney is a simple HTTP client.

Main features:

  • no message passing: response is directly streamed to the current process and a state is kept in a #client{} record.
  • binary streams
  • SSL support
  • Keepalive handling
  • basic authentication
  • stream the response
  • Can send files using the sendfile API
  • Chunked encoding support
  • Optionnal socket pool
  • Used parse transform for shorcut methods calls:hackney:get("")

Note: This is a work in progress, see the TODO for more informations on what still need to be done.


Download the sources from our Github repository

To buildd the application simply run 'make'. This should build .beam, .app files and documentation.

To run tests run 'make test'. To generate doc, run 'make doc'.

Or add it to your rebar config

{deps, [
    {hackney, ".*", {git, "git://", {branch, "master"}}}

Basic usage

The basic usage of hackney is:

Start hackney

hackney is an OTP application. You have to start it first before using all the functions. The hackney applications will start for you the default socket pool.

To start in the console run :

$ erl -pa ebin
1>> hackney:start().

It will start hackney and all the application it depends:


Or add hackney to the applications membe rof your relase an app

Simple request without pool
Method = get,

URL = <<"">>, Headers = [], Payload = <<>>, Options = [], {ok, StatusCode, RespHeaders, Client} = hackney:request(Method, URL, Headers, Payload, Options).

The request method return the tupple {ok, StatusCode, Headers, Client} or {error, Reason}.

If you enable the parse_transform, you can also do:

hackney:get(URL, Headers, Payload, Options)

To enable parse transform add the following option to the erlang compiler flags:

{parse_transform, hackney_transform}

Alternately, you can add it to the module you wish to compile:

-compile([{parse_transform, hackney_transform}]).

Read the body
{ok, Body, Client1} = hackney:body(Client).

hackney:body/1 fetch the body. To fetch it by chunk you can use the hackney:stream/body/1 function:

read_body(MaxLength, Client, Acc) when MaxLength > byte_size(Acc) ->
    case stream_body(Client) of
        {ok, Data, Client2} ->
            read_body(MaxLength, Client2, << Acc/binary, Data/binary >>);
        {done, Client2} ->
            {ok, Acc, Client2};
        {error, Reason} ->
            {error, Reason}

Reuse the client object

If your connection support the keepalive you can reuse the Client record using the hackney:send_request/2 function:

ReqBody = << "{
      \"id\": \"some_paste_id\",
      \"rev\": \"some_revision_id\",
      \"changeset\": \"changeset in unidiff format\"
}" >>,
ReqHeaders = [{<<"Content-Type">>, <<"application/json">>}],
NextPath = <<"/">>,
NextMethod = post,
NextReq = {NextMethod, NextPath, ReqHeaders, ReqBody}
{ok, _, _, Client2} = hackney:send_request(Client1, NextReq).
{ok, Body1, Client3} = hackney:body(Client2),

Here we are posting a JSON paylod to '/' on the service friendpaste to create a paste. Then we close the client connection.

Send a body

hackney helps you send different payload by passing different terms as the request body:

  • {form, PropList} : To send a form
  • {file, File} : To send a file
  • Bin: To send a binary

Use a pool

To reuse a connection globally in your application you can also use a socket pool. On startup, hackney launch a pool named default. To use it do the following:

Method = get,
URL = <<"">>,
Headers = [],
Payload = <<>>,
Options = [{pool, default}],
{ok, StatusCode, RespHeaders, Client} = hackney:request(Method, URL, Headers,
                                                        Payload, Options).

By adding the tuple {pool, default} to the options, hackney will use the connections stored in that pool.

You can also use different pools in your application which will allows you to maintain some kind of group of connections.

PoolName = mypool,
Options = [{timeout, 150000}, {pool_size, 100}],
{ok, Pid} = hackney:start_pool(PoolName, Options),

timeout is the time we keep alive the conneciton in the pool, pool_size is the number of connections maintained in the pool. Each connection in a pool is monitored and closed connections are removed automatically.

To close a pool do:



For issues, comments or feedback please [create an issue!] [1][1]: "hackney issues"


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