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https://issues.apache.org/jira/browse/CASSANDRA-5632?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13688838#comment-13688838
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Ryan McGuire commented on CASSANDRA-5632:
-----------------------------------------
I've [written a dtest|https://github.com/riptano/cassandra-dtest/pull/13/files]
that automates the testing of this issue.
This test clearly shows that the coordinator was talking to more than one node
in a different datacenter, and the patch resolves that issue. It also verifies
that [~hayato.shimizu]'s comment about using the same forwarder is not
happening now.
[~jbellis] - I noticed in your [blog post about
tracing|http://www.datastax.com/dev/blog/advanced-request-tracing-in-cassandra-1-2]
you said not to rely on the activity field, well, that's exactly what I'm
doing here. So, +1 to the idea of making those enums so this doesn't break in
the future.
> Cross-DC bandwidth-saving broken
> --------------------------------
>
> Key: CASSANDRA-5632
> URL: https://issues.apache.org/jira/browse/CASSANDRA-5632
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Affects Versions: 1.2.0
> Reporter: Jonathan Ellis
> Assignee: Jonathan Ellis
> Fix For: 1.2.6
>
> Attachments: 5632.txt, 5632-v2.txt, cassandra-topology.properties,
> fix_patch_bug.log
>
>
> We group messages by destination as follows to avoid sending multiple
> messages to a remote datacenter:
> {code}
> // Multimap that holds onto all the messages and addresses meant for
> a specific datacenter
> Map<String, Multimap<Message, InetAddress>> dcMessages
> {code}
> When we cleaned out the MessageProducer stuff for 2.0, this code
> {code}
> Multimap<Message, InetAddress> messages =
> dcMessages.get(dc);
> ...
>
> messages.put(producer.getMessage(Gossiper.instance.getVersion(destination)),
> destination);
> {code}
> turned into
> {code}
> Multimap<MessageOut, InetAddress> messages =
> dcMessages.get(dc);
> ...
> messages.put(rm.createMessage(), destination);
> {code}
> Thus, we weren't actually grouping anything anymore -- each destination
> replica was stored under a separate Message key, unlike under the old
> CachingMessageProducer.
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