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https://issues.apache.org/jira/browse/CASSANDRA-5632?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jonathan Ellis updated CASSANDRA-5632:
--------------------------------------

    Attachment: 5632.txt

Backport of 62f429337caf0aa83b68720a5904e8527b840c80 from 2.0 to fix.
                
> 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
>
>
> 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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