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From "Sebastian Nagel (JIRA)" <>
Subject [jira] [Commented] (NUTCH-2420) Bug in variable generate.max.count and fetcher.server.delay
Date Mon, 06 Nov 2017 15:06:00 GMT


Sebastian Nagel commented on NUTCH-2420:

That's really ugly! It will work in local mode or on a small cluster with not too many hosts,
but on a larger cluster a HostDb with many partitions and millions of hosts, it will slow
down of Generator significantly. 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...

+1 to commit this fix and to open a new one to speed up the merging of HostDb entries

> Bug in variable generate.max.count and fetcher.server.delay
> -----------------------------------------------------------
>                 Key: NUTCH-2420
>                 URL:
>             Project: Nutch
>          Issue Type: Bug
>          Components: generator
>            Reporter: Markus Jelsma
>            Assignee: Markus Jelsma
>             Fix For: 1.14
>         Attachments: NUTCH-2420.patch
> Feature added by NUTCH-2368 does not work for multiple hosts. Once a HostDatum has been
read by getHostDatum(), the next host cannot be read. Apparantly i need to open and close
the SequenceFile.Readers for every HostDatum it needs. Reader has no reset() method or whatsoever.

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