Microservices: Packs small, plays BIG!

Microservices:
Packs small, plays BIG!

Stephan Hochdörfer // 24.06.2016

About me

Stephan Hochdörfer
Head of Technology, bitExpert AG
(Mannheim, Germany)
S.Hochdoerfer@bitExpert.de
@shochdoerfer
#PHP, #DevOps, #Automation
#phpugffm, #phpugmrn, #unKonf

The curse of the monolith

Intimidating "old" codebase

Small change, big impact

Long-term commitment

What about a rewrite?

The legacy truth

« Legacy code is a business asset that helped
the business get where it is. Treat it with respect. »
- @ylarrivee

The LTS truth

« good long term software is not commonly about reuse,
its about the ability to rewrite completely isolated bits
without hitting the big bang » - @gregyoung

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?

« I guess it is easier to use a new name (Microservices)
rather than say that this is what SOA actually meant [...] »
- @arnonrgo

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...

Segmented feature toggles

Microservices Challenges

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

Not easy!

« If you can’t build a monolith, what makes you think
microservices are the answer? » - Simon Brown

Small services win!

« Small teams typically work better than big teams.
Small services typically work better than monoliths.
#microservices #microservice » - @microsvcs

What does "small" mean?

« @olivergierke Micro Services are neither
micro nor service. :-) » - @ewolff

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

« @olivergierke No. I meant to says that REST is not the
most difficult problem for Microservices. E.g. resilience
is probably harder. » - @ewolff

Resilience

Release early, release often!

Automate all the things!

Dependency Inversion

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

Service Discovery

Service Discovery Example

$> composer.phar require sensiolabs/consul-php-sdk

<?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

$> composer.phar require zendframework/zend-diactoros
$> composer.phar require zendframework/zend-stratigility

use Zend\Stratigility\MiddlewarePipe;
use Zend\Stratigility\MiddlewareInterface;
use Psr\Http\Message\ServerRequestInterface as Request;
use Psr\Http\Message\ResponseInterface as Response;
use Zend\Diactoros\Response\JsonResponse;

class SearchMiddleware implements MiddlewareInterface
{
    public function __invoke(Request $request, Response $response,
        callable $next = null)
    {
        $params = $request->getQueryParams();
        $service = new SearchService();
        return new JsonResponse($service->search($params['search']));
    }
}

Microservice Example

use Zend\Stratigility\MiddlewarePipe;
use Zend\Diactoros\ServerRequestFactory;
use Zend\Diactoros\Response;

$api = new MiddlewarePipe();
$api->pipe(new SearchMiddleware());
$response = $api(ServerRequestFactory::fromGlobals(), new Response());

Extending your Microservice

$> composer.phar require oscarotero/psr7-middlewares

use Zend\Stratigility\MiddlewarePipe;
use Zend\Diactoros\ServerRequestFactory;
use Zend\Diactoros\Response;
use Psr7Middlewares\Middleware\Firewall;

$api = new MiddlewarePipe();
$api->pipe(new Firewall(['127.0.0.1']));
$api->pipe(new SearchMiddleware());
$response = $api(ServerRequestFactory::fromGlobals(), new Response());

Thank you! Questions?

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