What is the reason for "No input file specified" after a while of successful NGINX + PHP-FPM?

Question

PHP

For more than a year, a bunch of nginx + php-fpm has been working on a laptop and server. It works quite quickly, but at some point nginx starts to issue "No input file specified"
This problem did not bother me before, it was solved by restarting nginx and php-fpm. On the server even added this restart to cron. Now the loads have increased and this error has begun to interfere.
server: ubuntu server 14.04

uname -a
Linux punct.ru 3.13.0-37-generic #64-Ubuntu SMP Mon Sep 22 21:28:38 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

nginx -V
nginx version: nginx/1.4.6 (Ubuntu)
built by gcc 4.8.2 (Ubuntu 4.8.2-19ubuntu1) 
TLS SNI support enabled
configure arguments: --with-cc-opt='-g -O2 -fstack-protector --param=ssp-buffer-size=4 -Wformat -Werror=format-security -D_FORTIFY_SOURCE=2' --with-ld-opt='-Wl,-Bsymbolic-functions -Wl,-z,relro' --prefix=/usr/share/nginx --conf-path=/etc/nginx/nginx.conf --http-log-path=/var/log/nginx/access.log --error-log-path=/var/log/nginx/error.log --lock-path=/var/lock/nginx.lock --pid-path=/run/nginx.pid --http-client-body-temp-path=/var/lib/nginx/body --http-fastcgi-temp-path=/var/lib/nginx/fastcgi --http-proxy-temp-path=/var/lib/nginx/proxy --http-scgi-temp-path=/var/lib/nginx/scgi --http-uwsgi-temp-path=/var/lib/nginx/uwsgi --with-debug --with-pcre-jit --with-ipv6 --with-http_ssl_module --with-http_stub_status_module --with-http_realip_module --with-http_addition_module --with-http_dav_module --with-http_flv_module --with-http_geoip_module --with-http_gzip_static_module --with-http_image_filter_module --with-http_mp4_module --with-http_perl_module --with-http_random_index_module --with-http_secure_link_module --with-http_spdy_module --with-http_sub_module --with-http_xslt_module --with-mail --with-mail_ssl_module --add-module=/build/nginx-BU0ZJt/nginx-1.4.6/debian/modules/headers-more-nginx-module --add-module=/build/nginx-BU0ZJt/nginx-1.4.6/debian/modules/nginx-auth-pam --add-module=/build/nginx-BU0ZJt/nginx-1.4.6/debian/modules/nginx-cache-purge --add-module=/build/nginx-BU0ZJt/nginx-1.4.6/debian/modules/nginx-dav-ext-module --add-module=/build/nginx-BU0ZJt/nginx-1.4.6/debian/modules/nginx-development-kit --add-module=/build/nginx-BU0ZJt/nginx-1.4.6/debian/modules/nginx-echo --add-module=/build/nginx-BU0ZJt/nginx-1.4.6/debian/modules/ngx-fancyindex --add-module=/build/nginx-BU0ZJt/nginx-1.4.6/debian/modules/nginx-http-push --add-module=/build/nginx-BU0ZJt/nginx-1.4.6/debian/modules/nginx-lua --add-module=/build/nginx-BU0ZJt/nginx-1.4.6/debian/modules/nginx-upload-progress --add-module=/build/nginx-BU0ZJt/nginx-1.4.6/debian/modules/nginx-upstream-fair --add-module=/build/nginx-BU0ZJt/nginx-1.4.6/debian/modules/ngx_http_substitutions_filter_module

php -v
PHP 5.6.14-1+deb.sury.org~trusty+1 (cli) 
Copyright (c) 1997-2015 The PHP Group
Zend Engine v2.6.0, Copyright (c) 1998-2015 Zend Technologies
with Zend OPcache v7.0.6-dev, Copyright (c) 1999-2015, by Zend Technologies

nginx host config

server {
listen 80;
server_name server.punct.ru;

underscores_in_headers on;

access_log /var/log/nginx/server.punct.ru-access.log;
error_log /var/log/nginx/server.punct.ru-error.log;

root /home/server/public;
index index.php index.html index.htm;

try_files $uri $uri/ @rewrite;

location @rewrite {
rewrite ^(.*)$ /index.php?_url=$1;
}

location ~* ^/(assets|files|robots\.txt) { }

error_page 404 /404.html;

error_page 500 502 503 504 /50x.html;
location = /50x.html {
root /home/server/public;
}

#PHP-FPM connect
include extended/php-fpm;

location ~ /\.ht {
deny all;
}
}

/etc/nginx/extended/php-fpm

location ~ \.php$ {
    #   try_files $uri =404;
    try_files $fastcgi_script_name =404;
    fastcgi_split_path_info ^(.+\.php)(/.+)$;
    fastcgi_pass unix:/var/run/php5-fpm.sock;
    fastcgi_index index.php;

    include fastcgi_params;

    fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
    fastcgi_param PATH_TRANSLATED $document_root$fastcgi_script_name;
    fastcgi_param SERVER_ADMIN [email protected];
    fastcgi_param SERVER_SIGNATURE nginx/$nginx_version;
}

cat /etc/php5/fpm/php-fpm.conf | grep -v '^;' | sed '/^$/d'

[global]
pid = /run/php5-fpm.pid
error_log = /var/log/php5-fpm.log
include=/etc/php5/fpm/pool.d/*.conf

cat /etc/php5/fpm/pool.d/www.conf | grep -v '^;' | sed '/^$/d'

[www]
user = www-data
group = www-data
listen = /var/run/php5-fpm.sock
listen.owner = www-data
listen.group = www-data
listen.mode = 0660
 
pm = dynamic
pm.max_children = 5
pm.start_servers = 2
pm.min_spare_servers = 1
pm.max_spare_servers = 3 
chdir = /
security.limit_extensions = .php .php3 .php4 .php5

Answer 1

Turn on fpm logs
If you are not a hoster, then you should set yourself a process manager static load yourself with requests and select pm.max_children so that you have enough memory for the database and front
Read what they write to you in the default fpm config

; Error log file
; If it's set to "syslog", log is sent to syslogd instead of being written
; in a local file.
; Note: the default prefix is /var
; Default Value: log/php-fpm.log
error_log = /var/log/php5-fpm.log

; Log level
; Possible Values: alert, error, warning, notice, debug
; Default Value: notice
;log_level = notice

; Choose how the process manager will control the number of child processes.
; Possible Values:
;   static  - a fixed number (pm.max_children) of child processes;
;   dynamic - the number of child processes are set dynamically based on the
;             following directives. With this process management, there will be
;             always at least 1 children.
;             pm.max_children      - the maximum number of children that can
;                                    be alive at the same time.
;             pm.start_servers     - the number of children created on startup.
;             pm.min_spare_servers - the minimum number of children in 'idle'
;                                    state (waiting to process). If the number
;                                    of 'idle' processes is less than this
;                                    number then some children will be created.
;             pm.max_spare_servers - the maximum number of children in 'idle'
;                                    state (waiting to process). If the number
;                                    of 'idle' processes is greater than this
;                                    number then some children will be killed.
;  ondemand - no children are created at startup. Children will be forked when
;             new requests will connect. The following parameter are used:
;             pm.max_children           - the maximum number of children that
;                                         can be alive at the same time.
;             pm.process_idle_timeout   - The number of seconds after which
;                                         an idle process will be killed.
; Note: This value is mandatory.
pm = static