[ 
https://issues.apache.org/jira/browse/CASSANDRA-12884?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16122224#comment-16122224
 ] 

Jeff Jirsa commented on CASSANDRA-12884:
----------------------------------------

[~iamaleksey] will have a more comprehensive review, I'm sure, but a few notes 
from a very cursory glance:

1) I don't see the purpose of stubbing out {{BatchlogManager::shuffle}} as a 
helper function here.

2) In the case where {{validated.keySet().size() == 1}} , shuffling all of the 
IPs in a given rack may not be all that efficient - may be quicker to just pick 
2 random ints, and grab the IPs at those offsets (like we do for the case where 
we have more than 2 racks, 
{{result.add(rackMembers.get(getRandomInt(rackMembers.size())));}} )



> Batch logic can lead to unbalanced use of system.batches
> --------------------------------------------------------
>
>                 Key: CASSANDRA-12884
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-12884
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>            Reporter: Adam Hattrell
>            Assignee: Daniel Cranford
>             Fix For: 3.0.x, 3.11.x
>
>         Attachments: 0001-CASSANDRA-12884.patch
>
>
> It looks as though there are some odd edge cases in how we distribute the 
> copies in system.batches.
> The main issue is in the filter method for 
> org.apache.cassandra.batchlog.BatchlogManager
> {code:java}
>  if (validated.size() - validated.get(localRack).size() >= 2)
>  {
>         // we have enough endpoints in other racks
>         validated.removeAll(localRack);
>   }
>  if (validated.keySet().size() == 1)
>  {
>        // we have only 1 `other` rack
>        Collection otherRack = 
> Iterables.getOnlyElement(validated.asMap().values());
>        
>         return Lists.newArrayList(Iterables.limit(otherRack, 2));
>  }
> {code}
> So with one or two racks we just return the first 2 entries in the list.  
> There's no shuffle or randomisation here.



--
This message was sent by Atlassian JIRA
(v6.4.14#64029)

---------------------------------------------------------------------
To unsubscribe, e-mail: commits-unsubscr...@cassandra.apache.org
For additional commands, e-mail: commits-h...@cassandra.apache.org

Reply via email to