[jira] [Created] (POOL-396) Exceptions in validation can cause an object's lifecycle to be stuck in EVICTION state

[Jeremy Kong (Jira)]

Jeremy Kong created POOL-396:
--------------------------------

             Summary: Exceptions in validation can cause an object's lifecycle 
to be stuck in EVICTION state
                 Key: POOL-396
                 URL: https://issues.apache.org/jira/browse/POOL-396
             Project: Commons Pool
          Issue Type: Bug
    Affects Versions: 2.9.0, 2.4.2
            Reporter: Jeremy Kong


Currently, if validation of an object throws an exception when testing an idle 
object during eviction, an exception will be thrown from the evict() method. 
This causes the object to be left in the EVICTION state, but still be present 
in the idleObjects queue.

Future runs of the eviction thread will run into an infinite loop, because they 
pick up the afflicted object from the queue, fail to set its state to EVICTION, 
don't count it as a test, and repeat ad infinitum. This infinite loop means 
that no further evictions will take place; it also causes increases in garbage 
collection owing to allocation of the EvictionIterator on each loop iteration.

This test added to TestGenericObjectPool (plus a small change allowing 
exceptions to be thrown from the validateObject method of SimpleFactory) 
reproduces the issue.
{code:java}
@Test
@Timeout(value = 60000, unit = TimeUnit.MILLISECONDS)
public void testExceptionInValidationDuringEviction() throws Exception {
    genericObjectPool.setMaxIdle(1);
    genericObjectPool.setMaxTotal(2);
    genericObjectPool.setNumTestsPerEvictionRun(1);
    genericObjectPool.setMinEvictableIdleTime(Duration.ofMillis(0));
    genericObjectPool.setTestWhileIdle(true);

    String active = genericObjectPool.borrowObject();
    genericObjectPool.returnObject(active);

    simpleFactory.setThrowExceptionOnValidate(true);

    try {
        genericObjectPool.evict();
    } catch (Exception e) {
        // OK that a given run fails. But the object should still be evicted.
    }
    genericObjectPool.evict(); // currently fails: causes an infinite loop!
    assertEquals(0, genericObjectPool.getNumActive());
    assertEquals(0, genericObjectPool.getNumIdle());
}

{code}
It seems that protection against exceptions thrown by validation code exist 
elsewhere (e.g. in borrowObject()); similarly, protections against exceptions 
thrown by user eviction policy code exist in evict(). So it looks like the 
testWhileIdle() portion of evict() needs to similarly be protected.

Thanks!
Jeremy



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