CF7 Multiserver configuration question

Question

The CFMX 7 install guide states;
<quote>
Load balancing and failover You deploy the same application
to each server instance and add
the instances to a cluster. The web server connector
optimizes performance and stability by
automatically balancing load and by switching requests to
another server instance when a server
instance stops running.
</quote>
What exactly does "stops running" mean here from the
connector perspective ? Is it;
* HTTP requests fail (and if so what status codes are
regarded as permanent failures)
* TCP connectivity is lost
* Something else ?

Answer 1

paulkeogh wrote:
> What exactly does "stops running" mean here from the
connector perspective ?
> Is it;
>
> * HTTP requests fail (and if so what status codes are
regarded as permanent
> failures)
> * TCP connectivity is lost
> * Something else ?
In my experience with this, if you're talking about the CF
level of
clustering specifically, the failover from one CF instance to
another
occurs when a CF request fails. This doesn't have anything to
do with
HTTP requests so if your web server isn't clustered the CF
clustering
isn't going to help you there.
We did a lot of analysis on this recently as we built a new
high-availability environment. The basic question you have to
answer is
when a physical server is considered "down" and should be
taken out of
service. At a high level you have three situations to
consider:
1. Box is up and running and responding to TCP/IP traffic,
but IIS is down
2. Box is up and running, but CF is down
3. Box is dead
CF clustering doesn't help you with IIS being down, and of
course it
doesn't help you if the box is down. The absolute best
solution overall
is a hardware load balancer because that can (depending on
your load
balancer) help you at both the box level and the IIS level,
and with a
bit of extra work even with the CF level.
In our situation we decided that since we have three servers,
if any one
of the three situations above occurs, the box is considered
out of
service and the load balancer fails over to another box. We
could
cluster CF but decided it wasn't worth the effort and
additional
overhead in our situation. Your needs may dictate otherwise
of course.
Hope that helps,
Matt
Matt Woodward
[email protected]
Adobe Community Expert - ColdFusion