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https://issues.apache.org/jira/browse/CASSANDRA-11170?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Matt Stump updated CASSANDRA-11170:
-----------------------------------
    Attachment: 11170.patch

> Uneven load can be created by cross DC mutation propagations, as remote 
> forwarding node is not randomly picked
> --------------------------------------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-11170
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-11170
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Coordination
>            Reporter: Wei Deng
>            Assignee: Wei Deng
>            Priority: Major
>         Attachments: 11170.patch
>
>
> I was looking at the o.a.c.service.StorageProxy code and realized that it 
> seems to be always picking the first IP in the remote DC target list as the 
> destination, whenever it needs to send the mutation to a remote DC. See these 
> lines in the code:
> https://github.com/apache/cassandra/blob/1944bf507d66b5c103c136319caeb4a9e3767a69/src/java/org/apache/cassandra/service/StorageProxy.java#L1280-L1301
> This could cause one node in the remote DC receiving more mutation messages 
> than the other nodes, and hence uneven workload distribution.
> A trivial test (with TRACE logging level enabled) on a 3+3 node cluster 
> proved the problem, see the system.log entries below:
> {code}
> INFO  [RMI TCP Connection(18)-54.173.227.52] 2016-02-13 09:54:55,948  
> StorageService.java:3353 - set log level to TRACE for classes under 
> 'org.apache.cassandra.service.StorageProxy' (if the level doesn't look like 
> 'TRACE' then the logger couldn't parse 'TRACE')
> TRACE [SharedPool-Worker-1] 2016-02-13 09:55:15,148  StorageProxy.java:1284 - 
> Adding FWD message to 8996@/52.53.215.74
> TRACE [SharedPool-Worker-1] 2016-02-13 09:55:15,149  StorageProxy.java:1284 - 
> Adding FWD message to 8997@/54.183.23.201
> TRACE [SharedPool-Worker-1] 2016-02-13 09:55:15,149  StorageProxy.java:1289 - 
> Sending message to 8998@/54.183.209.219
> TRACE [SharedPool-Worker-1] 2016-02-13 09:55:22,939  StorageProxy.java:1284 - 
> Adding FWD message to 9032@/52.53.215.74
> TRACE [SharedPool-Worker-1] 2016-02-13 09:55:22,940  StorageProxy.java:1284 - 
> Adding FWD message to 9033@/54.183.23.201
> TRACE [SharedPool-Worker-1] 2016-02-13 09:55:22,941  StorageProxy.java:1289 - 
> Sending message to 9034@/54.183.209.219
> TRACE [SharedPool-Worker-1] 2016-02-13 09:55:28,975  StorageProxy.java:1284 - 
> Adding FWD message to 9064@/52.53.215.74
> TRACE [SharedPool-Worker-1] 2016-02-13 09:55:28,976  StorageProxy.java:1284 - 
> Adding FWD message to 9065@/54.183.23.201
> TRACE [SharedPool-Worker-1] 2016-02-13 09:55:28,977  StorageProxy.java:1289 - 
> Sending message to 9066@/54.183.209.219
> TRACE [SharedPool-Worker-1] 2016-02-13 09:55:33,464  StorageProxy.java:1284 - 
> Adding FWD message to 9094@/52.53.215.74
> TRACE [SharedPool-Worker-1] 2016-02-13 09:55:33,465  StorageProxy.java:1284 - 
> Adding FWD message to 9095@/54.183.23.201
> TRACE [SharedPool-Worker-1] 2016-02-13 09:55:33,478  StorageProxy.java:1289 - 
> Sending message to 9096@/54.183.209.219
> TRACE [SharedPool-Worker-1] 2016-02-13 09:55:39,243  StorageProxy.java:1284 - 
> Adding FWD message to 9121@/52.53.215.74
> TRACE [SharedPool-Worker-1] 2016-02-13 09:55:39,244  StorageProxy.java:1284 - 
> Adding FWD message to 9122@/54.183.23.201
> TRACE [SharedPool-Worker-1] 2016-02-13 09:55:39,244  StorageProxy.java:1289 - 
> Sending message to 9123@/54.183.209.219
> TRACE [SharedPool-Worker-1] 2016-02-13 09:55:44,248  StorageProxy.java:1284 - 
> Adding FWD message to 9145@/52.53.215.74
> TRACE [SharedPool-Worker-1] 2016-02-13 09:55:44,249  StorageProxy.java:1284 - 
> Adding FWD message to 9146@/54.183.23.201
> TRACE [SharedPool-Worker-1] 2016-02-13 09:55:44,249  StorageProxy.java:1289 - 
> Sending message to 9147@/54.183.209.219
> TRACE [SharedPool-Worker-1] 2016-02-13 09:55:49,731  StorageProxy.java:1284 - 
> Adding FWD message to 9170@/52.53.215.74
> TRACE [SharedPool-Worker-1] 2016-02-13 09:55:49,734  StorageProxy.java:1284 - 
> Adding FWD message to 9171@/54.183.23.201
> TRACE [SharedPool-Worker-1] 2016-02-13 09:55:49,735  StorageProxy.java:1289 - 
> Sending message to 9172@/54.183.209.219
> INFO  [RMI TCP Connection(22)-54.173.227.52] 2016-02-13 09:56:19,545  
> StorageService.java:3353 - set log level to INFO for classes under 
> 'org.apache.cassandra.service.StorageProxy' (if the level doesn't look like 
> 'INFO' then the logger couldn't parse 'INFO')
> {code}



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