Scalatra MongoDB Seed

A seed for building microservices with Scalatra, MongoDB and Docker.

Project goals and assumptions:

• provide a project template based on technologies, that are easily accessible for most Java developers (e.g. Scalatra and Jetty).
• showcase selected features of Scala, sbt and Docker.

Development mode

For rapid development feedback use the sbt-revolver plugin:

sbt ~re-start

It will respawn the server process whenever a project file changes and a fresh build is required.

Docker deployment

This section provides a step-by-step guide for hosting the service in a virtual Docker environment, including a standalone MongoDB instance. Prerequisites:

1. Install Docker.
2. Install Docker Machine, if it isn't included in the Docker distribution (useful for managing multiple servers in your local environment).

Create virtual Docker servers

Create a virtual machine for each component of the system:

docker-machine create --driver virtualbox service1
docker-machine create --driver virtualbox mongo1

Setup MongoDB

You'll need a MongoDB instance and some sample data to get started. Make sure, that your Docker client is connecting to the Mongo server:

eval "$(docker-machine env mongo1)"

Spawn a new Mongo process:

docker run -d --restart=always --name mongo -p 27017:27017 mongo:latest    

You can test your connection from your development box by running:

mongo $(docker-machine ip mongo1)/test

Don't worry, if you don't have a Mongo client available locally. You can always launch it directly in the container:

docker exec -it mongo mongo test

Import sample data and create some custom indexes:

docker exec -i mongo mongoimport -d test -c locations --jsonArray < data/sample_locations.json
docker exec -i mongo mongo test < data/sample_location_indexes.js

Deploy an application image

Switch your Docker client to the target environment:

eval "$(docker-machine env service1)"

Build an image using the sbt-docker plugin:

sbt docker

You can verify the list of available images by running:

docker images

Run the image in a new Docker container as such:

docker run \
        --name=location-provider \
        -d --restart=always \
        -e MONGO_HOST=$(docker-machine ip mongo1) \
        -e MONGO_PORT=27017 \
        -e MONGO_DB=test \
        -p 8080:8080 \
        com.mintbeans/scalatra-mongodb-seed:v0.1-SNAPSHOT

The -d switch implies detaching the process from the current session. You can always follow the logs by executing:

docker logs -f location-provider

Check if everything works correctly by fetching the list of locations:

curl -v http://$(docker-machine ip service1):8080/locations

Swagger integration

Swagger should be integrated by default. Point Swagger UI to http://localhost:8080/api-docs/ to interact with all exposed methods and to find out their specs.

Links

• Working with Docker.