This crate is a small tutorial example of creating a custom AWS Lambda runtime.
The process is very simple, the AWS Lambda Runtime API currently contains only four endpoints:
- Initalization error - for if the initialization steps fail (i.e. doing one-time initializations for global resources, etc.) prior to calling the handler function.
- Next invocation - an endpoint from which to GET the invocation event and some metadata (AWS Request ID).
- Invocation response - an endpoint to POST the successful response of the handler function.
- Invocation error - an endpoint to POST the error message of the handler function, if it fails.
AWS Lambda also provide a simple tutorial using bash.
An extension of this would be to add support for the AWS Lambda Extensions API, but in the real world you should just use the lambda-runtime crate (which also provides support for async handler functions!).