FileBasedCachingSameAsRetriever can make the service get stuck

[MichaelRoeder]

Problem Description

While storing the cache, a thread can get issues if there is not enough memory available.

Got a throwable from task eTConfig("XXX (uploaded)","QALD9 Test Multilingual","QA","STRONG_ENTITY_MATCH").
Task=ExperimentTask("eTConfig("XXX (uploaded)","QALD9 Test Multilingual","QA","STRONG_ENTITY_MATCH")")	state=TERMINATED	progress=100.0% of dataset	with exception: java.lang.OutOfMemoryError: Java heap space
	at java.io.ObjectOutputStream$HandleTable.growEntries(ObjectOutputStream.java:2347)
	at java.io.ObjectOutputStream$HandleTable.assign(ObjectOutputStream.java:2276)
	at java.io.ObjectOutputStream.writeString(ObjectOutputStream.java:1302)
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1172)
	at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
	at org.aksw.gerbil.semantic.sameas.impl.cache.FileBasedCachingSameAsRetriever.performCacheStorage(FileBasedCachingSameAsRetriever.java:233)
	at org.aksw.gerbil.semantic.sameas.impl.cache.FileBasedCachingSameAsRetriever.retrieveSameURIs(FileBasedCachingSameAsRetriever.java:158)
	at org.aksw.gerbil.semantic.sameas.impl.AbstractSameAsRetrieverDecorator.addSameURIs(AbstractSameAsRetrieverDecorator.java:43)
	at org.aksw.gerbil.execute.ExperimentTask.runExperiment(ExperimentTask.java:560)
	at org.aksw.gerbil.execute.ExperimentTask.run(ExperimentTask.java:167)
	at org.aksw.simba.topicmodeling.concurrent.workers.WorkerImpl.run(WorkerImpl.java:44)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)

The main problem with the experiment failing is that the file-based cache is blocked by the dead thread since it didn't give back the Semaphore. In the running screen, it looks like the following:

eTConfig("ABC (uploaded)","QALD9 Test Multilingual","QA","STRONG_ENTITY_MATCH")
state=WAITING
progress=100.0% of dataset
sun.misc.Unsafe.park(Native Method)
java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(AbstractQueuedSynchronizer.java:997)
java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1304)
java.util.concurrent.Semaphore.acquire(Semaphore.java:312)
org.aksw.gerbil.semantic.sameas.impl.cache.FileBasedCachingSameAsRetriever.retrieveSameURIs(FileBasedCachingSameAsRetriever.java:132)
org.aksw.gerbil.semantic.sameas.impl.AbstractSameAsRetrieverDecorator.addSameURIs(AbstractSameAsRetrieverDecorator.java:43)
org.aksw.gerbil.execute.ExperimentTask.runExperiment(ExperimentTask.java:560)
org.aksw.gerbil.execute.ExperimentTask.run(ExperimentTask.java:167)
org.aksw.simba.topicmodeling.concurrent.workers.WorkerImpl.run(WorkerImpl.java:44)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
java.lang.Thread.run(Thread.java:748)

eTConfig("ABC (uploaded)","QALD9 Test Multilingual","QA","STRONG_ENTITY_MATCH")
state=WAITING
progress=100.0% of dataset
sun.misc.Unsafe.park(Native Method)
java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(AbstractQueuedSynchronizer.java:997)
java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1304)
java.util.concurrent.Semaphore.acquire(Semaphore.java:312)
org.aksw.gerbil.semantic.sameas.impl.cache.FileBasedCachingSameAsRetriever.retrieveSameURIs(FileBasedCachingSameAsRetriever.java:132)
org.aksw.gerbil.semantic.sameas.impl.AbstractSameAsRetrieverDecorator.addSameURIs(AbstractSameAsRetrieverDecorator.java:43)
org.aksw.gerbil.execute.ExperimentTask.runExperiment(ExperimentTask.java:560)
org.aksw.gerbil.execute.ExperimentTask.run(ExperimentTask.java:167)
org.aksw.simba.topicmodeling.concurrent.workers.WorkerImpl.run(WorkerImpl.java:44)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
java.lang.Thread.run(Thread.java:748)

