Opensource Layer4 Switching

[Scarpozzi]

I'm trying to create a load-balanced cluster of 2 linux servers.

My problem is that I don't have a layer 4 switch to provide a single ip address to access the two nodes. I could do an active/passive cluster, but I want a load balancer.

There are plenty of companies that sell load balancers, but I'm wondering if there is a open source application I can install on a Linux box that can do this. If anyone knows of anything, please let me know. Thanks.

 

[spidey07]

A reverse proxy would do the trick. I've never done it that way cause I'm used to hardware balancers, but look into Squid. It may contain that functionality but I wouldn't imagine the load balancing features to be very robust.

Do you need any L5 or L7 features? Or just a straight L4 load balancing? Some switches support straight L4 balancing.

 

[cmetz]

Scarpozzi, there are lots of free solutions for this high-level problem. Can you be more specific about what you need?

 

[spidey07]

Interested in the free solutions and their flexibility/features.

 

[Scarpozzi]

Originally posted by: cmetz
Scarpozzi, there are lots of free solutions for this high-level problem. Can you be more specific about what you need?

Well, I've got quite a few reverse proxy application servers, so I may just pull one of those in as a temporary fix. I just want to keep the network traffic simple if possible...

To be specific, I'm replacing my current reverse proxy servers with a more robust solution. It requires Layer4 switching out front to provide clustering of the resource servers in addition to that, it would be nice to provide L4 in front of the gateway servers.

The proxy has 2 gateway servers and 2 identity servers that cache all of the LDAP servers I host for provisioning and authentication.

This is kind of a chicken and egg problem so we'll probably just bite the bullet and buy the hardware and let it handle the active/passive configuration out front and leave the crude packet pushing to hardware. I was just wanting to know if there was a cheap/free alternative until we can find the money.

 

[brassbin]

I doubt a mere application running on the same Linux OS would work, a packet would still traverse through inbound TCP/IP stack, hit the supposed load balancing app, traverse another TCP/IP stack outbound, then hit one of the nodes in the clusters, the system sitting in front would then become the bottleneck, defeating the purpose of load balancing in the 1st place. There is an argument to be made that since we are only talking about a layer 4 app, layer 7 overhead is not involved, yes so the processing on the load balancing node is faster than any other destination node, but still you created a bottleneck that didn't exist before.

 

[spidey07]

Originally posted by: brassbin
I doubt a mere application running on the same Linux OS would work, a packet would still traverse through inbound TCP/IP stack, hit the supposed load balancing app, traverse another TCP/IP stack outbound, then hit one of the nodes in the clusters, the system sitting in front would then become the bottleneck, defeating the purpose of load balancing in the 1st place. There is an argument to be made that since we are only talking about a layer 4 app, layer 7 overhead is not involved, yes so the processing on the load balancing node is faster than any other destination node, but still you created a bottleneck that didn't exist before.

Don't try to reason with software architects/application people when it comes to performance. They just don't understand. If this is straight L4 load balancing then it can easily be done in processor. They're happy to have 1 million dollars in hardware to provide content but run everything through a 20K load balancer. Fix your application people.

FYI - professional level load balancers push the logic to hardware which is what gives them the performance.

 

[freegeeks]

maybe quagga has some loadbalancing option

anyway, I would go for a hardware solution like something from f5