On 04/14/2010 09:33 AM, Mekaraj, Prashant wrote:
Many thanks for the quick reply.
1) unnecessary -- clients already randomize their connect string
to balance the sessions across servers
The problems we are trying to solve are 1. updating the ensemble to
add new servers implies finding an updating every client who is
connecting to it(which implies we know who the clients are)
That's true. However the only real reason to change the ensemble size is
to increase reliability. We typically suggest 5 servers for on-line
production serving environments. This provides high reliability and also
allows for things like bringing down a server for maint, but still being
able to handle the case where another server may fail unexpectedly (but
the service will still stay up). Over 5 servers there is no significant
benefit to reliability, only the negative performance impact of having a
larger quorum.
2. if we deploy zookeeper in a region and put observers in other
regions, load balancers make it easy to preferably connect to a local
regional ip and failover to a remote one if the local ip is
unavailable
Yes, this is a good point. Also if you change the name/ip of a server
(say one fails and you need to replace)
3. load balancers offer more sophisticated balancing algo's - load
based for example.
2) unless you turn on some sort of session tracking in the
ballancer client's won't be able to use the service. ZK sessions
use long lived TCP connections to maintain a session with a
particular server.
The load balancer tracks sessions and makes sure that a client will
"stick" to a particular backend zookeeper server.
This is a trick question. ;-) One additional thing you would need to
ensure is that if the zk server fails the load balancer will take it out
of rotation.
I don't have any experience using LBs for this. It should be easy enough
for you to test in your environment/lbs though. I'd be interested to
know you results - if possible please post your findings!
Regards,
Patrick
Flavio,
Hi Seb, I was wondering how you're thinking about performing
session management interposing a load balancer between clients>
and zookeeper servers. I'm probably missing some important piece of
your design.
Load balancer stickiness should handle it if I understand your point
correctly.
-prashant
See session docs for more detail. http://bit.ly/db90Y5
Regards,
Patrick
On 04/14/2010 06:48 AM, Toader, Sebastian wrote:
Hi ZooKeeper Dev Team,
We are thinking of putting our ZooKeeper server behind load
balancer.
The client applications would connect to assemble through the load
balancer.
Can you let us know if there are any drawbacks in putting the
assemble behind a load balancer?
Thank you, Seb
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