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Optimise the strategy we use to reset the classloader in the Common ForkJoin ThreadPool #18889

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Jul 21, 2021
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Optimise the strategy we use to reset the classloader in the Common ForkJoin ThreadPool #18889

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55 changes: 33 additions & 22 deletions core/deployment/src/main/java/io/quarkus/runner/bootstrap/ForkJoinClassLoading.java
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Original file line number Diff line number Diff line change
Expand Up @@ -20,31 +20,42 @@ public class ForkJoinClassLoading {
* Really we should just not use the common pool at all.
*/
public static void setForkJoinClassLoader(ClassLoader classLoader) {
CountDownLatch allDone = new CountDownLatch(ForkJoinPool.getCommonPoolParallelism());
CountDownLatch taskRelease = new CountDownLatch(1);
for (int i = 0; i < ForkJoinPool.getCommonPoolParallelism(); ++i) {
ForkJoinPool.commonPool().execute(new Runnable() {
@Override
public void run() {
Thread.currentThread().setContextClassLoader(classLoader);
allDone.countDown();
try {
taskRelease.await();
} catch (InterruptedException e) {
log.error("Failed to set fork join ClassLoader", e);
final ForkJoinPool commonPool = ForkJoinPool.commonPool();

final int activeThreadCount = commonPool.getActiveThreadCount();

//The following approach is rather heavy, but there's good chances that there are actually no active threads,
//so skip it in this case.
//Additionally, if we can skip this this will prevent us from actually forcing to start all threads in the pool.
if (activeThreadCount > 0) {
//TODO we could theoretically improve this by using the system property java.util.concurrent.ForkJoinPool.common.threadFactory
//and force the common pool to register created threads so that we can reach and reset them.
CountDownLatch allDone = new CountDownLatch(ForkJoinPool.getCommonPoolParallelism());
CountDownLatch taskRelease = new CountDownLatch(1);
for (int i = 0; i < ForkJoinPool.getCommonPoolParallelism(); ++i) {
commonPool.execute(new Runnable() {
@Override
public void run() {
Thread.currentThread().setContextClassLoader(classLoader);
allDone.countDown();
try {
taskRelease.await();
} catch (InterruptedException e) {
log.error("Failed to set fork join ClassLoader", e);
}
}
});
}
try {
if (!allDone.await(1, TimeUnit.SECONDS)) {
log.error(
"Timed out trying to set fork join ClassLoader, this should never happen unless something has tied up a fork join thread before the app launched");
}
});
}
try {
if (!allDone.await(1, TimeUnit.SECONDS)) {
log.error(
"Timed out trying to set fork join ClassLoader, this should never happen unless something has tied up a fork join thread before the app launched");
} catch (InterruptedException e) {
log.error("Failed to set fork join ClassLoader", e);
} finally {
taskRelease.countDown();
}
} catch (InterruptedException e) {
log.error("Failed to set fork join ClassLoader", e);
} finally {
taskRelease.countDown();
}
}
}