Groovy with Dropwizard

for high performance and reliable web

services

Tomas Lin @tomaslin

!

• Quick tour of Dropwizard functionality written with Groovy & friends instead of pure Java.

• Showcase some of the “DevOps” friendly features in Dropwizard for easy setup, deployment and monitoring.

Goals for this talk

This is not a talk about REST Services

• Everything I tell you about REST will probably be a lie.

• Think JSON services over http.

REST Services

https://github.com/nebhale/spring-one-2013/tree/master/rest-ful-api-design

http://www.slideshare.net/stormpath/rest-jsonapisBeautiful REST + JSON APIs - Les Hazlewood

REST-ful API Design - Ben Hale

whoami• Senior Software Engineer at Netflix

• Grails developer since 2008

What is Dropwizard?

http://gunshowcomic.com/316

http://www.dropwizard.io

Dropwizard stack• Takes mature, well known Java frameworks

and glues them together.

• Jetty for HTTP

• Jersey for REST

• Jackson for JSON

• Metrics for metrics

• Etc. ( Logback, Hibernate, Liquibase, etc )

Additional Integrations• Scala

• Views ( Freemaker / Mustache )

• Liquibase migrations

• Authentication ( http and oAuth2 )

• Dropwizard Spring - https://github.com/SindicatoSource/dropwizard-spring

Who uses Dropwizard?

Carl Quinn : Dropwizard + Netflix OSS tools http://tekconf.com/conferences/codemash-2014/how-we-built-a-cloud-platform-at-riot-games-u

Fault Tolerant Job Scheduler https://github.com/airbnb/chronos

Fraud Detection & Gift Card Services

Dropwizard + Groovy?

• Bloom Health - Insurance carriers data exchange. Spring Batch, Dropwizard and Groovy. (25x faster than previous system)

• Sky Find and Watch - Powers the remote record / watch now functionality

• UnderwriteMe - Watch Marcin’s talk! http://skillsmatter.com/podcast/home/modern-groovy-enterprise-stack

• Editorial Expansion - Time inc. subsidiary in Mexico Gourmet Awards iPhone app backend.

Dropwizard + Groovy?

Why should I try Dropwizard?

Enable Service Oriented Architecture

Advantages• Scale up only some parts of your

application.

• Isolate services based depending on their security profiles.

• Fault tolerance.

• Cloud friendly!

vs.—-

+

vs.—-

+

Dropwizard with Grails at Sky Find and Watch

Performance

http://www.techempower.com/benchmarks/

Dropwizard is a very high performance, low latency framework.

Other niceties• Testable. Every part of the system can be

tested during development.

• Deployment friendly - easy to configure, deploy and monitor.

• Pure Java.

Getting Started with Dropwizard

and Groovy

Lazybones Starter Template

• By Kyle Boon from Bloom Health

• Available via Lazybones template tool by Peter Ledbrook

• You can get Lazybones via gvm

Lazybones Starter Template

• Gradle build

• Spock tests

• Hibernate persistance layer

• Fat Jars via Shadow ( like Maven’s Shade )

• CodeNarc for clean code

• Cobertura for test coverage

Tasks• Test the application ./gradlew test

• Build a Jar file for deploy ./gradlew shadow

• Drop a database ./gradlew dropAll

• Setup database ./gradlew migrate

• You can add your own like deployToCloud

Parts of a Dropwizard Application

Banner

src/main/resources/banner.txt

Services• Like an Application in Grails

• Central place where all the other building blocks are connected.

Services• The Dropwizard approach to services lets

us see one place where all our other components are bound and glued together.

• Relationships between other parts must be explicitly declared. There is no magic linking.

Configurations • Each service has a configuration that is

passed into the run method.

• Dropwizard has default configurations for clients, logging and Jetty that can be overwritten

ConfigurationsSame jar file, configuration is externalized.

!

java -jar application.jar server test.yml java -jar application.jar server stage.yml java -jar application.jar server prod.yml

gradleplugins/src/main/groovy/com/tomaslin/gradleplugins/ GradlePluginsConfiguration.groovy

Configurations

Configurations

Configurations

Configurations add to .yml file

Configuration• Mapped by Jackson. Uses Hibernate Validator.

• @Max / @Min

• @NotNull

• @Size(min=0, max=50)

• @Pattern(regex=, flag=)

• @Future / @Past

• @NotEmpty

• @CreditCardNumber

http://docs.jboss.org/hibernate/validator/4.2/reference/en-US/html_single/#validator-defineconstraints-builtin

Nesting Configurations

vs. Java version

Configurations • Configurations are vital because they allow

us to make sure we got all the details for our service right.

