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From "Christopher Batey (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (CASSANDRA-12625) Distinguish between CAS prepare and propose failures
Date Mon, 19 Sep 2016 12:02:20 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-12625?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15503208#comment-15503208
] 

Christopher Batey edited comment on CASSANDRA-12625 at 9/19/16 12:01 PM:
-------------------------------------------------------------------------

{quote}
We can, though my preferred way of adding that information would probably be to add a new
boolean to WriteTimeoutException when WriteType is CAS to indicate if we can guarantee it
won't be applied or not (could call it canSafelyReply for instance).
{quote}

Agreed. This can still be made applicable even if we entirely change our paxos algorithm e.g.
epaxos

I'll put together a patch.


was (Author: chbatey):
??
We can, though my preferred way of adding that information would probably be to add a new
boolean to WriteTimeoutException when WriteType is CAS to indicate if we can guarantee it
won't be applied or not (could call it canSafelyReply for instance). 
??

Agreed. This can still be made applicable even if we entirely change our paxos algorithm e.g.
epaxos

I'll put together a patch.

> Distinguish between CAS prepare and propose failures
> ----------------------------------------------------
>
>                 Key: CASSANDRA-12625
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-12625
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Christopher Batey
>            Assignee: Christopher Batey
>            Priority: Minor
>              Labels: cas
>             Fix For: 3.x
>
>
> I spoke to a lot of users at the summit and had the feedback that the hardest part of
building applications using LWTs is dealing with WriteTimeouts of type CAS.
> Following up from https://issues.apache.org/jira/browse/CASSANDRA-8672 I think we should
add a separate WriteType for timing out during the prepare phase assuming we can advise users
to retry the operation or be confident it has failed as it won't be completed by a later SERIAL
read or LWT.
> We can't remove the ambiguity at the propose phase but this will remove one of the unknown
cases.
> cc [~slebresne] [~bdeggleston] [~spodxx@gmail.com]
> Happy to do a patch for this but assuming it will need a native protocol change when
can we do it?



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