eTConfig("ABC (uploaded)","QALD9 Test Multilingual","QA","STRONG_ENTITY_MATCH")
state=WAITING
progress=100.0% of dataset
sun.misc.Unsafe.park(Native Method)
java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(AbstractQueuedSynchronizer.java:997)
java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1304)
java.util.concurrent.Semaphore.acquire(Semaphore.java:312)
org.aksw.gerbil.semantic.sameas.impl.cache.FileBasedCachingSameAsRetriever.retrieveSameURIs(FileBasedCachingSameAsRetriever.java:114)
org.aksw.gerbil.semantic.sameas.impl.AbstractSameAsRetrieverDecorator.addSameURIs(AbstractSameAsRetrieverDecorator.java:43)
org.aksw.gerbil.execute.ExperimentTask.runExperiment(ExperimentTask.java:565)
org.aksw.gerbil.execute.ExperimentTask.run(ExperimentTask.java:167)
org.aksw.simba.topicmodeling.concurrent.workers.WorkerImpl.run(WorkerImpl.java:44)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
java.lang.Thread.run(Thread.java:748)

eTConfig("ABC (uploaded)","QALD9 Test Multilingual","QA","STRONG_ENTITY_MATCH")
state=WAITING
progress=100.0% of dataset
sun.misc.Unsafe.park(Native Method)
java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(AbstractQueuedSynchronizer.java:997)
java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1304)
java.util.concurrent.Semaphore.acquire(Semaphore.java:312)
org.aksw.gerbil.semantic.sameas.impl.cache.FileBasedCachingSameAsRetriever.retrieveSameURIs(FileBasedCachingSameAsRetriever.java:132)
org.aksw.gerbil.semantic.sameas.impl.AbstractSameAsRetrieverDecorator.addSameURIs(AbstractSameAsRetrieverDecorator.java:43)
org.aksw.gerbil.execute.ExperimentTask.runExperiment(ExperimentTask.java:560)
org.aksw.gerbil.execute.ExperimentTask.run(ExperimentTask.java:167)
org.aksw.simba.topicmodeling.concurrent.workers.WorkerImpl.run(WorkerImpl.java:44)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
java.lang.Thread.run(Thread.java:748)

eTConfig("ABC (uploaded)","QALD9 Test Multilingual","QA","STRONG_ENTITY_MATCH")
state=WAITING
progress=100.0% of dataset
sun.misc.Unsafe.park(Native Method)
java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(AbstractQueuedSynchronizer.java:997)
java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1304)
java.util.concurrent.Semaphore.acquire(Semaphore.java:312)
org.aksw.gerbil.semantic.sameas.impl.cache.FileBasedCachingSameAsRetriever.retrieveSameURIs(FileBasedCachingSameAsRetriever.java:132)
org.aksw.gerbil.semantic.sameas.impl.AbstractSameAsRetrieverDecorator.addSameURIs(AbstractSameAsRetrieverDecorator.java:43)
org.aksw.gerbil.execute.ExperimentTask.runExperiment(ExperimentTask.java:560)
org.aksw.gerbil.execute.ExperimentTask.run(ExperimentTask.java:167)
org.aksw.simba.topicmodeling.concurrent.workers.WorkerImpl.run(WorkerImpl.java:44)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
java.lang.Thread.run(Thread.java:748)

eTConfig("ABC (uploaded)","QALD9 Test Multilingual","QA","STRONG_ENTITY_MATCH")
state=WAITING
progress=100.0% of dataset
sun.misc.Unsafe.park(Native Method)
java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(AbstractQueuedSynchronizer.java:997)
java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1304)
java.util.concurrent.Semaphore.acquire(Semaphore.java:312)
org.aksw.gerbil.semantic.sameas.impl.cache.FileBasedCachingSameAsRetriever.retrieveSameURIs(FileBasedCachingSameAsRetriever.java:132)
org.aksw.gerbil.semantic.sameas.impl.AbstractSameAsRetrieverDecorator.addSameURIs(AbstractSameAsRetrieverDecorator.java:43)
org.aksw.gerbil.execute.ExperimentTask.runExperiment(ExperimentTask.java:560)
org.aksw.gerbil.execute.ExperimentTask.run(ExperimentTask.java:167)
org.aksw.simba.topicmodeling.concurrent.workers.WorkerImpl.run(WorkerImpl.java:44)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
java.lang.Thread.run(Thread.java:748)

