Hello! On Tue, Aug 19, 2014 at 07:31:21AM -0400, yury_y wrote:
> Hi, > > I faced the following problem. Our server works under the constant load of > 300-400 requests per second. > From request execution time statistics I see that in some cases "fast" > request(that normally executes in few milliseconds) may hang for seconds. > > Here is an illustration of this problem. > I execute the following GET request "http://127.0.0.1:777/fcgi/auth...";(no > ssl, no dns lookup, just http on localhost) from local client(on the same > sever). > Usually this request executes in less then 1 millisecond, but in this case > execution time is 130 milliseconds. > > From tcpdump I can conclude following: > 16:18:43.095716 - client sent request to nginx > 16:18:43.225903 - nginx sent request to upstream > 16:18:43.226178 - upstream replied to nginx > 16:18:43.226235 - nginx replied to client > > So request was processed by upstream in less then 1 millisecond, but it took > about 130 microseconds to read request from client and pass it to upstream. > I observe similar behavior both for fcgi upstreams and for static requests. > > Does anybody have similar problems? In which direction should I > investigate? Most likely, the reason for such delays is that all nginx workers were busy doing some other work. In particular, this may happen with disk-bound workloads due to blocking on disk. You may try looking into top(1) output for states of nginx worker processes, it usually makes things much clearer. Some additional reading: http://nginx.org/r/sendfile_max_chunk http://nginx.org/r/aio http://nginx.org/r/output_buffers -- Maxim Dounin http://nginx.org/ _______________________________________________ nginx mailing list [email protected] http://mailman.nginx.org/mailman/listinfo/nginx
