Reading Modbus devices with Python from a PHP/Silex Application via Gearman worker

Yes. I know. I never know how to write a good tittle to my posts. Let me show one integration example that I’ve been working with this days. Let’s start.

In industrial automation there’re several standard protocols. Modbus is one of them. Maybe isn’t the coolest or the newest one (like OPC or OPC/UA), but we can speak Modbus with a huge number of devices.

I need to read from one of them, and show a couple of variables in a Web frontend. Imagine the following fake Modbus server (it emulates my real Modbus device)

#!/usr/bin/env python

##
# Fake modbus server
# - exposes "Energy" 66706 = [1, 1170]
# - exposes "Power" 132242 = [2, 1170]
##

from pymodbus.datastore import ModbusSlaveContext, ModbusServerContext
from pymodbus.datastore import ModbusSequentialDataBlock
from pymodbus.server.async import StartTcpServer
import logging

logging.basicConfig()
log = logging.getLogger()
log.setLevel(logging.DEBUG)

hrData = [1, 1170, 2, 1170]
store = ModbusSlaveContext(hr=ModbusSequentialDataBlock(2, hrData))

context = ModbusServerContext(slaves=store, single=True)

StartTcpServer(context)

This server exposes two variables “Energy” and “Power”. This is a fake server and it will returns always 66706 for energy and 132242 for power. Mobus is a binary protocol so 66706 = [1, 1170] and 132242 = [2, 1170]

I can read Modbus from PHP, but normally use Python for this kind of logic. I’m not going to re-write an existing logic to PHP. I’m not crazy enough. Furthermore my real Modbus device only accepts one active socket to retrieve information. That’s means if two clients uses the frontend at the same time, it will crash. In this situations Queues are our friends.

I’ll use a Gearman worker (written in Python) to read Modbus information.

from pyModbusTCP.client import ModbusClient
from gearman import GearmanWorker
import json

def reader(worker, job):
    c = ModbusClient(host="localhost", port=502)

    if not c.is_open() and not c.open():
        print("unable to connect to host")

    if c.is_open():

        holdingRegisters = c.read_holding_registers(1, 4)

        # Imagine we've "energy" value in position 1 with two words
        energy = (holdingRegisters[0] << 16) | holdingRegisters[1]

        # Imagine we've "power" value in position 3 with two words
        power = (holdingRegisters[2] << 16) | holdingRegisters[3]

        out = {"energy": energy, "power": power}
        return json.dumps(out)
    return None

worker = GearmanWorker(['127.0.0.1'])

worker.register_task('modbusReader', reader)

print 'working...'
worker.work()

Our backend is ready. Now we’ll work with the frontend. In this example I’ll use PHP and Silex.

<?php
include __DIR__ . '/../vendor/autoload.php';
use Silex\Application;
$app = new Application(['debug' => true]);
$app->register(new Silex\Provider\TwigServiceProvider(), array(
    'twig.path' => __DIR__.'/../views',
));
$app['modbusReader'] = $app->protect(function() {
    $client = new \GearmanClient();
    $client->addServer();
    $handle = $client->doNormal('modbusReader', 'modbusReader');
    $returnCode = $client->returnCode();
    if ($returnCode != \GEARMAN_SUCCESS) {
        throw new \Exception($this->client->error(), $returnCode);
    } else {
        return json_decode($handle, true);
    }
});
$app->get("/", function(Application $app) {
    return $app['twig']->render('home.twig', $app['modbusReader']());
});
$app->run();

As we can see the frontend is a simple Gearman client. It uses our Python worker to read information from Modbus and render a simple html with a Twig template

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Demo</title>
</head>
<body>
    Energy: {{ energy }}
    Power: {{ power }}
</body>
</html>

And that’s all. You can see the full example in my github account

Sending logs to a remote server using RabbitMQ

Time ago I wrote an article to show how to send Silex logs to a remote server. Today I want to use a messaging queue to do it. Normally, when I need queues, I use Gearman but today I want to play with RabbitMQ.

When we work with web applications it’s important to have, in some way or another, one way to decouple operations from the main request. Messaging queues are great tools to perform those operations. They even allow us to create our workers with a different languages than the main request. This days, for example, I’m working with modbus devices. The whole modbus logic is written in Python and I want to use a Frontend with PHP. I can rewrite the modbus logic with PHP (there’re PHP libraries to connect with modbus devices), but I’m not so crazy. Queues are our friends.

