[Enhancement] Bridge java.util.logging to slf4j to fix log leakage #67129

arvindKandpal-ksolves · 2025-12-23T07:42:56Z

Why I'm doing:

Currently, third-party libraries that rely on java.util.logging (JUL), such as jprotobuf-rpc-socket, print logs directly to stdout (which redirects to fe.out) instead of the standard log files. This happens because the JUL-to-SLF4J bridge is not properly initialized, causing log leakage and making debugging difficult as these logs are missing from fe.log.

What I'm doing:

I have implemented the standard bridging mechanism to route java.util.logging calls to SLF4J (Log4j2).

Changes:

Added the org.slf4j:jul-to-slf4j dependency in fe/pom.xml and fe/fe-core/pom.xml.
Initialized LogManager.getLogManager().reset() and SLF4JBridgeHandler.install() in Log4jConfig.java to redirect logs.
Added a unit test testJulToSlf4jBridge in Log4jConfigTest.java to verify that JUL logs are correctly captured by Log4j2.

This PR supersedes and fixes the unmerged PR #56156.

Fixes #31777

What type of PR is this:

Does this PR entail a change in behavior?

Yes, this PR will result in a change in behavior.
No, this PR will not result in a change in behavior.

If yes, please specify the type of change:

Interface/UI changes: syntax, type conversion, expression evaluation, display information
Parameter changes: default values, similar parameters but with different default values
Policy changes: use new policy to replace old one, functionality automatically enabled
Feature removed
Miscellaneous: upgrade & downgrade compatibility, etc. (Logging behavior improvement)

Checklist:

I have added test cases for my bug fix or my new feature
This pr needs user documentation (for new or modified features or behaviors)
I have added documentation for my new feature or new function
This is a backport pr

Bugfix cherry-pick branch check:

Note

Ensures logs from JUL-based libraries flow into the existing SLF4J/Log4j2 pipeline and match configured log levels.

Add org.slf4j:jul-to-slf4j dependency in fe/pom.xml and fe/fe-core/pom.xml
In Log4jConfig.reconfig(), install SLF4JBridgeHandler, remove root JUL handlers, and set JUL root level based on sys_log_level (DEBUG→FINE, INFO→INFO, WARN→WARNING, ERROR|FATAL→SEVERE)
Add unit tests in Log4jConfigTest: testJulToSlf4jBridge (JUL logs captured by Log4j2) and testJulLevelMapping (JUL level mapping and invalid level handling)

^{Written by Cursor Bugbot for commit d1aaf5e. This will update automatically on new commits. Configure here.}

fe/fe-core/src/main/java/com/starrocks/common/Log4jConfig.java

Copilot

Pull request overview

This PR fixes a log leakage issue where third-party libraries using java.util.logging (JUL) were printing logs directly to stdout/fe.out instead of the standard log files. The solution implements the standard JUL-to-SLF4J bridging mechanism to route all JUL logs through Log4j2.

Key changes:

Added jul-to-slf4j dependency to enable JUL bridge functionality
Initialized the SLF4J bridge in the logging configuration to redirect JUL logs
Added a unit test to verify JUL logs are correctly captured by Log4j2

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
fe/pom.xml	Added jul-to-slf4j dependency version 1.7.30 to parent POM dependency management
fe/fe-core/pom.xml	Added jul-to-slf4j dependency reference in fe-core module
fe/fe-core/src/main/java/com/starrocks/common/Log4jConfig.java	Added JUL bridge initialization by calling LogManager.reset() and SLF4JBridgeHandler.install() in reconfig()
fe/fe-core/src/test/java/com/starrocks/common/Log4jConfigTest.java	Added unit test to verify JUL logs are captured and routed through Log4j2

fe/fe-core/src/main/java/com/starrocks/common/Log4jConfig.java

fe/fe-core/src/test/java/com/starrocks/common/Log4jConfigTest.java

Copilot

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

fe/fe-core/src/main/java/com/starrocks/common/Log4jConfig.java

fe/fe-core/src/test/java/com/starrocks/common/Log4jConfigTest.java

arvindKandpal-ksolves · 2025-12-23T17:03:01Z

@kevincai I have pushed the final implementation addressing all feedback.

1. Regarding Logic in `reconfig()` (Addressing Copilot)

I noticed Copilot suggested using LogManager.getLogManager().reset(). However, I intentionally decided against it.

Reason: reset() is a destructive operation that closes all handlers across the entire JVM logging context. This is risky as it could break logging for other third-party components (like Hadoop/Netty) running in the same process.
Solution: I used SLF4JBridgeHandler.removeHandlersForRootLogger(). This is a surgical approach that strictly prevents the stdout leakage (our main goal) without wiping out the global logging state.

2. Implementation Updates

Dynamic Level Alignment: JUL levels now sync with StarRocks (sys_log_level) to ensure performance.
Validation: Added strict validation using DEBUG_LEVELS.contains() logic (defaulting to INFO for unknown levels like TRACE).
Test Isolation: Updated testJulLevelMapping to verify the validation logic and added a try-finally block to strictly restore the original log levels.

3. CI Failure

I noticed the SQL-Tester failed with Base Compaction Failing and Manual compaction task is running. Since this PR only modifies Logging Configuration and has no impact on Backend storage/compaction logic, this appears to be a flaky test/environment issue.

Could you please trigger the CI checks again?

kevincai · 2025-12-24T02:21:43Z

@Mergifyio rebase

mergify · 2025-12-24T02:22:36Z

rebase

✅ Branch has been successfully rebased

arvindKandpal-ksolves · 2025-12-24T05:54:42Z

@kevincai Thanks for the approval and the rebase!

