cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Ryan Hadley <r...@sgizmo.com>
Subject Re: Inconsistent data issues when running nodetool move.
Date Sat, 14 May 2011 14:06:15 GMT
Thanks Maki,

That makes sense with my symptoms...  I was doing a CL=ONE for write and a CL=ALL for read,
expecting that to be sufficient.  

I will try both set to ALL and see if I get better consistency.

-Ryan

On May 14, 2011, at 4:41 AM, Maki Watanabe wrote:

> It depends on what you really use which CL for your operations.
> Your RF is 2, so if you read/write with CL=ALL, your r/w will be
> always consistent. If your read is CL=ONE, you have chance to read old
> data anytime, decommission is not matter. CL=QUORUM on RF=2 is
> semantically identical with CL=ALL.
> 
> maki
> 
> 2011/5/13 Ryan Hadley <ryan@sgizmo.com>:
>> Hi,
>> 
>> I'm running Cassandra (0.7.4) on a 4 node ring.  It was a 3 node ring, but we ended
up expanding it to 4... So then I followed the many suggestions to rebalance the ring.  I
found a script that suggested I use:
>> 
>> # ~/nodes_calc.py
>> How many nodes are in your cluster? 4
>> node 0: 0
>> node 1: 42535295865117307932921825928971026432
>> node 2: 85070591730234615865843651857942052864
>> node 3: 127605887595351923798765477786913079296
>> 
>> So I started to migrate each node to those tokens.
>> 
>> I have my replication factor set to 2, so I guess I was expecting to be able to continue
to use this ring without issues.  But it seems that the node still accepts writes while it's
decommissioning?  I say this because if I interrupt the decommission by stopping Cassandra
and starting it again, it appears to run through several commit logs.  And as soon as it's
through with those commit logs, I no longer get consistency issues.
>> 
>> The issue I'm seeing is that writes to this ring will succeed, but it's possible
for a subsequent read to return an older object.  For several minutes even.
>> 
>> I'm not sure if I did something wrong... learning as I go here and this list archive
has been very useful.  But, is there anyway I can rebalance the node and get better consistency?
>> 
>> Thanks,
>> Ryan


Mime
View raw message