Hi Walter,
I believe the synchronization you're proposing is too wide and will cause
significant scalability degradation,
a more localized solution needs to be searched.
Which binding class are you referring to? The one
in org.geotools.filter.v2_0.bindings ?
(there are a few others, I believe this one would be used if you are doing
WFS 2.0 requests only).
Regards
Andrea
On Sat, Sep 2, 2017 at 12:31 PM, Walter Stovall <[email protected]>
wrote:
> https://osgeo-org.atlassian.net/browse/GEOS-7961
>
>
>
> This bug happens under load as a result of a multithreading bug in the
> implementation of BBOXTypeBinding.getProperties. More specifically, the
> partical.getContent() value there will be be corrupted/set to null by
> another thread executing that same code. I’m not certain what the correct
> fix is yet but I do have some good detail and can make it fail every time.
> I’m hoping that somebody with more knowledge on the XSD classes might have
> some insight that would help reach a solution.
>
>
>
> I encounter this bug very reliably by running a jMeter ThreadGroup that
> sends concurrent GetFeature requests that include a BBOX filter. I’ve
> since then figured out how to repro the bug in eclipse and identified a
> fairly narrow scope of code that is the root of the problem.
>
>
>
> To repro this problem in eclipse place a breakpoint in
> BBOXTypeBinding.getProperties at the following code:
>
> particle.setContent(GML.*getInstance*().getSchema().
> resolveElementDeclaration(GML.*Envelope*.getLocalPart()));
>
> particle.setMinOccurs(0);
>
>
>
> Put the breakpoint on the particle.setMinOccurs call right after the above
> call to setContent.
>
>
>
> Now execute the GetFeature request and hit the breakpoint. Note that as
> expected the particle.getContent() value at this point is not null, as it
> was set by the proceeding line of code.
>
>
>
> Now while sitting on that breakpoint execute another GetFeature and stop
> there on the other thread. Again the value of particle.getContent() is not
> null. But go to the original breakpoint in the first thread and see that
> particle.getContent() IS NOW NULL!
>
>
>
> In other words a GetFeature started on another thread has changed the
> particle.getContent() of the original thread. NullPointer exceptions like
> that shown in GEOS-7961 and others are now the result.
>
>
>
> Digging deeper I see that each thread has a unique “particle” instance
> (particle on one thread refers to a different object than particle on
> another thread) – as expected since the object is obtained from the factory
> on entry to getProperties. But in scenarios where this code works
> successfully (not forced to fail as above) it’s at least interesting that
> the value of particle.getContent() is the very same object instance on both
> threads.
>
>
>
> Ultimately the root of the problem has to do with the
> EObjectImpl.eContainer member – this is the object to which each particle
> refers.
>
>
>
> While I don’t know what the best fix is, I do how to make this specific
> failure *never* happen. I patched my code as follows by adding the
> thread synchronization you see below in GetFeature…
>
> *synchronized*(GetFeature.*class*) {
>
> Encoder e = *new* Encoder(*new* FESConfiguration());
>
> e.setOmitXMLDeclaration(*true*);
>
> filter.append(e.encodeAsString(q.getFilter(), FES.
> *Filter*));
>
> }
>
>
>
> A more targeted fix would of course be much better and might address
> potential failures other than GetFeature. I’m not sure what the right fix
> is but it would appear to be centered on the behavior of the following,
> which is rather convoluted for my brain to fully digest when considering
> changes.
>
> *if* (content != *null*)
>
> msgs = ((InternalEObject)content).eInverseRemove(*this*,
> *EOPPOSITE_FEATURE_BASE* - XSDPackage.*XSD_PARTICLE__CONTENT*, *null*,
> msgs);
>
> *if* (newContent != *null*)
>
> msgs = ((InternalEObject)newContent).eInverseAdd(*this*,
> *EOPPOSITE_FEATURE_BASE* - XSDPackage.*XSD_PARTICLE__CONTENT*, *null*,
> msgs);
>
>
>
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--
Regards,
Andrea Aime
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