We are using Nginx as a reverse proxy to an IIS back-end server serving .NET WCF application.
Recently I had noticed a degradation of the overhead response time. What I mean by that is I used to see 6ms difference between $request_time and $upstream_response_time, now I'm at 22ms.
The number of active connections had not augmented, neither the requests count, size, response size. CPU and disk IO are very low. Network traffic seem to be fine too.
I've tried :
- Disabling SSL, no change.
- Changing back the config of nginx back to default values, no change.
- The machine was rebuild from scratch, no change.
- A much slower VM with the original config and the overhead is very low, +/-6ms.
How can I investigate this problem... ?
Is there a way to see how much time nginx spent in every step of a request processing ? Can't find this answer by looking in error.log in debug mode.