Traefik2 LuaScript

LuaScript is middleware for Traefik v2 for execute lua script with access to API

Under cover used LUA VM from Yusuke Inuzuka

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About

This middleware allows you to write your business logic in LUA script

• get an incoming request
• add/modify request headers
• add/modify response headers
• interrupt the request
• make HTTP calls to foreign services
• write to traefik log

Usage example

-- middleware_example.lua

local traefik = require('traefik')
local log = require('log')

local h, err = traefik.getRequestHeader('X-Some-Header')
if err ~= nil then
  log.warn('error get header ' .. err)
  return
end

if h == '' then
    traefik.interrupt(401, 'HTTP Header empty or not exists')
    return
end

traefik.setRequestHeader('Authorized', 'SUCCESS')

log.info('continue')

Functions may return an error as a last variable. It is a string with an error message or nil, if no error

Benchmark

See into benchmark folder in this repo

Backend is a simple go application

package main

import (
	"log"
	"net/http"
)

var ok = []byte("ok")

func handler(w http.ResponseWriter, r *http.Request) {
	w.WriteHeader(200)
	w.Write(ok)
}

func main() {
	http.HandleFunc("/", handler)
	log.Printf("listen 2000")
	http.ListenAndServe("127.0.0.1:2000", nil)
}

Run load testing with vegeta

echo "GET http://localhost/" | vegeta attack -rate 2000 -duration=60s | tee results.bin | vegeta report

With LUA

A Traefik config

http:
  routers:
    router1:
      rule: "Host(`localhost`)"
      service: service1
      middlewares:
        - example

  middlewares:
    example:
      luascript:
        script: middleware.lua

  services:
    service1:
      loadBalancer:
        servers:
          - url: "http://127.0.0.1:2000"

A Lua script

local traefik = require('traefik')

traefik.setRequestHeader('X-Header', 'Example')
traefik.setResponseHeader('X-Header', 'Example')

A Result

Requests      [total, rate, throughput]  120000, 2000.02, 2000.00
Duration      [total, attack, wait]      59.999868062s, 59.999484357s, 383.705µs
Latencies     [mean, 50, 95, 99, max]    471.058µs, 365.053µs, 993.75µs, 1.26782ms, 18.771475ms
Bytes In      [total, mean]              240000, 2.00
Bytes Out     [total, mean]              0, 0.00
Success       [ratio]                    100.00%
Status Codes  [code:count]               200:120000
Error Set:

Without LUA

A Traefik config

http:
  routers:
    router1:
      rule: "Host(`localhost`)"
      service: service1

  services:
    service1:
      loadBalancer:
        servers:
          - url: "http://127.0.0.1:2000"

A Result

Requests      [total, rate, throughput]  120000, 2000.02, 2000.01
Duration      [total, attack, wait]      59.999708481s, 59.999466875s, 241.606µs
Latencies     [mean, 50, 95, 99, max]    257.527µs, 227.055µs, 339.606µs, 520.189µs, 28.70824ms
Bytes In      [total, mean]              240000, 2.00
Bytes Out     [total, mean]              0, 0.00
Success       [ratio]                    100.00%
Status Codes  [code:count]               200:120000
Error Set:

Installation from sources and run

Download the Traefik sources and go to the directory

git clone https://github.com/containous/traefik
cd traefik

Add this repo as a submodule

git submodule add https://github.com/negasus/traefik2-luascript pkg/middlewares/luascript

Add the code for the middleware config to the file pkg/config/dynamic/middleware.go

type Middleware struct {
  // ...
	LuaScript         *LuaScript         `json:"luascript,omitempty" toml:"luascript,omitempty" yaml:"luascript,omitempty"`
  // ...
}

// ...

// +k8s:deepcopy-gen=true

// LuaScript config
type LuaScript struct {
	Script string `json:"script,omitempty" toml:"script,omitempty" yaml:"script,omitempty"`
}

Add the code for register a middleware to the file pkg/server/middleware/middlewares.go

import (
  // ...
	"github.com/containous/traefik/v2/pkg/middlewares/luascript"  
  // ...
)

// ...

func (b *Builder) buildConstructor(ctx context.Context, middlewareName string, config config.Middleware) (alice.Constructor, error) {
  // ...
  
