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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 18:51:47 GMT
Yes that is correct – the log is from 146.  The client connects to nodes in AZ1.

From: Derek Williams [mailto:derek@fyrie.net]
Sent: Wednesday, March 20, 2013 11:50 AM
To: user@cassandra.apache.org
Subject: Re: Question regarding multi datacenter and LOCAL_QUORUM

I'm think I need help with pointing out what the problem is. The log you posted only contains
references to 143, 145, and 146, which all appear to be in the same datacenter as 146?

On Wed, Mar 20, 2013 at 11:29 AM, Dwight Smith <Dwight.Smith@genesyslab.com<mailto:Dwight.Smith@genesyslab.com>>
wrote:
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







--
Derek Williams
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