Re: cassandra for a inbox search with high reading qps
Chen Xinli chen.daqi at gmail.com writes: Hi, Despite our use cases, is't it a good feature to disable reading when a node is doing hinted handoff, just like bootstraping? It will be very useful for READ ONE consitency level. Or it can be an option in storage-conf.xml, and user can set it when necessary. I'd like to implement this feature if it's useful. Yes, we also use this failback policy, but currently doing it manually - returning node back to clients nodelist only after hinted handoff is completed. So at least for us this should be handy, if you'd implement this to happen automatically.
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Re: cassandra for a inbox search with high reading qps
2010/8/19 Oleg Anastasjev olega...@gmail.com Chen Xinli chen.daqi at gmail.com writes: Hi, Despite our use cases, is't it a good feature to disable reading when a node is doing hinted handoff, just like bootstraping? It will be very useful for READ ONE consitency level. Or it can be an option in storage-conf.xml, and user can set it when necessary. I'd like to implement this feature if it's useful. Yes, we also use this failback policy, but currently doing it manually - returning node back to clients nodelist only after hinted handoff is completed. So at least for us this should be handy, if you'd implement this to happen automatically. would you pls describe the manual operation with more details? I have not found any related information. -- Best Regards, Chen Xinli
questions regarding read and write in cassandra
Hi I have a question in the following scenario. Say we have 10 nodes, Replication factor is 5. Now, say, for Row X, Column Y, data is replicated to node 1,2,3,4,5 and current value is 10 Say, I issue a write command with value “20” to Row X, column Y with quorum(n/2+1=3 nodes). Say it updated 1 and 2 and failed to update any other node. So it failed to write to 3 nodes. What happens in such scenario? Q: Will the user returned failed? Now, assuming that the write failed. What value will I see if I want to read the same cell with Quorum? Now, say I read the data with quorum. It read from 1, 4, 5 and see that node 1 has the most recent data (“20” which is still there as cassandra does not roll back). Will it will return the data “20” to the user or will it return the earlier value 10 as it is returned by the node 4 and 5? Also, does read repair tries to propagate 20 to all the replicas although cassandra returned failed to the user? thanks
Re: questions regarding read and write in cassandra
The quorum write would fail, but the data would not be rolled back. Assuming the offline nodes recover, the data would eventually replicate. This question belongs on the user list, though. -Original Message- From: Maifi Khan maifi.k...@gmail.com Date: Thu, 19 Aug 2010 13:00:47 To: dev@cassandra.apache.org Reply-To: dev@cassandra.apache.org Subject: questions regarding read and write in cassandra Hi I have a question in the following scenario. Say we have 10 nodes, Replication factor is 5. Now, say, for Row X, Column Y, data is replicated to node 1,2,3,4,5 and current value is 10 Say, I issue a write command with value “20” to Row X, column Y with quorum(n/2+1=3 nodes). Say it updated 1 and 2 and failed to update any other node. So it failed to write to 3 nodes. What happens in such scenario? Q: Will the user returned failed? Now, assuming that the write failed. What value will I see if I want to read the same cell with Quorum? Now, say I read the data with quorum. It read from 1, 4, 5 and see that node 1 has the most recent data (“20” which is still there as cassandra does not roll back). Will it will return the data “20” to the user or will it return the earlier value 10 as it is returned by the node 4 and 5? Also, does read repair tries to propagate 20 to all the replicas although cassandra returned failed to the user? thanks
Re: questions regarding read and write in cassandra
Hi David Thanks for your reply. But what happens if I read and get 2 nodes has value 10 with older time stamp and the third node has 20 with more recent time stamp? Will cassandra return 10(majority) or 20(more recent)? thanks Maifi On Thu, Aug 19, 2010 at 1:20 PM, David Timothy Strauss da...@fourkitchens.com wrote: The quorum write would fail, but the data would not be rolled back. Assuming the offline nodes recover, the data would eventually replicate. This question belongs on the user list, though. -Original Message- From: Maifi Khan maifi.k...@gmail.com Date: Thu, 19 Aug 2010 13:00:47 To: dev@cassandra.apache.org Reply-To: dev@cassandra.apache.org Subject: questions regarding read and write in cassandra Hi I have a question in the following scenario. Say we have 10 nodes, Replication factor is 5. Now, say, for Row X, Column Y, data is replicated to node 1,2,3,4,5 and current value is 10 Say, I issue a write command with value “20” to Row X, column Y with quorum(n/2+1=3 nodes). Say it updated 1 and 2 and failed to update any other node. So it failed to write to 3 nodes. What happens in such scenario? Q: Will the user returned failed? Now, assuming that the write failed. What value will I see if I want to read the same cell with Quorum? Now, say I read the data with quorum. It read from 1, 4, 5 and see that node 1 has the most recent data (“20” which is still there as cassandra does not roll back). Will it will return the data “20” to the user or will it return the earlier value 10 as it is returned by the node 4 and 5? Also, does read repair tries to propagate 20 to all the replicas although cassandra returned failed to the user? thanks
Re: cassandra for a inbox search with high reading qps
On 8/19/10 7:18 AM, Chen Xinli wrote: 2010/8/19 Oleg Anastasjevolega...@gmail.com Chen Xinlichen.daqiat gmail.com writes: Hi, Despite our use cases, is't it a good feature to disable reading when a node is doing hinted handoff, just like bootstraping? It will be very useful for READ ONE consitency level. Or it can be an option in storage-conf.xml, and user can set it when necessary. I'd like to implement this feature if it's useful. Yes, we also use this failback policy, but currently doing it manually - returning node back to clients nodelist only after hinted handoff is completed. FWIW, this has been proposed before, and resolved Not A Problem. https://issues.apache.org/jira/browse/CASSANDRA-768 =Rob
