Hi Timothée, As discussed yesterday privately I absolutely support the idea of having an additional, 3rd-party based implementation of discovery.api. Whether it be etcd or zookeeper (or even something else) is up to feature comparison/discussion/etc.. One thing I thought was mentioned is that "we use ZooKeeper elsewhere already" and there might thus be synergies. But I haven't done a direct comparison of etcd vs zookeeper so far, so don't know if there is a clear winner anyway..
One thing to remember when implementing: one feature of discovery.api is that it groups instances hooked to the same repository into the same ClusterView and provides it with a stable (cluster)Id. In discovery.impl that is achieved by chatting and voting via said repository. When using an external mechanism, the fact that an instance belongs to a certain cluster needs special treatment as well in one way or another: either by still storing the id in the repository for example or via some configuration mechanism maybe. (Just something to keep in mind..) Cheers, Stefan On 2/4/15 2:40 PM, "Timothée Maret" <timothee.ma...@gmail.com> wrote: >Hi, > >I found some time to look closer to the Sling Discovery implementation on >AWS S3 proposal in [0]. >Doing so, I stumbled upon Etcd [1] based on Raft [2] which seems to covers >exactly what I wanted to do. > >Indeed, Etcd provides both persistent and temporal keys a well as >primitives to perform leader election. >Therefor, the Sling discovery API could be implemented on top of Etcd with >the notable addition of > >* multi-level leader election (e.g. at deploymen level, region level, or >any arbitrary segmentation). >* persistent properties > >Etcd would require to be deployed on dedicated HW (not embedded) but >offers >HTTP API for Sling instances to communicate with it. > >I have added this option in SLING-2939. > >Has someone already implemented it ? If not, I think it would make much >more sense to implement this integration rather than the idea in [0] and I >would give it a go. > >Regards, > >Timothee > > >[0] >http://apache-sling.73963.n3.nabble.com/Sling-Discovery-implementation-on- >AWS-S3-td4033160.html >[1] https://github.com/coreos/etcd >[2] https://raftconsensus.github.io
