Copyright (c) 2012-2013 Benoît Chesneau.
Version: 0.4.2
hackney is an HTTP client library for Erlang.
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 and the requests
- multipart support (stramed or not)
- chunked encoding support
- Can send files using the sendfile API
- Chunked encoding support
- Optionnal socket pool
- Used parse transform for shorcut methods calls:
hackney:get("https://friendpaste.com")
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://github.com/benoitc/hackney.git", {branch, "master"}}}
]}.
The basic usage of hackney is:
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().
ok
It will start hackney and all the application it depends:
application:start(crypto),
application:start(public_key),
application:start(ssl),
application:start(hackney).
Or add hackney to the applications member of your relase an app
Do a simple a requet that will return a client state:
Method = get,
URL = <<"https://friendpaste.com">>,
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}]).
{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}
end.
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),
hackney:close(Client3).
Here we are posting a JSON paylod to '/' on the service friendpaste to create a paste. Then we close the client connection.
hackney helps you send different payload by passing different terms as the request body:
{form, PropList}
: To send a form{multipart, KVs}
: to send you body using the multipart API. KVs can be under the form{file, Name, Content}
orValue
{file, File}
: To send a file- Bin: To send a binary or an iolist
Note: to send a chunked request, just add the
Transfer-Encoding: chunked
header to your headers. Binary and Iolist bodies will be then sent using the chunked encoding.
While the default is to diretcly send the request and fetch the status
and headers if the body is set as the atom stream
the request and
send_request function will return {ok, Client}. Then you can use the
function hackney:stream_request_body/2
to stream the request body and
hackney:start_response/1
to initialize the respone.
The function hackney:start_response/1
is waiting a Client with
theresponse state equal to the atom waiting
.
ex:
ReqBody = << "{
\"id\": \"some_paste_id2\",
\"rev\": \"some_revision_id\",
\"changeset\": \"changeset in unidiff format\"
}" >>,
ReqHeaders = [{<<"Content-Type">>, <<"application/json">>}],
Path = <<"https://friendpaste.com/">>,
Method = post,
{ok, Client} = hackney:request(Method, Path, ReqHeaders, stream,
[]),
{ok, Client1} = hackney:stream_request_body(ReqBody, Client),
{ok, _Status, _Headers, Client2} = hackney:start_response(Client1),
{ok, Body, Client3} = hackney:body(Client2),
hackney:close(Client3).
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 = <<"https://friendpaste.com">>,
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:
hackney:stop_pool(PoolName).
Note: Sometimes you want to always use the default pool in your app without having to set the client option each time. You can now do this by setting the hackney application environment key
use_default_pool
to true .
If the option {follow_redirect, true}
is given to the request, the
client will be abble to automatically follow the redirection and
retrieve the body. The maximum number of connection can be set using the
{max_redirect, Max}
option. Default is 5.
The client will follow redirection on 301, 302 & 307 if the method is
get or head. If another method is used the tuple
{ok, maybe_redirect, Status, Headers, Client}
will be returned. It
only follow 303 redirection (see other) if the method is a POST.
Last Location is stored in the client state in the location
property.
ex:
Method = get,
URL = "http://friendpaste.com/",
ReqHeaders = [{<<"accept-encoding">>, <<"identity">>}],
ReqBody = <<>>,
Options = [{follow_redirect, true}, {max_redirect, true}],
{ok, S, H, Client} = hackney:request(Method, URL, ReqHeaders,
ReqBody, Options),
{ok, Body, Client1} = hackney:body(Client).
For now only HTTP tunneling is supported. To use an HTTP tunnel add the
option {proxy, ProxyUrl}
where ProxyUrl
can be a simple url or an
{Host, Port}
tuple. If you need to authetnicate set the option
{proxy_auth, {User, Password}}
.
For issues, comments or feedback please create an issue.
If you want to contribute patches or improve the doc, you will need to
build hackney using the rebar_dev.config
file. It can also be built
using the Makefile:
$ make dev ; # compile & get deps
$ make devclean ; # clean all files