Building a Microservice Federation with Grails (and Spring Cloud)

Grails... microservices...

you must be crazy man!

About Me

1st Career

About Me

2nd Career

OCI Grails Team

The Story I'm About to Tell You is True

Microservices are here
Doing it the easy way
Building a small microservice federation

Microservices are here

Foundational concepts
Microservice advantages
Microservice disadvantages

What are microservices?

Microservices are small, autonomous services that work together.

Sam Newman Building Microservices, O'Reilly Media

Small is key

Small in functional scope...

http://www.whattofix.com/images/ComplexERDExample.gif

Probably not small functional scope...

... not necesarily size

Smaller is simpler

Everything should be made as simple as possible, but not simpler*

* though attributed to Einstein, this simple quote is actually from
Roger Sessions paraphrasing (and simplifying!) a statement by Albert Einstein

Simpler is better

A system that is hard to understand is hard to change.

— Eric Evans, Domain-Driven Design

Autonomy is key

Development autonomy*

Caveat: You* can't break my stuff

http://www.memes.com/meme/498049

Consumer Driven Contracts

http://bit.ly/thoughtworks-consumer-driven-contracts

Testing: How much & what kind?

http://famouswonders.com/wp-content/gallery/pyramids-of-egypt/pyramid-of-khafre.jpg

Data Autonomy

http://martinfowler.com/articles/microservices.html

Build/Deploy autonomy

http://www.openmakesoftware.com/images/ReleaseEngineer/CI-CD.png

Scale where the load is...

Operational Autonomy

https://media.licdn.com/mpr/mpr/p/8/005/083/1a8/257d716.jpg

All this sounds great, but...

...what about our monolith?

Identify bounded contexts...

... and divide along the seams

Favor choreography over orchestration

http://kennysilva.net/wp-content/uploads/2010/12/orchestra-conductor.jpg

Monolith

Microservice

class Passenger {
   String        accountNo
   String        firstName
   String        lastName
   Address       billingAddress
   Payment       paymentPreference
   List<Payment> paymentHistory
   Phone         home
   Phone         mobile
   Phone         work
   BloodType     bloodType
   ...
}

What about shared domain?

// For Trip Management
class Passenger {
   String accountNo
   String firstName
   String lastName
   Phone  mobile
   ...
}

// For Billing
class Passenger {
   String        accountNo
   String        firstName
   String        lastName
   Address       billingAddress
   List<Payment> paymentHistory
   Phone         home
   Phone         work
   ...
}

The evils of too much coupling between services are far worse than the problems caused by code duplication.

- Sam Newman, Building Microservices

Microservices Federation Cross-cutting Concerns

Logging
Security
Metrics and monitoring

Logging Tips

Use a Correlation ID
Use a consistent log message format
Use log aggregation

Logging Aggregators

"ELK Stack"

Security

None
At the gateway only
At every microservice

Security at the gateway only

"They're inside the room!"

"Yikes!"

"Mmm, you look tasty."

Perimeter security reminds me of the movie, Aliens

Security at every microservice

Metrics, Monitoring & More

Microservices need to report metrics
Resiliency requires monitoring & circuit breakers
Automatic service discovery
Gateway / reverse proxy
Load balancing

Coming up:

Spring Boot & Spring Cloud to the rescue!

Microservice Architecture Advantages

Scalable
Adaptable
Resilient
Testable
More future-proof
More greenfield

Managers: Developers more likely to join and stay where they can work on new stuff

Microservice Architecture Disadvantages

Solid domain understanding
Development more complicated
More builds
More databases
Log aggregation is essential
Metrics, monitoring & more essential

Doing it the easy way

Spring Boot
Spring Cloud with Netflix OSS
Grails

Spring Boot includes metrics endpoint

There are many metrics out of the box, but you can create your own.

http://docs.spring.io/spring-boot/docs/current/reference/html/production-ready-endpoints.html

Spring Boot includes many endpoints

http://docs.spring.io/spring-boot/docs/current/reference/html/production-ready-endpoints.html

Spring Cloud provides monitoring
... and much more

Service discovery with Eureka

Gateway /Rev Proxy with Zuul

http://bit.ly/vignette2_wikia_nocookie_net_ghostbusters

Gateway /Rev Proxy with Zuul

Hystrix for Resilience

Monitoring & Circuit Breakers w/ Hystrix

http://martinfowler.com/bliki/CircuitBreaker.html

Grails plays well

Grails full stack development
Grails REST
Grails plugin architecture

Full stack != monolith

Grails full stack development

Web UI, SQL / NOSQL Database Support, Spring, Hibernate, Security, REST, Java, Groovy...

