Loadbalancer and failover issues

[Ajay Sonawane]

I am using nginx as a reverse proxy for my backend servers. My client is able to communicate to backend servers through proxy ( I have setup correct configuration).
To setup a load balancer I have used upstream directive to define a cluster of backend servers and default method of round robin. My clients are now connecting to backend servers in round robin fashion.

Now I want to see how load balancers handles the failover. To test this, I deliberately stopped one server so all connection will go to second server.

I have used below directive as well.

proxy_next_upstream_error timeout invalid_header http_500 http_502
proxy_connect_timeout 2

The problem I am facing is I get error 502 at client side intermittently. This is when one of the server is down. I was expecting that client will get connected to second server when first server is down. This works for most of time but intermittently I get 502 error.

Let me know if I am missing anything.

Ajay
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