DayspringLambdaBundle - Run Symfony on Lambda

This bundle provides tooling for using Lambda to run Symfony code. Your application will run as a custom Lambda runtime

This is based on bref's console example bootstrap script and removes the need to use only console commands. It also boots the Symfony kernel once for the lifetime of the Lambda worker.

bref provides a Lambda runtime API client implementation. This handles communication with the Lambda runtime API

Using this bundle

1. Add this bundle to your Symfony project.

• Add this package to your project by running composer require dayspring-tech/lambda-bundle
• Package your project in a docker image.
• Add Bootstrap/service.php to your image as /var/run/bootstrap, and make it executable. This is the foundation of your custom Lambda runtime.

  # this is really what does the magic
  COPY symfony/vendor/dayspring-tech/lambda-bundle/Bootstrap/service.php /var/runtime/bootstrap
  RUN chmod a+x /var/runtime/bootstrap
  

2. Create a class that implements LambdaHandlerServiceInterface

• Create a class that implements LambdaHandlerServiceInterface and register it with Symfony's dependency injection container. It should be marked as public so it can be fetched by name.
• Implement the handle() function
  • The custom runtime will call the handle() function for each Lambda event, passing the event object as the $event argument.
  • Lambda context information will be provided via the $context argument.
  • The custom runtime will provide an OutputInterface object with which you can provide any output that should be returned from the Lambda function.

3. Register a Lambda function

• Create a Lambda function in AWS using your docker image. Set the Lambda command to the service name.

Background on the custom Lambda runtimes and the Lambda Runtime API

If there's a /var/run/bootstrap file in your docker image, Lambda will execute it. This is your custom runtime.

1. The Lambda runtime API exposes three APIs. Your custom runtime should call the /next API to request the next event.
2. Your custom runtime should execute code to handle the event. For LambdaBundle, this is calling the handle() function on the LambdaHandlerServiceInterface specified via the Lambda function's command parameter.
3. If successful, your custom runtime calls the /response API and POSTs the function's response.
4. On an error, your custom runtime calls the /error API with details of the error.

See also:

• https://docs.aws.amazon.com/lambda/latest/dg/runtimes-custom.html
• https://docs.aws.amazon.com/lambda/latest/dg/runtimes-api.html

Provided Handlers

The following handlers are provided as examples or common implementations of LambdaHandlerServiceInterface

EchoLambdaHandlerService

This handler will echo the event body value to Lambda's output. Useful for testing your container and Lambda configuration.

{
    "body": "hello world"
}

ServiceFunctionHandlerService

This handler can handle lambda events and call any public function on any service available via Symfony's dependency injection container.

It expects a lambda event in the format:

{
    "serviceName": "AppBundle\\Service\\EchoService",
    "function": "echo", 
    "args": [
        "hello"
    ]
}

• serviceName: any service identifier valid with Container::get(). This will likely be a service class name.
• function: the function name
• args: an array of arguments to the function

SqsServiceFunctionHandlerService

This handler does the same thing as ServiceFunctionHandlerService but for messages sent via SQS

It expects payloads to be sent via SQS instead of directly to Lambda.

Other implementation possibilities

• API Gateway - Configure a Lambda integration with API Gateway and use Symfony to handle API requests
• SNS - Subscribe Lambda to a SNS topic and handle messages from SNS
• Custom events - Configure Lambda as a task within Step Functions