Add a kubernetes-log4j module

[ppkarwasz]

Description

The kubernetes-log4j module adds the ability to Log4j Core to use Kubernetes attributes in a configuration file.

It is a cleaned-up version of the org.apache.logging.log4j:log4j-kubernetes, which is also released under ASL 2.0.

As explained in #5682, it does make more sense to host is here since:

• it only depends on a very stable StrLookup dependency from log4j-core,
• the number and kind of properties available through kubernetes-client depend on its version.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• Feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change
• Chore (non-breaking change which doesn't affect codebase;
  test, version modification, documentation, etc.)

Checklist

• Code contributed by me aligns with current project license: Apache 2.0
• I Added CHANGELOG entry regarding this change
• I have implemented unit tests to cover my changes
• I have added/updated the javadocs and other documentation accordingly
• No new bugs, code smells, etc. in SonarCloud report
• I tested my code in Kubernetes
• I tested my code in OpenShift

[ppkarwasz]

For compatibility with org.apache.logging.log4j:log4j-kubernetes the lookup allows to override the automatic Kubernetes Client configuration using Log4j property sources. If this does not make sense in this project, I can remove the ClientBuilder and ClientProperties classes.

[sonarcloud]

Quality Gate failed

Failed conditions

23.7% Coverage on New Code (required ≥ 80%)
E Reliability Rating on New Code (required ≥ A)

See analysis details on SonarCloud

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[ppkarwasz]

I am converting this to draft, since I need to add tests for most of the code.

Do you have an util to replace the ContainerUtil from the original log4j-kubernetes? The class tries to determine the id of the Kubernetes container, by parsing /proc/self/cgroup on Linux, which is error prone and not easy to test.

[manusa]

If this does not make sense in this project, I can remove the ClientBuilder and ClientProperties classes.

I'm not sure how does this play with our own property inference logic:

kubernetes-client/kubernetes-client-api/src/main/java/io/fabric8/kubernetes/client/Config.java

Line 409 in 315f486

public static void configFromSysPropsOrEnvVars(Config config) {

I assume that for backwards-compatibility this is necessary, so I'm fine keeping it.

[manusa]

Do you have an util to replace the ContainerUtil from the original log4j-kubernetes?

Not that I know of.

[ppkarwasz]

@manusa,

Thank you for your review. I finally had some time to work on this PR.

Apart from addressing your remarks above:

• I introduced a system property kubernetes.log4j.useProperties. When set to false (default) Log4j properties are not used to configure the Kubernetes client. I think that this is a good compromise to maintain compatibility with log4j-kubernetes, but require users to set a special property to enable it.
• I increased the test coverage.

[ppkarwasz]

The OpenShift failures seem unrelated to my PR.

[rohanKanojia]

@ppkarwasz You're right. These have been failing for a while now #5545

[rohanKanojia]

@ppkarwasz : Is it possible to add some README or user documentation in doc folder regarding how to use this?

[ppkarwasz]

@rohanKanojia,

I have added a doc/KubernetesLog4j.md file in the /doc folder.

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
81.7% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[manusa]

LGTM, thx!

[ppkarwasz]

@manusa,

Thank you for offering to maintain this component. If some Log4j-specific issues were to appear with it, feel free to @-mention me.

[manusa]

@manusa,

Thank you for offering to maintain this component. If some Log4j-specific issues were to appear with it, feel free to @-mention me.

Will do :) Thanks for the contribution!