Create App

$grails create-app HelloWorld

Hello World app... easy as 1 - 2 - 3

grails> create-controller demo.Hello

package demo

class HelloController {

    def index() { 
        render 'Hello SpringOne2GX 2015!'
    }
}

Full stack CRUD apps are about as easy...

1. Create controller

2. Make it do something

3. See it to believe it!

Create a Domain Class

Define demo.Person

package demo

class Person {
    String firstName
    String lastName
    String email
    String twitterHandle

    static constraints = {
        firstName blank:false, maxSize: 32
        lastName blank: false, maxSize: 64
        email blank: false, maxSize: 128, email:true
        twitterHandle nullable:true, maxSize:64
    }
}

Generate Scaffolding...

.. to bootstrap CRUD app

After generation

Run App

grails> run-app

Retrieve Persons List

Create Person form

Create a Person record

Show a Person record

Retrieve Persons List

Delete a Person record

Grails REST URI patterns

What if I want to do more than CRUD?

package demo

import grails.rest.RestfulController

class PersonController extends RestfulController<Person> {
    static responseFormats =['json', 'xml']

    PersonController() {
        super(Person)
    }

    def findPersonsWithLastNameLike(String likeness) {
        respond Person.findByLastNameLike("${likeness}%")
    }
}

class UrlMappings {

    static mappings = {
        "/persons"(resources:'person')

        "/persons/search/withLastNameLike/$likeness"(controller: 'person', 
                                                     action: 'findPersonsWithLastNameLike')
    }
}

Restfully create a Person...

... yields a 201 created response

Test Rest

$ curl -i -X GET http://localhost:8080/persons.xml

HTTP/1.1 200 OK
Server: Apache-Coyote/1.1
X-Application-Context: application:development
Content-Type: text/xml;charset=UTF-8
Transfer-Encoding: chunked
Date: Mon, 07 Sep 2015 21:26:16 GMT

<?xml version="1.0" encoding="UTF-8"?><list />

$

200 OK good ... XML weird, but you wanted weird

Test Rest

$ curl -i -X GET http://localhost:8080/persons

HTTP/1.1 200 OK
Server: Apache-Coyote/1.1
X-Application-Context: application:development
Content-Type: text/xml;charset=UTF-8
Transfer-Encoding: chunked
Date: Mon, 07 Sep 2015 21:26:16 GMT

[]

$

200 OK good ... JSON good.

Change @Resource to prefer JSON

package demo

import grails.rest.Resource

@Resource(uri='/persons', formats=['json', 'xml'])
class Person {
    String firstName
    String lastName
    String email
    String twitterHandle

    static constraints = {
        firstName blank:false, maxSize: 32
        lastName blank: false, maxSize: 64
        email blank: false, maxSize: 128, email:true
        twitterHandle nullable:true, maxSize:64
    }
}

Grails content negotiation

$ curl -i -X GET --header "Accept:application/json" http://localhost:8080/persons

HTTP/1.1 200 OK
Server: Apache-Coyote/1.1
X-Application-Context: application:development
Content-Type: text/xml;charset=UTF-8
Transfer-Encoding: chunked
Date: Mon, 07 Sep 2015 21:26:16 GMT

[]

$

200 OK good ... JSON good.

Grails content negotiation

$ curl -i -X GET http://localhost:8080/persons.json

HTTP/1.1 200 OK
Server: Apache-Coyote/1.1
X-Application-Context: application:development
Content-Type: text/xml;charset=UTF-8
Transfer-Encoding: chunked
Date: Mon, 07 Sep 2015 21:26:16 GMT

[]

$

200 OK good ... JSON good.

Besides UI CRUD, what about REST?

package demo

import grails.rest.Resource

@Resource(uri='/persons')
class Person {
    String firstName
    String lastName
    String email
    String twitterHandle

    static constraints = {
        firstName blank:false, maxSize: 32
        lastName blank: false, maxSize: 64
        email blank: false, maxSize: 128, email:true
        twitterHandle nullable:true, maxSize:64
    }
}

grails create-app RestfulCrud

With an IDE...

Test Rest

$ curl -i -X GET http://localhost:8080/persons

[jfrosch@localhost demo]$ HTTP/1.1 200 OK
Server: Apache-Coyote/1.1
X-Application-Context: application:development
Content-Type: text/xml;charset=UTF-8
Transfer-Encoding: chunked
Date: Mon, 07 Sep 2015 21:26:16 GMT

<?xml version="1.0" encoding="UTF-8"?><list />

$

Hmm... 200 OK good ... XML bad.