Workshop

Develop microservices in PHP

by Enrico Zimuel
Principal Software Engineer @ Elastic

PHPDay, Verona, 10th May 2019

About me

Developer since 1996 Principal Software Engineer at Elastic Open source contributor: Elasticsearch-php, Expressive, Zend Framework, etc TEDx and international speaker Author of Sviluppare in PHP 7 and other books Co-founder of PUG Torino

Microservice

...the microservice architectural style is an approach to developing a single application as a suite of small services, each running in its own process and communicating with lightweight mechanisms, often an HTTP resource API

- Martin Fowler

Source: Introduction to microservices

Source: Introduction to microservices

Benefit

• Separation of concerns
  • Modularity
  • Encapsulation
• Scalability
  • Horizontally scaling
  • Workload partitioning

Cons

• Network latency
• Debugging
• New architecture challenges:
  • Autodiscovery
  • Telemetry
  • Everything needs to be automated

Web APIs

Building a Web API

• Managing the HTTP request and response
• Choosing a representation format
• Choosing an error format
• Filtering & validating input data
• Authenticating HTTP requests
• Authorizing HTTP requests
• Documentation

HTTP Methods (REST approach)

• GET: read a resource
• HEAD: read without body
• POST: create a resource
• PUT: replace a resource
• PATCH: update a resource
• DELETE: delete a resource
• OPTIONS: information about a resource

HTTP Status-code

• Informational 1xx: 100 Continue
• Successful 2xx: 200 OK, 201 Created, 202 Accepted
• Redirection 3xx: 301 Moved Permanently, 307 Temporary Redirect
• Client Error 4xx: 401 Unauthorized, 404 Not Found, 405 Method Not Allowed
• Server Error 5xx: 500 Internal Server Error, 503 Service Unavailable

Representation format

• JSON (JavaScript Object Notation)
  in PHP json_encode(), json_decode()
• XML (eXtensible Markup Language)
  in PHP SimpleXML, libxml, DOM, etc

HAL-JSON

HAL-JSON (Hypertext Application Language JSON), Internet-Draft

GET /api/user/ezimuel
{
    "_links": {
        "self": {
            "href": "http://domain/api/user/ezimuel"
        },
        "contacts": [
            { "href": "http://domain/api/user/mwop" },
            { "href": "http://domain/api/user/zeevs" }
        ]
    },
    "id": "ezimuel",
    "name": "Enrico Zimuel"
}

Error format

Problem Details (RFC 7807)

HTTP/1.1 400 Bad Request
Content-Type: application/problem+json
Content-Language: en

{
    "type": "https://example.net/validation-error",
    "title": "Your request parameters didn't validate.",
    "invalid-params": [
        {
            "name": "age",
            "reason": "must be a positive integer"
        },
    ]
}

Authentication

• Basic/Digest access authentication
• OAuth2

Documentation

• Swagger
• APIDOC

HTTP in PHP

HTTP message in PHP

Global variables:

• $_SERVER
• $_POST
• $_GET
• $_FILES
• $_COOKIE

HTTP functions in PHP

• http_response_code()
• header(), header_remove(), headers_list(), headers_sent()
• setcookie(), setrawcookie()
• gethostname(), etc

Manage HTTP in PHP

• PHP does not offer an object representation of HTTP request/response
• Unfortunately, It's quite hard to manage HTTP messages in PHP!

PHP-FIG

PHP FIG

• PHP Framework Interop Group (PHP FIG)
• A working group for defining common standards to interop between PHP frameworks/libraries
• PHP Standards Recommendations (PSR)
• More information at php-fig.org

PSR-7

Common interfaces for representing HTTP messages as described in RFC 7230 and RFC 7231, and URIs for use with HTTP messages as described in RFC 3986

PSR-7 interfaces

• github: psr/http-message
• Psr\Http\Message\MessageInterface
• Psr\Http\Message\RequestInterface
• Psr\Http\Message\ResponseInterface
• Psr\Http\Message\ServerRequestInterface
• Psr\Http\Message\StreamInterface
• Psr\Http\Message\UploadedFileInterface
• Psr\Http\Message\UriInterface

Example

// Returns an empty array if not found:
$header = $request->getHeader('Accept');
// Returns an empty string if not found:
$header = $request->getHeaderLine('Accept');
// Test for a header:
if (! $request->hasHeader('Accept')) {}
// Get query string parameters
$query = $request->getQueryParams();

Immutability

• PSR-7 Request and Response model immutability
• Messages are modeled as value objects; a change to any value results in a new instance
• PSR-7 Stream does not model immutability

zendframework/zend-diactoros implements PSR-7

Example

$response = $response->withStatus(418, "I'm a teapot");

$response = $response->withBody($body);

PSR-7 implementation

• guzzle/psr7
• zendframework/zend-diactoros
• slim/slim
• nyholm/psr7

Swoole

• Swoole is an async programming framework for PHP 7
• PHP extension, install:

  
  pecl install swoole
  

• Released under Apache license 2.0
• More info at swoole.co.uk

Features

• Event-driven, asynchronous programming for PHP
• Async TCP / UDP / HTTP / Websocket / HTTP2 client/server side API
• IPv4 / IPv6 / Unixsocket / TCP/ UDP and SSL / TLS support
• High performance and scalable
• Fast serializer / unserializer
• Milliseconds task scheduler

Swoole vs. PHP-FPM

• Forks a number of worker processes based on CPU core number
• Fupports Long-live connections
• Manage and reuse the status in memory
• Executes Non-blocking code (async, coroutine)

HTTP Server

use Swoole\Http\Server;

$http = new Server("127.0.0.1", 9501);

