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https://issues.apache.org/jira/browse/CASSANDRA-21539?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18100373#comment-18100373
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Dmitry Konstantinov commented on CASSANDRA-21539:
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Just wondering, are virtual tables considered part of Cassandra public API? If 
I understand correctly, this column has been present since 4.0, and some users 
may have logic that relies on its presence. Removing it could cause their 
queries to fail... (I don't personally rely on this field.)

> 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-1.html, ci_summary.html, 
> result_details.tar-1.gz, 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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