The idea in this post is the same than the previous post. We’ll use event dispatcher to emit events and we’ll send those events to a RabitMQ queue. We’ll use a Service Provider called.

<?php
include __DIR__ . '/../vendor/autoload.php';

use PhpAmqpLib\Connection\AMQPStreamConnection;
use RabbitLogger\LoggerServiceProvider;
use Silex\Application;
use Symfony\Component\HttpKernel\Event;
use Symfony\Component\HttpKernel\KernelEvents;

$connection = new AMQPStreamConnection('localhost', 5672, 'guest', 'guest');
$channel    = $connection->channel();

$app = new Application(['debug' => true]);
$app->register(new LoggerServiceProvider($connection, $channel));

$app->on(KernelEvents::TERMINATE, function (Event\PostResponseEvent $event) use ($app) {
    $app['rabbit.logger']->info('TERMINATE');
});

$app->on(KernelEvents::CONTROLLER, function (Event\FilterControllerEvent $event) use ($app) {
    $app['rabbit.logger']->info('CONTROLLER');
});

$app->on(KernelEvents::EXCEPTION, function (Event\GetResponseForExceptionEvent $event) use ($app) {
    $app['rabbit.logger']->info('EXCEPTION');
});

$app->on(KernelEvents::FINISH_REQUEST, function (Event\FinishRequestEvent $event) use ($app) {
    $app['rabbit.logger']->info('FINISH_REQUEST');
});

$app->on(KernelEvents::RESPONSE, function (Event\FilterResponseEvent $event) use ($app) {
    $app['rabbit.logger']->info('RESPONSE');
});

$app->on(KernelEvents::REQUEST, function (Event\GetResponseEvent $event) use ($app) {
    $app['rabbit.logger']->info('REQUEST');
});

$app->on(KernelEvents::VIEW, function (Event\GetResponseForControllerResultEvent $event) use ($app) {
    $app['rabbit.logger']->info('VIEW');
});

$app->get('/', function (Application $app) {
    $app['rabbit.logger']->info('inside route');
    return "HELLO";
});

$app->run();

Here we can see the service provider:

<?php
namespace RabbitLogger;

use PhpAmqpLib\Channel\AMQPChannel;
use PhpAmqpLib\Connection\AMQPStreamConnection;
use Silex\Application;
use Silex\ServiceProviderInterface;

class LoggerServiceProvider implements ServiceProviderInterface
{
    private $connection;
    private $channel;

    public function __construct(AMQPStreamConnection $connection, AMQPChannel $channel)
    {
        $this->connection = $connection;
        $this->channel    = $channel;
    }

    public function register(Application $app)
    {
        $app['rabbit.logger'] = $app->share(
            function () use ($app) {
                $channelName = isset($app['logger.channel.name']) ? $app['logger.channel.name'] : 'logger.channel';
                return new Logger($this->connection, $this->channel, $channelName);
            }
        );
    }

    public function boot(Application $app)
    {
    }
}

And here the logger:

<?php
namespace RabbitLogger;

use PhpAmqpLib\Channel\AMQPChannel;
use PhpAmqpLib\Connection\AMQPStreamConnection;
use PhpAmqpLib\Message\AMQPMessage;
use Psr\Log\LoggerInterface;
use Psr\Log\LogLevel;
use Silex\Application;

class Logger implements LoggerInterface
{
    private $connection;
    private $channel;
    private $queueName;

    public function __construct(AMQPStreamConnection $connection, AMQPChannel $channel, $queueName = 'logger')
    {
        $this->connection = $connection;
        $this->channel    = $channel;
        $this->queueName  = $queueName;
        $this->channel->queue_declare($queueName, false, false, false, false);
    }

    function __destruct()
    {
        $this->channel->close();
        $this->connection->close();
    }

    public function emergency($message, array $context = [])
    {
        $this->sendLog($message, $context, LogLevel::EMERGENCY);
    }

    public function alert($message, array $context = [])
    {
        $this->sendLog($message, $context, LogLevel::ALERT);
    }

