Configure Micronaut for

The end goal of this guide is to deploy your Micronaut application to a project on In many ways, a project is just a collection of tools around a Git repository. A project replicates the branching structure of a repository exactly, but with one important addition: any branch can be activated to become an environment on Activated environments go through's build and deploy phases, resulting in a fully isolated running site for each activated branch (or pull request) on that repo.

Once an environment is activated, will provision a cluster of containers to deploy your application, and the configuration of that cluster is controlled by three YAML files:

  • .platform/routes.yaml controls how incoming requests are routed to your application, or applications if running a multi-app setup. It also controls the built-in HTTP cache.
  • .platform/services.yaml controls what additional services are created to support your application, such as databases or search servers. Every environment has its own independent copy of every service.
  • controls the configuration of the container where your application lives. It is the most powerful with the most options, and therefore can also get somewhat long depending on your configuration.

Each project on needs at least these three files, and each can be customized however you need. However, most Micronaut sites will have a fairly similar configuration, at least to start. More details of each are available below.

You can start by creating empty versions of each of these files in your repository:

# Create empty configuration files
$ touch && mkdir -p .platform && touch .platform/routes.yaml && touch .platform/services.yaml

Now that you've added these files to your project, you can go through and configure each of them for Micronaut one by one in the sections below. Each section covers a particular configuration file, defines what each attribute configures, and then shows a final code snippet that includes the recommended configuration for Micronaut pulled from its template. Within that snippet, be sure to read each of the comments as they provide additional information and reasoning for why Micronaut requires those values.

Requests configuration: routes.yaml 

The routes.yaml file controls the routing and caching of all HTTP requests sent to your application cluster. Typically you will just route all incoming requests to your one application container, where your site lives, but many more elaborate configurations are possible.

The two most important parts to configure are the main route itself and its caching rules. A route can have a placeholder of {default}, which will be replaced with a branch-specific generated domain name or, in production, with your configured domain name.

The route then has an upstream, which is the name of the container that it should forward requests to. 99% of the time you want the name property in the file.

You can (and should) enable the HTTP cache. The router includes a basic HTTP cache that will obey the HTTP cache headers produced by your application. However, by default HTTP caches will include all cookies in the cache key, which if you have any cookies at all makes the site uncacheable. Instead, the cookies key allows you to select which cookies should matter for the cache; generally that will be just the user session cookie, which for Micronaut is included below. However, depending on what additional modules you have installed there may be other cookies you need to add.

Finally, routes can also be HTTP redirects, either fully or partially. In this example, all www.{default} requests will be redirected to the equivalent non-www URL. You could also configure it the other way around if desired. More complex redirects are also possible.

Don't worry about unencrypted HTTP routes. All requests on are TLS-enabled, and we automatically redirect HTTP requests to HTTPS.

# The routes of the project.
# Each route describes how an incoming URL is going
# to be processed by

  type: upstream
  upstream: "app:http"

  type: redirect
  to: "https://{default}/"

Service configuration: services.yaml 

The services.yaml file lists the pre-packaged services you need for your application to run. You pick the major version of the service, and updates the patch version periodically so that you always get the newest version when you deploy.

Deploying Micronaut does not in itself require you to configure a database or another service, but in all likelihood you will want to add one at some point. Below is the example configuration for adding a MariaDB (named db) and Redis (named cache) container to your cluster.

# The services of the project.
# Each service listed will be deployed
# to power your project.

    type: mariadb:10.4
    disk: 2048

    type: redis:6.0

You can add other services if desired, such as Solr or Elasticsearch. You will need to configure Micronaut to use those services as well once the service is enabled.

Each service entry has a name (db and cache in the example below), as well as a type that specifies the service and version to use. Note that not all services support clean version upgrades, and none support downgrades. If you want to try upgrading a service, confirm on its service page that it’s supported and test on a branch before pushing to your master branch.

If a service stores persistent data then it will also have a disk key, which specifies the amount of storage to give it, in MB.

Application container: 

The file is the heart of your application. It has an extensive set of options that allow you to configure nearly any aspect of your application. Most of it is explained with comments inline. You can and likely will evolve this file over time as you build out your site.

Explaining the file line by line, notice the following settings:

  1. name: The application name
  2. type where you’ll define the language, in this case, Java, and the version.
  3. disk: the disk space that the application needs in megabytes.
  4. the command to package the application
  5. web.commands: The order to start the application, where the port is overwritten using the PORT environment variable provided by to the application container.

# This file describes an application. You can have multiple applications
# in the same project.
# See

# The name of this app. Must be unique within a project.
name: app

# The runtime the application uses.
type: "java:11"

disk: 1024

# The hooks executed at various points in the lifecycle of the application.
    build: mvn clean package

# The relationships of the application with services or other applications.
# The left-hand side is the name of the relationship as it will be exposed
# to the application in the PLATFORM_RELATIONSHIPS variable. The right-hand
# side is in the form `<service name>:<endpoint name>`.
#    database: "db:mysql"

# The configuration of app when it is exposed to the web.
        start: java -Xmx$(jq .info.limits.memory /run/config.json)m -XX:+ExitOnOutOfMemoryError -jar target/micronaut-1.0-SNAPSHOT.jar