just-maven-clojurescript-aws-lambda-archetype

A Maven archetype for creating ClojureScript AWS Lambda projects

See just-maven-clojurescript-archetype

• See README.md for just-maven-clojurescript-archetyp for details on ClojureScript projects.
• https://github.com/seltzer1717/just-maven-clojurescript-archetype
• There are many details not discussed here as they are already described above.

AWS Lambda Details

• This archetype adds a couple of configurations to support the creation of AWS Lambda Node projects

A new compile target cljs-lambda-compile

• This is the same compile script as cljs-compile except that it adds a global export for the AWS Lambda handler names
• Notice also that the handler name is specified in the properties section.
• AWS expects a single JS file and an exports.blah = [async] function definition. ClojureScript is producing a library that can be loaded via a single JS file. After which you can execute namespace differentiated functions. You need the extra export to satisfy AWS Lambda deployment semantics.

Creating an Output Artifact

• This archetype also produces a package artifact.
• It uses the Maven Assembly plugin which is a very mature plugin for creating all sorts for output artifacts of all types
  • In fact this archetype uses the Maven Assembly plugin to create placeholder javadoc and javasource artifacts to satisfy the requirements of sonatype.org.
• Notice there are two output artfacts created by the created project
  • A layer artifact for node_modules and
  • A application artifact

The Assembly Descriptors

The output artifacts are defined by assembly descriptors. These are defined in XML in the src/assembly folder.

• The dependencies.xml descriptor.
  • This basically creates a zip file of the node_modules folder
  • This will become the artifact for a Lambda layer meaning you only have to deploy this once.
  • It defines an id
  • Specifies that the parent folder should not be included
  • Specifies that the format should be zip
  • Lastly, it specifies the fileset (folder) that should be added to the zip output file
• The handler.xml defines the rest of your application so includes:
  • The index.html file
  • Your namespaced application folder
  • The Google Closure dependency folder etc.

The maven deployment lifecycle phase

• There are many ways to deploy this Lambda function to AWS:
  • Cloud Formation - https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/Welcome.html
  • The AWS CDK (coming soon - an archetype for the AWS CDK) - https://docs.aws.amazon.com/cdk/
  • The AWS console - https://docs.aws.amazon.com/lambda/latest/dg/foundation-console.html
  • AWS CLI - https://docs.aws.amazon.com/lambda/latest/dg/gettingstarted-awscli.html
  • AWS language SDKs - https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/Lambda.html
  • The AWS Code Build service - https://aws.amazon.com/codedeploy/
• This archetype uses the AWS CLI by executing it via the Maven deploy lifecycle phase
• A new execution is added that use the exec-maven-plugin exec goal
• This just calls the AWS CLI and executes a deployment script.
• The exec goal execution runs completely separately from the Maven java execution.

AWS CLI and input JSON files

• The AWS CLI can execute in two different ways:
  • Directly by providing attributes at the command line
  • Indirectly but supplying an input JSON file containing all the attributes for the command
• This archetype uses the latter form. I think this is the preferred way in that it lets you see each attribute that can be provided by using the aws --generate-cli-skeleton
• This can then be populated
• Then you can run aws --cli-input-json with the JSON file

Separate deployment script just for the Lambda layer Deployment

• Lastly there is a separate standalone deployment execution for the Lambda layer for the node_modules used by the sample app.