    public function critical($message, array $context = [])
    {
        $this->sendLog($message, $context, LogLevel::CRITICAL);
    }

    public function error($message, array $context = [])
    {
        $this->sendLog($message, $context, LogLevel::ERROR);
    }

    public function warning($message, array $context = [])
    {
        $this->sendLog($message, $context, LogLevel::WARNING);
    }

    public function notice($message, array $context = [])
    {
        $this->sendLog($message, $context, LogLevel::NOTICE);
    }

    public function info($message, array $context = [])
    {
        $this->sendLog($message, $context, LogLevel::INFO);
    }

    public function debug($message, array $context = [])
    {
        $this->sendLog($message, $context, LogLevel::DEBUG);
    }
    public function log($level, $message, array $context = [])
    {
        $this->sendLog($message, $context, $level);
    }

    private function sendLog($message, array $context = [], $level = LogLevel::INFO)
    {
        $msg = new AMQPMessage(json_encode([$message, $context, $level]), ['delivery_mode' => 2]);
        $this->channel->basic_publish($msg, '', $this->queueName);
    }
}

And finally the RabbitMQ Worker to process our logs

require_once __DIR__ . '/../vendor/autoload.php';
use PhpAmqpLib\Connection\AMQPStreamConnection;
$connection = new AMQPStreamConnection('localhost', 5672, 'guest', 'guest');
$channel = $connection->channel();
$channel->queue_declare('logger.channel', false, false, false, false);
echo ' [*] Waiting for messages. To exit press CTRL+C', "\n";
$callback = function($msg){
    echo " [x] Received ", $msg->body, "\n";
    //$msg->delivery_info['channel']->basic_ack($msg->delivery_info['delivery_tag']);
};
//$channel->basic_qos(null, 1, null);
$channel->basic_consume('logger.channel', '', false, false, false, false, $callback);
while(count($channel->callbacks)) {
    $channel->wait();
}
$channel->close();
$connection->close();

To run the example we must:

Start RabbitMQ server

rabbitmq-server

start Silex server

php -S 0.0.0.0:8080 -t www

start worker

php worker/worker.php

You can see whole project in my github account

Foreign Data Wrappers with PostgreSQL and PHP

PostgreSQL is more than a relational database. It has many cool features. Today we’re going to play with Foreign Data Wrappers (FDW). The idea is crate a virtual table from an external datasource and use it like we use a traditional table.

Let me show you an example. Imagine that we’ve got a REST datasource on port 8888. We’re going to use this Silex application, for example

use Silex\Application;

$app = new Application();

$app->get('/', function(Application $app) {

    return $app->json([
        ['name' => 'Peter', 'surname' => 'Parker'],
        ['name' => 'Clark', 'surname' => 'Kent'],
        ['name' => 'Bruce', 'surname' => 'Wayne'],
    ]);
});

$app->run();

We want to use this datasource in PostgreSQL, so we need to use a “www foreign data wrapper”.

First we create the extension (maybe we need to compile the extension. We can follow the installation instructions here)

CREATE EXTENSION www_fdw;

Now with the extension we need to create a “server”. This server is just a proxy that connects to the real Rest service

CREATE SERVER myRestServer FOREIGN DATA WRAPPER www_fdw OPTIONS (uri 'http://localhost:8888');

Now we need to map our user to the server

CREATE USER MAPPING FOR gonzalo SERVER myRestServer;

And finally we only need our “Foreign table”

CREATE FOREIGN TABLE myRest (
    name text,
    surname text
) SERVER myRestServer;

Now we can perform SQL queries using our Foreign table

SELECT * FROM myRest

We must take care with one thing. We can use WHERE clauses but if we run

SELECT * FROM myRest WHERE name='Peter'

We’ll that the output is the same than “SELECT * FROM myRest”. That’s because if we want to filter something with WHERE clause within Foreign we need to do it in the remote service. WHERE name=‘Peter’ means that our Database will execute the following request:

http://localhost:8888?name=Peter

And we need to handle this parameter. For example doing something like that

use Silex\Application;
use Symfony\Component\HttpFoundation\Request;

$app = new Application();

$app->get('/', function(Application $app, Request $request) {
    $name = $request->get('name');

