AWS Glue SBT Quickstart

This repo provides a quickstart for new AWS Glue projects using Scala. Using SBT and the AWS Glue SDK, this repo enables local development and unit testing of AWS Glue scripts.

Monorepo Pattern

AWS Glue restricts users to submitting a single file to execute a job. These files are then compiled by AWS during the initial stage of job execution (to ensure that they are compiled using the correct Spark version as the Spark executors it will be run on). This means that any generic or shared logic used by multiple scripts would have to be repeated in each file, which is against DRY principles. To correct this we can abstract any shared logic into a separate module, package it ourselves, and provide it as an internal dependency to our Glue scripts. To accomplish this we structure the quickstart as a monorepo containing two modules:

• shared - this contains abstracted shared logic for interfacing with the underlying Glue & Spark contexts, and any other functionality we may miss to shared cross multiple scripts (e.g. abstract base classes, traits, dataclasses, cleansers, readers, metrics, reporting, etc). This is made available as a compiled jar and provided to the Glue job via the --extra-jars parameter. The purpose of this jar is to simplify each script by abstracting complex code patterns into base classes and simple reusable functions.

• scripts - this contains individual Glue scripts, using elements from the shared library. This will be compiled by AWS Glue prior to execution.

Getting Started

1. Fork or clone the repo git clone git@github.com/jhole89/aws-glue-sbt-quickstart.git
2. In build.sbt update the projectName and organization
3. Run a full sanity check sbt sanity

You should now have a running quickstart which you can further develop for your needs. A typical pattern would be

1. Start writing your Glue scripts & tests
2. Abstract any shared functionality into the shared lib
3. Run a full sanity check sbt sanity
4. Upload your Glue scripts (located at scripts/src/main/scala/scripts/Script.scala) and shared library jar (located at shared/target/scala-*/*-assembly-*.jar) to AWS S3 buckets
5. Create a AWS Glue Job which points to the script, set the main class using the parameter --class scripts.Script, set the shared dependency using the parameter --extra-jars <your_jar_name>.jar

sbt sanity? Thats not a command!

sbt sanity is simply an alias used to bind multiple stages of building together. So instead of having to run sbt compile, sbt test, sbt scalafmtAll, sbt scalastyle, and sbt assembly separately, we can just run sbt sanity to call each of these sequentially. It's definition is in the build.sbt via addCommandAlias("sanity", ";clean ;compile ;test ;scalafmtAll ;scalastyle ;assembly").

Extending

Maybe this simple structure doesn't suit all your needs. Maybe you need another module within the monorepo for something else, or maybe you need multiple shared libs for different business logic? This is fine and easily done within this framework. If you need other modules, simply declare them in the build.sbt as was done for the shared, and copy over the relevant settings and options. Remember to link your dependencies together using the .dependsOn syntax.