AWS Lambda now supports Serverless applications including WebApi

One of the most exciting areas that I’ve seen emerging in the Cloud space recently is Serverless computing. Both AWS and Azure have their own flavour: AWS Lambda and Azure Functions.

An intro into Serverless

It really does what it says on the tin. You can run code but without dedicated infrastructure that you host. A good example is when building Alexa Skills.

You create AWS lambda function, in most of the languages of your choice, and then deploy into the cloud. Whenever someone uses your skill the lambda gets invoked and returns the content you need.

Behind the scenes AWS host your function in a container, if it receives traffic the container remains hot. If it doesn’t receive traffic its ‘frozen’. There is a very good description of this at https://medium.com/@tjholowaychuk/aws-lambda-lifecycle-and-in-memory-caching-c9cd0844e072

Your language of choice

AWS Lambda supports a raft of languages: Python, Node, Java, .net core and others. Recently this has been upgraded so that it supports .net core 2.

Doing the legwork

With a basic lambda function you can concoct different handlers (methods) which respond to requests. This allows one lambda to service several endpoints. However, you need to do quite a lot of wiring and it doesn’t feel quite like normal WebApi programming.

Enter the serverless applications

This came right out the blue, but was very cool – Amazon released some starter kits that allow you run both RazorPage and WebApi applications in Lambdas!!! https://aws.amazon.com/blogs/developer/serverless-asp-net-core-2-0-applications/

Woah, you can write normal WebApi and deploy into a lambda. That is big.

Quick, migrate all the things

So I tried this. And in the most part everything worked pretty seamlessly. All the code I’d already written easily mapped into WebApi controllers I could then run locally. Tick.

Deploying was simple, either via Visual Studio or the dotnet lambda tools. Tick.

Using the serverless.template that ships with the starter pack it even setup my Api Gateway. Tick.

Dependency injection thats inherently available in .net core all worked. Tick.

WebApi attribute routing all works. Tick.

So far so good right 🙂

What I haven’t quite cracked yet?

In my original deployment (pre WebApi) I was using API level caching over a couple specific endpoints. This was path based as it was for specific methods. The new API Gateway deployment directs all traffic to a {/proxy+} url in order to route any request to the routing in your WebApi. If you turn caching on here, its a bit of a race, whichever url is hit first will fill the cache for all requests. Untick!

Debugging errors locally don’t always bubble startup errors very well. I have a feeling this isn’t anything Amazon related but is something worth being aware of. E.g. if you mess up your DI, it takes some ctor null debugging to find the cause. Untick.

Summary

I was hugely impressed with WebApi integration. Once the chinks in the path based caching at the API Gateway can get ironed out I’d consider this a very good option for handling API requests.

Watch this space 🙂

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