    $data = [
        ['name' => 'Peter', 'surname' => 'Parker'],
        ['name' => 'Clark', 'surname' => 'Kent'],
        ['name' => 'Bruce', 'surname' => 'Wayne'],
    ];
    return $app->json(array_filter($data, function($reg) use($name){
        return $name ? $reg['name'] == $name : true;
    }));
});

$app->run();

Calling Silex backend from command line. Creating SAAS command line tools

Sometimes we need to create command line tools. We can build those tools using different technologies. In Symfony world there’s Symfony Console. I feel very confortable using it. But if we want to distribute our tool we will need to face with one “problem”. User’ll need to have PHP installed. It sounds trivial but it isn’t installed in every computer. We can use nodeJs to build our tool. Nowadays nodeJs is a de-facto standard but we still have the problem. Another “problem” is how to distribute new version of our tool. Problems everywhere.

Software as a service tools are great. We can build a service (a web based service for example) and we can even monetize our service with one kind of paid-plan or another. With our SAAS we don’t need to worry about redistribute our software within each release. But, what happens when our service is a command line one?

Imagine for example that we’re going to build one service to convert text to uppercase (I thing this idea will become me rich, indeed 🙂

We can create one simple Silex example to convert to upper case strings:

<?php
include __DIR__ . "/../vendor/autoload.php";

use Silex\Application;
use Symfony\Component\HttpFoundation\Request;

$app = new Application();
$app->post("/", function (Request $request) {
    return strtoupper($request->getContent());
});
$app->run();

And now we only to call this service from the command line. We can use curl for example and convert one file content to upper case:

cat myfile.txt | curl -d @- localhost:8080 > MYFILE.txt

You can see the example in my github account here

Working with Ionic and PHP Backends. Remote debugging with PHP7 and Xdebug working with real devices

Sometimes I speak with PHP developers and they don’t use remote debugging in their development environments. Some people don’t like to use remote debugging. They prefer to use TDD and rely on the unit tests. That’s a good point of view, but sometimes they don’t use remote debugging only because they don’t know how to do it, and that’s inadmissible. Remote debugger is a powerful tool especially to handle with legacy applications. I’ve using xdebug for years with my linux workstation for years. This days I’m using Mac and it’s also very simple to set up xdebug here.

First we need to install PHP:

brew install php70

Then Xdebug

brew install php70-xdebug

(in a Ubuntu box we only need to use apt-get instead of brew)

Now we need to setup xdebug to enable remote debugging:
In a standard installation xdebug configuration is located at: /usr/local/etc/php/7.0/conf.d/ext-xdebug.ini

[xdebug]
zend_extension="/usr/local/opt/php70-xdebug/xdebug.so"

xdebug.remote_enable=1
xdebug.remote_port=9000
xdebug.profiler_enable=0
xdebug.profiler_output_dir="/tmp"
xdebug.idekey= "PHPSTORM"
xdebug.remote_connect_back = 1
xdebug.max_nesting_level = 250

And basically that’s all. To set/unset the cookie you can use one bookmarklet in your browser (you can generate your bookmarklets here). Or use a Chrome extension to enable xdebug.

Now se only need to start the built-in server with

php -S 0.0.0.0:8080

And remote debugging will be available
Remote debugger works this way:

  • We open on port within our IDE. In my case PHPStorm (it happens when we click on “Start listening for PHP debug connections”)
  • We set one cookie in our browser (it happens when click on Chrome extension)
  • When our server receives one request with the cookie, it connects to the port that our IDE opens (usually port 9000). If you use a personal firewall in your workstation, ensure that you allow incoming connections to this port.

Nowadays I’m involved with several projects building hybrid applications with Apache Cordova. In the Frontend I’m using ionic and Silex in the Backend. When I’m working with hybrid applications normally I go through two phases.

