When PluginProcessor.java will be migrated from 2.24.x version to 2.x version to remove unnecessary printMessages

[treyfarmigoni]

This is the version that is in 2.24.x: https://github.com/apache/logging-log4j2/blob/2.24.x/log4j-core/src/main/java/org/apache/logging/log4j/core/config/plugins/processor/PluginProcessor.java
This version contains unnecessary printMessage statements

This is the version that is in 2.x: https://github.com/apache/logging-log4j2/blob/2.x/log4j-core/src/main/java/org/apache/logging/log4j/core/config/plugins/processor/PluginProcessor.java
This version does not contain those printMessage statements

It would be great in the next release (2.25.x?) if the 2.x version could be incorporated. Gradle complains about,

Note: Processing Log4j annotations
Note: Annotations processed
Note: Processing Log4j annotations
Note: No elements to process
Note: Processing Log4j annotations
Note: No elements to process
Note: Processing Log4j annotations
Note: No elements to process

and considers those problems, but this appears to have already been resolved in the latest version.

Thanks,
Trey

[ppkarwasz]

@treyfarmigoni,

The latest Log4j 2 release is always published from the 2.x branch.

IMHO the fact the log messages of the PluginProcessor are not a problem. The problem is that you are using PluginProcessor (and other annotation processors), even if you don't have any Log4j plugins in your application. To solve that:

• Instead of relying on Java's auto-detection of annotation processors, consider specifying them explicitly. This is the recommended behavior that will become default in Java 23. Therefore, if you don't have any annotation processors, add -proc:none to your compiler arguments:

  compileJava {
    options.compilerArgs << '-proc:none' 
  }

  If you do use annotation processor, add them explicitly to the annotationProcessor dependency configuration. If the annotationProcessor classpath is empty the Java compiler falls back to compileClasspath, which is not something you want.
• Remove log4j-core from the compileClasspath Gradle dependency configuration and put it into runtimeOnly:

  dependencies {
    runtimeOnly 'org.apache.logging.log4j:log4j-core'
  }

  Log4j Core is a logging implementation and is not required at compile time. See our installation guide for more details.

[treyfarmigoni]

@ppkarwasz

The latest Log4j 2 release is always published from the 2.x branch.

I downloaded the source for the latest log4j release (https://github.com/apache/logging-log4j2/releases/tag/rel%2F2.24.3). I am still not seeing the 2.x version of Plugin Processor in the latest release. As stated above, the release contains the old version
https://github.com/apache/logging-log4j2/blob/2.24.x/log4j-core/src/main/java/org/apache/logging/log4j/core/config/plugins/processor/PluginProcessor.java
and not the new 2.x version: https://github.com/apache/logging-log4j2/blob/2.x/log4j-core/src/main/java/org/apache/logging/log4j/core/config/plugins/processor/PluginProcessor.java

Please verify if I am misunderstanding.

My use case is I need to register plugins. I am following this documentation: https://logging.apache.org/log4j/2.x/manual/plugins.html#plugin-registry
This indicates I used should the annotationProcessor like:

    annotationProcessor 'org.apache.logging.log4j:log4j-core:2.24.3'

which will process my source code to generate the Log4j2Plugins.dat. This is all functioning correctly and working.
The only matter is the PluginProcessor logging during compile time printing those logs messages.

Thank you for your response and appreciate further guidance in the matter.

[ppkarwasz]

The latest Log4j 2 release is always published from the 2.x branch.

I downloaded the source for the latest log4j release (https://github.com/apache/logging-log4j2/releases/tag/rel%2F2.24.3). I am still not seeing the 2.x version of Plugin Processor in the latest release.

The patch releases for 2.24.x, were published from a separate branch (2.24.x), but this is the exception, rather than the norm. Release 2.25.0 will be published from 2.x. You can test our 2.25.0-SNAPSHOT snapshots available at https://repository.apache.org/snapshots/.

My use case is I need to register plugins. I am following this documentation: https://logging.apache.org/log4j/2.x/manual/plugins.html#plugin-registry This indicates I used should the annotationProcessor like:

    annotationProcessor 'org.apache.logging.log4j:log4j-core:2.24.3'

which will process my source code to generate the Log4j2Plugins.dat. This is all functioning correctly and working. The only matter is the PluginProcessor logging during compile time printing those logs messages.

If you have Log4j plugins, the compiler notes will still be there:

logging-log4j2/log4j-core/src/main/java/org/apache/logging/log4j/core/config/plugins/processor/PluginProcessor.java

Lines 102 to 120 in 5496c72

	// Write the cache file
	if (roundEnv.processingOver() && !processedElements.isEmpty()) {
	try {
	messager.printMessage(
	Diagnostic.Kind.NOTE,
	String.format(
	"%s: writing plugin descriptor for %d Log4j Plugins to `%s`.",
	PluginProcessor.class.getSimpleName(), processedElements.size(), PLUGIN_CACHE_FILE));
	writeCacheFile(processedElements.toArray(EMPTY_ELEMENT_ARRAY));
	} catch (final Exception e) {
	StringWriter sw = new StringWriter();
	sw.append(PluginProcessor.class.getSimpleName())
	.append(": unable to write plugin descriptor to file ")
	.append(PLUGIN_CACHE_FILE)
	.append("\n");
	e.printStackTrace(new PrintWriter(sw));
	processingEnv.getMessager().printMessage(Diagnostic.Kind.ERROR, sw.toString());
	}
	}

How exactly does Gradle fail in the presence of these messages?

[treyfarmigoni]

Good insight on the additional compiler notes I missed in the new version. Thank you.

It is not that the build is failing, but gradle is interpreting it as a "problem"

Using gradle 8.12, here is the output from my gradle build

> Task :...:compileJava
Note: Processing Log4j annotations
Note: Annotations processed
Note: Processing Log4j annotations
Note: No elements to process
Note: Processing Log4j annotations
Note: No elements to process
Note: Processing Log4j annotations
Note: No elements to process

[Incubating] Problems report is available at: file:///.../build/reports/problems/problems-report.html

[treyfarmigoni]

@ppkarwasz any suggestions?
Thank you in advance sir.

[ppkarwasz]

As you can see, most Apache projects don't use Gradle, so I couldn't say why Notes are classified as problems. You should probably ask the Gradle community.

From our side, we could probably offer a configuration option for the processor to skip the generation of notes, although I am not sure what purpose would that serve. @vy any ideas?

[vy]

@ppkarwasz, I am okay with the following plan, if @treyfarmigoni volunteers to submit a PR for it:

• Add an log4j.plugin.processor.minAllowedMessageKind argument to PluginProcessor and use it to filter printMessage() calls based on the provided Diagnostic.Kind
• Document the issue and the property in Registering plugins in a %collapsible