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Erlang in the Land of Lisp
with Jan Stępień @janstepien
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No content
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api.stylefruits.de
↑ ↓ ↑↑↑ ↓↓↓
mobile client
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GET /v1/give-me-all-i-need-right-now
Host: api.stylefruits.de
Accept: applica on/truckload-of-json
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api.stylefruits.de
↑ ↓ ↑↑↑ ↓↓↓
batching proxy
↑ ↓
mobile client
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↑↑↑ ↓↓↓
HTTP client
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JSON processing
↑ ↓
HTTP server
↑ ↓
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͜
Rib
Requests in Batches
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Erlang
The syntax and the beauty beneath
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-module(qsort).
-export([qsort/1]).
qsort([]) -> [];
qsort([Pivot|Rest]) ->
qsort([Front || Front <- Rest, Front < Pivot])
++ [Pivot] ++
qsort([Back || Back <- Rest, Back >= Pivot]).
en.wikipedia.org/wiki/Erlang (programming language)
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The Erlang VM
where processes dwell
p1 p2
↕
p4 ↔ p3
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CPU CPU CPU CPU
sched sched sched sched
p0 p1 p2 p3 p4 p5 p6 p7 p8 p9
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Processes’ heaps are separated
p0 p1 p2 p3 p4 p5
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Back to Rib
Se ng the environment up
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$ rebar create-app appid=rib
==> rib (create-app)
Writing src/rib.app.src
Writing src/rib_app.erl
Writing src/rib_sup.erl
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%% rebar.config
{deps,
[{jiffy, ".*",
{git,
"git://github.com/davisp/jiffy",
{tag, "0.13.3"}}},
{ejsonpath, ".*",
{git,
"git://github.com/rustyio/sync",
"de3c42df58"}}]}.
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$ rebar sh
==> rib (shell)
Erlang/OTP 18
Eshell V7.0 (abort with ^G)
1> sync:go().
Starting Sync (Automatic Code Compiler / Reloader)
Scanning source files...
ok
2>
=INFO REPORT==== 7-Feb-2016::12:21:23 ===
src/rib.erl:0: Recompiled.
=INFO REPORT==== 7-Feb-2016::12:21:23 ===
rib: Reloaded! (Beam changed.)
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Elli
and callback modules
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-module(elli_minimal_callback).
-behaviour(elli_handler).
handle(Req, _Args) ->
handle(Req#req.method, elli_request:path(Req), Req).
handle('GET',[<<"hello">>, <<"world">>], _Req) ->
{200, [], <<"Hello World!">>};
handle(_, _, _Req) ->
{404, [], <<"Not Found">>}.
github.com/knu n/elli
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Let’s make it all concurrent
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pmap(Fun, List) ->
Parent = self(),
Workers =
[spawn(fun() ->
Parent ! {self(), Fun(X)}
end)
|| X <- List],
[receive
{Worker, Value} -> Value
end
|| Worker <- Workers].
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pmap(Fun, List) ->
Parent = self(),
Workers =
[spawn_link(fun() ->
Parent ! {self(), Fun(X)}
end)
|| X <- List],
[receive
{Worker, Value} -> Value
end
|| Worker <- Workers].
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pmap(Fun, List) ->
Parent = self(),
Workers =
[spawn_link(fun() ->
Parent ! {self(), Fun(X)}
end)
|| X <- List],
[receive
{Worker, Value} -> Value
after
1000 -> error(timeout)
end
|| Worker <- Workers].
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You shall not
!
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OTP
and generic behaviours in par cular
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Use case
HTTP connec on killer
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-module(rib_conn_killer).
-export([start_link/0]).
start_link() ->
{ok, spawn_link(fun go/0)}.
go() ->
{ok, Url} = application:get_env(rib, backend),
Headers = [{"connection", "close"}],
{ok, _} = httpc:request(get, {Url, Headers}),
ok = timer:sleep(30000),
go().
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-module(rib_conn_killer_sup).
-behaviour(supervisor).
-export([start_link/0, init/1]).
start_link() ->
supervisor:start_link({local, ?MODULE},
?MODULE,
[]).
init([]) ->
{ok, {{one_for_one, 5, 10},
[{rib_conn_killer, ...}]}}.
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Use case
Request limiter
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-module(rib_limiter).
-behaviour(gen_server).
start_link(Opts) ->
gen_server:start_link(?MODULE, Opts, []).
subtract(ServerRef, N) ->
gen_server:cast(ServerRef, {subtract, N}).
init({max, N}) ->
{ok, N}.
handle_cast({subtract, N}, State) ->
NewState = State - N,
case NewState >= 0 of
true -> {noreply, NewState};
false -> {stop, limit_exceeded, NewState}
end.
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Deployment
Lightweight Docker images
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Something completely different
Happy path programming, le ng it crash
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On shoulders of giants
Virtual machine, OTP
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Needs more research
Polymorphism, editor integra on
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Can’t stand the syntax?
LFE, Joxa, Elixir
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github.com/stylefruits/rib
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Erlang in the Land of Lisp
with Jan Stępień @janstepien