On Fri, 2009-03-13 at 20:26 -0500, Brad Knowles wrote:
> For example, putting NTP time servers behind load balancers
> are a really bad idea.
The only real issue with load-balancers, is with applications/clients
that keep server state, outside of a single transaction. Since the next
transaction could be on a different server.
With the NTP reference above, the NTP client keeps offset/jitter
information about each server (based on IP) that is references. So,
unless the server pool is in EXACT lock step time synchronization, the
clients will see a large jitter factor for the cluster IP.
Applications like LDAP do not have this type of issue, as there is no
session state, outside of the TCP connection containing the query.
Though you can think of the data being referenced as a state, in which
case the state is shared with all servers in the pool. That makes it
safe for load-balancing.
For things like web applications, state is usually handled in one of two
ways. Either a load-balancer that looks into the http transaction for
things like URL and HTTP Cookie info to base its decision on. Or, the
state is shared with all servers in the pool, so it doesn't matter which
server the query is forwarded to.
So, back to the original question...
Any TCP oriented load-balancer will work for LDAP.
--
END OF LINE
--MCP
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