In the first one I build a working prototype. To to this I run a local server and I use my browser to develop the application. This phase is very similar than a traditional Web development process. If we also set up properly LiveReload, our application will be reloaded each time we change one javaScript file. Ionic framework integrates LiveReload and we only need to run:

ionic serve -l

to start our application. We also need to start our backend server. For example

php -S 0.0.0.0:8080 -t api/www

Now we can debug our Backend with remote debugger and Frontend with Chrome’s developer’s tools. Chrome also allows us to edit Frontend files and save them within the filesystem using workspaces. This phase is the easy one. But sooner or later we’ll need start working with a real device. We need a real device basically if we use plugins such as Camera plugin, Geolocation plugin, or things like that. OK there are emulators, but usually emulators don’t allow to use all plugins in the same way than we use then with a real device. Chrome also allow us to see the console logs of the device from our workstation. OK we can see all logs of our plugged Android device using “adb logcat” but follow the flow of our logs with logcat is similar than understand Matrix code. It’s a mess.

If we plug our android device to our computer and we open with Chrome:

chrome://inspect/#devices

We can see our device’s console, use breakpoints and things like that. Cool, isn’t it? Of course it only works if we compile our application without “–release” option. We can do something similar with Safary and iOS devices.

With ionic if we want to use LiveReload from the real device and not to recompile and re-install again and again our application each time we change our javaScript files, we can run the application using

ionic run android --device -l

When we’re developing our application and we’re in this phase we also need to handle with CORS. CORS isn’t a problem when we run our hybrid application in production. When we run the hybrid application with our device our “origin” is the local filesystem. That’s means CORS don’t apply, but when we run our application in the device, but served from our computer (when we use “-l” option), our origin isn’t local filesystem. So if our Backend is served from another origin we need to enable CORS.

We can enable CORS in the backend. I’ve written about it here, but ionic people allows us a easier way. We can set up a local proxy to serve our backend through the same origin than the application does and forget about CORS. Here we can read a good article about it.

Anyway if we want to start the remote debugger we need to create one cookie called XDEBUG_SESSION. In the browser we can use chrome extension, but when we inspect the plugged device isn’t so simple. It would be cool that ionic people allows us to inject cookies to our proxy server. I’ve try to see how to do it with ionic-cli. Maybe is possible but I didn’t realize how to do it. Because of that I’ve created a simple AngularJS service to inject this cookie. Then, if I start listening debug connections in my IDE I’ll be able to use remote debugger as well as I do when I work with the browser.

First we need to install service via Bower:

bower install ng-xdebugger --save

Now we need to include javaScript files

<script src="lib/angular-cookies/angular-cookies.min.js"></script>
<script src="lib/ng-xdebugger/dist/gonzalo123.xdebugger.min.js"></script>

then we add our service to the project.

angular.module("starter", ["ionic", "gonzalo123.xdebugger"])

Now we only need to configure our application and set de debugger key (it must be the same key than we use within the server-side configuration of xdebug)

.config(function (xdebuggerProvider) {
        xdebuggerProvider.setKey('PHPSTORM');
    })
})

And that’s all. The service is very simple. It only uses one http interceptor to inject the cookie in our http requests:

(function () {
    "use strict";

    angular.module("gonzalo123.xdebugger", ["ngCookies"])
        .provider("xdebugger", ['$httpProvider', function ($httpProvider) {
            var debugKey;

            this.$get = function () {
                return {
                    getDebugKey: function () {
                        return debugKey;
                    }
                };
            };

            this.setKey = function (string) {
                if (string) {
                    debugKey = string;
                    $httpProvider.interceptors.push("xdebuggerCookieInterceptor");
                }
            };
        }])

        .factory("xdebuggerCookieInterceptor", ['$cookieStore', 'xdebugger', function ($cookieStore, xdebugger) {
            return {
                response: function (response) {
                    $cookieStore.put("XDEBUG_SESSION", xdebugger.getDebugKey());

                    return response;
                }
            };
        }])
    ;
})();

And of course you can see the whole project in my github account.

POST Request logger using websockets

Last days I’ve been working with background geolocation with an ionic application. There’s a cool plugin to do that. The free version of the plugin works fine. But there’s a also a premium version with improvements, especially in battery consumption with Android devices.

Basically this plugin performs a POST request to the server with the GPS data. When I was developing my application I needed a simple HTTP server to see the POST requests. Later I’ll code the backend to handle those requests. I can develop a simple Silex application with a POST route and log the request in a file or flush those request to the console. This’d have been easy but as far as I’m a big fan of WebSockets (yes I must admit that I want to use WebSockets everywere 🙂 I had one idea in my mind. The idea was create a simple HTTP server to handle my GPS POST requests but instead of logging the request I will emit a WebSocket. Then I can create one site that connects to the WebSocket server and register on screen the POST request. Ok today I’m a bit lazy to fight with the Frontend so my log will be on the browser’s console.