I noticed the SQL-Tester failed with couldn't get JNIEnv (BE:10003) and Backend node not found.

Since this PR touches the Java logging initialization, could this be a side effect causing the JVM/BE to crash, or does this look like a known flaky CI issue to you?

Please let me know if you want me to revert anything.

kevincai · 2025-12-24T05:56:53Z

@kevincai Thanks for the approval and the rebase!

I noticed the SQL-Tester failed with couldn't get JNIEnv (BE:10003) and Backend node not found.

Since this PR touches the Java logging initialization, could this be a side effect causing the JVM/BE to crash, or does this look like a known flaky CI issue to you?

Please let me know if you want me to revert anything.

It's an CI env issue, I will take care of it.

alvin-celerdata · 2025-12-24T05:57:14Z

@cursor review

fe/fe-core/src/main/java/com/starrocks/common/Log4jConfig.java

fe/fe-core/src/test/java/com/starrocks/common/Log4jConfigTest.java

arvindKandpal-ksolves · 2025-12-26T06:41:19Z

@kevincai @alvin-celerdata The latest CI (FE UT) run failed on QueryPlannerTest (specifically testSqlDigestBlackList and others).

The error message <d != java.lang.String> indicates a weird environment/serialization issue, and QueryPlanner logic is completely unrelated to the logging configuration changes in this PR.

Could you please re-trigger the CI to clear this flake?

alvin-celerdata · 2025-12-26T16:25:35Z

@cursor review

cursor

✅ Bugbot reviewed your changes and found no bugs!

kevincai · 2025-12-27T10:40:26Z

@Mergifyio rebase

Fixes StarRocks#31777. This PR bridges java.util.logging logs to slf4j so they are handled by log4j2 configuration instead of being leaked to stdout. This is necessary for libraries like jprotobuf-rpc-socket which use java.util.logging. Changes: 1. Add jul-to-slf4j dependency. 2. Initialize SLF4JBridgeHandler in Log4jConfig with dynamic level alignment. 3. Replace LogManager.reset() with removeHandlersForRootLogger() for safety. 4. Add unit test to verify the bridge. Signed-off-by: arvindksi274-ksolves <[email protected]>

Fixes StarRocks#31777. This PR bridges java.util.logging logs to slf4j so they are handled by log4j2 configuration instead of being leaked to stdout. This is necessary for libraries like jprotobuf-rpc-socket which use java.util.logging. Changes: 1. Add jul-to-slf4j dependency. 2. Initialize SLF4JBridgeHandler in Log4jConfig with dynamic level alignment. 3. Replace LogManager.reset() with removeHandlersForRootLogger() for safety. 4. Add validation logic to default to INFO for unsupported levels. 5. Add unit test to verify the bridge, level mapping, and fallback logic. Signed-off-by: arvindksi274-ksolves <[email protected]>

mergify · 2025-12-27T10:40:54Z

rebase

✅ Branch has been successfully rebased

sonarqubecloud · 2025-12-27T10:50:32Z

Quality Gate passed

Issues
4 New issues
0 Accepted issues

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

See analysis details on SonarQube Cloud

github-actions · 2025-12-27T11:48:21Z

[Java-Extensions Incremental Coverage Report]

✅ pass : 0 / 0 (0%)

github-actions · 2025-12-27T11:49:16Z

[FE Incremental Coverage Report]

✅ pass : 15 / 16 (93.75%)

file detail

	path	covered_line	new_line	coverage	not_covered_line_detail
🔵	com/starrocks/common/Log4jConfig.java	15	16	93.75%	[361]

github-actions · 2025-12-27T11:49:32Z

[BE Incremental Coverage Report]

✅ pass : 0 / 0 (0%)

alvin-celerdata · 2025-12-27T18:29:59Z

@cursor review

cursor

✅ Bugbot reviewed your changes and found no bugs!

github-actions · 2025-12-27T18:40:05Z

@Mergifyio backport branch-4.0

mergify · 2025-12-27T18:40:12Z

backport branch-4.0

✅ Backports have been created

Details

#67279 [Enhancement] Bridge java.util.logging to slf4j to fix log leakage (backport #67129) has been created for branch branch-4.0

…67129) Signed-off-by: arvindksi274-ksolves <[email protected]> (cherry picked from commit 5b244bd)

…ackport #67129) (#67279) Signed-off-by: arvindksi274-ksolves <[email protected]> Co-authored-by: Arvind Kandpal <[email protected]>

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kevincai merged commit 5b244bd into StarRocks:main Dec 27, 2025
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[Enhancement] Bridge java.util.logging to slf4j to fix log leakage (#…

0991d23

…67129) Signed-off-by: arvindksi274-ksolves <[email protected]> (cherry picked from commit 5b244bd)

mergify bot mentioned this pull request Dec 27, 2025

[Enhancement] Bridge java.util.logging to slf4j to fix log leakage (backport #67129) #67279

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[Enhancement] Bridge java.util.logging to slf4j to fix log leakage (b…

9d0cec2

…ackport #67129) (#67279) Signed-off-by: arvindksi274-ksolves <[email protected]> Co-authored-by: Arvind Kandpal <[email protected]>

github-actions bot added the 4.0-merged label Dec 27, 2025

[Enhancement] Bridge java.util.logging to slf4j to fix log leakage #67129

[Enhancement] Bridge java.util.logging to slf4j to fix log leakage #67129

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arvindKandpal-ksolves commented Dec 23, 2025

1. Regarding Logic in reconfig() (Addressing Copilot)

2. Implementation Updates

3. CI Failure

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1. Regarding Logic in `reconfig()` (Addressing Copilot)

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