[jira] [Commented] (CASSANDRA-21539) Querying system_views.clients causes a DNS lookup for each unique connected client address

["David Capwell (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-21539?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18110866#comment-18110866 ] 

David Capwell commented on CASSANDRA-21539:
-------------------------------------------

This patch makes a breaking change to our public API and back ported to 4.x+ with the intent to release in a patch release; this breaks our process for these types of changes, [~brandon.williams] / [~smiklosovic] can you revert before we try to schedule any releases?

.bq I think we established a long time ago that system views are free to be changed / follow different / relaxed path than system tables on disk, that is why we just want to nuke it here

I can not find any evidence of this, only the opposite. Are there any ML threads you can link to back up this statement?  The best 2 threads I can see are

- "Discuss CASSANDRA-16999 introduction of a column in system.peers_v2" - this argues we should not break public api
- "DISCUSS How we version our releases" this says dev@ ML thread + deprecate + min(2 releases, 1 year)... and even this gets pushback arguing not to break the public api "would hugely break trust if we just decided 'well technically it's a major release so we removed this thing'"

> 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: 4.0.22, 4.1.13, 5.0.10, 6.0-alpha3, 7.0
>
>         Attachments: 4.0-ci_summary.html, 4.0-result_details.tar.gz.zip, 5.0-ci_summary.html, 5.0-result_details.tar.gz, 6.0-ci_summary.html, 6.0-result_details.tar.gz, ci_summary-1.html, ci_summary.html, result_details.tar-1.gz, result_details.tar.gz
>
>          Time Spent: 1h 40m
>  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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