$http->on("start", function ($server) {
    echo "Started at http://127.0.0.1:9501\n";
});
$http->on("request", function ($request, $response) {
    $response->header("Content-Type", "text/plain");
    $response->end("Hello World\n");
});

$http->start();

Test: 16K req/sec on CPU i5-2500, 16 GB RAM, PHP 7.2.12, Swoole 4.2.9

Event loop

Middleware

Middleware

A function that gets a request and generates a response

function ($request)
{
    // do something with $request
    return $response;
}

Delegating middleware

function ($request, callable $delegate)
{
    // delegating $request to another middleware
    $response = $delegate($request);
    return $response;
}

Middleware onion

Execution pipeline

Example: cache

function ($request, callable $delegate) use ($cache)
{
    if ($cache->has($request)) {
        return $cache->get($request);
    }
    $response = $delegate($request);
    $cache->set($request, $response);
    return $response;
}

PSR-15

Common interfaces for HTTP server request handlers and HTTP server middleware components that use HTTP messages as described by PSR-7

PSR-15: Handler

namespace Psr\Http\Server;

use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\ServerRequestInterface;

interface RequestHandlerInterface
{
    public function handle(
        ServerRequestInterface $request
    ): ResponseInterface;
}

An handler returns a response, without delegate

PSR-15: Middleware

namespace Psr\Http\Server;

use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\ServerRequestInterface;

interface MiddlewareInterface
{
    public function process(
        ServerRequestInterface $request,
        RequestHandlerInterface $handler
    ): ResponseInterface;
}

A middleware participates in processing an HTTP message, it may deletegate.

Expressive

The PHP framework for middleware applications

• PSR-7 support (using zend-diactoros)
• PSR-15 support
• Piping workflow (using zend-stratigility)
• Features: routing, dependency injection, templating, error handling
• Last release 3.2.3, 5th Nov 2018
• Official website: getexpressive.org

Installation

You can install Expressive using composer:

composer create-project zendframework/zend-expressive-skeleton api

Routes

$app->get('/api/ping', function ($request) {
    return JsonResponse(['ack' => time()])
});

// or implement a RequestHandlerInterface
$app->get('/api/ping', App\Handler\PingHandler::class);

PingHandler

namespace App\Handler;

use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\ServerRequestInterface;
use Psr\Http\Server\RequestHandlerInterface;
use Zend\Diactoros\Response\JsonResponse;

class PingHandler implements RequestHandlerInterface
{
    public function handle(
        ServerRequestInterface $request
    ) : ResponseInterface {
        return new JsonResponse(['ack' => time()]);
    }
}

Pipeline

$app->pipe(ErrorHandler::class);
$app->pipe(ServerUrlMiddleware::class);
$app->pipe(RouteMiddleware::class);
$app->pipe(ImplicitHeadMiddleware::class);
$app->pipe(ImplicitOptionsMiddleware::class);
$app->pipe(MethodNotAllowedMiddleware::class);
$app->pipe(UrlHelperMiddleware::class);
$app->pipe(ProblemDetailsMiddleware::class);
$app->pipe(DispatchMiddleware::class);
$app->pipe(NotFoundHandler::class);

Route a REST API

$app->route('/api/users[/{id}]', [
    Authentication\AuthenticationMiddleware::class,
    Authorization\AuthorizationMiddleware::class,
    Api\Action\UserAction::class
], ['GET', 'POST', 'PATCH', 'DELETE'], 'api.users');

// or route each HTTP method
$app->get('/api/users[/{id}]', ..., 'api.users.get');
$app->post('/api/users', ..., 'api.users.post');
$app->patch('/api/users/{id}', ..., 'api.users.patch');
$app->delete('/api/users/{id}', ..., 'api.users.delete');

Tools for Web API

• HAL-JSON: zend-expressive-hal
• Problem details: zend-problem-details
• Filtering & validation: zend-inputfilter
• Authentication (HTTP Basic, OAuth2): zend-expressive-authentication
• Authorization (ACL, RBAC): zend-expressive-authorization

Expressive with Swoole

Install:

composer require zendframework/zend-expressive-swoole

Usage:

vendor/bin/zend-expressive-swoole start

Open your browser at localhost:8080

PHP + Expressive + Swoole

Run a web application from CLI

Simplify the deploy (only 1 container)

A web server (nginx) can be used as load balancer

Benchmark

2-4x faster than Nginx and Apache

Testing environment:
Ubuntu 18.04, Expressive Skeleton 3.2.3, PHP 7.2.12, Nginx 1.14 + FPM,
Apache 2.4.29 + mod_php, Swoole 4.2.9, CPU i5-2500, 16 GB RAM, HD SSD

Elasticsearch

• Elasticsearch is a highly scalable open-source full-text search and analytics engine
• Near Realtime (NRT)
• Designed for scale (horizontally)
• REST API
• Based on Lucene
• More information here

Elasticsearch & PHP

• elastic/elasticsearch-php
• Elastica

Example

use Elasticsearch\ClientBuilder;

$client = ClientBuilder::create()->build();
$params = [
    'index' => 'my_index',
    'type' => 'my_type',
    'id' => 'my_id',
    'body' => ['testField' => 'abc']
];
$response = $client->index($params);
print_r($response);

• Kibana is an open source data visualization plugin for Elasticsearch
• It provides visualization capabilities on top of the content indexed on an Elasticsearch cluster
• More information here

Hands-on

github.com/ezimuel/php-microservices-workshop

References

Thanks!

Contact me: enrico.zimuel [at] elastic.co

Follow me: @ezimuel

This work is licensed under a
Creative Commons Attribution-ShareAlike 3.0 Unported License.
I used reveal.js to make this presentation.