aws-lambda-runtime-interface-emulator VS awslogs

Enter the aws-lambda-runtime-interface-emulator. This tool will allow us to emulate the AWS Lambda Runtime API locally (I suspect that the AWS SAM uses this tool under the hood as well). The aws-lambda-runtime-interface-emulator is designed to be used with Docker. Still, nothing stops us from containerizing our code for the sake of development and then, whenever we are ready, proceeding with deployment how we wish to. This local workflow is a bit more involved than the previous one, but it might be a valid alternative for those not using AWS SAM or are already using containers to deploy their Lambdas.

There is a special tool to test AWS Lambda images locally. It's called AWS Lambda Runtime Interface Emulator (RIE). You have two options: include RIE in your image or install it locally. We don't need it in the production image, so let's choose the second option. We will download binary locally and mount it to our image if we need to test it.

Suggestions:

1. If you are building APIs and using Lambda functions as targets from an API Gateway API, look into libraries like serverless-wsgi (Python) or wai-handler-hal (Haskell) that translate between API Gateway request/response payloads and some kind of ecosystem-native representation. Then as long as you're writing code where all state gets persisted outside of the request/response cycle, you can develop locally as if you were writing for a more normal deploy environment.

2. Look into the lambda runtime interface emulator ( https://github.com/aws/aws-lambda-runtime-interface-emulator... ). This lets you send invoke requests to a fake listener and locally test the lambda more easily. While the emulator is provided in the AWS container base images, you don't need to run it inside a container if you're deploying with zip files. (AWS-provided container images automatically enable the emulator if not running in a lambda runtime environment, and using docker for port remapping is nice. But not at all required.)

3. Get really good at capturing all requests to external services, and mocking them out for local testing. Whether this is with free monads, effect systems, gateway classes will depend on your language and library choices.

Using the official CLI (aws logs get-log-events) or https://github.com/jorgebastida/awslogs is pretty close to SSH-ing and grepping.

cw is a native executable targeting your OS, and not needed external dependencies such as pip and npm. Compared to awslogs which is famous helpful tool for CloudWatch Logs1, cw is written in golang and faster.

Its a command line tool but some people I know also use awslogs

Not a full solution, but when I was doing this I really got to love the awslogs utility:

https://github.com/jorgebastida/awslogs

It allows you to stream Cloudwatch logs from the command line, so you can grep them, save them to files, etc... (The web based Cloudwatch interface is terrible.)

Another suggestion is to try to modularize the core business logic in your lambda such that you separate the lambda-centric stuff from the rest of it. Obviously, though, if "the rest of it" is hitting other AWS services, you're going to hit the same testing roadblock.

Or you can try mocking, which may or may not provide much value for you. There's a python library for that, (moto), but it's not 100% up to date wrt AWS services/interfaces, last I had checked. Might be worth a try though.

https://github.com/spulec/moto

Cloudwatch Logs is pretty meh visually, but awslogs can give you a pretty good `tail -f`-like experience, and Insights is pretty good. Cloudwatch Metric Filters give you a 'StatsD'-like experience, in that you can log out a certain message or code and then use its appearance as a metric.

Check out https://github.com/jorgebastida/awslogs , you can define a `--start`, and it also has a `--watch`, and can be piped the `grep` or whatever you want. It's a pretty flexible tool.

📖 awslogs - a simple command-line tool for querying groups, streams, and events from Amazon CloudWatch logs.