Aaron, Thank you for your answers. On 10 Jan 2013 00:27, "aaron morton" <aa...@thelastpickle.com> wrote:
> I thought Hinted Handoff was for downed replica's in the local datacentre. > I didn't realise that it would work with a remote datacenter. > > If the coordinator will store a hint if it detects a replica is down > before the request starts, or that the node did not return within > rpc_timeout. > > Likewise for Anti Entropy I thought it only worked for the replicas in the > local datacentre. I yet to find any definitive references which mention > that this works across multiple datacentres. > > It works on the cluster as a whole paying attention to the replication > settings. > > So if you have replicas in 2 dc's it will repair across them. > > Does the local coordinator send the updates asynchronously to the local >> replicas and the remote coordinator node?**** >> > Yes. All iternode communication is async. > > What happens if the bandwidth is severely restricted to the remote >> datacentre? Do the updates for the remote coordinator keep getting buffered >> up in the local coordinator?**** >> > There is a local queue of messages to send, if the messages are in the > queue for more than rpc_timeout they will not be sent. > > What happens if the connection to the remote coordinator is down? >> > It depends on the CL you are using. If you are using CL QUOURM your writes > will probably fail, depending on the RF settings. If you are using CL > LOCAL_QUOURM they will work so long as there is a local quourm. If you are > using EACH_QUOURM they will fail. > > Hope that helps. > > ----------------- > Aaron Morton > Freelance Cassandra Developer > New Zealand > > @aaronmorton > http://www.thelastpickle.com > > ----------------- > Aaron Morton > Freelance Cassandra Developer > New Zealand > > @aaronmorton > http://www.thelastpickle.com > > On 10/01/2013, at 11:40 AM, Jabbar <aja...@gmail.com> wrote: > > Hello Simon, > > I thought Hinted Handoff was for downed replica's in the local datacentre. > I didn't realise that it would work with a remote datacenter. > > Likewise for Anti Entropy I thought it only worked for the replicas in the > local datacentre. I yet to find any definitive references which mention > that this works across multiple datacentres. > > I'll keep looking. Obviously there'll probably be some documents I haven't > read read yet. > > > On 9 January 2013 18:38, Simon Guindon <simon.guin...@jsitelecom.com>wrote: > >> Here’s a good document on how hinted handoff works**** >> >> http://www.datastax.com/dev/blog/modern-hinted-handoff**** >> >> ** ** >> >> I believe if I understand that document correctly that a hinted handoff >> will get created if the replica is down in the other data center. Also >> since Cassandra is self-healing, reads will cause read repairs to correct >> any inconsistent data.**** >> >> ** ** >> >> Also Cassandra has an anti-entropy mechanism that actively updates >> replicas to the newest version using a Merkle tree.**** >> >> ** ** >> >> Here’s some text on Anti-entropy**** >> >> http://wiki.apache.org/cassandra/AntiEntropy**** >> >> ** ** >> >> ** ** >> >> *From:* Jabbar [mailto:aja...@gmail.com] >> *Sent:* January-08-13 5:34 PM >> *To:* user@cassandra.apache.org >> *Subject:* remote datacentre consistency**** >> >> ** ** >> >> I'm a bit confused about how a two datacentre apache cassandra cluster >> keeps the data consistent.**** >> >> From what I understand a client application in datacentre1 contacts a >> coordinator node which sends the data to the local replicas and it also >> sends the updates to the remote coordinator in the remote data centre.*** >> * >> >> ** ** >> >> Does the local coordinator send the updates asynchronously to the local >> replicas and the remote coordinator node? **** >> >> What happens if the bandwidth is severely restricted to the remote >> datacentre? Do the updates for the remote coordinator keep getting buffered >> up in the local coordinator?**** >> >> What happens if the connection to the remote coordinator is down? Would >> hinted hand off be used to recover from this scenario? What options are >> there to synchronise the remote datacentre if the connectivity comes back >> after a couple of days?**** >> >> ** ** >> >> -- >> Thanks >> >> A Jabbar Azam**** >> > > > > -- > Thanks > > A Jabbar Azam > > >
