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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