  // BEGIN LUASCRIPT BLOCK
	if config.LuaScript != nil {
		if middleware == nil {
			middleware = func(next http.Handler) (http.Handler, error) {
				return luascript.New(ctx, next, *config.LuaScript, middlewareName)
			}
		} else {
			return nil, badConf
		}
	}
  // END LUASCRIPT BLOCK
  
	if middleware == nil {
		return nil, fmt.Errorf("invalid middleware %q configuration: invalid middleware type or middleware does not exist", middlewareName)
	}

	return tracing.Wrap(ctx, middleware), nil
}

Build the Traefik

go generate
go build -o ./traefik ./cmd/traefik

Create a config file config.yml

log:
  level: warn

providers:
  file:
    filename: "/path/to/providers.yml"

and providers.yml

http:
  routers:
    router1:
      rule: "Host(`localhost`)"
      service: service1
      middlewares:
        - example

  middlewares:
    example:
      luascript:
        script: /path/to/example.lua

  services:
    service1:
      loadBalancer:
        servers:
          - url: "https://api.github.com/users/octocat/orgs"

Create a lua script example.lua

local traefik = require('traefik')
local log = require('log')

log.warn('Hello from LUA script')
traefik.setResponseHeader('X-New-Response-Header', 'Woohoo')

Run the traefik

./traefik --configFile=config.yml

Call the traefik (from another terminal)

curl -v http://localhost

And, as result, we see a traefik log

WARN[...] Hello from LUA script 	middlewareName=file.example-luascript middlewareType=LuaScript

A response from the github API with our header

...
< X-New-Response-Header: Woohoo
...

Done!

API

Traefik

Traefik module allows get information about current request. Add request/response headers, or interrupt the request.

Usage:

traefik = require('traefik')

Get Request Header

getRequestHeader(name string) value string, error

If header not exists, returns no error and empty string value!

local traefik = require('traefik')
local log = require('log')

local h, err = traefik.getRequestHeader('X-Authorization')
if err ~= nil then
  log.debug('error get header' .. err)
end

Set Request Header

setRequestHeader(name string, value string) error

Set header for pass to backend

err = traefik.setRequestHeader('X-Authorization', 'SomeSecretToken')

Set Response Header

setResponseHeader(name string, value string) error

Set header for return to client

err = traefik.setResponseHeader('X-Authorization', 'SomeSecretToken')

** Interrupt the request and return StatusCode and Body

interrupt(code int, [message string]) error

err = traefik.interrupt(403)

-- or

err = traefik.interrupt(422, 'Validation Error')

Get Request Query Argument

getQueryArg(name string) value string, error

Get value from query args

-- Get 'foo' for URL http://example.com/?token=foo
v, err = traefik.getQueryArg('token')

Get Request

getRequest() value table

Get request info

info = traefik.getRequest()

{
    method = 'GET',
    uri = '...',
    host = '...',
    remoteAddr = '...',
    referer = '...',
    headers = {
        key = 'value',
        ...
    }
}

LOG

Send a message to a traefik logger

error(message string)

warn(message string)

info(message string)

debug(message string)

local log = require('log')

log.error('an error occured')
log.debug('header ' .. h .. ' not exist')

HTTP

Set HTTP requests to remote services

Usage:

http = request('http')

request

request( table) response[, error string]

Send a request

OPTIONS is a table with request options

{
    method = 'POST',    -- http method. By default: GET
    url     = '',       -- URL
    body    = '',       -- request body. By default: empty
    timeout = 100,      -- timeout in milliseconds. By default: 250 (ms)
    headers = {         -- request heders
        key = 'value',
        ...
    }
}

RESPONSE

{
    status  = 200,      -- response status code
    body    = '',       -- response body
    headers = {         -- response headers
        key = value,
        ...
    }
}

get, post, put, delete

get('url', [OPTIONS]) response[, error string]

post('url', [OPTIONS]) response[, error string]

put('url', [OPTIONS]) response[, error string]

delete('url', [OPTIONS]) response[, error string]

Aliases for request with predefined Method and URL