Hi Bo, > In our case, I would like for the cluster to wait for the write to be persisted on the relevant nodes before returning an ok to the client. But I don't know which knobs to turn to accomplish this? or if it is even possible :)
This is what write consistency option is for. Have a look at https://docs.datastax.com/en/cassandra/2.0/cassandra/dml/dml_config_consistency_c.html. Note, however that if you use ALL, your clients will fail (throw exception, depending on language) as soon as a single partition can't be written. This means you can't do online maintenance of a Cassandra node (such as upgrading it etc.) without experiencing write issues. Cheers, Jens On Wed, Apr 20, 2016 at 3:39 PM Bo Finnerup Madsen <bo.gunder...@gmail.com> wrote: > Hi, > > We have a small 5 node cluster of m4.xlarge clients that receives writes > from ~20 clients. The clients will write as fast as they can, and the whole > process is limited by the write performance of the cassandra cluster. > After we have tweaked our schema to avoid large partitions, the load is > going ok and we don't see any warnings or errors in the cassandra logs. But > we do see quite a lot of hint handoff activity. During the load, the > cassandra nodes are quite loaded, with linux reporting a load as high as 20. > > I have read the available documentation on how hints works, and to my > understanding hints should only be written if a node is down. But as far as > I can see, none of the nodes are marked as down during the load. So I > suspect I am missing something :) > We have configured the servers with write_request_timeout_in_ms: 120000 > and the clients with a timeout of 130000, but still get hints stored. > > In our case, I would like for the cluster to wait for the write to be > persisted on the relevant nodes before returning an ok to the client. But I > don't know which knobs to turn to accomplish this? or if it is even > possible :) > > We are running cassandra 3.0.3, with 8Gb heap and a replication factor of > 3. > > Thank you in advance! > > Yours sincerely, > Bo Madsen > -- Jens Rantil Backend Developer @ Tink Tink AB, Wallingatan 5, 111 60 Stockholm, Sweden For urgent matters you can reach me at +46-708-84 18 32.
