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From "Robert Stupp (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-9429) Revert CASSANDRA-7807 (tracing completion client notifications)
Date Tue, 19 May 2015 20:28:00 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-9429?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Robert Stupp updated CASSANDRA-9429:
------------------------------------
    Attachment: 9429.txt

Attached patch that reverts CASSANDRA-7807 (but leaves the "good side effects" like debug-client,
SimpleClient)

> Revert CASSANDRA-7807 (tracing completion client notifications)
> ---------------------------------------------------------------
>
>                 Key: CASSANDRA-9429
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9429
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Adam Holmberg
>            Assignee: Robert Stupp
>            Priority: Minor
>             Fix For: 2.2.0 rc1
>
>         Attachments: 9429.txt
>
>
> Follow-on to CASSANDRA-7807, where I opened a discussion without realizing the version
was released:
> I know I'm late to this ticket, but as I began to integrate this feature for the Python
driver, I developed some reservations about its usefulness. I understand the original intent
to avoid polling and eventually simplify trace handling. However, it introduces some complexity
supporting multiple protocol versions, and I'm not sure it will even avoid the need for polling,
due to replication lag.
> Here are some of the things required to take advantage:
> - Extra registration overhead per connection, or dynamically register on first trace
> - Extra book-keeping – trace ID per connection
> - New modes of failure (polling is resilient as the cluster)
> - Event may arrive before trace data is replicated
> - Drivers must still implement polling following event, and for lesser protocol versions
> Given the above, I'm not sure it's worth it to implement to save a few polling round-trips,
especially when it's only client-initiated traces (which will typically not be in a hot path).
> I'm open to discussion on the matter.



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