feat:structured logging

[FAUST-BENCHOU]

What type of PR is this?

What this PR does / why we need it:

Which issue(s) this PR fixes:
Fixes #26

Special notes for your reviewer:

You can use logging-format like below

multicluster-cloud-provider % ./controller-manager --logging-format=json --multicluster-provider=fake --provider-ingress-class=fake
{"ts":1766906188213.9038,"caller":"app/manager.go:104","msg":"multicluster-controller-manager version: version.Info{GitVersion:\"v0.0.0-master\", GitCommit:\"unknown\", GitShortCommit:\"unknown\", GitTreeState:\"unknown\", BuildDate:\"unknown\", GoVersion:\"go1.25.1\", Compiler:\"gc\", Platform:\"darwin/arm64\"}","v":0}
{"ts":1766906188216.369,"caller":"cluster/cluster.go:170","msg":"Failed to get API Group-Resources","err":"Get \"https://127.0.0.1:64753/api?timeout=32s\": dial tcp 127.0.0.1:64753: connect: connection refused"}
{"ts":1766906188216.387,"caller":"app/manager.go:137","msg":"Failed to build controller manager: Get \"https://127.0.0.1:64753/api?timeout=32s\": dial tcp 127.0.0.1:64753: connect: connection refused"}
{"ts":1766906188216.395,"caller":"cli/run.go:72","msg":"command failed","err":"Get \"https://127.0.0.1:64753/api?timeout=32s\": dial tcp 127.0.0.1:64753: connect: connection refused"}

Does this PR introduce a user-facing change?:

[karmada-bot]

Welcome @FAUST-BENCHOU! It looks like this is your first PR to karmada-io/multicluster-cloud-provider 🎉

[gemini-code-assist]

Summary of Changes

Hello @FAUST-BENCHOU, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the multicluster-controller-manager by integrating structured logging. This change improves the observability of the application by enabling logs to be generated in a consistent, machine-readable format, which is crucial for efficient analysis and monitoring in complex distributed systems. It modernizes the logging infrastructure by adopting Kubernetes' component-base/logs/api/v1 package for configuration.

Highlights

• Structured Logging Implementation: This pull request introduces structured logging capabilities to the multicluster-controller-manager, allowing logs to be output in a machine-readable format, such as JSON.
• Logging Configuration Update: The logging flag handling has been migrated from klogflag to k8s.io/component-base/logs/api/v1, providing a more standardized way to configure logging options, including the --logging-format flag.
• Early Logging Application: The structured logging configuration is now applied early in the application's Run function to ensure all subsequent logs adhere to the specified format.

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[gemini-code-assist]

Code Review

This pull request successfully adds support for structured logging by integrating the k8s.io/component-base/logs package. The implementation correctly introduces the necessary options, command-line flags, and initialization logic to enable formats like JSON, which is a significant improvement for observability.

To fully capitalize on this new feature, I recommend a follow-up effort to refactor existing logging statements. For instance, calls like klog.Infof and klog.Errorf could be converted to their structured counterparts, klog.InfoS and klog.ErrorS. A good example is the version logging in app/manager.go, which could be changed from klog.Infof("multicluster-controller-manager version: %s", version.Get()) to klog.InfoS("multicluster-controller-manager version", "version", version.Get()). This would log the version details as a structured object, making the logs much easier to parse and query automatically. Adopting this pattern throughout the codebase would greatly enhance the utility of the structured logging feature you've introduced.

[XiShanYongYe-Chang]

Thanks~
/assign

[XiShanYongYe-Chang]

Thanks a lot @FAUST-BENCHOU

I noticed a few differences compared to the changes made in the Karmada main repository. I want to confirm whether these also need to be modified.

flush log in the main function:

        // Ensure any buffered log entries are flushed
	logs.FlushLogs()

and other questions in the comments.

[XiShanYongYe-Chang]

ValidateAndApply has been added to the PersistentPreRunE function under cmd, and some feature gates have been included. Do we also need the same setup and provide these feature gates?

https://github.com/karmada-io/karmada/blob/010b8024926b0de6a77342fa6fd93dc3819d81ff/pkg/features/features.go#L84-L105

[XiShanYongYe-Chang]

Should we set logsFlagSet as follows?

logs.AddFlags(logsFlagSet, logs.SkipLoggingConfigurationFlags())

[karmada-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[FAUST-BENCHOU]

Updated.Use default featuregate

[XiShanYongYe-Chang]

Updated.Use default featuregate

Thanks~, let me take a look.

[FAUST-BENCHOU]

[FAUST-BENCHOU]

useless now,the feature gate log will not print out

[XiShanYongYe-Chang]

Thanks
/lgtm
cc @RainbowMango

[RainbowMango]

/assign