AWS Lambda Scala Hello World

The smallest example of using Scala with AWS Lambda.

For other examples of using AWS Lambda, see the following branches:

• logging
• sns
• github-sns

Create a build.sbt with the following:

scalaVersion  := "2.12.1"

libraryDependencies ++= Seq(
  "com.amazonaws" % "aws-lambda-java-core" % "1.1.0"
)

Create source file, Main.scala, that writes to standard out, and returns a result.

package example

import scala.collection.JavaConverters._

object Main extends LambdaApp  {

  def handler()  = {

    println("Hello Cloudwatch")

    List("Hello Lambda").toSeq.asJava
  }
}

The LambdaApp trait is defined to enforce the type signature for AWS Lambda functions. It can also help with testing the function locally.

> run
[info] Running example.Main
START RequestId: 82c9bda8-a14e-4436-8805-f6a15f2aa238 Version: $LATEST
Hello Cloudwatch
END RequestId: 82c9bda8-a14e-4436-8805-f6a15f2aa238
REPORT RequestId: 82c9bda8-a14e-4436-8805-f6a15f2aa238  Duration: 133.473084 ms  Memory Size: 119 MB  Max Memory Used: 23 MB
[
  "Hello Lambda"
]

To run on AWS, run the task provided by SBT Assembly,

> assembly
[info] Including: aws-lambda-java-core-1.1.0.jar
[info] Including: scala-library-2.12.1.jar
[info] Checking every *.class/*.jar file's SHA-1.
[info] Merging files...
[info] SHA-1: 169142dab8b01e507e8e312a95b335a21cae9c8f
[info] Packaging target/scala-2.12.1/aws-lambda-scala-hello-world-assembly-0.1-SNAPSHOT.jar ...
[info] Done packaging.

Uploading to AWS Lambda

1. From the AWS console, click on "Configure function" from the Lambda service.

2. For name, give "ScalaHelloWorld". Leave the description blank.

3. Choose "Java 8" as the runtime.

4. Upload the JAR file created by SBT assembly at target/scala-x.y.z/package-0.1-SNAPSHOT.jar.

5. Enter the handler as, example.Main::handler

6. Choose "Create new role from template(s)".

7. Enter "LambdaTestRole" as the role name.

8. Leave "Policy templates" blank.

9. Reduce the memory to 128 MB, and leave the timeout at 15 seconds.

10. Keep the setting for VPC to none.

11. Click "Next".

12. Click "Create function"

13. Click "Test"

References

• https://aws.amazon.com/blogs/compute/writing-aws-lambda-functions-in-scala/