What happens on Load Balancing Timeout (and when?)

Hi I have a load balancing setup.

I was wondering if a user requests a URL, CF will pick a server. Is there a timeout value for that request? For example after 30s the load balancer will stop to wait for an answer? If that happens, what will the load balancer do? Request the same URL from a different server or return a timeout error?

Just to clarify, I don’t ask about monitors, I ask about an actual user request.

I don’t personally use load balancers but I believe it just selects a ‘healthy’ server, although it does rely on monitors determining what’s healthy. See

Standard failover

Standard failover directs traffic from unhealthy pools to the next healthy pool in the configuration.

Standard failover uses the pool order to determine failover priority (the failover order).

If all pools are marked unhealthy, Load Balancing will direct traffic to the fallback pool. The default fallback pool is the last pool listed in the Load Balancing configuration.

Yes that’s what I thought as well. However, I made two subjective observations, and I wanted to get some more information on this.

  • When I reboot a server in my load balancing setup and send a request, it can happen, that a request to the loadbalancer is running pretty long, even though my server might handle it in 300-400ms, but it runs, let’s say 15s. The server that is rebooting hasn’t been removed from the pool, so the request would have been send to the server in question, wasn’t answered and then moved over to a healthy server - that’s my theory.

  • My servers handle requests that require quite a bit to answer, it can be > 20-30s. When I hit a traffic spike and I scale up and add more servers, I have the feeling that the load is not reduced as much as it should.

My theory is, that CF will send out a second request to a different server after a certain threshold/timeout, because it seems that the server is not responsive (but it’s actually working, but it takes some time to answer). Before setting up an experiment, I figured it would be easier to ask first. I haven’t found anything specific about this in the docs.

The docs contain some (probably marketing text), which made me think CF might be doing something like this:

Load balancing and failover : Deliver traffic evenly across healthy servers, automatically failing over when a server is unhealthy or not responsive.

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