Introduction to Lua Luajit Openresty Luvit

Lua & co - @LDuboeuf - Novembre 2016
Lua & co

About me
network & sys admin (far away)
programmer
And more recently,
Trainer/Facilitator @Afpa (adult training)

Introduction to Lua
● Built in 1993 by Roberto Lerusalimschy, Waldemar Celes,
Luiz Henrique de Figueiredo – Brazil
● Lightweigth ( 24000 loc written in ANSI C), fast and easy to
integrate scripting language.
● Multi-paradigm : procedural, OO, fonctionnal
● Run on every Unix et Windows flavors, smartphones
(Android, iOS, Symbian, Windows Phone) , on embedded
( ARM, Rabbit), IBM mainframes, etc.
● C<->Lua bindings
● MIT License

Where it is used and what for ?
redis Used as :
● Extension
● Monitoring
● Scripting (DSL)
● Proxy – Load balancing
● Cache management
● Web Application
Firewall
● Robotic
● Game play
● Etc...

First step
https://gist.github.com/lduboeuf/66e87d2d18e26d0f48ec70539534e574

First step...
https://gist.github.com/lduboeuf/13a8f75b1701e9204c1202d9bab7a482

Metatable concept...
– Allows you to modify tables behavior
● Override « +, -, /, * » operators (example : table1 + table2 )
● Comparisons
● Inheritance, interface (OOP)
– Allows you to hook tables :
● When a new elements is added,
● When a table element is accessed,
● custom concatenation
● etc...

OOP
Module pattern : Class like pattern :

More about...
● Multithreading : coroutines :
– Not as OS multithreading, non pre-emptive. Allows you
non I/O blocking operations.
● Weirdness:
– Array indices start at 1 !
– Not equals : if (i~=1) then … end
– No ternary operator ( x>3 ? 1 : 0; )
– No increment shortcut : i = i + 1
–

Luajit
● JIT compiler for lua (mainly created by Mike
Pall )
● Super fast! : 3 to 100x faster
● Small : < 100 KB
● Easy Native C library integration thanks to ffi
(foreign function include)

Luajit : ffi - example

Support & tools
● Tools:
– Package management : Luarocks
– Unit tests : « busted » or « luaunit » and more…
– Debugger :IDE ZeroBrane Studio
● Support
– Mailing list
– irc.freenode.net #lua
– Workshops

Lua for the web
● Choose between :
– 100 % Lua :
● Xavante, Pegasus
– existing server extension for :
● LightHttpd, Apache, Nginx, Tornado...
– nodeJs like :
● Luvit

Openresty
Openresty = Nginx + Luajit + Modules

Nginx
● HTTP server, reverse proxy, mail proxy
● Asynchronous
● Low memory footprint
● Modular
● Extensible

Nginx model
Source : http://www.aosabook.org/en/nginx.html

Nginx – min server
worker_processes 1;
error_log logs/error.log;
events {
worker_connections 1024;
}
http {
server {
listen 8000;
location / {
index index.html;
root public/;
}
}
$> curl http://0.0.0.0:8000/index.html

Openresty
● Created and maintained mainly by Yichun Zhang (@agentzh)
.( Taobao.com then Clouflare )
● In production on high trafic site (Alibaba group, Clouflare,...)
● Non blocking I/O modules for :
● Memcached
● Redis
● MySQL / Drizzle
● PostgreSQL
● Websockets, CLI, Json, etc..

