[squid-users] Re: Behavior multiple reverse proxies when origin server down

Eliezer Croitoru-2 wrote
> There are couple solutions that can be considered but it depends on the
> LoadBalancer size and functionality.
> Also it depends on what level there is access from the LoadBalancer to
> squid instances and source pages\instances.
>
> You can do something like squid2 to forward the requests from one
> instance to the other in a case of a failure in one of the web-servers.
>
> If all that the LoadBalancer does is FailOver it will be much simpler to
> implement but if it's also a Traffic Balancing over two services it's
> one more complication from the LoadBalancer Angle.

Providing a failover is the primary function of the Load Balancer, balancing
the load between multiple servers is secondary.

Based on Amos' reply I think it should be possible to do both. If one web
server goes down the Squid server in front knows, based on (the lack of?)
HTTP request status codes, that that server is indeed down and traffic will
be directed to the remaining web server in the other location. In normal
operation load is balanced between the two servers.

Eliezer Croitoru-2 wrote
> I think that there is an option in a LoadBalancer to use a specific user
> designed Targer testing script which can answer the basic question to
> the LoadBalancer if one route of traffic is down or up.

Do you mean the Monitor URL feature:
http://wiki.squid-cache.org/Features/MonitorUrl ?
It's not available in Squid 3 yet, and I guess it's not necessary because of
the above.

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