<snip>
I guess it's good news that CI hit the error below when reviewing the PR
that I had prepared for the POOL-391 fixes. I only saw it once in many
test runs and only on OpenJDK 20.0.1. Looks like CI is running 17 on
azure-linux. I am pretty sure it has nothing to do with the changes in the
PR, partly because I saw it once running the first RC code.
This is very strange and troubling. More eyeballs most welcome. Here is
the problem:
The NPE below happens inside GKOP addIdleObject, which is called by
addObject. The code for addObject follows the standard pattern:
register(key);
try {
addIdleObject(key, create(key));
} finally {
deregister(key);
}
So addIdleObject is called while the owning thread has the key
"registered." To register is key is basically sayinig you are interested
in / about to do something to its associated pool. There is a
numInterested counter (attached to the keyed pool) that gets incremented
when a thread registers a key and decrremented when the key is
deregistered. Registration creates a pool and iniitializes its counter if
there is no pool under the given key. When pools are deregistered, the
counter is checked and if the pool has no instances under management and
the counter is zero, the pool is removed. In this case, the registration
in addObject should prevent the pool being removed before or during
execution of addIdleObject, but the NPE means it has been removed. Somehow
numInterested is getting corrupted.
I will keep trying to get this to happen and see if I can find scenarios
where deregister is somehow called twice for one register. Any suggestions
or success getting this to happen with the code now in master most
appreciated.
Phil
> 2. On MacOS 13.4.1, OpenJDK 20.0.1, I got the following test failure just one
> time and can't reproduce:
>
> java.util.concurrent.ExecutionException: java.lang.NullPointerException:
> Cannot invoke
> "org.apache.commons.pool2.impl.GenericKeyedObjectPool$ObjectDeque.getIdleObjects()"
> because the return value of "java.util.Map.get(Object)" is null
>
> at java.base/java.util.concurrent.FutureTask.report(FutureTask.java:122)
> at java.base/java.util.concurrent.FutureTask.get(FutureTask.java:191)
> at
> org.apache.commons.pool2.impl.TestGenericKeyedObjectPool.lambda$testConcurrentBorrowAndClear$2(TestGenericKeyedObjectPool.java:1056)
> ... 71 more
> Caused by: java.lang.NullPointerException: Cannot invoke
> "org.apache.commons.pool2.impl.GenericKeyedObjectPool$ObjectDeque.getIdleObjects()"
> because the return value of "java.util.Map.get(Object)" is null
> at
> org.apache.commons.pool2.impl.GenericKeyedObjectPool.addIdleObject(GenericKeyedObjectPool.java:307)
> at
> org.apache.commons.pool2.impl.GenericKeyedObjectPool.addObject(GenericKeyedObjectPool.java:332)
> at
> org.apache.commons.pool2.KeyedObjectPool.addObjects(KeyedObjectPool.java:136)
> at
> org.apache.commons.pool2.KeyedObjectPool.addObjects(KeyedObjectPool.java:113)
> at
> org.apache.commons.pool2.impl.TestGenericKeyedObjectPool.lambda$testConcurrentBorrowAndClear$0(TestGenericKeyedObjectPool.java:1036)
> at
> java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:577)
> at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:317)
> at
> java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
> at
> java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
> at java.base/java.lang.Thread.run(Thread.java:1623)
>
>
>
>
