Is anybody using this in large production systems?
We don't have permission at this time to share some of our big users (we're working on approvals!), but I can say that that some very big companies you've certainly heard of and probably use right now have deployed Consul across every server. And Consuls deployment in just companies were working with is in the hundreds of thousands of machines.
At this point were very confident in its stability and it's well proven at very large scale.
If you're a big user and need references to other large users, email me and I'd be happy to set that up.
Without divilging too many details, what would be the ratio of agents running '-server' to overall agents?
All machines using consul will (generally) run the agent locally.
In general you are going to set up an N+M topology of n servers and n+m agents -- but for a network of 100k nodes does consul scale to 100k agents? Plus what goes unstated is how those 100k nodes are laid out in DCs and racks.
Anyway, this isn't to slag on consul. I think consul is like chocolate and peanut butter.
I use it in my mesos cluster and just am genuinely curious how large it can scale!
Started with Serf plus customizations and then migrated over to Consul. Happy to share technical details or answer questions.