Is there something special of this kind regarding counters over multiDC ?No. Counters behave exactly as other writes as far the consistency level is concerned.Technically, the counter write path is different from the normal write path in the sense that a counter writewill be written to one replica first and then written to the rest of the replicas in a second time (with a localread on the first replica in between, which is why counter writes are slower than normal ones). But,outside of the obvious performance impact, this has no impact on the behavior observed from aclient point of view. The consistency level has the exact same meaning in particular (though onesmall difference is that counters don't support CL.ANY).--SylvainThank you anyway Sylvain2013/6/12 Sylvain Lebresne <email@example.com>
It is the normal behavior, but that's true of any update, not only of counters.The consistency level does *not* influence which replica are written to. Cassandra always write to all replicas. The consistency level only decides how replica acknowledgement are waited for.--SylvainOn Wed, Jun 12, 2013 at 4:56 AM, Alain RODRIGUEZ <firstname.lastname@example.org> wrote:
"counter will replicate to all replicas during write regardless the consistency level"
I that the normal behavior or a bug ?2013/6/11 Daning Wang <email@example.com>
It is counter caused the problem. counter will replicate to all replicas during write regardless the consistency level.In our case. we don't need to sync the counter across the center. so moving counter to new keyspace and all the replica in one center solved problem.There is option replicate_on_write on table. If you turn that off for counter might have better performance. but you are on high risk to lose data and create inconsistency. I did not try this option.DaningOn Sat, Jun 8, 2013 at 6:53 AM, srmore <firstname.lastname@example.org> wrote:
Thanks !I am seeing the similar behavior, in my case I have 2 nodes in each datacenter and one node always has high latency (equal to the latency between the two datacenters). When one of the datacenters is shutdown the latency drops.I am curious to know whether anyone else has these issues and if yes how did to get around it.
On Fri, Jun 7, 2013 at 11:49 PM, Daning Wang <email@example.com> wrote:
We have deployed multi-center but got performance issue. When the nodes on other center are up, the read response time from clients is 4 or 5 times higher. when we take those nodes down, the response time becomes normal(compare to the time before we changed to multi-center).We have high volume on the cluster, the consistency level is one for read. so my understanding is most of traffic between data center should be read repair. but seems that could not create much delay.What could cause the problem? how to debug this?Here is the keyspace,[default@dsat] describe dsat;Keyspace: dsat:Replication Strategy: org.apache.cassandra.locator.NetworkTopologyStrategyDurable Writes: trueOptions: [dc2:1, dc1:3]Column Families:ColumnFamily: categorization_cacheRingDatacenter: dc1===============Status=Up/Down|/ State=Normal/Leaving/Joining/Moving-- Address Load Tokens Owns (effective) Host ID RackUN xx.xx.xx..111 59.2 GB 256 37.5% 4d6ed8d6-870d-4963-8844-08268607757e rac1DN xx.xx.xx..121 99.63 GB 256 37.5% 9d0d56ce-baf6-4440-a233-ad6f1d564602 rac1UN xx.xx.xx..120 66.32 GB 256 37.5% 0fd912fb-3187-462b-8c8a-7d223751b649 rac1UN xx.xx.xx..118 63.61 GB 256 37.5% 3c6e6862-ab14-4a8c-9593-49631645349d rac1UN xx.xx.xx..117 68.16 GB 256 37.5% ee6cdf23-d5e4-4998-a2db-f6c0ce41035a rac1UN xx.xx.xx..116 32.41 GB 256 37.5% f783eeef-1c51-4f91-ab7c-a60669816770 rac1UN xx.xx.xx..115 64.24 GB 256 37.5% e75105fb-b330-4f40-aa4f-8e6e11838e37 rac1UN xx.xx.xx..112 61.32 GB 256 37.5% 2547ee54-88dd-4994-a1ad-d9ba367ed11f rac1Datacenter: dc2===============Status=Up/Down|/ State=Normal/Leaving/Joining/Moving-- Address Load Tokens Owns (effective) Host ID RackDN xx.xx.xx.199 58.39 GB 256 50.0% 6954754a-e9df-4b3c-aca7-146b938515d8 rac1DN xx.xx.xx..61 33.79 GB 256 50.0% 91b8d510-966a-4f2d-a666-d7edbe986a1c rac1Thank you in advance,Daning