[jira] [Created] (NUTCH-1790) solrdedup in local mode causes OutOfMemoryError in Solr

["Greg Padiasek (JIRA)" <ji...@apache.org>]

Greg Padiasek created NUTCH-1790:
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             Summary: solrdedup in local mode causes OutOfMemoryError in Solr
                 Key: NUTCH-1790
                 URL: https://issues.apache.org/jira/browse/NUTCH-1790
             Project: Nutch
          Issue Type: Improvement
          Components: indexer
    Affects Versions: 2.2, 1.7
         Environment: Nutch in local mode.
            Reporter: Greg Padiasek


Nutch 1.7 and 2.2.1 use Hadoop 1.2. In this version Hadoop overwrites "mapred.map.tasks" variable set in mapred-site.xml and in local mode always sets it to 1. As a result Nutch creates a giant query to read ALL Solr documents at once. This in turn causes Solr to consume all RAM given number of documents is high. I found this issue with Solr running with 2M+ docs, 1GB JVM RAM, 20% of which is used under normal conditions. When running "solrdedup", memory usage exceeds available RAM, solr throws OutOfMemoryError and the dedup job fails.

Think this could be solved in one of two ways. Either by upgrading Nutch to a later version of Hadoop lib (which hopefully does not hard-coded "mapred.map.tasks" value anymore), or changing the SolrDeleteDuplicates class to "stream" documents in batches. The later would make Nutch less dependent on Hadoop version and this was my choice. Attached is a patch that implements batch reading in local mode with user defined batch size. The "streaming" is potentially also applicable in distributed mode.



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