AWS Lambda and SNS notifications with Scala

The smallest example of using Scala with AWS Lambda and Simple Notification Service (SNS)

Create a build.sbt with the following:

scalaVersion  := "2.11.8"

libraryDependencies ++= Seq(
  "com.amazonaws" % "aws-lambda-java-core" % "1.1.0",
  "com.amazonaws" % "aws-lambda-java-events" % "1.3.0",
  "io.code-check" %% "github-api" % "0.2.0-SNAPSHOT",
  "org.json4s"    %% "json4s-native" % "3.4.0"
)

Create source file, Main.scala, that processes an SNSEvent, extracts a GitHub event, and returns a list of the .

package example

import com.amazonaws.services.lambda.runtime.events.SNSEvent

import scala.collection.JavaConverters._

import codecheck.github.events.GitHubEvent

import com.amazonaws.services.lambda.runtime.events.SNSEvent

import org.json4s._
import org.json4s.native.JsonMethods._

object Main extends LambdaApp  {

  def handler(e: SNSEvent)  = {

    val rs = for {
      r <- safeList(e.getRecords)
      (key, attribute) <- r.getSNS.getMessageAttributes.asScala
      if key == "X-GitHub-Event"
    } yield {
      GitHubEvent(attribute.getValue, parse(r.getSNS.getMessage))
    }

    rs.map(_.name).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: dc8beb69-1858-41f0-884c-9058930ea98f Version: $LATEST
END RequestId: dc8beb69-1858-41f0-884c-9058930ea98f
REPORT RequestId: dc8beb69-1858-41f0-884c-9058930ea98f  Duration: 209.349397 ms  Memory Size: 2047 MB  Max Memory Used: 518 MB
[
  "pull_request"
]
[success] Total time: 2 s, completed Oct 16, 2016 10:20:10 PM

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

> assembly
[info] Including: json4s-jackson_2.11-3.3.0.jar
[info] Including: joda-convert-1.7.jar
[info] Including from cache: httpcore-4.4.4.jar
[info] Including from cache: commons-codec-1.9.jar
[info] Including from cache: jackson-dataformat-cbor-2.5.3.jar
[info] Including from cache: aws-java-sdk-sns-1.11.0.jar
[info] Including: paranamer-2.8.jar
[info] Including from cache: aws-java-sdk-sqs-1.11.0.jar
[info] Including from cache: aws-java-sdk-cognitoidentity-1.11.0.jar
[info] Including: logback-classic-1.1.3.jar
[info] Including from cache: aws-java-sdk-kinesis-1.11.0.jar
[info] Including: scala-xml_2.11-1.0.5.jar
[info] Including from cache: aws-java-sdk-dynamodb-1.11.0.jar
[info] Including: github-api_2.11.jar
[info] Including from cache: scala-library-2.11.8.jar
[info] Including from cache: aws-lambda-java-core-1.1.0.jar
[info] Including from cache: aws-lambda-java-events-1.3.0.jar
[info] Including: logback-core-1.1.3.jar
[info] Including from cache: aws-java-sdk-s3-1.11.0.jar
[info] Including from cache: aws-java-sdk-kms-1.11.0.jar
[info] Including from cache: aws-java-sdk-core-1.11.0.jar
[info] Including from cache: commons-logging-1.1.3.jar
[info] Including from cache: httpclient-4.5.2.jar
[info] Including: jackson-databind-2.6.2.jar
[info] Including: slf4j-api-1.7.7.jar
[info] Including from cache: jackson-annotations-2.6.0.jar
[info] Including: jackson-core-2.6.2.jar
[info] Including: scopt_2.11-3.3.0.jar
[info] Including: json4s-ext_2.11-3.3.0.jar
[info] Including: json4s-native_2.11-3.4.0.jar
[info] Including: json4s-core_2.11-3.4.0.jar
[info] Including: joda-time-2.8.2.jar
[info] Including: json4s-ast_2.11-3.4.0.jar
[info] Including: json4s-scalap_2.11-3.4.0.jar
[info] Checking every *.class/*.jar file's SHA-1.
[info] Merging files...
[info] SHA-1: 502aa723ff628dd6568883c13ec47cdaf93a4b71
[info] Packaging target/scala-2.12.1/aws-lambda-scala-hello-world-assembly-0.1-SNAPSHOT.jar ...
[info] Done packaging.
[success] Total time: 35 s, completed Oct 16, 2016 10:31:38 PM

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 "Actions" and then "Configure test event"

14. From the "Sample event template" drop-down, choose "SNS"

15. Click "Save and Test"

References

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