Hello! On Thursday, January 15, 2015 at 8:50:23 AM UTC+2, Patrik Nordwall wrote: > > On Wed, Jan 14, 2015 at 6:58 PM, Oleg Mürk <[email protected] > <javascript:>> wrote: > >> I'd like to better understand what happens to a Leader if it becomes >> unreachable. Auto-down is impossible because it can only be performed by >> the Leader, right? Can I execute Down command on non-leader member of >> cluster when the Leader is unreachable? >> > > Akka Cluster doesn't require a strict leader for managing the cluster > membership. The membership data is a Conflict Free Replicated Data Type > (CRDT) so if there are conflicting updates they can be merged anyway. The > leader is just a role for a node that performs certain actions and it is > alright if several nodes thinks they have this role. >
Got it, thanks! > So Persistence and consequently Sharding cannot be used in potential >> split-brain cluster configurations? Because ShardCoordinator could >> potentially run on both partitions simultaneously? >> > > It is right that you must only be one active instance of a PersistentActor > with a given persistenceId, i.e. single writer to the journal. That is true > also for the ShardCoordinator, since it is a PersistentActor. That means > that you must handle network partitions carefully and use a proper downing > strategy as discussed earlier. We have acknowledged that a packaged > solution for improving this have been requested by many users. > <...> > We don't need strong coordination for cluster membership and we have the > goal to support large clusters > <http://typesafe.com/blog/running-a-2400-akka-nodes-cluster-on-google-compute-engine>, > > which I believe would not be possible with Zookeeper. Zookeeper is great, > but it is solving a different set of problems. > I agree that current Akka's CRDT based group membership protocol serves its purpose well. It's also possible to build coordination services on top of Akka Cluster, > as illustrated by Konrad's akka-raft > <https://www.google.com/url?q=https%3A%2F%2Fgithub.com%2Fktoso%2Fakka-raft&sa=D&sntz=1&usg=AFQjCNFeBbv21ujT_X6PqpivN5ZMzZHkYw> > > prototype. > I suppose one could use Zookeeper for ensuring uniqueness of a Singleton or ShardCoordinator/ShardRegion? AFAIK Zookeeper scales to 1000s of *clients*? Another question I had is how to handle situations when eg ShardCoordinator/ShardRegion cannot communicate with Zookeeper, while ShardRegion's persistent Entities can communicate with, say, HBase. But I guess it a question for another mailig list :) Thanks! Oleg > -- >>>>>>>>>> Read the docs: http://akka.io/docs/ >>>>>>>>>> Check the FAQ: >>>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html >>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user --- You received this message because you are subscribed to the Google Groups "Akka User List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/akka-user. For more options, visit https://groups.google.com/d/optout.
