Restrict workload selection

[dohnto-s1]

Is your feature request related to a problem? Please describe.
One might have a huge cluster and want to focus on optimizing just a particular workload.
Prometheus queries while analysing all worklaods in a cluster/namespace might take too long otherwise.

Describe the solution you'd like
Introduce a new command line argument as kubectl has:

    -l, --selector='':
	Selector (label query) to filter on, supports '=', '==', and '!='.(e.g. -l key1=value1,key2=value2). Matching
	objects must satisfy all of the specified label constraints.

to limit the workload selection. E. g:

krr simple --context my-cluster --namespace kube-system --selector app-instance=metrics-server
# or
krr simple --context my-cluster --namespace kube-system --selector owner=devops

Describe alternatives you've considered

krr simple --context my-cluster --namespace kube-system --workload Deployment/metrics-server

Additional context

Thanks for this wonderful tool. Happy to learn if there is alternative solution for me.

[dohnto-s1]

Now I hit an issue when Prometheus is unable to give me the results and the request fails with 431. I don't understand the details krr, but would implementation of feature above help as well?

PrometheusApiClientException: HTTP Status Code 431 (b'431 Request Header Fields Too Large')

[arikalon1]

Thanks for reporting it @dohnto-s1

I think this issue is similar to #60

Does limiting krr to a specific namespace using krr simple -n default can be a workaround until we fix it?

[dohnto-s1]

This unfortunately happens when running with -n.

[arikalon1]

Thanks for the update.

We'll try to fix it soon.
We're also open for PRs

[LeaveMyYard]

Now I hit an issue when Prometheus is unable to give me the results and the request fails with 431. I don't understand the details krr, but would implementation of feature above help as well?

PrometheusApiClientException: HTTP Status Code 431 (b'431 Request Header Fields Too Large')

Hey, sorry for long time waiting :)

It looks like your issue could be handled by #96
Can you check that?

If it does not, please provide logs after running with -v flag

[LeaveMyYard]

And I really like your proposal for selector flag, we should 100% implement it

[dohnto-s1]

@LeaveMyYard Looks awesome, thanks!

EDIT: Let me test it first on some of my use-cases.
EDIT2: Works!