Openresty
● Allows you to scripts in Lua during Nginx phases
– Init phase
– Rewrite phase.
– Access phase.
– Content phase.
– Log phase
– And more…
● Lua API to access Ngninx environment

Openresty
● Lua code is executed within workers

Openresty – Hello world
location /hellolua {
default_type 'text/plain';
content_by_lua_block {
local name = ngx.var.arg_name or "Anonymous"
ngx.say("Hello, ", name, "!")
};
}
$> curl http://localhost/hellolua?name=Lua
Hello, Lua

Openresty : load external module
location /xxxx {
rewrite_by_lua_file /path/to/rewrite.lua;
access_by_lua_file /path/to/access.lua;
content_by_lua_file /path/to/content.lua;
}
● Modules are loaded once per worker at first request

Openresty : sub request
location / {
content_by_lua '
local res = ngx.location.capture("/memcached",
{ args = { cmd = "incr", key = ngx.var.uri } }
)
';
}
location /memcached {
set $memc_cmd $arg_cmd;
set $memc_key $arg_key;
memc_pass 127.0.0.1:11211;
}

Openresty – cosocket
● Non blocking I/O thanks to Cosocket library :
– TCP or Unix Domain sockets
– Allows you to write asynchronous sequential code !
(bye bye callback hell)
– « Keepalive » for reuse connections.

Openresty : TCP client
location /memcached {
content_by_lua_block {'
local sock = ngx.socket.connect("127.0.0.1", 11211)
sock:send("SET foo bar 3600rn")
local line = sock:receive()
if line then
ngx.say(line)
end
sock:setkeepalive()
};
}
$> curl http://localhost/memcached
STORED

Openresty : mysql
location /todos {
local mysql = require "resty.mysql"
local db, err = mysql:new()
if not db then
ngx.say("failed to instantiate mysql: ", err)
return
end
db:set_timeout(1000) -- 1 sec
--connect…
local res, err, errcode, sqlstate = db:query("select * from tasks")
if not res then
ngx.say("bad result: ", err, ": ", errcode, ": ", sqlstate, ".")
return
end
local cjson = require "cjson"
ngx.say("result: ", cjson.encode(res))
} ;
}

Openresty : mini app
location /api/v0.1/todos {
default_type application/json;
local todo_api = require "todo-app"
--get location after /api/v0.1/todos
local sub_loc = string.sub(ngx.var.request_uri, string.len(ngx.var.location)+1)
if sub_loc == "" then sub_loc = "/" end
local router = require "router"
local r = router.new()
r:get("/", todo_api.getAll)
r:post("/", todo_api.create)
r:delete("/:id", todo_api.delete)
r:put("/:id", todo_api.update)
--execute routes
r:execute(ngx.var.request_method, sub_loc, ngx.req.get_uri_args())
}
● }
https://github.com/lduboeuf/openresty-todo-app

Openresty - tools
● Real time profiling
● Test suite
● Package manager (OPM)
● Mailing list

Openresty : built with
● Lapis ( http://leafo.net/lapis/ ) = openresty +
libs utils + templating html + sessions
● Sailor ( http://sailorproject.org/ ) = MVC, routing,
templating, model generator, etc.

Bonus !

Protocol agnostic : Luvit
● Built by Tim Caswell (@creationix) , a former NodeJs contributor.
● In production within Rackspace for their monitoring agents.
● Primary goal was to port Node to Lua : Memory gain : 20x !
● Built on top of LibUV (same as Node) : event loop,
Asynchronous I/O,…
● Use of OpenSSL, zlib libs.
● Allows you to build self-executable apps, fast and lightweight.

Luvit
● We can create apps « nodeJs like » (call-back based)
or with sequential code (thanks to coroutine)
● Lit : Package manager, repository and compiler
git clone git@github.com:creationix/hexes.git
cd hexes
lit install
lit make
./hexes
lit make lit://creationix/hexes
./hexes
When published to repository, this is simple as :
Example : compile and execute

Luvit : example
https://github.com/creationix/hexes

Luvit
● Really cool if :
– Not afraid of sporadic docs
– Not afraid with programing your own connector ;-)
( a connector for Prostgresql, Redis exist )
● Community : freenode IRC #luvit , mailing list
https://luvit.io

Voilà, merci !
http://openresty.org/en/
http://luajit.org/
https://luvit.io/
https://www.lua.org/

Introduction to Lua Luajit Openresty Luvit

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