Hello! On Thu, Mar 26, 2020 at 08:08:01PM +0100, Jan Prachař wrote:
> Hello, > > the upstream module documentation says: > > > max_fails=number > sets the number of unsuccessful attempts to communicate with the server > that should happen in the duration set by the fail_timeout parameter to > consider the server unavailable for a duration also set by the > fail_timeout parameter. > > > And also: > > > fail_timeout=time > sets > the time during which the specified number of unsuccessful attempts to > communicate with the server should happen to consider the server > unavailable; > > > Load balancing documentation at > http://nginx.org/en/docs/http/load_balancing.html says: > > > The max_fails directive sets the number of consecutive unsuccessful > attempts to communicate with the server that should happen during > fail_timeout. > > > But I have found that the actual nginx behaviour is different. Every > time an upstream fails, peer->accessed and peer->checked is set to now > and peers->fails is incremented. peer->checked is set to now also > before connecting to upstream, if > > now - peer->checked > peer->fail_timeout. (1) > > peer->fails is set to 0 only for sucessful request if peer->accessed < > peer->checked, which can happen only if condition (1) was fulfilled. > Therefore, peers->fails is set to zero only if no upstream error > happens during fail_timeout interval. So for example, if upstream fails > once every fail_timeout, after max_fails*fail_timeout will be marked as > unavailable. > > Or if there are no succesful requests to an upstream, peers->fails is > incremented with every request independetly on fail_timeout settings. > My test confirms that nginx indeed behaves like this. > > Is the documented behavior only part of the commercial subscription, or > am I missing somthing? Documentation somewhat oversimplifies things. The fail_timeout setting is essentially a session timeout, and things work as follows: 1. As long as there are failures, the fails counter is incremented. If fail_timeout passes since last failure, the fails counter is reset to 0 on the next successful request. 2. If the fails counter reaches max_fails, no more requests are routed to the peer for fail_timeout time. After fail_timeout passes, one request is allowed. If the request is successful, the fails counter is reset to 0, and further requests to the peer are allowed without any limits. -- Maxim Dounin http://mdounin.ru/ _______________________________________________ nginx-devel mailing list nginx-devel@nginx.org http://mailman.nginx.org/mailman/listinfo/nginx-devel
