[jira] [Created] (NUTCH-1712) Use MultipleInputs in Injector to make it a single mapreduce job

["Tejas Patil (JIRA)" <ji...@apache.org>]

Tejas Patil created NUTCH-1712:
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             Summary: Use MultipleInputs in Injector to make it a single mapreduce job
                 Key: NUTCH-1712
                 URL: https://issues.apache.org/jira/browse/NUTCH-1712
             Project: Nutch
          Issue Type: Improvement
          Components: injector
    Affects Versions: 1.7
            Reporter: Tejas Patil
            Assignee: Tejas Patil
             Fix For: 1.8


Currently Injector creates two mapreduce jobs:
1. sort job: get the urls from seeds file, emit CrawlDatum objects.
2. merge job: read CrawlDatum objects from both crawldb and output of sort job. Merge and emit final CrawlDatum objects.

Using MultipleInputs, we can read CrawlDatum objects from crawldb and urls from seeds file simultaneously and perform inject in a single map-reduce job.

Also, there are few other things adressed in this patch:
1. Pushed filtering and normalization above metadata extraction so that the unwanted records are ruled out quickly.
2. Migrated to new mapreduce API
3. Improved documentation 
4. New junits with better coverage

Relevant discussion over nutch-dev can be found here:
http://mail-archives.apache.org/mod_mbox/nutch-dev/201401.mbox/%3CCAFKhtFyXO6WL7gyUV+a5Y1pzNtdCoqPz4jz_up_bkp9cJe80kg@mail.gmail.com%3E



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