To build the application I’ll reuse one of my projects in github: The PHP dumper. The idea is almost the same. I’ll create a simple HTTP server with Silex with two routes. One to handle POST requests (the GPS ones) and another GET to allow me to connect to the WebSocket

That’s the server. Silex, a bit of Twig, another bit of Guzzle and that’s all

use GuzzleHttp\Client;
use Silex\Application;
use Silex\Provider\TwigServiceProvider;
use Symfony\Component\HttpFoundation\Request;

$app = new Application([
    'debug'       => true,
    'ioServer'    => '//localhost:8888',
    'wsConnector' => 'http://127.0.0.1:26300'
]);

$app->register(new TwigServiceProvider(), [
    'twig.path' => __DIR__ . '/../views',
]);

$app['http.client'] = new Client();

$app->get("/{channel}", function (Application $app, $channel) {
    return $app['twig']->render('index.twig', [
        'channel'  => $channel,
        'ioServer' => $app['ioServer']
    ]);
});

$app->post("/{channel}", function (Application $app, $channel, Request $request) {
    $app['http.client']->get($app['wsConnector'] . "/info/{$channel}/" . json_encode($request->getContent()));

    return $app->json('OK');
});

$app->run();

That’s the Twig template. Nothing especial: A bit of Bootstrap and one socket.io client. Each time user access to one “channel”‘s url (GET /mychannel). It connects to websocket server

var CONF = {
        IO: {HOST: '0.0.0.0', PORT: 8888},
        EXPRESS: {HOST: '0.0.0.0', PORT: 26300}
    },
    express = require('express'),
    expressApp = express(),
    server = require('http').Server(expressApp),
    io = require('socket.io')(server, {origins: 'localhost:*'})
    ;

expressApp.get('/:type/:session/:message', function (req, res) {
    console.log(req.params);
    var session = req.params.session,
        type = req.params.type,
        message = req.params.message;

    io.sockets.emit('dumper.' + session, {title: type, data: JSON.parse(message)});
    res.json('OK');
});

io.sockets.on('connection', function (socket) {
    console.log("Socket connected!");
});

expressApp.listen(CONF.EXPRESS.PORT, CONF.EXPRESS.HOST, function () {
    console.log('Express started');
});

server.listen(CONF.IO.PORT, CONF.IO.HOST, function () {
    console.log('IO started');
});

And each time background geolocation plugin POSTs GPS data Silex POST route will emit a WebSocket to the desired channel. Our WebSocket client just logs the GPS data using console.log. Is hard to explain but very simple process.

We also can emulate POST requests with this simple node script:

var request = require('request');

request.post('http://localhost:8080/Hello', {form: {key: 'value'}}, function (error, response, body) {
    if (!error && response.statusCode == 200) {
        console.log(body)
    }
});

And that’s all. You can see the whole code within my github account.

Book review: Socket.IO Cookbook

Last summer I collaborated as a technical reviewer in the book “Socket.IO Cookbook” written by Tyson Cadenhead and finally I’ve got the book in my hands

I’m a big fan of real time technologies and I’m normally Socket.io user. Because of that, when people of Packt Publishing contacted me to join to the project as technical reviewer my answer was yes. I’ve got serious problems nowadays to find time to pet projects and extra activities, but if there’re WebSockets inside I cannot resists.

The book is correct and it’s a good starting point to event-based communication with JavaScript. I normally don’t like beginners books (even if I’m a beginner in the technology). I don’t like the books where author explains how to do one thing that I can see how to do it within the website of the. OK. This book isn’t one of those of books. The writer don’t assume reader is a totally newbie. Because of that newbies sometimes can be lost in some chapters, but this exactly the way we all learn new technologies. I like the way Tyson introduces concepts about socket.io.

The book is focused in JavaScript and also uses JavaScript to the backend (with node). Maybe I miss the integration with non-JavaScript environments, but as socket.io is a javascript library I understand that the usage of JavaScript in all application lifecycle is a good approach.

