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<title>Gun 2.0</title>
<meta name="description" content"Gun 2 Erlang Paris 2019.09 talk">
<meta name="author" content="Loïc Hoguin">
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<section>
<h1>Gun 2.0</h1>
<p>The right of <em>Erlang nodes</em> to keep and<br/>bear arms shall not be infringed. #2A</p>
<p><small>Loïc Hoguin, <a href="https://ninenines.eu">Nine Nines</a></small></p>
</section>
<section>
<h1>What is Gun?</h1>
</section>
<section>
<h2>Erlang Web client</h2>
<ul>
<li>HTTP/1.1</li>
<li>HTTP/2</li>
<li>Websocket</li>
<li>SSE (server-sent events / eventsource)</li>
<li>CONNECT and Socks proxies</li>
</ul>
</section>
<section>
<h2>Asynchronous</h2>
<ul>
<li>Functions to perform actions</li>
<li>Most functions return immediately</li>
<li>Messages sent on input</li>
<li>
Works very well with <code>gen_statem</code>:
<ul><li><a href="https://github.com/inaka/apns4erl/blob/master/src/apns_connection.erl"><code>apns_connection.erl</code></a> is a good example</li></ul>
</ul>
</section>
<section>
<h2>Close to specs</h2>
<p>If the specification allows it, Gun must allow it</p>
<p>Allow Gun to work through the<br/>most exotic network topologies</p>
</section>
<section>
<h1>Features</h1>
</section>
<section>
<h2>Connection management</h2>
<ul>
<li>One process per connection</li>
<li>Supervised under Gun by default, configurable</li>
<li>No connection pooling in Gun itself</li>
</ul>
</section>
<section>
<h2>Always connected</h2>
<ul>
<li>Gun is built as an always-connected client</li>
<li>Retries connecting after losing the connection</li>
<li><code>retry</code> and <code>retry_timeout</code> by default</li>
<li><code>retry_fun</code> for more complex needs</li>
</ul>
</section>
<section>
<h2>One function per method</h2>
<ul>
<li>gun:get, gun:head</li>
<li>gun:patch, gun:post, gun:put</li>
<li>gun:delete</li>
<li>gun:options</li>
<li>gun:headers (and gun:data), gun:request</li>
</ul>
</section>
<section>
<h2>Responses as messages</h2>
<ul>
<li>gun_up, gun_down</li>
<li>gun_upgrade</li>
<li>gun_error</li>
<li>gun_push</li>
<li>gun_inform, gun_response</li>
<li>gun_data, gun_trailers</li>
<li>gun_ws</li>
</ul>
</section>
<section>
<h2>Semi-synchronous mode</h2>
<pre><code data-trim data-noescape>
{ok, Pid} = gun:open("host.name", 443),
{ok, http2} = gun:await(Pid),
Ref = gun:get(Pid, "/"),
{response, nofin, 200, RespHeaders} = gun:await(Pid, Ref),
{ok, RespBody} = gun:await_body(Pid, Ref).
</code></pre>
</section>
<section>
<h2>Flow control</h2>
<pre><code data-trim data-noescape>
Ref = gun:get(Pid, "/", [], #{flow => 1}),
{response, nofin, 200, _} = gun:await(Pid, Ref)
{data, nofin, _} = gun:await(Pid, Ref),
{error, timeout} = gun:await(Pid, Ref),
gun:update_flow(Pid, Ref, 2),
{data, nofin, _} = gun:await(Pid, Ref),
{data, nofin, _} = gun:await(Pid, Ref),
{error, timeout} = gun:await(Pid, Ref).
</code></pre>
<p>Configurable per stream or per protocol:</p>
<pre><code data-trim data-noescape>
{ok, Pid} = gun:open("host.name", 443, #{
http_opts => #{flow => 10}
}).
</code></pre>
</section>
<section>
<h2>Websocket</h2>
<pre><code data-trim data-noescape>
{ok, Pid} = gun:open("host.name", 443),
{ok, _} = gun:await_up(Pid),
Ref = gun:ws_upgrade(Pid, "/ws"),
{upgrade, [<<"websocket">>], _} = gun:await(Pid, Ref),
gun:ws_send(Pid, Ref, [
{text, <<"Hello!">>},
{binary, <<1,2,3,4>>}
]),
{ws, Frame} = gun:await(Pid, Ref).
</code></pre>
<p>Websocket over HTTP/2 currently missing.</p>
</section>
<section>
<h2>SSE</h2>
<pre><code data-trim data-noescape>
CommonOpts = #{content_handlers => [gun_sse_h, gun_data_h]},
{ok, Pid} = gun:open("host.name", 443, #{
http_opts => CommonOpts,
http2_opts => CommonOpts
}).
</code></pre>
<pre><code data-trim data-noescape>
Ref = gun:get(Pid, "/events", #{
<<"accept">> => <<"text/event-stream">>}),
]),
{response, nofin, 200, RespHeaders} = gun:await(Pid, Ref),
{sse, Event} = gun:await(Pid, Ref),
#{
last_event_id := LastEventID,
event_type := <<"message">>,
data := Data
} = Event.
</code></pre>
</section>
<section>
<h2>CONNECT support</h2>
<section>
<pre><code data-trim data-noescape>
{ok, Pid} = gun:open("proxy1.name", 443),
Ref1 = gun:connect(Pid, #{
host => "proxy2.name", port => 443
}),
{response, fin, 200, _} = gun:await(Pid, Ref1),
Ref2 = gun:connect(Pid, #{
host => "origin.name", port => 443
}),
{response, fin, 200, _} = gun:await(Pid, Ref2),
Ref3 = gun:get(Pid, "/"),
{response, nofin, 200, RespHeaders} = gun:await(Pid, Ref3),
{ok, Body} = gun:await_body(Pid, Ref3).
