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katipo

An HTTP/HTTP2 client library for Erlang built around libcurl-multi and libevent.

Status

Beta

Build Status Hex pm Coverage Status

Usage

{ok, _} = application:ensure_all_started(katipo).
Pool = api_server,
{ok, _} = katipo_pool:start(Pool, 2, [{pipelining, multiplex}]).
Url = <<"https://example.com">>.
ReqHeaders = [{<<"User-Agent">>, <<"katipo">>}].
Opts = #{headers => ReqHeaders,
         body => <<"0d5cb3c25b0c5678d5297efa448e1938">>,
         connecttimeout_ms => 5000,
         proxy => <<"http://127.0.0.1:9000">>,
         sslverifyhost => false,
         sslverifypeer => false},
{ok, #{status := 200,
       headers := RespHeaders,
       cookiejar := CookieJar,
       body := RespBody}} = katipo:post(Pool, Url, Opts).

Or passing the entire request as a map

{ok, _} = application:ensure_all_started(katipo).
Pool = api_server,
{ok, _} = katipo_pool:start(Pool, 2, [{pipelining, multiplex}]).
ReqHeaders = [{<<"User-Agent">>, <<"katipo">>}].
Req = #{url => <<"https://example.com">>.
        method => post,
        headers => ReqHeaders,
        body => <<"0d5cb3c25b0c5678d5297efa448e1938">>,
        connecttimeout_ms => 5000,
        proxy => <<"http://127.0.0.1:9000">>,
        ssl_verifyhost => false,
        ssl_verifypeer => false},
{ok, #{status := 200,
       headers := RespHeaders,
       cookiejar := CookieJar,
       body := RespBody}} = katipo:req(Pool, Req).

Session interface. Cookies handled automatically and options merged. Inspired by Requests sessions.

{ok, _} = application:ensure_all_started(katipo).
Pool = api_server,
{ok, _} = katipo_pool:start(Pool, 2, [{pipelining, multiplex}]).
ReqHeaders = [{<<"User-Agent">>, <<"katipo">>}].
Opts = #{url => <<"https://example.com">>.
         method => post,
         headers => ReqHeaders,
         connecttimeout_ms => 5000,
         proxy => <<"http://127.0.0.1:9000">>,
         sslverifyhost => false,
         sslverifypeer => false}.
{ok, Session} = katipo_session:new(Pool, Opts).
{{ok, #{status := 200}}, Session2} =
    katipo_session:req(#{body => <<"some data">>}, Session).
{{ok, #{status := 200}}, Session3} =
    katipo_session:req(#{body => <<"different payload data">>}, Session2).

Why

We wanted a compatible and high-performance HTTP client so took advantage of the 15+ years of development that has gone into libcurl. To allow large numbers of simultaneous connections libevent is used along with the libcurl-multi interface.

Documentation

API

-type method() :: get | post | put | head | options.
katipo_pool:start(Name :: atom(), size :: pos_integer(), PoolOptions :: proplist()).
katipo_pool:stop(Name :: atom()).

katipo:req(Pool :: atom(), Req :: map()).
katipo:Method(Pool :: atom(), URL :: binary()).
katipo:Method(Pool :: atom(), URL :: binary(), ReqOptions :: map()).

Application Config

Option Values Default Notes
mod_metrics folsom | exometer | noop noop see erlang-metrics

Request options

Option Type Default Notes
headers [{binary(), iodata()}] []
cookiejar opaque (returned in response) []
body iodata() <<>>
connecttimeout_ms pos_integer() 30000 docs
followlocation boolean() false docs
ssl_verifyhost boolean() true docs
ssl_verifypeer boolean() true docs
capath binary() undefined
cacert binary() undefined
timeout_ms pos_integer() 30000
maxredirs non_neg_integer() 9
proxy binary() undefined docs
return_metrics boolean() false
tcp_fastopen boolean() false docs curl >= 7.49.0
interface binary() undefined docs
unix_socket_path binary() undefined docs curl >= 7.40.0
lock_data_ssl_session boolean() false docs curl >= 7.23.0
doh_url binary() undefined docs curl >= 7.62.0
http_version curl_http_version_none
curl_http_version_1_0
curl_http_version_1_1
curl_http_version_2_0
curl_http_version_2tls
curl_http_version_2_prior_knowledge
curl_http_version_none docs curl >= 7.62.0

Responses

{ok, #{status := pos_integer(),
       headers := headers(),
       cookiejar := cookiejar(),
       body := body(),
       metrics => proplist()}}

{error, #{code := atom(), message := binary()}}

Pool Options

Option Type Default Note
pipelining `nothing http1 multiplex`
max_pipeline_length non_neg_integer() 100
max_total_connections non_neg_integer() 0 (no limit) docs

Metrics

  • ok
  • error
  • status.XXX
  • total_time
  • curl_time
  • namelookup_time
  • connect_time
  • appconnect_time
  • pretransfer_time
  • redirect_time
  • starttransfer_time

Dependencies

Ubuntu Trusty

sudo apt-get install git libwxgtk2.8-0 libwxbase2.8-0 libevent-dev libcurl4-openssl-dev libcurl4-openssl-dev

wget http://packages.erlang-solutions.com/site/esl/esl-erlang/FLAVOUR_1_esl/esl-erlang_18.0-1~ubuntu~trusty_amd64.deb

sudo dpkg -i esl-erlang_18.0-1~ubuntu~trusty_amd64.deb

Fedora

sudo dnf install libevent.x86_64 libcurl.x86_64 libevent-devel.x86_64

OSX

brew install --with-c-ares --with-nghttp2 curl
brew install libevent

Building

rebar3 compile

TODO

  • A more structured way to ifdef features based on curl version
  • Better session interface

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