SAM template environment variables use map, list, associative array?

Question

I've only seen examples with single values in SAM templates:

Environment:
  Variables:
    TABLE_NAME: my-table

I want to do something like this but doesn't seem to work:

Environment:
  Variables:
      myVar:
      -   prop1: aaa
          prop2: sdfsdfsd
          prop3: ssss
      -   prop1: bbb
          prop2: wwwwww
          prop3: aaaaa

I want to have an environment variable that is like a list of objects. I could store a delimited string and parse it myself but I'd prefer to have it be like an object/map/list like if I'm ready a YAML file.

Answer 1

The closest you can do is to json encode the value for your environmental variable and decode it using the runtime language:

 Environment:
  Variables:
    USER: '{"name": "john", "surname": "galt"}'

If you want to prevent decoding json on each request, move your decoding logic outside the handler, in this case code won't be re-executed while lambda is hot.

Any declarations in your Lambda function code (outside the handler code, see Programming Model) remains initialized, providing additional optimization when the function is invoked again. For example, if your Lambda function establishes a database connection, instead of reestablishing the connection, the original connection is used in subsequent invocations. We suggest adding logic in your code to check if a connection exists before creating one.

Read about lambda execution model

I personally would create a json file, store it in s3 bucket and use an environment variable to specify s3 url to that file. Additionally, use the same technique I mentioned above or use even more complicated caching mechanism depending on the situation when retrieving the config file