I find that error to , My Configuration is 4 upstreams, three upstreams is 1 cpu、2G memory,one is 2cpu、4Gmemory,the 2cpu's doesn't have this error,but the three 1cpus have this error,those server all in the same LAN ,anyone have the suggestion? Posted at Nginx Forum: http://forum.nginx.org/read.php?2,37426,66936#msg-66936