How to get haproxy to use a specific cluster computer via the URI

Question

I have successfully set haproxy on my server cluster. I have run into one snag that I can't find a solution for...

TESTING INDIVIDUAL CLUSTER COMPUTERS

It can happen that for one reason or another, one computer in the cluster gets a configuration variation. I can't find a way to tell haproxy that I want to use a specific computer out of a cluster.

Basically, mysite.com (and several other domains) are served up by boxes web1, web2 and web3. And they round-robin perfectly.

I want to add something to the URL to tell haproxy that I specifically want to talk to web2 only because in a specific case, only that server is throwing an error on one web page.

Anyone know how to do that without building a new cluster with a URI filter and only have one computer in that cluster? I am hoping to use the cluster as-is but add something to the URI that will tell haproxy which server to use out of the cluster.

Thanks!

Answer 1

Basically, haproxy cannot do what I was hoping. There is no way to add a param to the URL to suggest which host in the cluster to use.

I solved my testing issue by setting up unique ports for each server in the cluster at the firewall. This could also be done at the haproxy level.

To secure this path from the outside world, I told the firewall to only accept traffic from inside our own network.

This lets us test specific servers within the cluster. We did have to add a trap in our PHP app to deal with a session cookie that is too large because we have haproxy manipulating this cookie to keep users on the server they first hit. So when the invalid session cookie is detected, we have the page simply drop the session and reload the page.

This is working well for our testing purposes.

Answer 2

Have you thought about using different port for this? Defining new listen section with different port, because, as I understand, you can modify your URL by any means?