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From "stone (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-12257) data consistency of multi datacenter
Date Thu, 21 Jul 2016 09:45:20 GMT
stone created CASSANDRA-12257:
---------------------------------

             Summary: 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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