IMG_20151106_204902_jpg

Also those days I was reading and playing a little bit with WebRTC and the book has one chapter about it! #cool

Alternative way to inject providers in a Silex application

I normally use Silex when I need to build one Backend. It’s simple and straightforward to build one API endpoint using this micro framework. But there’s something that I don’t like it: The “array access” way to access to the dependency injection container. I need to remember what kind of object provides my service provider and also my IDE doesn’t help me with autocompletion. OK I can use PHPDoc comments or even create one class that inherits from Silex\Application and use Traits. Normally I’m lazy to do it. Because of that I’ve create this simple service provider to help me to do what I’m looking for. Let me explain it a little bit.

Imagine that I’ve got this class

namespace Foo

class Math
{
    public function sum($i, $j)
    {
        return $i+$j;
    }
}

And I want to add this service to my DIC

$app['math'] = $app->share(function () {
    return new Math();
});

Now I can use my service within my Silex application

$app->get("/", function () use ($app) {
    return $app['math']->sum(1, 2);
});

But I want to use my service in the same way that I’m using my services within my AngularJS applications. I what to do something like that:

use Foo\Math;
...
$app->get("/", function (Math $math) {
    return $math->sum(1, 2);
});

And that’s exactly what my service provider does. I only need to append my provider to my Application and tell to the provider what’s the relationship between Pimple’s services keys and its provided Instance

$app->register(new InjectorServiceProvider([
    'Foo\Math' => 'math',
]));

This is one example

composer require gonzalo123/injector
include __DIR__ . "/../vendor/autoload.php";

use Silex\Application;
use Injector\InjectorServiceProvider;
use Foo\Math;

$app            = new Application(['debug' => true]);

$app->register(new InjectorServiceProvider([
    'Foo\Math' => 'math',
]));

$app['math'] = function () {
    return new Math();
};

$app->get("/", function (Math $math) {
    return $math->sum(1, 2);
});

$app->run();

And this is the Service Provider

namespace Injector;
use Silex\Application;
use Silex\ServiceProviderInterface;
use Symfony\Component\HttpKernel\Event\FilterControllerEvent;
use Symfony\Component\HttpKernel\KernelEvents;
class InjectorServiceProvider implements ServiceProviderInterface
{
    private $injectables;
    public function __construct($injectables = [])
    {
        $this->injectables = $injectables;
    }
    public function appendInjectables($providedClass, $key)
    {
        $this->injectables[$providedClass] = $key;
    }
    public function register(Application $app)
    {
        $app->on(KernelEvents::CONTROLLER, function (FilterControllerEvent $event) use ($app) {
            $reflectionFunction = new \ReflectionFunction($event->getController());
            $parameters         = $reflectionFunction->getParameters();
            foreach ($parameters as $param) {
                $class = $param->getClass();
                if ($class && array_key_exists($class->name, $this->injectables)) {
                    $event->getRequest()->attributes->set($param->name, $app[$this->injectables[$class->name]]);
                }
            }
        });
    }
    public function boot(Application $app)
    {
    }
}

As we can see I’m listening to CONTROLLER event from event dispatcher and I inject the dependency form container to requests attributes.

Full code in my github account

Building one HTTP client in PostgreSQL with PL/Python

Don’t ask me way, but I need to call to a HTTP server (one Silex application) from a PostgreSQL database.

I want to do something like this:

select get('http://localhost:8080?name=Gonzalo')->'hello';

PostgreSQL has a datatype for json. It’s really cool and it allows us to connect our HTTP server and our SQL database using same datatype.

PostgreSQL also allows us to create stored procedures using different languages. The default language is PL/pgSQL. PL/pgSQL is a simple language where we can embed SQL. But we also can use Python. With Python we can easily create HTTP clients, for example with urllib2. That means that develop our a HTTP client for a PostgreSQL database is pretty straightforward.

