[jira] [Commented] (NUTCH-2455) Speed up the merging of HostDb entries for variable fetch delay

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[jira] [Commented] (NUTCH-2455) Speed up the merging of HostDb entries for variable fetch delay

JIRA jira@apache.org

    [ https://issues.apache.org/jira/browse/NUTCH-2455?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16278926#comment-16278926 ]

Sebastian Nagel commented on NUTCH-2455:
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Hi [~[hidden email]], you're right, it's not possible to check for the global -topN limit with secondary sorting. The only solution I see is to split the "select" job into two steps/jobs:
# existing Selector.map(), partition by URL (not host/domain/IP which avoids some extra work), apply topN limit in reduce()
# read output from job 1 and add HostDb entries as MultipleInput, secondary sorting by host and score, reducer: apply per-host/domain/IP limits (limit ev. taken from HostDb), assign segments


> Speed up the merging of HostDb entries for variable fetch delay
> ---------------------------------------------------------------
>
>                 Key: NUTCH-2455
>                 URL: https://issues.apache.org/jira/browse/NUTCH-2455
>             Project: Nutch
>          Issue Type: Improvement
>          Components: generator
>    Affects Versions: 1.13
>            Reporter: Markus Jelsma
>         Attachments: NUTCH-2455.patch
>
>
> Citing Sebastian at NUTCH-2420:
> ??The correct solution would be to use <host,score> pairs as keys in the Selector job, with a partitioner and secondary sorting so that all keys with same host end up in the same call of the reducer. If values can also hold a HostDb entry and the sort comparator guarantees that the HostDb entry (entries if partitioned by domain or IP) comes in front of all CrawlDb entries. But that would be a substantial improvement...??



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