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https://issues.apache.org/jira/browse/NUTCH-2455?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18136268#comment-18136268
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ASF GitHub Bot commented on NUTCH-2455:
---------------------------------------
lewismc commented on PR #888:
URL: https://github.com/apache/nutch/pull/888#issuecomment-6568116492
Hi @sebastian-nagel, I measured the follow-up that hashes the extracted host
directly and drops the HostDb partition cache.
## What changed
`SelectorWithHostDb` now sends both the HostDb hostname and the host parsed
from each CrawlDb URL through `URLPartitioner.getPartitionForRoot`. Those
CrawlDb rows no longer run `URLNormalizers.SCOPE_PARTITION`. If
`generate.hostdb` is set and `partition.url.mode` is not `byHost`, the selector
logs an error and still partitions by host. The job configuration is left
unchanged. The no-HostDb job is still the `FloatWritable` selector.
## Same 4 GB setup
Same 50M CrawlDb and 1M-host HostDb, local mode, Java 17, the default 4 GB
heap, and eight reducers. Three runs of each, median of `Generator: finished`.
Every run exited 0. The cache build and the new build were measured in the same
session. Profiles went to the same `nutch.generator` service on the
`profiles-prod-008` data source of my Grafana Cloud stack. Note: apologies, I
actually cannot add you there after all as it is a staff account. Sorry!
The cache rows are `variant=nutch-2455-hostcache`,
`git_sha=d4cb33ba8-hostcache`. The new rows are `variant=nutch-2455-hostroot`,
`git_sha=d4cb33ba8-hostroot`. The window is 2026-11-02T01:35:00Z through
2026-11-02T02:45:00Z.
**50,000,000 URLs, 1,000,000 hosts**
| Path | Partition cache | Extracted-host hash | Peak RSS |
| -
> Use secondary sorting for memory-efficient HostDb integration in Generator
> --------------------------------------------------------------------------
>
> 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
> Assignee: Lewis John McGibbney
> Priority: Major
> Fix For: 1.24
>
> 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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