Microservices:
Packs small, plays BIG!

Stephan Hochdörfer // 24.01.2015

About me


  • Stephan Hochdörfer
  • Head of Technology, bitExpert AG
    (Mannheim, Germany)
  • S.Hochdoerfer@bitExpert.de
  • @shochdoerfer

  • #PHP, #DevOps, #Automation

The curse of the monolith

Intimidating "old" codebase

Small change, big impact

Long-term commitment

What about a rewrite?

The legacy truth



The LTS truth



The solution?




« [...] This is the Unix philosophy: Write
programs that do one thing and do it well. »
- Doug McIlroy

Programs need to cooperate




« [...] Write programs to work together. Write programs to
handle text streams, because that is a universal interface. »
- Doug McIlroy

What are Microservices?




« [...] approach to developing a single application as a suite of small services, each running in its own process and communicating with lightweight mechanisms. »
- James Lewis, Martin Fowler

Just SOA? Or better?



Small problem domain

Single Responsibility




« A class should have one, and
only one, reason to change. »
- Robert C. Martin

"Isolated process"

Docker



Microservices platform

Deployment Automation

Built and deployed in isolation

Owns its data storage

Simple communication layer

Smart endpoints, dumb pipes




« Be of the web, not behind the web. »
- Ian Robinson

Open/closed principle




« You should be able to extend a classes
behavior, without modifying it. »
- Robert C. Martin

Data structures evolution

{
  "id": 123,
  "name": "My Product",
  "categories": [{
    "id": 12,
    "name": "My category"
  }],
  "price": 12.34
  "currency": "EUR"
}

{
  "id": 123,
  "name": "My Product",
  "categories": [{
    "id": 12,
    "name": "My category"
  }],
  "price": [12.34, 14.26]
  "currency": ["EUR", "USD"]
}

Data structures evolution

{
  "id": 123,
  "name": "My Product",
  "categories": [{
    "id": 12,
    "name": "My category"
  }],
  "prices": [{
    "price": 12.34,
    "currency": "EUR"
  }, {
    "price": 14.26,
    "currency": "USD"    
  }]
}

You build it, you own it

Why Microservices?




« Microservices are organised around
business capabilities. » - Martin Fowler

The OODA loop

Team organization

Small Focused Teams

Empower developers

Pick the right tool for the job

Replace it if it does not work

Liskov substitution principle




« Derived classes must be substitutable
for their base classes. » - Robert C. Martin

Easy scaling

Increase development speed

...but choose a healthy pace!

Try out new ideas...

Microservices Challenges




« There ain’t no such thing as a free lunch. »
- Robert A. Heinlein

Small services win!



What does "small" mean?



Interface Segregation




« Make fine grained interfaces that
are client specific. » - Robert C. Martin

Standardise in between

Monitoring and Logging

Avoid distributed transactions

Avoid cascading failures

Design for failure

Release early, release often!

Automate all the things!

Dependency Inversion




« Depend on abstractions, not on concretions. »
- Robert C. Martin

Service Discovery


Service Discovery Example

{
  "require": {
    "sensiolabs/consul-php-sdk": "1.0.*@dev"
  }
}

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

$sf = new SensioLabs\Consul\ServiceFactory();
$kv = $sf->get('kv');

$kv->put('test/foo/bar', 'bazinga');
$kv->get('test/foo/bar', ['raw' => true]);
$kv->delete('test/foo/bar');

Document your APIs!

Microservice Example

Microservice Example

{
  "require": {
    "silex/silex": "~1.2@stable"
  }
}

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

$app = new Silex\Application(); 
$app->register(new MyApp\Service\SearchServiceProvider());

$app->get('/search/{term}', function($term) use($app) { 
    
    $result = $app['search']->search($term);
    return $app->json($result);
});

$app->run();

Composing your microservice

Microservice Example

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

$app = new Silex\Application(); 
$app->register(new MyApp\Service\SearchServiceProvider());

$app->get('/search/{term}', function($term) use($app) { 
    
    $result = $app['search']->search($term);
    return $app->json($result);
});

$app = new Alsar\Stack\IpRestrict($app, ['127.0.0.1']);

$app->run();







Thank you!







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