On Tue, 22 Mar 2005, Fred Clark wrote:
A couple of months ago we started seeing forwarding loop errors in the cache.log indicating issue with our Plumtree Portal environment - extract as follows:
2005/03/04 16:23:03| WARNING: Forwarding loop detected for: GET /ptcs/gadgets/admin/gadget.jsp HTTP/1.0 Host: X.X.X.X:9080
(Note that the true IP of the host has been changed to X.X.X.X)
A forwarding loop is when the same request is seen more than once by the same Squid, i.e. it forwarded (directly or indirectly) the request to itself.
You should be able to determine why this happened by looking at the request headers reported together with this message, giving you the exact path how the request was forwarded among your Squids. This is the same method used by Squid to determines that there was a forwarding loop.
Once you know the nature of the loop it is easier to try to picture how to avoid the loop. The reasons to forwarding loops can be many, but nearly always involves circular peering relationships.
It may also be worth noticing that forwarding loops most often is not harmful as Squid when detecting a forwarding loop simply restricts it's forwarding methods to go direct, or if not allowed (never_direct) only use parents.
Regards Henrik
