Use klog for katib

[gyliu513]

/kind feature

Describe the solution you'd like
[A clear and concise description of what you want to happen.]

Use the permanent forked version of glog for kubernetes instead of log.

ref:
kubernetes/kubernetes#70264
https://github.com/kubernetes/klog/blob/master/README.md

Anything else you would like to add:
[Miscellaneous information that will assist in solving the issue.]

/cc @hougangliu @richardsliu @gaocegege

[gaocegege]

I think we are using it now, with the help of kube-builder.

[hougangliu]

#112 traced log solution

[gyliu513]

@gaocegege The klog was not used by katib but using log. Now all of the kubernetes projects are migrating to klog, I think katib should also move this way?

[hougangliu]

#388 also traces it, we can keep one about log solution

[gyliu513]

@YujiOshima @richardsliu look forward to more comments from you as well.

[hougangliu]

I think klog is good solution for me

[YujiOshima]

SGTM. klog is the standard logging in k8s ecosystem and developed actively.

[gyliu513]

/assign

[johnugeorge]

@gyliu513 Katib v1alpha2 version uses log solution that is provided by controller-runtime and it is not the standard log package.. It is a flexible package where users can configure their own logger. See the current usage: https://github.com/kubeflow/katib/blob/master/cmd/katib-controller/v1alpha2/main.go#L35 configures zap logger

It can support Klog also. kubernetes-sigs/controller-runtime#291

Since we are using controller-runtime library for implementation, I feel that we should use the log package provided by controller-runtime and configure the logger(instead of using klog directly)

[gyliu513]

@johnugeorge I actually want to use klog instead of using klog in controller-runtime, using klog directly can always enable us to upgrade as we want to leverage the latest feature in klog. Comments?

[johnugeorge]

Sorry. I didn't understand. Why can't klog be upgraded in the latter case? Can you please explain the difference between both?

Another side effect is that logs in controller-runtime will get hidden(including error logs) if the log library is not initialized. https://github.com/kubernetes-sigs/controller-runtime/blob/master/pkg/internal/controller/controller.go#L41

[gyliu513]

Sorry. I didn't understand. Why can't klog be upgraded in the latter case? Can you please explain the difference between both?

@johnugeorge If I want to upgrade klog, do I need to upgrade controller-runtime? Let me check more detail for how does federation v2 works kubernetes-retired/kubefed#857

[johnugeorge]

No. You don't need to upgrade controller-runtime. Klog will be an external dependency.

[gyliu513]

@johnugeorge I see, so we do not need to add klog to Gopkg.toml but depending on klog in controller-runtime is good enough. Comments?

[gyliu513]

There is an issue for klog at kubernetes/klog#22 , the klog cannot handle the case of some sort with a predefined set of variables which are used as suffix for each log line.

Will hold on for some files in katib like https://github.com/kubeflow/katib/blob/master/pkg/controller/v1alpha2/experiment/experiment_util.go#L24 etc.

[gaocegege]

I think it may affect us deeply. We rely on this feature in many files.

[gyliu513]

@gaocegege I will check how we can workaround for this, but meantime, can we avoid try to using child logger for future new added files?

[gaocegege]

I have no objection on it, LGTM

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