On Fri, 7 Oct 2016, at 02:57, Adam Kocoloski wrote: > Hi all, > > Lately I’ve been thinking about how to ease the onramp for users to get a > clustered CouchDB setup running. I think the Kubernetes work shows a lot > of promise. One of the aspects of that work is the service discovery > element; each node in a cluster should be able to automatically find its > peers and connect to them. Kubernetes accomplishes this using SRV > records; a DNS lookup for a given named service will return the FQDNs of > all the live members of the “Pet Set”. > > The SRV approach is enough of a standard[1] that I wonder if we ought to > code for it directly in mem3. It’d eliminate the need for a “sidecar” > container in Kubernetes deployments and I can imagine that it will prove > more generally useful. The idea would be for mem3 to check if the CouchDB > node is running in distributed node, and if it is, fire off a DNS lookup > on the domain name, then attempt to connect with any other targets that > are included in the record set in the DNS response. > > What do you think? If no one objects I’ll file a JIRA and see what we > come up with.
belated +1 for _SRV records, +1000 for combining that with MDNS also for initial cluster setup. There are a number of erlang libraries already to help with this - below. the key issue with _SRV records is that, just like A records and CNAMEs is that you need to put them manually into DNS already. I am not sure this makes discovery easier... Something like mdns provides a multicast DNS lookup service, and nails this problem squarely. It is the bonjour/rendezvous/zeroconf tech used heavily by Apple devices, HP for printers etc. super nice. I am using this atm for service discovery albeit non-erlang stuff. It didnt quite get out of the RFC stage but its the defacto standard at least for consumer gear. http://www.zeroconf.org/ https://github.com/shortishly/mdns or https://github.com/Licenser/erlang-mdns-server | client Also worth a look is https://github.com/shortishly/haystack with more docker sauce Another alternative is zbeacon, http://czmq.zeromq.org/manual:zbeacon , also with erlang implementation https://github.com/zeromq/ezmq which I've only given a passing glance to. A+ Dave
