On Thu, May 8, 2014 at 5:35 PM, Lawrence Wagerfield < [email protected]> wrote:
> Fascinating and very helpful! > > Out of interest, where does RAFT sit on the aforementioned spectrum? I > only ask as there's a few Akka RAFT implementations floating around... > We have not talked about adding Raft (or similar, like Paxos/VR) to the Akka distribution. As everything in Akka, features are driven by need. If it turns out to be an important building block, either as an abstraction/tool for our users, or internally (if we f.e. decide to implement our own replicated Akka Persistence Journal) then we will add it. Many of the good things in Akka started out as external contributions, that after proven essential, was added to the core distribution—examples are Spray, eventsourced and Akka Camel. > > On Monday, May 5, 2014 7:07:16 AM UTC+1, shikhar wrote: >> >> I have been hacking on a discovery plugin for >> elasticsearch<https://github.com/shikhar/eskka> using >> akka cluster and I wanted to add some automated downing, and the >> auto-down-unreachable-after is not really an option since it can lead to >> split brain. >> >> So I went with the approach of using a quorum of members to determine >> whether the unreachable node should be downed. I'm curious to hear what you >> think of this. >> >> see https://github.com/shikhar/eskka/blob/master/src/main/scala/eskka/ >> QuorumBasedPartitionMonitor.scala >> >> 1. The >> VotingMembers<https://github.com/shikhar/eskka/blob/release-0.1/src/main/scala/eskka/VotingMembers.scala>passed >> in the constructor are the seed nodes. Using seed nodes was just an >> easy choice since they are specified before-hand. So ideally there should >> be 3 or more seed nodes. >> >> 2. I am using an app-level ping >> layer<https://github.com/shikhar/eskka/blob/master/src/main/scala/eskka/Pinger.scala>on >> top of the UNREACHABLE events. When a ping request to an unreachable >> node, made via the seed nodes "affirmatively times-out" (i.e. they must >> explicitly return a timeout response rather than the ping request timing >> out, so that we don't consider an unreachable seed-node as a voter!), then >> we DOWN that unreachable node. Instead of these app-level pings maybe it >> makes sense to utilize the Akka private[cluster] metadata >> like Reachability.isReachable(observer, node) but I'm not entirely sure >> of the semantics. >> >> 3. Currently this QuorumBasedPartitionMonitor actor gets started on every >> seed node. So in case a member becomes unreachable, they'd all end up >> trying to arrange for a distributed ping to the unreachable node via one >> another, and possibly downing it. This seems a bit like a thundering herd >> so not ideal. But on the other hand I don't want to use a cluster-singleton >> because this partition resolver is trying to be the layer that allows for >> singleton failover to happen smoothly. I'd love to hear ideas on how to >> handle this better. >> >> 4. Maybe a generic solution for quorum-based partition resolution should >> be a part of Akka proper/contrib? It seems AutoDown is rarely a good answer. >> > -- > >>>>>>>>>> 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. > -- *Jonas Bonér*Phone: +46 733 777 123 Home: jonasboner.com Twitter: @jboner <https://twitter.com/jboner> -- >>>>>>>>>> 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.
