Dropwizard Heroku Support

Using Dropwizard on Heroku? This module takes care of some common cases automatically.

Installing

All modules are hosted on Bintray's JCenter repository.

To add to Maven:

<repositories>
    <!-- ... -->
    <repository>
        <id>jcenter</id>
        <url>https://jcenter.bintray.com/</url>
    </repository>
</repository>

To add to Gradle:

repositories {
    jcenter()
}

You can also download the JARs by hand from Bintray, but you'll need Dropwizard and its dependencies, too. Really, use a dependency manager. You'll be happier.

Easy Mode

The dropwizard-heroku-config module provides a configuration base class that automatically applies the Logging and HTTP configurations below, without requiring any additional config file entries.

To use, add com.loginbox.heroku:dropwizard-heroku-config:+ to your dependencies, then subclass com.loginbox.heroku.config.HerokuConfiguration in your application config:

import com.loginbox.heroku.config.HerokuConfiguration;

public class ExampleConfiguration extends HerokuConfiguration {
    /* your configuration fields here */
}

If you prefer more control, read on…

PostgreSQL Databases

The dropwizard-heroku-db module provides automatic detection of databases configured using Heroku's PostgreSQL add-ons.

To use, add com.loginbox.heroku:dropwizard-heroku-db:+ to your dependencies, then add a com.loginbox.heroku.db.HerokuDataSourceFactory to your application config class:

import io.dropwizard.Configuration;
import com.loginbox.heroku.db.HerokuDataSourceFactory;

public class ExampleConfiguration extends Configuration {
    @NotNull
    @Valid
    private HerokuDataSourceFactory dataSourceFactory = new HerokuDataSourceFactory();

    @JsonProperty("database")
    public HerokuDataSourceFactory getDataSourceFactory() {
        return dataSourceFactory;
    }
}

The resulting configuration can be used with Dropwizard's usual database access layers.

Logging

Heroku expects applications to log to standard output, and provides its own log handling to add things like source attribution and timestamps. The default Dropwizard logging is a bit overzealous, and adds a lot of the same information. The dropwizard-heroku-logging module provides a more Heroku-appropriate behaviour.

To use, add com.loginbox.heroku:dropwizard-heroku-logging:+ to your dependencies, then add

logging:
    appenders:
        - type: heroku

to your Dropwizard application config.

Logs using the Heroku appender will include the severity, logger name, message, and (for exceptions) the exception and stack trace. For example:

INFO  org.eclipse.jetty.server.Server: Started @2775ms

In combination with Heroku's own log decorations, this becomes

2015-03-20T02:22:14.921851+00:00 app[web.1]: INFO  org.eclipse.jetty.server.Server: Started @4471ms

Note that Heroku occasionally reorders log messages, which can mangle multi-line messages such as stack traces. It will also interleave logs from multiple dynos.

HTTP

Heroku passes HTTP configuration to your app via the PORT environment variable. Dropwizard, normally, expects the HTTP port to be set via a config file, or using an awkward -Ddw.… system property. The dropwizard-heroku-http module automates the process, providing some sane defaults.

To use, add com.loginbox.heroku:dropwizard-heroku-http:+ to your dependencies, then add

server:
    - type: heroku

The heroku server factory is a subclass of Dropwizard's own [SimpleServerFactory](http://dropwizard.github.io/dropwizard/0.8.0/dropwizard-co re/apidocs/io/dropwizard/server/SimpleServerFactory.html), and behaves much the same way. Both the application context (at /) and the admin context (at /!/admin/) are served on the same listener. The port automatically defaults to $PORT, if set, or to 5000 otherwise.