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From A J <s5a...@gmail.com>
Subject Re: Coordinator node
Date Fri, 18 Feb 2011 15:38:02 GMT
Hi,
Are there any blogs/writeups anyone is aware of that talks of using
primary replica as coordinator node (rather than a random coordinator
node) in production scenarios ?

Thank you.


On Wed, Feb 16, 2011 at 10:53 AM, A J <s5alye@gmail.com> wrote:
> Thanks for the confirmation. Interesting alternatives to avoid random
> coordinator.
> Are there any blogs/writeups of they (primary node as co-ordinator) been
> used in production scenarios. I googled but could not find anything
> relevant.
> On Wed, Feb 16, 2011 at 3:25 AM, Oleg Anastasyev <oleganas@gmail.com> wrote:
>>
>> A J <s5alye <at> gmail.com> writes:
>>
>> >
>> >
>> > Makes sense ! Thanks.
>> > Just a quick follow-up:
>> > Now I understand the write is not made to coordinator (unless it is part
>> > of
>> the replica for that key). But does the write column traffic 'flow'
>> through the
>> coordinator node. For a 2G column write, will I see 2G network traffic on
>> the
>> coordinator node  or just a few bytes of traffic on the co-ordinator of it
>> reading the key and talking to nodes/client etc ?
>>
>> Yes, if you talk to random (AKA coordinator) node first - all 2G traffic
>> will
>> flow to it first and then forwarded to natural nodes (those owning
>> replicas of a
>> row to be written).
>> If you want to avoid extra traffic, you should determine natural nodes of
>> the
>> row and send your write directly to one of natural nodes (i.e. one of
>> natural
>> nodes became coordinator). This natural coordinator node will accept write
>> locally and submit write to other replicas in parallel.
>> If your client is written in java this can be implemented relatively easy.
>> Look
>> at TokenMetadata.ringIterator().
>>
>> If you have no requirement on using thrift interface of cassandra, it
>> could be
>> more efficient to write using StorageProxy interface. The latter plays a
>> local
>> coordinator role, so it talks directly to all replicas, so these 2G will
>> be
>> passed directly from your client to all row replicas.
>>
>>
>> >
>> > This will be a factor for us. So need to make sure exactly.
>>
>>
>
>

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