[common-go] Add file watcher

[aledbf]

Description

Refactor watch of configuration files and reload and remove duplication

How to test

• Change ws-daemon or ws-daemon configmap and check the reload message appears in the log

{"level":"info","message":"reloading file after change","path":"/config/config.json","serviceContext":{"service":"ws-daemon","version":"commit-5de52b5daf5c35fe22f46adcff90cbaca78b075b"},"severity":"INFO","time":"2022-05-16T05:23:37Z"}}

Release Notes

[common-go] Add file watcher
[registry-facade] Refactor watch of configuration file
[ws-daemon] Refactor watch of configuration file

[aledbf]

/werft run

👍 started the job as gitpod-build-aledbf-watcher.14
(with .werft/ from main)

[utam0k]

I love this feature. Do you have a plan to apply it to other components (e.g. ws-manager)?

[aledbf]

I love this feature. Do you have a plan to apply it to other components (e.g. ws-manager)?

Not really. The only two components that support partial configuration reload are ws-daemon and ws-registry. That said, if we add such a feature to any other component, like ws-manager, we can add the four lines required to detect changes.

[utam0k]

works fine

[easyCZ]

https://github.com/spf13/viper looks to solve this problem, perhaps we could simplify our usage with it.

[csweichel]

Change makes a ton of sense.
Left two comments.

[jenting]

Having a Kubernetes controller and watches the ConfigMap change (resourceVersion change) is also a way.

[aledbf]

Having a Kubernetes controller and watches the ConfigMap change (resourceVersion change) is also a way.

That means we need to watch the configmap using client-go. I would prefer to not add that here.

[aledbf]

https://github.com/spf13/viper looks to solve this problem, perhaps we could simplify our usage with it.

Almost the same code https://github.com/spf13/viper/blob/v1.11.0/viper.go#L440

I am ok to use that but right now we are not using viper (another new dependency)

[easyCZ]

LGTM. Left a couple of comments but those do not block this PR and can be done as follow-up. Adding hold in case you want to tackle them in this PR (approvals will persist after a commit).

/hold

[aledbf]

/werft run

👍 started the job as gitpod-build-aledbf-watcher.21
(with .werft/ from main)

[jenting]

/lgtm

[jenting]

/unhold