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https://issues.apache.org/jira/browse/CASSANDRA-21539?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18100054#comment-18100054
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Stefan Miklosovic edited comment on CASSANDRA-21539 at 7/29/26 12:16 PM:
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Is this safe to do? While it looks innocent, when I tried this locally it
stopped to report DNS name and started to report IP addresses, basically. So
the row "hostname" might not be hostname anymore and I am not sure under what
circumstances we will ever see a proper hostname in that column ever again.
Clients vtable as the primary key as (address, port) where {{address}} is of
type {{inet}}. That will report IP address without translation. {{hostname}}
column, in my view, is meant to be DNS-resolved name, not IP, because we will
end up with two same values.
was (Author: smiklosovic):
Is this safe to do? While it looks innocent, when I tried this locally it
stopped to report DNS name and started to report IP addresses, basically. So
the row "hostname" might not be hostname anymore and I am not sure under what
circumstances we will ever see a proper hostname in that column ever again.
> Querying system_views.clients causes a DNS lookup for each unique connected
> client address
> ------------------------------------------------------------------------------------------
>
> Key: CASSANDRA-21539
> URL: https://issues.apache.org/jira/browse/CASSANDRA-21539
> Project: Apache Cassandra
> Issue Type: Bug
> Components: Feature/Virtual Tables
> Reporter: Nivy Kani
> Assignee: Nivy Kani
> Priority: Normal
> Fix For: 7.x
>
> Attachments: ci_summary.html, result_details.tar.gz
>
> Time Spent: 10m
> Remaining Estimate: 0h
>
> It looks like queries to the system_views.clients table does a DNS lookup for
> each unique address:
> https://github.com/apache/cassandra/blob/trunk/src/java/org/apache/cassandra/db/virtual/ClientsTable.java#L91
>
> Given Java's internal DNS caches, this is really only potentially slow on the
> first query, but we should avoid doing DNS lookups here as a workflow that
> queries this table on each node to collect client information could
> potentially overwhelm DNS this way.
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