CREATE OR REPLACE FUNCTION get(uri character varying)
  RETURNS json AS
$BODY$
import urllib2

data = urllib2.urlopen(uri)

return data.read()

$BODY$
  LANGUAGE plpython2u VOLATILE
  COST 100;
ALTER FUNCTION get(character varying)
  OWNER TO gonzalo;

Ok that’s a GET client, but we also want a POST client to do something like this:

select post('http://localhost:8080', '{"name": "Gonzalo"}'::json)->'hello';

As you can see I want to use application/json instead of application/x-www-form-urlencoded to send request parameters. I wrote about it here time ago. So I will create one endpoint within my Silex server to handle my POST requests to:

<?php
include __DIR__ . '/../vendor/autoload.php';

use Silex\Application;
use Symfony\Component\HttpFoundation\Request;
use G\AngularPostRequestServiceProvider;

$app = new Application(['debug' => true]);

$app->register(new AngularPostRequestServiceProvider());

$app->post('/', function (Application $app, Request $request) {
    return $app->json(['hello' => $request->get('name')]);
});

$app->get('/', function (Application $app, Request $request) {
    return $app->json(['hello' => $request->get('name')]);
});

$app->run();

And now we only need to create one stored procedure to send POST requests

CREATE OR REPLACE FUNCTION post(
    uri character varying,
    paramenters json)
  RETURNS json AS
$BODY$
import urllib2

clen = len(paramenters)
req = urllib2.Request(uri, paramenters, {'Content-Type': 'application/json', 'Content-Length': clen})
f = urllib2.urlopen(req)
return f.read()

$BODY$
  LANGUAGE plpython2u VOLATILE
  COST 100;
ALTER FUNCTION post(character varying, json)
  OWNER TO gonzalo;

And that’s all. At least this simple script is exactly what I need.

Generating push notifications with Pushbullet and Silex

Sometimes I need to send push notifications to mobile apps (Android or IOS). It’s not difficult. Maybe it’s a bit nightmare the first times, but when you understand the process, it’s straightforward. Last days I discover a cool service called PushBullet. It allows us to install one client in our Android/IOS or even desktop computer, and send push notifications between them.

Pushbullet also has a good API, and it allows us to automate our push notifications. I’ve play a little bit with the API and my Raspberry Pi – home server. It’s really simple to integrate the API with our Silex backend and send push notifications to our registered devices.

I’ve created one small service provider to enclose the API. The idea is to use one Silex application like this

use Silex\Application;
use PushSilex\Silex\Provider\PushbulletServiceProvider;

$app = new Application(['debug' => true]);

$myToken = include(__DIR__ . '/../conf/token.php');

$app->register(new PushbulletServiceProvider($myToken));

$app->get("/", function () {
    return "Usage: GET /note/{title}/{body}";
});

$app->get("/note/{title}/{body}", function (Application $app, $title, $body) {
    return $app->json($app['pushbullet.note']($title, $body));
});

$app->run();

As we can see we’re using one service providers called PushbulletServiceProvider. This service provides us ‘pushbullet.note’ and allows to send push notifications. We only need to configure our Service Provider with our Pushbulled’s token and that’s all.

<?php
namespace PushSilex\Silex\Provider;
use Silex\ServiceProviderInterface;
use Silex\Application;
class PushbulletServiceProvider implements ServiceProviderInterface
{
    private $accessToken;
    const URI = 'https://api.pushbullet.com/v2/pushes';
    const NOTE = 'note';
    public function __construct($accessToken)
    {
        $this->accessToken = $accessToken;
    }
    public function register(Application $app)
    {
        $app['pushbullet.note'] = $app->protect(function ($title, $body) {
            return $this->push(self::NOTE, $title, $body);
        });
    }
    private function push($type, $title, $body)
    {
        $data = [
            'type'  => $type,
            'title' => $title,
            'body'  => $body,
        ];
        $ch = curl_init();
        curl_setopt_array($ch, [
            CURLOPT_URL            => self::URI,
            CURLOPT_HTTPHEADER     => ['Content-Type' => 'application/json'],
            CURLOPT_CUSTOMREQUEST  => 'POST',
            CURLOPT_POSTFIELDS     => $data,
            CURLOPT_HTTPAUTH       => CURLAUTH_BASIC,
            CURLOPT_USERPWD        => $this->accessToken . ':',
            CURLOPT_RETURNTRANSFER => true
        ]);
        $out = curl_exec($ch);
        curl_close($ch);

        return json_decode($out);
    }
    public function boot(Application $app)
    {
    }
}

Normally I use Guzzle to handle HTTP clients, but in this example I’ve created a raw curl connection.

You can see the project in my github account