On Mon, Jul 2, 2018 at 5:20 PM, John Wilson <sami.hailu...@gmail.com> wrote:
> Regarding 1. I'm referring to the documentation here, > https://apacheignite.readme.io/docs/topology-validation, which states > "*Topology > validator is used to verify that cluster topology is valid for further > cache operations*." and "*If topology validator is not configured, then the > cluster topology is always considered to be valid.*" > Yup. In this case, my answer is correct. > > Thanks, > > On Mon, Jul 2, 2018 at 4:21 PM, Dmitriy Setrakyan <dsetrak...@apache.org> > wrote: > > > On Mon, Jul 2, 2018 at 4:03 PM, John Wilson <sami.hailu...@gmail.com> > > wrote: > > > > > Hi, > > > > > > > > > 1. What exactly is a cluster topology? What makes a cluster topology > > > invalid for further cache operations? > > > > > > > Cluster topology is a set of Ignite nodes in the cluster. I do not think > a > > cluster topology could be invalid on its own. Perhaps you are asking > about > > a situation when after a certain number of node failures/stops we can be > in > > a situation where all primary and backup copies become inaccessible. In > > that case, the cluster should enter a read-only state for the lost > > partitions. > > > > > > > 2. Why do we have the concept of partitions in Ignite? Why don't we > > > have a key-to-node mapping rather than a key-to-partition and a > > > partition-to-node mapping? > > > > > > > Main reason is because there is a finite number of partitions and there > is > > an infinite number of keys. Whenever ignite topology changes, Ignite must > > rebalance data to the new nodes (or to the existing nodes). In this case, > > Ignite needs to know when a certain partition is moved to another node. > If > > there were no partitions, then it would be impossible to tell when to > > finish the rebalancing process. > > > > D. > > >
