On 11/25/2013 8:43 AM, Shyamsunder R Mutcha wrote: > > > Following exception is found in solr logs. We are using Solr 3.2. As the > stack trace is not referring to any application classes, I couldn't figure > out the piece of code that throws this exception. Is there any way to debug > this issue? > > Is it related to the issue ConcurrentModificationException from > BinaryResponseWriter > > Nov 25, 2013 7:10:56 AM org.apache.solr.common.SolrException log > SEVERE: java.util.ConcurrentModificationException > at > java.util.LinkedHashMap$LinkedHashIterator.nextEntry(LinkedHashMap.java:373) > at java.util.LinkedHashMap$EntryIterator.next(LinkedHashMap.java:392) > at java.util.LinkedHashMap$EntryIterator.next(LinkedHashMap.java:391) > at org.apache.solr.response.XMLWriter.writeMap(XMLWriter.java:644)
The exception is coming from LinkedHashMap, a built-in Java object type. http://docs.oracle.com/javase/6/docs/api/java/util/LinkedHashMap.html The code that made the call that's failing is line 644 of this source code file: solr/core/src/java/org/apache/solr/response/XMLWriter.java I looked at the 3.2 source code. What's going on here is fairly normal - it's interating through a Map and outputting the data contained there to the writer. The actual problem is occurring elsewhere, it's only showing up in XMLWriter due to the way LinkedHashMap objects work. Another thread has modified the Map while the iterator is being used. This is something you're not allowed to do with this object type, so it throws the exception. I can't find any existing Solr bugs, so the question is: Are you using any custom code with Solr? Perhaps something you downloaded or purchased, or something you wrote in-house? If so, then that code has some bugs. If this *is* a bug in Solr 3.x, it is highly unlikely that it will get fixed, at least in a 3.x version. If it still exists in version 4.x (which is unlikely), then it will get fixed there. Version 3.2 is two years old, and the entire 3.x branch is in maintenance mode, meaning that only EXTREMELY severe bugs will be fixed. Thanks, Shawn
