nginx closes every night; I could not find the cause ..

my nginx.conf

user nobody;
# no need for more workers in the proxy mode
worker_processes 4;

error_log /var/log/nginx/error.log;
pid /var/run/nginx.pid;

worker_rlimit_nofile 8192;

events {
worker_connections 2048; # you might need to increase this setting for busy servers
use epoll; # Linux kernels 2.4.x change to rtsig
}

http {
server_names_hash_max_size 8192;
server_names_hash_bucket_size 256;
include mime.types;
default_type application/octet-stream;

sendfile on;
tcp_nopush on;
tcp_nodelay on;

keepalive_timeout 70;
server_tokens off;

gzip on;
gzip_min_length 1100;
gzip_buffers 4 32k;
gzip_types text/plain application/x-javascript text/xml text/css;
ignore_invalid_headers on;

client_header_timeout 10;
client_body_timeout 10;
send_timeout 10;
connection_pool_size 256;
client_header_buffer_size 4k;
large_client_header_buffers 4 32k;
request_pool_size 4k;
output_buffers 4 32k;
postpone_output 1460;

include "/usr/local/nginx/conf/vhost.conf";
}

Is there a line or the wrong value?