WATCH_NAMESPACE for ScaledObjects

[AmanGarg-hub]

Hey,

I've been trying to implement WATCH_NAMESPACE env variable in my keda to watch a specific set of namespaces like

env:

• name: WATCH_NAMESPACE
    value: namespace-a,namespace-b
   
   as suggested in the docs
   
   but as soon as i change this env variable's value from "" to "namespace-a,namespace-b", I start seeing errors like:
   

2025-09-25T06:42:55Z	ERROR	scale_handler	failed to get ScaledObject	{"name": "app-a-scaledobject", "namespace": "default", "error": "unable to get: default/app-a-scaledobject because of unknown namespace for the cache"}
github.com/kedacore/keda/v2/pkg/scaling.(*scaleHandler).performGetScalersCache
	/workspace/pkg/scaling/scale_handler.go:319
github.com/kedacore/keda/v2/pkg/scaling.(*scaleHandler).getScalersCacheForScaledObject
	/workspace/pkg/scaling/scale_handler.go:291
github.com/kedacore/keda/v2/pkg/scaling.(*scaleHandler).GetScaledObjectMetrics
	/workspace/pkg/scaling/scale_handler.go:428
github.com/kedacore/keda/v2/pkg/metricsservice.(*GrpcServer).GetMetrics
	/workspace/pkg/metricsservice/server.go:48
github.com/kedacore/keda/v2/pkg/metricsservice/api._MetricsService_GetMetrics_Handler.func1
	/workspace/pkg/metricsservice/api/metrics_grpc.pb.go:118
github.com/kedacore/keda/v2/pkg/metricsservice.(*GrpcServer).Start.(*ServerMetrics).UnaryServerInterceptor.UnaryServerInterceptor.func6
	/workspace/vendor/github.com/grpc-ecosystem/go-grpc-middleware/v2/interceptors/server.go:22
github.com/kedacore/keda/v2/pkg/metricsservice/api._MetricsService_GetMetrics_Handler
	/workspace/pkg/metricsservice/api/metrics_grpc.pb.go:120
google.golang.org/grpc.(*Server).processUnaryRPC
	/workspace/vendor/google.golang.org/grpc/server.go:1405
google.golang.org/grpc.(*Server).handleStream
	/workspace/vendor/google.golang.org/grpc/server.go:1815
google.golang.org/grpc.(*Server).serveStreams.func2.1
	/workspace/vendor/google.golang.org/grpc/server.go:1035

 
Although the namespaces being watched work as expected and i don't see any error message for them, but why do we see errors like this for other namespaces (like default ns in this case)? Shouldn't we just get n INFO log instead that this namespace scaledobject is not being watched?
 
Just want to understand this, as i want to put this in production and before going there i wanna know why is this an error and does it affect the performance of keda in any way?