cassandra-commits mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Lyuben Todorov (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-6440) Repair should allow repairing particular endpoints to reduce WAN usage.
Date Tue, 21 Jan 2014 02:33:19 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6440?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13877114#comment-13877114
] 

Lyuben Todorov commented on CASSANDRA-6440:
-------------------------------------------

bq. Neighbors will not be the same so whatever you provide in -hosts will be wrong.

I think the correct thing to do in this scenario is just log the exception, but provide enough
details for users to understand why an exception is being thrown. We need to tell people that
they need to provide all the hosts that they did (in the scenario [~kohlisankalp]  described),
but that this exception occurs because not all hosts are neighbours. 

> Repair should allow repairing particular endpoints to reduce WAN usage. 
> ------------------------------------------------------------------------
>
>                 Key: CASSANDRA-6440
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6440
>             Project: Cassandra
>          Issue Type: New Feature
>            Reporter: sankalp kohli
>            Assignee: sankalp kohli
>            Priority: Minor
>         Attachments: 6440_repair.log, JIRA-6440-v2.diff, JIRA-6440.diff
>
>
> The way we send out data that does not match over WAN can be improved. 
> Example: Say there are four nodes(A,B,C,D) which are replica of a range we are repairing.
A, B is in DC1 and C,D is in DC2. If A does not have the data which other replicas have, then
we will have following streams
> 1) A to B and back
> 2) A to C and back(Goes over WAN)
> 3) A to D and back(Goes over WAN)
> One of the ways of doing it to reduce WAN traffic is this.
> 1) Repair A and B only with each other and C and D with each other starting at same time
t. 
> 2) Once these repairs have finished, A,B and C,D are in sync with respect to time t.

> 3) Now run a repair between A and C, the streams which are exchanged as a result of the
diff will also be streamed to B and D via A and C(C and D behaves like a proxy to the streams).
> For a replication of DC1:2,DC2:2, the WAN traffic will get reduced by 50% and even more
for higher replication factors.
> Another easy way to do this is to have repair command take nodes with which you want
to repair with. Then we can do something like this.
> 1) Run repair between (A and B) and (C and D)
> 2) Run repair between (A and C)
> 3) Run repair between (A and B) and (C and D)
> But this will increase the traffic inside the DC as we wont be doing proxy.



--
This message was sent by Atlassian JIRA
(v6.1.5#6160)

Mime
View raw message