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From "stone (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-12257) data consistency of multi datacenter
Date Fri, 22 Jul 2016 00:58:20 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-12257?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15388694#comment-15388694
] 

stone commented on CASSANDRA-12257:
-----------------------------------

 need measure the latency between DC real time so we can look back the data.


> data consistency of multi datacenter 
> -------------------------------------
>
>                 Key: CASSANDRA-12257
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-12257
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Coordination
>            Reporter: stone
>
> Environment:
> serveral active-active cassandra datacenter.
> set write consistency level=local_quorum to get a high resquest response.
> Concern:
> we dont know the time of the data arrive other datacenter.
> we dont know the size of data that need to be transferred  to other datacenter.
> Thought:
> 1.we can get the latency with ping or other monitor tool,but it can not represent the
latency of cassandra data to be transferred from one dc to another dc.
> 2.we can measure the latency between dc.but there is a accumulated value from node started,it
cannot represent the latency now.
> https://issues.apache.org/jira/browse/CASSANDRA-11569
> Scenanio:
> one project need to collect information from sensors,which in different region.2 datacenter,DC1,DC2.sensor1,sensor2
in DC1 region.sensor3,sensor4 in DC2.
> one client in DC1,pull data every 10 minutes.
> 1.sensor3 in DC2 write a record to DC2 at 8:59:55 ,and arrived DC1 at 9:00:05
> 2.client in DC1 pull data at 9:00,it should get the record,but it cannot as the 
> record have not arrive DC1.
> 3.then client in DC1 will pull data at 9:10.it also can not get the record as it will
pull data from 9:00---9:10,but the record created on 8:59:55
> so we will miss the record.



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