[FEATURE REQUEST] hot reload functions

[mstrYoda]

My actions before raising this issue

• Followed the troubleshooting guide
• Read/searched the docs
• Searched past issues

Expected Behaviour

What about supporting hot-reload functionality for local test purposes? So this allows faster execution cycle for test purposes.

I would like to test my function without rebuilding&pushing an image on every change something like below:

faas-cli up-test my-function -f function.yaml 

I am imagining a behavior like skaffold does.

Current Behaviour

Currently we need to run faas-cli up and it builds & pushes docker image to registry.

Possible Solution

When we run faas-cli up-test -f function.yml it can do the following steps:

• spawn a pod with a test image like golang:alpine-x
• watch the current directory
• push changes to test image
• run new codes

I am not aware of internals of openfaas so the solution I describe above may sound meaningless. But I believe that functionality can supported.

Context

Testing etc.

[alexellis]

Thanks for your interest in OpenFaaS.

A summary of the discussion on Slack with yourself and several others.

There is a WIP but abandoned PR (no changes in 1 year) in the faas-cli for this, to rebuild upon save. Some users also use tilt for the same purpose. openfaas/faas-cli#763

A live-reload feature is beyond the scope of the current roadmap so I'll close this issue out and point you at something like Okteto - they have a few guides for "hot reload" where they do relatively insecure tricks that you won't want in production, but can make development faster. They also have a good debug story.

For the fastest development you may want to build / run the container locally without deploying it to openfaas. Here's an example with the node12 template: https://simonemms.com/blog/2020/08/12/live-reload-for-openfaas/

You should also consider using unit tests to verify your code before doing a build. That's one of the fastest options available.