Context is metadata associated with each invocation. If the handler function accepts a context argument then it will automatically receive at runtime a named list consisting of these values along with the arguments in the body (if any). For example, a function such as my_func(x, context) will receive the context argument automatically. The context argument must be named (... will not work).

The following context is made available as a named list:

  • aws_request_id - The identifier of the invocation request
  • invoked_function_arn – The Amazon Resource Name (ARN) that’s used to invoke the function. Indicates if the invoker specified a version number or alias.
  • function_name
  • function_version
  • memory_limit_in_mb
  • log_group_name
  • log_stream_name

Event class-specific context

This section concerns future functionality for the lambdr package. It is not yet implemented.

A particular event class (determined by invocation method) can implement an extract_context method. This could be used to say, include details about the HTTP request if an invocation is coming via an API Gateway.

In all cases the context should be a named list. The new context is appended to the default values listed above.