On Wed, Jul 21, 2010 at 10:30 AM, Avinash Lakshman < avinash.laksh...@gmail.com> wrote:
> > (1) Is it possible to increase the number of observers in the cluster > dynamically? > Not quite, but practically speaking you can do as good as this. In general, pretty much any ZK configuration change can be done without service interruption by using a rolling restart. > (2) How many observers can I add given that I will seldom write into the > cluster but will have a lot of reads coming into the system? Can I run a > cluster with say 100 observers? > Others will give more authoritative answers, but I am pretty sure that the limitation on the number of observers is strictly related to write rate x number of observers. This is related to the fact that writes need to come from the current master. It isn't hard to imagine how to write a reflector that watches for all changes and writes these to a secondary cluster. That would essentially eliminate the limit on number of observers. Something like that may already be possible within the current system (I couldn't say since I haven't looked into observers that much).
