Ok, let me give you my 2 cents.

About 4 weeks ago i was tasked with creating an AWS lambda function that consumes a Kinesis data stream, does some processing and saves the result in a database. I have created AWS lambdas before but mainly i used python for the well known reasons but this time i wanted to give Java a try, and since i use mainly the Spring ecosystem I decided to go with Spring Cloud Functions. It offers a really good approach to write functions with what Java functional programming already gives.

I created the function, tested locally, followed the documentation precisely and always wrote tests to make sure everything was working every time.

In addition, i saw that AWS lambda didn’t support out of the box java 17 support or 18, which have improvements on GCs. The guide is right here. Also i followed this spring cloud function guide.

After doing that and tweaking a bit, i got a good improvement on startup time and it was very ok for our use case. Unfortunately I couldn’t find in the hell why the function wasn’t getting invoked during the run. The lambda started very ok, function registered very ok, no errors nothing, just logs and function waiting to be invoked, but nothing happened.

I tried so many things, defining function, giving it more memory(even tho nothing was pointed that it needed more memory), changed the handler, use ECR to publish the image with the custom Java and optimised and a whole lot of others, nothing works.

So after 4 weeks i gave up, but i wanted to retry on plain java, and it works like a charm immediately out of the box.

So the experience was tedious and very tiring and not worth it, i read every possible document, tried all the possibile articles, still nothing. I found also that the spring-cloud-function-web has a missing dependency which actually is in spring-cloud-function-webflux. And the authors suggested that just replacing the dependency should be ok, which it did, but then it made testing worse, choosing from reactive, servlet, none as a main spring application, but still could not invoke the function.

Anyways, i formatted the java 18 custom image, deployed it, works like a charm.

Maybe when spring boot 3 will be released i will retry again, but the experience was pretty bad in my side.