Re: Heisenbug-ish NullPointerExceptions in DataContext.flushToParent()

> On 7 May 2021, at 13:34, John Huss <[email protected]> wrote:
> 
> On Fri, May 7, 2021 at 8:18 AM Hugi Thordarson <[email protected]> wrote:
> 
>> Well I'll be… Over two decades of full time Java and I somehow didn't know
>> about that stack trace omission. Yikes. Thanks!
> 
> You’ve just never caused an error that bad before right? 😉

*cough* yes. Of course, that must be it 😁

>> ....
>> So it seems either 'snapshot' or 'objAttribute' is null, probably the
>> snapshot, right? Any ideas why that might be?
>> 
> 
> Yeah, it would be the snapshot is null. The snapshot cache is limited in
> size, so it may have purged that entry if you have a busy server. You could
> try increasing the size of the snapshot cache:
> 
> org.apache.cayenne.configuration.Constants.SNAPSHOT_CACHE_SIZE_PROPERTY

Good thinking, but I've already got a ginormous snapshot cache (3.000.000) for the traffic, so I don't think that's it.
Going to hammer away on this code path a bit and see if I can replicate the error.


>> 
>> - hugi
>> 
>> 
>> 
>>> On 7 May 2021, at 12:53, John Huss <[email protected]> wrote:
>>> 
>>> Or if you have older logs, you can look back farther to find one without
>>> the cause omitted.
>>> 
>>> On Fri, May 7, 2021 at 7:52 AM John Huss <[email protected]> wrote:
>>> 
>>>> It will omit the trace if it has happened a very large number of times.
>> If
>>>> you restart the server it will start printing it again when it happens.
>>>> 
>>>> On Fri, May 7, 2021 at 7:26 AM Hugi Thordarson <[email protected]>
>> wrote:
>>>> 
>>>>> One would think so, but there's just no stack trace printed for the
>>>>> NullPointerException.
>>>>> 
>>>>> 
>>>>>> On 7 May 2021, at 12:24, John Huss <[email protected]> wrote:
>>>>>> 
>>>>>> The first line of the stack after the Caused By line would tell you
>> the
>>>>>> line with the problem, wouldn't it? What was that line?
>>>>>> 
>>>>>> On Fri, May 7, 2021 at 7:16 AM Hugi Thordarson <[email protected]>
>>>>> wrote:
>>>>>> 
>>>>>>> Hi all,
>>>>>>> 
>>>>>>> occasionally my users encounter errors when committing changes to the
>>>>> DB.
>>>>>>> The relevant part of the stack trace looks like this:
>>>>>>> 
>>>>>>> ---------
>>>>>>> org.apache.cayenne.CayenneRuntimeException: [v.4.1 Jul 14 2020
>>>>> 10:26:08]
>>>>>>> Commit Exception
>>>>>>>      at
>>>>>>> 
>>>>> 
>> org.apache.cayenne.access.DataContext.flushToParent(DataContext.java:774)
>>>>>>>      at
>>>>>>> 
>>>>> 
>> org.apache.cayenne.access.DataContext.commitChanges(DataContext.java:691)
>>>>>>>      [...removed rest of trace…]
>>>>>>> Caused by: java.lang.NullPointerException
>>>>>>> ---------
>>>>>>> 
>>>>>>> Unfortunately I've been unable to reproduce this error, so before I
>>>>> dive
>>>>>>> into it I'm wondering if this looks familiar to anyone, if there are
>>>>>>> obvious places to look or if there are recommendations for strategies
>>>>> to
>>>>>>> debug?
>>>>>>> 
>>>>>>> Cheers,
>>>>>>> - hugi
>>>>> 
>>>>> 
>> 
>>