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From "Roland (JIRA)" <j...@apache.org>
Subject [jira] [Created] (GORA-210) thread safety
Date Tue, 26 Feb 2013 10:26:12 GMT
Roland created GORA-210:
---------------------------

             Summary: thread safety
                 Key: GORA-210
                 URL: https://issues.apache.org/jira/browse/GORA-210
             Project: Apache Gora
          Issue Type: Bug
          Components: storage-cassandra
    Affects Versions: 0.2
         Environment: nutch 2.1 / cassandra 1.2.1 / gora-cassandra 0.2 / gora-core 0.2.1
running fetch with parse=true
fetcher.threads.per.queue>1
            Reporter: Roland
            Priority: Critical


This is the result of debugging one of my issues described in NUTCH-1534.
I think there is a wrong assumpation about thread safety of LinkedHashMap, it is not enough
to not iterate over the buffer (which is a LinkedHashMap).
My patch fixes this error for me:
{code}
java.util.ConcurrentModificationException
        at java.util.LinkedHashMap$LinkedHashIterator.nextEntry(LinkedHashMap.java:394)
        at java.util.LinkedHashMap$KeyIterator.next(LinkedHashMap.java:405)
        at java.util.AbstractCollection.toArray(AbstractCollection.java:141)
        at org.apache.gora.cassandra.store.CassandraStore.flush(CassandraStore.java:200)
        at org.apache.gora.mapreduce.GoraRecordWriter.write(GoraRecordWriter.java:65)
        at org.apache.hadoop.mapred.ReduceTask$NewTrackingRecordWriter.write(ReduceTask.java:587)
        at org.apache.hadoop.mapreduce.TaskInputOutputContext.write(TaskInputOutputContext.java:80)
        at org.apache.nutch.fetcher.FetcherReducer$FetcherThread.output(FetcherReducer.java:664)
        at org.apache.nutch.fetcher.FetcherReducer$FetcherThread.run(FetcherReducer.java:534)
{code}

It may not be perfect from a performance point of view...

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