Bug Report

Which version of the demo you are using? 1.10.0

Symptom

Changing a feature flag defaultVariant while the demo application is running doesn't dynamically update services

What is the expected behavior?

Changing a feature flag defaultVariant to on while demo is running dynamically updates services

What is the actual behavior?

Changing a feature flag defaultVariant to on while demo is running is a noop.

Reproduce

Per https://opentelemetry.io/docs/demo/feature-flags/, To enable a flag, change the defaultVariant value in the config file for a given flag to “on”, while the demo application is running edit src/flagd/demo.flagd.json and change a defaultVariant to on

Additional Context

Perhaps this is expected behavior. If it is, then the documentation should be updated to state that if the demo application is running and a feature flag defaultVariant is changed then you need to restart the flagd service (make restart service=flagd) or restart the demo application for it to take effect.

I can make the documentation change if this is the recommended approach.

Hey @flands I've actually tested that on docker and it works fine. Any Feature Flag in specific you have tested?

I know that for K8s, that may be different as we are not using the flagd operator, but for Docker it worked fine.

@julianocosta89 Interesting! I'm on Darwin (ARM-based) running the latest Docker desktop. I tried the first two feature flags multiple times (for example productCatalogFailure) and the only way I can get it to work is to restart the flagd service.

Hey @flands, do you see an event in the flagd logs when you make a change in the config? Flagd uses fsnotify to detect changes. Perhaps your setup is triggering an event that we're currently not reacting to.

We're considering more robust file watching approaches.

https://github.com/open-feature/flagd/issues/1344

It starts with the logs shown below and after changing the JSON file no new logs are recorded

2024-07-03T21:39:32.527Z	info	cmd/start.go:107	flagd version: v0.10.2 (d58fe3c3ac67843571d8fdc7d04b75996444befd), built at: 2024-05-10	{"component": "start"}
2024-07-03T21:39:32.528Z	info	flag-sync/sync_service.go:54	starting flag sync service on port 8015	{"component": "FlagSyncService"}
2024-07-03T21:39:32.530Z	info	file/filepath_sync.go:45	Starting filepath sync notifier	{"component": "sync", "sync": "filepath"}
2024-07-03T21:39:32.531Z	info	ofrep/ofrep_service.go:56	ofrep service listening at 8016	{"component": "OFREPService"}
2024-07-03T21:39:32.531Z	info	flag-evaluation/connect_service.go:243	metrics and probes listening at 8014	{"component": "service"}
2024-07-03T21:39:32.531Z	info	flag-evaluation/connect_service.go:223	Flag IResolver listening at [::]:8013	{"component": "service"}
2024-07-03T21:39:32.532Z	info	file/filepath_sync.go:74	watching filepath: ./etc/flagd/demo.flagd.json	{"component": "sync", "sync": "filepath"}

I had the same experience (docker/macos/arm64/colima). To reliably switch the feature toggles both flagd and the service that uses the flag had to be restarted.

vim src/flagd/demo.flagd.json
docker-compose restart flagd
docker-compose restart productcatalogservice

flagd v0.11.2 appears to be working better and reloading the file on disk properly whenever it changes.

Yes, version 0.11.2 added more sophisticated file-watching capabilities. You can see the PR here if you're interested in the details.

@Starefossen, thanks for bumping the version in the demo.