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Date: Thu, 2 Dec 2010 12:09:14 -0500 (EST)
From: "T Jake Luciani (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
Subject: [jira] Updated: (CASSANDRA-1530) More-efficient cross-DC
 replication
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     [ https://issues.apache.org/jira/browse/CASSANDRA-1530?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

T Jake Luciani updated CASSANDRA-1530:
--------------------------------------

    Attachment: 1530_v1.txt

First pass at this.

1) refactored code
2) let FWD hints be 4 bytes per address as jbellis requested
3) avoid fwd hints when already in local DC
4) remove fwd hint header when we send to final destination to avoid infinite loops

I'm not sure how I can unit test this yet, there are very few ProxyService tests overall.

I will fully test on a live cluster soon.


> More-efficient cross-DC replication
> -----------------------------------
>
>                 Key: CASSANDRA-1530
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1530
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Jonathan Ellis
>            Assignee: T Jake Luciani
>             Fix For: 0.7.1
>
>         Attachments: 1530-cleaned.txt, 1530-joaquin.txt, 1530_v1.txt
>
>
> Currently the coordinator node sends writes to each replica.  In multi-dc situations, it would be more efficient to have the coordinator talk to a single node in each DC, which would forward the writes to the other replicas local to it.  (All replicas would continue to ack to the coordinator.)
> Shouldn't be difficult to add a header to RMVH saying "consult the Strategy to see who else is local to you and queue it off to them as well."
> For example, consider two data centers with the following nodes:
> DC1: A, B, C
> DC2: D, E, F
> A client connected to node A performs an insert that should be replicated to {B,C,E,F}.  Currently, A will send a MUTATION verb to each of those nodes directly.  But communication to E and F is relatively expensive since they are in the other data center from A.  So we'd like to send the mutation to just one, say E, with a tag saying "forward this to F as well."

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