Hi ,

Please note that we are using nginx v 1.10.2 and on one of our webserver (centos 7.2) we are observing below error and sudden stopping of nginx service repeatedly at fix time i.e. at 2:00 am. Below are error lines for your reference :

2017/02/26 02:00:01 [alert] 57550#57550: *131331605 open socket #97 left in connection 453
2017/02/26 02:00:01 [alert] 57550#57550: *131334225 open socket #126 left in connection 510
2017/02/26 02:00:01 [alert] 57550#57550: *131334479 open socket #160 left in connection 532
2017/02/26 02:00:01 [alert] 57550#57550: *131334797 open socket #121 left in connection 542
2017/02/26 02:00:01 [alert] 57550#57550: *131334478 open socket #159 left in connection 552
2017/02/26 02:00:01 [alert] 57550#57550: *131334802 open socket #194 left in connection 633
2017/02/26 02:00:01 [alert] 57570#57570: aborting
2017/02/26 02:00:01 [alert] 57553#57553: aborting
2017/02/26 02:00:01 [alert] 57539#57539: aborting
2017/02/26 02:00:01 [alert] 57550#57550: aborting

Also find below nginx conf files for your reference :

worker_processes auto;
events {
worker_connections 4096;
use epoll;
multi_accept on;
}
worker_rlimit_nofile 100001;

http {
include mime.types;
default_type video/mp4;
proxy_buffering on;
proxy_buffer_size 4096k;
proxy_buffers 5 4096k;
sendfile on;
keepalive_timeout 30;
tcp_nodelay on;
tcp_nopush on;
reset_timedout_connection on;
gzip off;
server_tokens off;
log_format access '$remote_addr $http_x_forwarded_for $host [$time_local] ' '$upstream_cache_status ' '"$request" $status $body_bytes_sent ' '"$http_referer" "$http_user_agent" $request_time'

Also note that we have similar servers with exact same nginx config running but those servers are not giving any such errors. Also we are not running any script or cron at this point of time.
Kindly help us to resolve this issue. Also let me know in case any other details are required from my end.