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Custom Lambda Runtime for Perl

This is an experiment to get Perl support in Lambda.

It consists of an implementation of the bootstrap script as AWS documentation suggests.

The implementation is not complete yet, though it does work to some extent :)

Install AWS::Lambda::Toolkit

cpanm AWS::Lambda::Toolkit

(Note: you might need to install the cpanminus system package to get access to the cpanm command).

This installs the utilities that help us bootstrap the Lambda environment.

Note2: While the distribution is not uploaded to CPAN, you can install this way:

git clone [email protected]:pplu/perl-lambda-byor.git
make dist
cpanm AWS-Lambda-Toolkit-0.01.tar.gz

Create your Lambda function

  • Create a directory for your Lambda project:
mkdir my-lambda-project
cd my-lambda-project
  • Initialize the directory as a lambda project: Create a config file named lambda-perl.config for your project
init-lambda-perl
  • Create a runtime layer

Although Perl is installed in the Lambda environment, since AWS bases the OS on CentOS, the Perl runtime is quite old (5.16, where at the time of this writing Perl has gone through 5.18, 5.20, 5.22, 5.24, 5.26 and 5.28 releases). Added to that, the Perl installation is lacking the 'perl-core' yum package, which makes that Perl very hard to deal with, since it's lacking almost all of the "core" modules that you would normally find installed on a system. Because of that, we're going to use custom compiled, modern versions of Perl as the runtime.

build-lambda-perl-runtime 5.28

will generate a layers/perl_5.28.zip. This can be uploaded to Lambda as a layer with install-lambda-perl-runtime.

  • Create a cpanfile with the dependencies of your project
requires 'Moo';

Generate the dependencies layer with:

build-lambda-deps-layer

this will generate another zip file in the layers directory that can be uploaded with install-lambda-deps

  • Write code. Start a file called lambda. Write a Perl subroutine:
sub main {
  return "I'm alive!"
}

Create a zip with with the build-lambda-function. This creates a zip with the code in the layers directory

Configure the lambda-perl.config file:

Add the config keys:

handler: lambda.main
role: arn:aws:iam::XXXXX:role/XXXXX

handler is formed by the name of the file that contains the lambda function (lambda in this example), followed by . and the subroutine to invoke in that file.

Invoke install-lambda-function to up create the lambda function in AWS.

  • Invoke the function

You can invoke the function with the AWS CLI, or with Paws: paws Lambda --region x Invoke FunctionName TheNameOfYourLambda Payload ''

The bootstrap script will require the lambda file (or whatever the handler of the Lambda function tells it to), and will invoke the main sub in the lambda file with the parsed JSON payload passed to the function as a hashref as it's first argument.

TODO

Make bootstrap include '/var/task/lib' so the libs in your project directory are usable from the lambda function

automatically encode the return value from the function to JSON? (should it be overridable?)

Adaptor for ALB incoming message format to Plack environment

Follow all the Processing Tasks in custom runtimes section

Handle errors in compilation phase of the Lambda function

See if Dist::Zilla can build the zip for distributing to Lambda

Notes

Finding out what you can or can't do inside the Lambda runtime can be exhausting if you do it directly inside Lambda. The make explore-lambda-environment target runs a shell inside a Docker container that resembles the Lambda runtime environment.

License

This software is released under an Apache 2.0

Copyright

(c) 2018 CAPSiDE

Author

Jose Luis Martinez Torres