mod_cluster not balancing load after discover

Question

I have cluster setup up and running ...Jboss 7.1.1.Final and mod_cluster mod_cluster-1.2.6.Final.

mod_cluster load balancing is happening bitween two nodes - nodeA nodeB.

But when I stop one node and start, mod_cluster still sends the all load to the other node. It is not distributing load after comeback.

What is configuration changes required this ? I could see both nodes enabled in mod_cluster_manager. But it directs load only to one node even after the other node comeback after fail over.

Thanks

Answer 1

If you are seeing existing requests being forwarded to the active node, then it's because of sticky session being enabled. This is the default behavior.

If you are seeing new requests are not being forwarded to the new node (even when it's not busy) then it is a different issue. You may want to look at the load balancing factor/algorithm that you are currently utilizing in your mod-cluster subsystem.

Answer 2

It came to my mind, that you might actually be seeing the correct behaviour -- within a short time span. Take a look at my small FAQ: I started mod_cluster and it looks like it's using only one of the workers.

TL;DR: If you send only a relatively small amount of requests, it might look like the load balancing doesn't work whereas it's actually correct not to flood fresh newcomers with a barrage of requests at once.