Nginx response with persistence session and backend server failure
vl at nginx.com
Mon Jul 27 18:04:18 UTC 2015
On Mon, Jul 27, 2015 at 12:40:04PM +0530, Bhuvan Gupta wrote:
> Hello all,
> I was reading Nginx documentation
> persistence session using cookie and below is from documentation
> A request that comes from a client not yet bound to a particular server is
> passed to the server selected by the configured balancing method. Further
> requests with this cookie will be passed to the designated server. *If the
> designated server cannot process a request*, *the new server is selected as
> if the client has not been bound yet*.
> The last line says that
> *If the designated server cannot process a request*.
> What does it mean to say "the server cannot process a request."
- nginx either failed to contact upstream server and get
response from it (within configured timeouts - see
proxy_*_timeout directives), or some limit was hit (i.e.
- either the response was obtained, but considered inadequate
and nginx decided not to deliver the answer to client and
instead try other server (or return an error immediately - see
> Question 1:
> Does it mean the server was down ?
> or does it mean server responded with some error code ?
> or does it mean that it did not responded in a certain time interval ?
> or does it mean that max number of connection limit is reached on that
> server ?
in short: this is configurable, see above.
> Question 2:
> Let say there were 3 backend-server and we are using session persistence
> using cookie.
> Now assume that 2 of the backed server goes down so niginx will route all
> request to 3rd server
> Now 2 other server came back online, will niginx use the other 2 server to
> route the request even if request have the persistence cookie for 3rd
obviously, not. If a request has a cookie for 3rd server and it is
available, it will be routed to a 3rd server.
Requests without cookies will be routed to servers according load
More information about the nginx