On Wed, Jul 21, 2010 at 10:30 AM, Avinash Lakshman <
> (1) Is it possible to increase the number of observers in the cluster
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).