With limited experience in AWS Lambda & API Gateway, it's struggling to find the correct way to return plain text. Why plain text? It's plain text in the empty function template of Python runtime.

When watching the tutorial video about using AWS Lambda on Youtube, I think it's quite easy to run the hello world example. The videos use Node.js runtime which is friendly to JSON strings. In python, the function template just return plain text, not JSON. When finishing the Lambda part and running the test, everything was just fine.

It's the API Gateway to expose Lambda function for HTTP access. Adding a API Gateway trigger will result in a resource with ANY method. If openning the URL in a browser, it just complains a 500 error "Internal Server Error". After some searches and digging in the log, I found the calling of Lambda function was OK, but the result was not parsed correctly. To parse the result plain text, you have to add Content-Type in the response header. Also body mapping template has to be updated.

Key points

* Create a new GET method.

* In Method Response, add a header "Content-Type" and empty model.

* In Integration Response, add Content-Type and 'plain/text' (including the quote signs) in Header Mapping. In Body Mapping Template, add "plain/text" and "$input.path('$')".

[1] https://kennbrodhagen.net/2016/01/31/how-to-return-html-from-aws-api-gateway-lambda/