RFR: JDK-8014045 - test/java/lang/management/PlatformLoggingMXBean/LoggingMXBeanTest.java failing intermittently

Daniel Fuchs daniel.fuchs at oracle.com
Wed Jun 19 09:03:01 UTC 2013

On 6/19/13 11:00 AM, Daniel Fuchs wrote:
> On 6/13/13 10:05 PM, Mandy Chung wrote:
>> Daniel,
>> I wonder what the list of logger names (loggers1 and loggers2) returned
>> by LoggingMXBean contains and that may include loggers in the running VM
>> other than the ones created and kept a strong reference by the test. In
>> other words,  would it be possible for the running VM that has loggers
>> that are not created by the test and got GC'ed?
> Hi Mandy,
> I have added a System.out.println to print the list of logger names.
> By running jtreg on my machine I could see that this list does contain
> system logger names (mostly JMX loggers).
> I believe those loggers are strongly referenced by JMX.
> Other than those I could see "" and "global".
> <http://cr.openjdk.java.net/~dfuchs/JDK-8014045/webrev.00/>


-- daniel

> However - since this seems to be an intermittent failure - maybe the
> logger that was causing the problem had already been gc'ed before
> getLoggerNames() and therefore didn't appear in this list.
> The test would fail when that 'transient' logger appears in the
> list but is gc'ed before getLoggerLevel() is called.
> Anyway - it's possible that some platform class
> is calling:
>     Logger log = Logger.getLogger(<some-name>);
>     if (log.isLoggable(<some-leve>)) {...}
> without keeping a strong reference to the logger in the class.
> In that case I guess it would be possible for that <some-name>
> to appear transiently in the logger's name list - and be gc'ed
> just after...
> -- daniel
>> Mandy
>> On 6/13/2013 6:47 AM, Daniel Fuchs wrote:
>>> Hi,
>>> Please find below an attempt at fixing
>>> test/java/lang/management/PlatformLoggingMXBean/LoggingMXBeanTest.java
>>> This is an intermittent failure which I haven't managed to reproduce,
>>> so I am reduced to figure out what could have gone wrong by analyzing
>>> the code.
>>> AFAICT the NPE is thrown when LoggingMXBean.getLogerLevel(logger)
>>> returns null - which I believe can only happen
>>> when LogManager.getLogger() returns null.
>>> I see that LogManager uses weak references to hold loggers - so my
>>> suspicion is that one of the logger whose name had been returned by
>>> getLoggerNames() has been gc'ed in between the two calls.
>>> I have modified the code to accept this possibility - excluding the
>>> two loggers for which the test itself holds a strong reference, as
>>> these should not have been gc'ed.
>>> I can't guarantee that it will fix the issue, but if it does not,
>>> we will at least be able to disregard this possibility :-)
>>> <http://cr.openjdk.java.net/~dfuchs/JDK-8014045/webrev.00/>
>>> -- daniel

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