Hi Fabrice,
Have you considered using "each_quorum" instead of "all"?
Each_quorum will require replies from a quorum of nodes from all
datacenters.
This could be used either:
Producer using each_quorum and consumer local_quroum. (better read
latencies at the cost of write latencies)
or
Producer using local_quorum and consumer each_quorum. (better write
latencies at the cost of read latencies)
BR
Marcus Olsson
On 06/02/2015 01:00 PM, Fabrice Douchant wrote:
Hi everyone.
For a project, we use a Cassandra cluster in order to have fast
reads/writes on a large number of (column oriented) generated data.
Until now, we only had 1 datacenter for prototyping.
We now plan to split our cluster in 2 datacenters to meet performance
requirements (the data transfer between both datacenter is quite slow):
datacenter #1 : located near our data producer services : intensively
writes all data in Cassandra periodically (each writes has a “run_id”
column in its primary key)
datacenter #2 : located near our data consumer services: intensively
reads all data produced by datacenter #1 for a given “run _id”.
However, we would like our consumer services to access data only in
the datacenter near them (datacenter #2) and when all data for a given
“run_id” have been completely replicated from datacenter #1 (data
generated by the producer services).
My question is : how can we ensure that all data have been replicated
in datancenter #2 before telling producer services (near datacenter
#2) to start using them ?
Our best solutions so far (but still not good enough :-P):
producer services (datacenter #1) writes in consistency “all”. But
this leads to poor partitioning failure tolerance AND really bad
writes performances.
producer services (datacenter #1) writes in consistency “local_quorum”
and a last “run finished” value could be written in consistency “all”.
But it seems Cassandra does not ensure replication ordering.
Do you have any suggestion ?
Thanks a lot,
Fabrice
