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JAVA-6155 add thread dumps to evergreen logs on failed test cases #1932

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JAVA-6155 add thread dumps to evergreen logs on failed test cases #1932

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3f71147
JAVA-6155 add thread dumps to failed test cases
Apr 1, 2026
8102cec
address copilot review
Apr 1, 2026
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1 change: 1 addition & 0 deletions driver-core/src/test/resources/META-INF/services/org.junit.jupiter.api.extension.Extension
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com.mongodb.internal.diagnostics.ThreadDumpOnFailureExtension
1 change: 1 addition & 0 deletions driver-core/src/test/resources/junit-platform.properties
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junit.jupiter.extensions.autodetection.enabled=true
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Copilot AI Apr 1, 2026

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junit-platform.properties is included in driver-core’s testArtifacts JAR (see buildSrc/src/main/kotlin/conventions/test-artifacts.gradle.kts:26-29), and several other modules depend on :driver-core:testArtifacts for their tests (e.g., driver-sync/build.gradle.kts:37-39). That means this setting may unintentionally enable JUnit Jupiter extension autodetection beyond driver-core depending on classpath resource resolution. If the intent is to scope this behavior to a specific module/test task, consider enabling it via the Gradle Test task/system property instead, or placing a shared properties file in a deliberately shared test-resources location.

Suggested change
junit.jupiter.extensions.autodetection.enabled=true
# NOTE:
# This file is included in driver-core's testArtifacts JAR and is therefore
# visible on the test classpath of other modules that depend on :driver-core:testArtifacts.
# Enabling JUnit Jupiter extension autodetection here would unintentionally
# turn it on for those modules as well.
#
# If you need autodetection, configure it in the specific module or Gradle
# Test task instead (e.g. via system property junit.jupiter.extensions.autodetection.enabled=true),
# or in a module-local junit-platform.properties that is not shared via testArtifacts.
#
# Example (do NOT uncomment here unless you really want it shared globally):
# junit.jupiter.extensions.autodetection.enabled=true

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57 changes: 57 additions & 0 deletions driver-core/src/test/unit/com/mongodb/internal/diagnostics/ThreadDumpOnFailureExtension.java
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/*
* Copyright 2008-present MongoDB, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

package com.mongodb.internal.diagnostics;

import java.lang.management.ManagementFactory;
import java.lang.management.ThreadInfo;
import java.lang.management.ThreadMXBean;


import com.mongodb.internal.diagnostics.logging.Logger;
import com.mongodb.internal.diagnostics.logging.Loggers;

import org.junit.jupiter.api.extension.ExtensionContext;
import org.junit.jupiter.api.extension.TestWatcher;


Comment on lines +19 to +30
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Import order/grouping here is inconsistent with the repo’s established convention (typically project com.mongodb.* imports first, then org.*, then java.*, e.g. driver-core/src/test/unit/com/mongodb/internal/connection/ConnectionPoolTest.java:19-28). Reorder the imports to match the surrounding codebase style to keep diffs consistent and reduce merge noise.

Suggested change
import java.lang.management.ManagementFactory;
import java.lang.management.ThreadInfo;
import java.lang.management.ThreadMXBean;
import com.mongodb.internal.diagnostics.logging.Logger;
import com.mongodb.internal.diagnostics.logging.Loggers;
import org.junit.jupiter.api.extension.ExtensionContext;
import org.junit.jupiter.api.extension.TestWatcher;
import com.mongodb.internal.diagnostics.logging.Logger;
import com.mongodb.internal.diagnostics.logging.Loggers;
import org.junit.jupiter.api.extension.ExtensionContext;
import org.junit.jupiter.api.extension.TestWatcher;
import java.lang.management.ManagementFactory;
import java.lang.management.ThreadInfo;
import java.lang.management.ThreadMXBean;

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/**
* A JUnit 5 extension that prints a thread dump to the log when a test fails.
*/
public final class ThreadDumpOnFailureExtension implements TestWatcher {

private static final Logger LOGGER = Loggers.getLogger(ThreadDumpOnFailureExtension.class.getName());
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Logger naming is inconsistent with other driver-core tests: most use a short suffix like ClassName.class.getSimpleName() (e.g., ConnectionPoolTest / ConnectionPoolAsyncTest). Passing class.getName() here yields a very long logger name (org.mongodb.driver.com.mongodb...) that’s harder to filter/read in logs; consider switching to getSimpleName() or a conventional test logger suffix.

Suggested change
private static final Logger LOGGER = Loggers.getLogger(ThreadDumpOnFailureExtension.class.getName());
private static final Logger LOGGER = Loggers.getLogger(ThreadDumpOnFailureExtension.class.getSimpleName());

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@strogiyotec strogiyotec Apr 1, 2026

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replaced to use simple name


@Override
public void testFailed(final ExtensionContext context, final Throwable cause) {
String testName = context.getDisplayName();
String threadDump = getAllThreadsDump();
LOGGER.error("Test failed: " + testName + "\nThread dump:\n" + threadDump);
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testFailed ignores the provided cause, so the log entry won’t include the exception/stack trace that triggered the failure. Logging the throwable (e.g., using the error(String, Throwable) overload) would keep the failure reason adjacent to the thread dump in Evergreen/local logs.

Suggested change
LOGGER.error("Test failed: " + testName + "\nThread dump:\n" + threadDump);
LOGGER.error("Test failed: " + testName + "\nThread dump:\n" + threadDump, cause);

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@strogiyotec strogiyotec Apr 1, 2026 •
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the cause will already be provided on assertion fail I don't think duplicating it for thread dumps makes sense

}
Comment on lines +39 to +43
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This logs a full JVM thread dump on every failed test. When failures cascade (e.g., environment outage causing many tests to fail), this can produce very large Evergreen logs and make the original failures harder to find. Consider throttling (e.g., only dump once per JVM via an AtomicBoolean, or once per test class) and/or adding a clear header/footer delimiter so each dump is easy to locate in the log stream.

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private static String getAllThreadsDump() {
final ThreadMXBean threadMXBean = ManagementFactory.getThreadMXBean();
ThreadInfo[] threadInfos = threadMXBean.dumpAllThreads(
threadMXBean.isObjectMonitorUsageSupported(),
threadMXBean.isSynchronizerUsageSupported()
);
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getAllThreadsDump() (via ThreadMXBean.dumpAllThreads) can throw at runtime (e.g., SecurityException). If this happens inside testFailed, the extension itself may error and you’ll lose the diagnostic output. Consider wrapping thread-dump generation in a try/catch and logging a clear fallback message so the original test failure reporting isn’t impacted.

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@strogiyotec strogiyotec Apr 1, 2026

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good point, wrapped it with try catch

StringBuilder sb = new StringBuilder(1024);
for (ThreadInfo info : threadInfos) {
sb.append(info);
}
return sb.toString();
}
}
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