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Movies DB

Scala CI

The point of the exercise was to write an application with a REST-like API, OpenAPI documentation, JSON encoding and a database. I've decided to use these libraries:

  • Tapir (to easily generate OpenAPI docs)
  • Doobie (seems to be popular and is close to plain SQL, which is my preference)
  • Circe (seems to be popular, I thought it's worth to play with it)
  • SQLite (I wanted something very simple, H2 could be a good candidate as well)
  • Flyway (I don't know any good alternative, I haven't worked with Liquibase)

I've focused on writing an application with a good overall structure and getting to know the libraries I've chosen. Writing a useful app hasn't been my objective this time, so I've made some simplifications, like using SQLite or creating a simple, suboptimal the data model. The one I've created allowed me to create some interesing queries (actually quite common, but rather new to me in case of Doobie), like fetching master+detail and fetching data from different tables in one transaction.

How to build?

You can use sbt compile, but it's usually easier to work with a Fatjar or Docker.

Fatjar

sbt assembly Read the output carefully, it will show you where is the Fatjar (ie. the jar archive without external dependencies).

Docker

docker build -t moviesdb .

How to run?

Provide these env variables:

  • MOVIESDB_HOST - by default localhost
  • MOVIESDB_PORT - by default 8080
  • MOVIESDB_DBPATH - by default movies.db (pun intended, see the project name)
  • MOVIESDB_DBPOOLSIZE - by default 32 (I'm curious if SQLite can handle this gracefully...)

Invoke sbt run and go to http://localhost:8080/docs (or wherever it is in case you're using a nondefault configuration). If you've the fatjar, use java -jar /path/to/this/jar/archive.jar.

If you want to use a Docker container: docker run -d -v .:/var/db -p 8080:8080 moviesdb

Note that I bind current dir to /var/db and forward the port 8080 to 8080. Change these parameters if needed.

Lessons learned

  • how to create endpoints described with Tapir, involving autogenerated OpenAPI schemas
  • how to use Doobie in an application and its tests
  • how to write unit tests with in memory implementations, in an OOP/FP lang (I usually write in procedural langs, it's a different kettle of fish)
  • how to use Flyway in a Scala app (before I've used it only via Maven or CLI)
  • how to use Circe (not much to learn here, it just works when configured correctly)

Worth doing but it's out of scope

  • endpoints tests (at the moment there is just one to fix a bug I've found)
  • E2E tests (and maybe test service layer and repos together in UTs, they are mean't to be used together anyway; it would be less code to maintain),
  • load tests (to be sure that SQLite can handle that..., anyway it wouldn't by my choice for a proper app, ofc.)
  • better data model (especially Episodes and its lack of id...)
  • some validations
  • proper logging
  • proper configuration parser
  • separate DTO and domain (not necessary in such a simple app)
  • scalafmt (I'll learn to use one day)

Why out of scope? Well, I need to take a break from coding, sometimes :D I would pursue these points if it were a proper app (not just an exercise) or something I have no idea how to implement.

PS How to add a user?

Well... You can use the ones from V1.1__example_users.sql or insert another one somehow. That's it for now ¯_(ツ)_/¯