[RFC] Supporting API Gateway Lambda custom authorizers in sam local start-api

[lucashuy]

#137 - Github Issue Feature Request

API Gateway Lambda custom authorizers are a way to authenticate and validate an incoming API Gateway request before routing to an endpoint by first invoking a custom Lambda function. Currently, AWS SAM CLI does not support emulating the Lambda authorizer workflow using sam local start-api.

We are looking for general comments and discussions about what the community is looking for regarding Lambda authorizer support in sam local start-api, as well as some thoughts on the following:

• Emulation of the time-to-live (TTL) of Lambda authorizers
  • API Gateway caches the Lambda authorizer responses for as long as the TTL dictates
  • The cache key is determined by the identity sources and the route key
  • Subsequent requests that match that key will fetch from the cache instead of invoking the Lambda authorizer again
• Invocation of deployed Lambda authorizers
  • Lambda authorizers can reference an existing, already deployed Lambda function in some cases
  • sam local commands are able to download remotely deployed Lambda function layers when invoking functions locally, however sam local commands currently do not download Lambda function code

We are looking to gather feedback on the above use cases, as well as any other thoughts the community may have regarding Lambda authorizer support in local emulation.