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https://issues.apache.org/jira/browse/NUTCH-392?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12508812
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Doğacan Güney commented on NUTCH-392:
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OK, I have done a bit of testing on compression but I'm stuck. Here it is:
* I changed Content to be a regular Writable instead of a CompressedWritable
and turned on BLOCK compression. Results were pretty impressive. Content size
went down from ~1GB to ~500MB. Unfortunately, I haven't figured out how we can
change Content in a backward compatible way. Reading first byte as version
won't work (because first byte is not version, the first thing written is the
size of the compressed data as int).
* This is where it gets strange. I was trying to test the performance impact of
BLOCK compression (when generating summaries). I fetched a sample 250000 url
segment (a subset of dmoz). Then I made a small modification to
ParseOutputFormat so that it outputs parse_text in all three compression
formats ( http://www.ceng.metu.edu.tr/~e1345172/comp_parse.patch ). After
parsing, segment looks like this:
828M crawl/segments/20070626163143/content
35M crawl/segments/20070626163143/crawl_fetch
23M crawl/segments/20070626163143/crawl_generate
345M crawl/segments/20070626163143/crawl_parse
196M crawl/segments/20070626163143/parse_data
244M crawl/segments/20070626163143/parse_text # NONE
232M crawl/segments/20070626163143/parse_text_block # BLOCK
246M crawl/segments/20070626163143/parse_text_record # RECORD
Not only parse_text_record is larger than parse_text and parse_text_block is
only slightly smaller, but also crawl_parse is larger than any of them!
I probably messed up somewhere and I can't see it. Any help would be welcome.
> OutputFormat implementations should pass on Progressable
> --------------------------------------------------------
>
> Key: NUTCH-392
> URL: https://issues.apache.org/jira/browse/NUTCH-392
> Project: Nutch
> Issue Type: New Feature
> Components: fetcher
> Reporter: Doug Cutting
> Assignee: Andrzej Bialecki
> Fix For: 1.0.0
>
> Attachments: NUTCH-392.patch
>
>
> OutputFormat implementations should pass the Progressable they are passed to
> underlying SequenceFile implementations. This will keep reduce tasks from
> timing out when block writes are slow. This issue depends on
> http://issues.apache.org/jira/browse/HADOOP-636.
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