</code></pre>
</section>
<section>
<pre><code data-trim data-noescape>
#{
transport := tls, protocol := http,
origin_scheme := <<"http">>,
origin_host := "origin.name", origin_port := 443,
intermediaries := [
#{ type := connect,
host := "proxy1.name", port := 443,
transport := tls, protocol := http},
#{ type := connect,
host := "proxy2.name", port := 443,
transport := tls, protocol := http}]
} = gun:info(Pid).
</code></pre>
</section>
<section>
<p>CONNECT over HTTP/2 currently missing.</p>
</section>
</section>
<section>
<h2>Socks support</h2>
<ul>
<li>Currently being worked on</li>
<li>Similar to CONNECT</li>
<li>Open connection to Socks server using <code>gun_socks</code></li>
<li>Options determine where to connect next</li>
<li>Exotic scenarios: Socks -> CONNECT -> Socks -> ...</li>
<li>Support Socks4a, Socks5</li>
<li>Socks6 to be supported as well once available</li>
</ul>
</section>
<section>
<h2>Events</h2>
<section>
<ul>
<li>init, terminate</li>
<li>domain_lookup_start, domain_lookup_end</li>
<li>connect_start, connect_end</li>
<li>tls_handshake_start, tls_handshake_end</li>
<li>disconnect</li>
</ul>
</section>
<section>
<ul>
<li>request_start, request_headers, request_end</li>
<li>push_promise_start, push_promise_end</li>
<li>response_start, response_inform, response_headers, response_trailers, response_end</li>
</ul>
</section>
<section>
<ul>
<li>ws_upgrade</li>
<li>ws_recv_frame_start, ws_recv_frame_header, ws_recv_frame_end</li>
<li>ws_send_frame_start, ws_send_frame_end</li>
</ul>
</section>
<section>
<ul>
<li>protocol_changed</li>
<li>transport_changed</li>
<li>origin_changed</li>
<li>cancel</li>
</ul>
</section>
</section>
<section>
<h1>Wishlist</h1>
<p>Some features might make it into 2.0.<br/>Others in 2.x releases.</p>
</section>
<section>
<h2>Raw socket mode</h2>
<ul>
<li>Using HTTP/1.1 Upgrade to non-Web protocols</li>
<li>
Using CONNECT to access non-HTTP servers
<ul><li>Including over HTTP/2</li></ul>
</li>
</ul>
</section>
<section>
<h2>Cookie jars</h2>
<ul>
<li>Automatic storing and retrieving of cookies</li>
<li>Jars exclusive to one connection</li>
<li>Jars shared between connections</li>
<li>Options for a per-request jar</li>
<li>Filters to allow/reject specific cookies</li>
<li>Configurable storage (memory, disk, DB)</li>
</ul>
</section>
<section>
<h2>Client-side cache</h2>
<ul>
<li>RFC 7234 (or corresponding httptre RFC)</li>
<li>Cache responses per connection/shared</li>
<li>Skip requests for which we have a cached response</li>
<li>Option to skip the cache when doing a request</li>
<li>Configurable storage (memory, disk, DB)</li>
</ul>
</section>
<section>
<h1>Internals</h1>
</section>
<section>
<h2>gen_statem</h2>
<section>
<ul>
<li><code>not_connected</code></li>
<li><code>domain_lookup</code></li>
<li><code>connecting</code></li>
<li><code>tls_handshake</code></li>
<li><code>connected</code></li>
<li><code>closing</code></li>
</ul>
</section>
<section>
<ul>
<li>One callback module per protocol</li>
<li>
Most callbacks return commands
<ul><li>For example to switch the protocol</li></ul>
</li>
</ul>
</section>
</section>
<section>
<h2>HTTP/2 machine</h2>
<ul>
<li>HTTP/2 code shared with Cowboy</li>
<li>Improvements benefit both projects</li>
<li>Same options available for both projects</li>
</ul>
</section>
<section>
<h2>TLS over TLS</h2>
<ul>
<li><a href="https://github.com/ninenines/gun/blob/master/src/gun_tls_proxy.erl"><code>gun_tls_proxy</code></a> and <a href="https://github.com/ninenines/gun/blob/master/src/gun_tls_proxy_cb.erl"><code>gun_tls_proxy_cb</code></a></li>
<li>Uses <code>ssl</code>'s callback module option</li>
<li>Routes the output to Gun, not a socket</li>
<li>Makes data go through multiple layers of encryption</li>
</ul>
</section>
<section>
<h1>Upcoming</h1>
<ul>
<li>
Gun 2.0.0-pre.1 to be released in September 2019
<ul><li>Contains many improvements for elixir-grpc</li></ul>
</li>
<li>Cowboy 2.7 with many improvements for elixir-grpc</li>
<li>
Ranch 2.0:
<ul>
<li>num_acceptors</li>
<li>num_conns_sups</li>
<li>num_listen_sockets</li>
</ul>
</li>
<li>Serious work started on REST framework</li>
</ul>
</section>
<section>
<h1>Thanks</h1>
<p>Sponsors:</p>
<ul>
<li>SameRoom.io / 8x8 (long term sponsorship)</li>
<li>Pleroma (Socks5 and more)</li>
<li>Kobil (elixir-grpc related improvements)</li>
</ul>
<p><a href="https://ninenines.eu">ninenines.eu</a></p>
</section>
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