Walter, I have reopened GEOT-7961 and linked and pasted your email.
Kind regards, Ben. On 02/09/17 22:31, Walter Stovall 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); ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Geoserver-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/geoserver-devel
-- Ben Caradoc-Davies <[email protected]> Director Transient Software Limited <http://transient.nz/> New Zealand ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Geoserver-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/geoserver-devel