• One config file instead of merged conflict from many sources eliminates confusion and makes it easy to automate / swap out.

Resources • Represent a set of service endpoints

• Like Controllers in Grails

• They are just Jersey Resources: https://jersey.java.net/nonav/documentation/latest/user-guide.html#jaxrs-resources

Resource

Resources• @GET, @POST, @PUT, @DELETE,

@HEAD, @OPTIONS, and even @HttpMethod

• @Path("/{user}/notifications") @PathParam("user") LongParam userId, @QueryParam("count") @DefaultValue("20") IntParam count

Resources

Resources• Tested not as Unit mocks, but as Jersey

components with a real Jersey server.

• Similar to the FakeServer in Grails Rest Client

• Dropwizard comes with a ResourceTest that works with Mockito / JUnit

• I wrote a Spock equivalent available at http://fbflex.wordpress.com/2013/01/30/dropwizard-with-spock-and-groov/

Resources

In your IDE

Representations • Lets you formally describe the data flowing

in and out of your REST API.

• Data Transfer Objects that can be validated.

• It gives you a way to easily map them into your database objects either directly or via a DAO.

• Recommended approach is to share representations between servers and clients.

Representations• The use of representations ensure the

contract between our REST endpoints and clients that consume this endpoint.

• You could also just skip this and go straight to your other endpoints or JSON friendly database.

Caching

Metrics• Uses Coda Hale’s own Metrics Library

• Integrates with JMX, http, Ganglia and Graphite

Metrics@Timed - duration and rate of events @Metered - rate of events @ExceptionMetered - rate of exceptions

Metrics

Kim Betti Dropwizard

Dashboard with Vert.x

https://github.com/kimble/

dropwizard-dashboard

Metrics• They are first class citizens within

Dropwizard.

• Very flexible. You can define custom metrics, set Gauges, etc.

• It’s about communicating the actual state of your server back to the mothership so it can be coordinated.

Logging• Dropwizard has a pretty robust default

logging configuration.

Logging• We can use the @Slf4j annotation in Groovy

Logging

Logging• I am lazy.

• Don’t realize logs are needed until it is too late.

• Logs are time machines to past malfunctions, making them easy to set up allows us to use them.

Client Support

• Dropwizard has available both the Apache HttpClient and the Jersey Client.

• Jersey Client can use same deserialization available to the server

We can now use the client within the Resource to fetch http data from other sources

Clients• Returns a fully wrapped object that emits

metrics. This allows us to monitor how they are used and identify bottlenecks or bugs.

Managed Objects• Classes that have a start and end phase

attached to the service.

• Often have their own configurations.

• Easy way to encapsulate integrations into other services / systems.

Health Checks• Runtime checks that the service is

operating correctly

• If an exception is thrown, this is shown on the health monitoring screen

• Also throws a 500 error code on the health check page for tools

Health Checks• Quick diagnostics on running instance.

• Better to kill a sick service than to keep it running and potentially corrupting your data.

• Also helps when you are deploying and building out your infrastructure.

Other Features• Tasks - Like Grails Scripts

• Commands - Jobs that can be invoked via an URL. Lots of power since you’re using the same stack as your runtime service.

• Others - Filters, Bundles, etc.

http://www.dropwizard.io/manual/

Deployment

Make Jars, not Wars

One jar file from CI to deploy

Deploying Dropwizard java $JAVA_OPTS -Ddw.http.port=$PORT

-Ddw.http.adminPort=$PORT -jar application.jar server prod.yml

Grails Equivalents• Dropwizard Plugin by Burt Beckwith

http://grails.org/plugin/dropwizard

• Health Control Plugin by Kim Betti http://grails.org/plugin/health-control

• Validate Config Plugin by Andy Miller http://grails.org/plugin/validate-config

• Metrics Plugin by Jeff Ellishttp://grails.org/plugin/yammer-metrics

Using Groovy• Less verbose objects. Can use map

constructors.

• Nice annotations for logging.

• Gradle / Spock / Betamax / Lazybones.

• Not sure if @CompileStatic has any changes that are significant - 6%[ http://kyleboon.org/blog/2013/09/26/does-compile-static-make-your-website-faster/ ]

Development• A lot faster since there is very little magic

and user interface to test.

• Excellent support in IntelliJ for Gradle project and tasks.

Final Thoughts• Think about the deployed application.

• Grails + Dropwizard. Not Grails or Dropwizard.

• This is just mini-scale. What happens when you have 100 services/servers? 1,000? 1,000,000? ( Come work at Netflix! )

Thank you

• Email : tomaslin@gmail.com

• Twitter : @tomaslin

• Slides will be posted on my blog:

• http://bit.ly/tomaslin