DO Load Balancer: what happens if a server becomes unavailable before it is detected as unhealthy?

June 17, 2017 1.3k views
Load Balancing

I mean, suppose that the healthy check is performed every 10 seconds and the server is removed from the list after 3 consecutive failures. The whole process takes 30 seconds.
What happens in that 30 seconds if I turn off a server or when the server produces failures?
When a connection from the load balancer to the server fails, does the load balancer retry automatically with a different server? Or does it return an error to the client?

I think that this question actually refers to two distinct scenarios:

  1. TCP connection fails (e.g. the server is turned off)
  2. the server is returning HTTP errors (e.g. misconfiguration) <- I’ve found the answer for this second scenario: the load balancer can’t do anything because has no way to detect it, obviously
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