eTConfig("ABC (uploaded)","QALD9 Test Multilingual","QA","STRONG_ENTITY_MATCH")
state=WAITING
progress=100.0% of dataset
sun.misc.Unsafe.park(Native Method)
java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(AbstractQueuedSynchronizer.java:997)
java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1304)
java.util.concurrent.Semaphore.acquire(Semaphore.java:312)
org.aksw.gerbil.semantic.sameas.impl.cache.FileBasedCachingSameAsRetriever.retrieveSameURIs(FileBasedCachingSameAsRetriever.java:132)
org.aksw.gerbil.semantic.sameas.impl.AbstractSameAsRetrieverDecorator.addSameURIs(AbstractSameAsRetrieverDecorator.java:43)
org.aksw.gerbil.execute.ExperimentTask.runExperiment(ExperimentTask.java:560)
org.aksw.gerbil.execute.ExperimentTask.run(ExperimentTask.java:167)
org.aksw.simba.topicmodeling.concurrent.workers.WorkerImpl.run(WorkerImpl.java:44)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
java.lang.Thread.run(Thread.java:748)

eTConfig("ABC (uploaded)","QALD9 Test Multilingual","QA","STRONG_ENTITY_MATCH")
state=WAITING
progress=100.0% of dataset
sun.misc.Unsafe.park(Native Method)
java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(AbstractQueuedSynchronizer.java:997)
java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1304)
java.util.concurrent.Semaphore.acquire(Semaphore.java:312)
org.aksw.gerbil.semantic.sameas.impl.cache.FileBasedCachingSameAsRetriever.retrieveSameURIs(FileBasedCachingSameAsRetriever.java:132)
org.aksw.gerbil.semantic.sameas.impl.AbstractSameAsRetrieverDecorator.addSameURIs(AbstractSameAsRetrieverDecorator.java:43)
org.aksw.gerbil.execute.ExperimentTask.runExperiment(ExperimentTask.java:560)
org.aksw.gerbil.execute.ExperimentTask.run(ExperimentTask.java:167)
org.aksw.simba.topicmodeling.concurrent.workers.WorkerImpl.run(WorkerImpl.java:44)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
java.lang.Thread.run(Thread.java:748)

eTConfig("ABC (uploaded)","QALD9 Test Multilingual","QA","STRONG_ENTITY_MATCH")
state=WAITING
progress=100.0% of dataset
sun.misc.Unsafe.park(Native Method)
java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(AbstractQueuedSynchronizer.java:997)
java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1304)
java.util.concurrent.Semaphore.acquire(Semaphore.java:312)
org.aksw.gerbil.semantic.sameas.impl.cache.FileBasedCachingSameAsRetriever.retrieveSameURIs(FileBasedCachingSameAsRetriever.java:132)
org.aksw.gerbil.semantic.sameas.impl.AbstractSameAsRetrieverDecorator.addSameURIs(AbstractSameAsRetrieverDecorator.java:43)
org.aksw.gerbil.execute.ExperimentTask.runExperiment(ExperimentTask.java:560)
org.aksw.gerbil.execute.ExperimentTask.run(ExperimentTask.java:167)
org.aksw.simba.topicmodeling.concurrent.workers.WorkerImpl.run(WorkerImpl.java:44)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
java.lang.Thread.run(Thread.java:748)

Solutions

• Try to give back the Semaphore even in severe cases (<- might not be possible).
• Get rid of the Semaphore and use synchronize for thread synchronization
• Check why the file based retriever has issues when it simply has to write it's data to the disk.

[MichaelRoeder]

The file-based cache uses two semaphores to allow concurrent read access to the cache. This might not be possible with a synchronize block. 🤔

[MichaelRoeder]

Check why the file based retriever has issues when it simply has to write it's data to the disk.

It already seriliazes the objects one by one. A further improvement is possible by serializing them as Strings instead of objects. However, this may lead to quite some overhead without a big impact.

The issue should be solved.