Probably the most used, versatile and oldest combination between AWS cloud services is REST APIs (public) with Lambda integration on the backend [1]. While RESTful API development is not at all new, if you are relatively new to developing in the cloud, working with these two services may be somewhat challenging. This article requires a basic understanding of these two services. Its focus is beyond the point where you are able to invoke a Lambda function and receive status code 200 from the API. Given the availability of SNS and CloudWatch Logs, why would one bother integrating the API Method & Integration Responses past returning code 200? The answer is that would be a half implemented feature, which lets users speculating about what the result of the invocation was. This article shows how to program an API to return status codes that make sense to your application.

My Use Case

I shall focus on a Lambda function which may throw unexpected exceptions, errors and return a response. To make this more challenging, I am going to use Python. This language is a big hit with developers transitioning from traditional scientific and engineering roles, who have not used any “JS” languages. The intention is to create a foundation on which further API development can be done or at least leave the API in a minimum viable state.

My Solution

I started creating the Lambda function, which I called DanielHTTP. The function uses the latest Python runtime and the IAM policy AWSLambdaBasicExecutionRole which allows CloudWatch logs to be created. I created a role called the same and attached the policy. Alternatively, when this function is created, I could have selected Create New Role to have this done automatically. The function code is available in my GitHub repository [2]. The code is designed to throw an exception by performing an illegal operation, to raise exceptions and errors and to return an Ok response. All cases are individually handled in the API.

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