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From Dwight Smith <Dwight.Sm...@genesyslab.com>
Subject RE: Question regarding multi datacenter and LOCAL_QUORUM
Date Wed, 20 Mar 2013 18:10:05 GMT
>From the yamls

.143
  initial_token: 0
.145
  initial_token: 56713727820156410577229101238628035242
.146
  initial_token: 113427455640312821154458202477256070485


From: Tycen Stafford [mailto:tstafford@medio.com]
Sent: Wednesday, March 20, 2013 10:43 AM
To: user@cassandra.apache.org
Subject: RE: Question regarding multi datacenter and LOCAL_QUORUM

Did you alternate your tokens?  I may be off base - but if not then that's why you might be
seeing cross-dc request.

-Tycen


From: Dwight Smith [mailto:Dwight.Smith@genesyslab.com]
Sent: Wednesday, March 20, 2013 10:30 AM
To: user@cassandra.apache.org<mailto:user@cassandra.apache.org>
Subject: Question regarding multi datacenter and LOCAL_QUORUM

Hi

I have 2 data centers - with 3 nodes in each DC - version 1.1.6 -  replication factor 2 -
 topology properties:

# Cassandra Node IP=Data Center:Rack
xx.yy.zz.143=AZ1:RAC1
xx.yy.zz.145=AZ1:RAC1
xx.yy.zz.146=AZ1:RAC1
xx.yy.zz.147=AZ2:RAC2
xx.yy.zz.148=AZ2:RAC2
xx.yy.zz.149=AZ2:RAC2

Using LOCAL_QUORUM, my understanding was that reads/writes would process locally ( for the
coordinator ) and send requests to the remaining nodes in the DC, but in the system log for
146 I observe that this is not the case, extract from the log:


DEBUG [Thrift:1] 2013-03-19 00:00:53,312 CassandraServer.java (line 306) get_slice

DEBUG [Thrift:1] 2013-03-19 00:00:53,313 ReadCallback.java (line 79) Blockfor is 2; setting
up requests to /xx.yy.zz.146,/xx.yy.zz.143,/xx.yy.zz.145

DEBUG [Thrift:1] 2013-03-19 00:00:53,334 CassandraServer.java (line 306) get_slice

DEBUG [Thrift:1] 2013-03-19 00:00:53,334 ReadCallback.java (line 79) Blockfor is 2; setting
up requests to /xx.yy.zz.146,/xx.yy.zz.143

DEBUG [Thrift:1] 2013-03-19 00:00:53,366 CassandraServer.java (line 306) get_slice

DEBUG [Thrift:1] 2013-03-19 00:00:53,367 ReadCallback.java (line 79) Blockfor is 2; setting
up requests to /xx.yy.zz.146,/xx.yy.zz.143,/xx.yy.zz.145

DEBUG [Thrift:1] 2013-03-19 00:00:53,391 CassandraServer.java (line 589) batch_mutate

DEBUG [Thrift:1] 2013-03-19 00:00:53,418 CassandraServer.java (line 589) batch_mutate

DEBUG [Thrift:1] 2013-03-19 00:00:53,429 CassandraServer.java (line 306) get_slice

DEBUG [Thrift:1] 2013-03-19 00:00:53,429 ReadCallback.java (line 79) Blockfor is 2; setting
up requests to /xx.yy.zz.146,/xx.yy.zz.145

DEBUG [Thrift:1] 2013-03-19 00:00:53,441 CassandraServer.java (line 306) get_slice

DEBUG [Thrift:1] 2013-03-19 00:00:53,441 ReadCallback.java (line 79) Blockfor is 2; setting
up requests to /xx.yy.zz.146,/xx.yy.zz.143



The batch mutates are as expected - locally, two replicas, and hints to DC AZ2, but why the
unexpected behavior for the get_slice requests.  This is observed throughout the log.



Thanks much




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