Nginx 502 bad gateaway

Either connection to Mandril and/or PHP-FPM most likely

Centmin Mod is provide as is, so short of scripted related bugs or issues, any further optimisation to the web stack components - nginx, php-fpm, mariadb mysql, csf firewall etc or web app specific configurations are left to the Centmin Mod user to deal with. So I do not provide any free support for such.

Nginx 502 Bad Gateway Errors

Bad gateway 502 is usually related to Nginx timing out waiting on PHP-FPM to respond as PHP-FPM is overloaded or overwhelmed with requests, so may need to tune PHP-FPM values. It also maybe due to PHP-FPM in turn being queued and backed up waiting on MariaDB MySQL server to respond - so also need to look at MySQL. Or could be delays in PHP-FPM connecting to Mandrill.

You'll need to tune your PHP-FPM settings and this is left up to end user to do but here's a thread for starters to enable php status page output outlined at PHP PHP-FPM - Centmin Mod - Menu based Nginx installer for CentOS servers and PHP-FPM - pm.max_children | Centmin Mod Community which outlines the official PHP-FPM config documentation as well.

Checking PHP-FPM etc logs

You'll also need to check into your PHP-FPM, Nginx and MariaDB logs which you can find as outlined at How to troubleshoot Centmin Mod initial install issues

Server logs include Nginx, PHP-FPM, MariaDB MySQL error logs as well as others. You can find your Centmin Mod install/menu logs at FAQ 7 and server logs at FAQ 19 at Centmin Mod FAQ (most up to date info in FAQ so always read that first). Spoiler tag below has info too but may not be up to date.

Some of Centmin Mod's installed software will have their own access and error logs which maybe useful for diagnosing errors or give info, notes, or warning notices.

Note: There's no support provided by me for diagnosing such errors which may occur for various reasons including misconfiguration of installed php/mysql scripts or applications.

In SSH2 telnet you can use tail command to view the last X number of lines in the file.

For example for viewing last 10 lines in the file for:

For Nginx access and error logs:
Code (Text):

tail -10 /usr/local/nginx/logs/access.log
tail -10 /usr/local/nginx/logs/error.log

For specific domainname.com access and error log:
Code (Text):

tail -10 /home/nginx/domains/domainname.com/log/access.log
tail -10 /home/nginx/domains/domainname.com/log/error.log

For other system error logs located at /var/log:

list /var/log files in ascending time order so the most recently modified files are at the bottom
Code (Text):

ls -lhrt /var/log

Code (Text):

total 2.7M
-rw------- 1 root root 0 Aug 29 15:33 tallylog
-rw------- 1 root root 0 Aug 29 15:33 spooler
drwx------ 3 root root 4.0K Aug 29 15:35 samba
drwxr-xr-x 2 root root 4.0K Aug 29 15:35 mail
-rw-r--r-- 1 root 500 0 Oct 8 18:13 dmesg.old
-rw------- 1 root 500 0 Oct 8 18:13 boot.log
-rw-r--r-- 1 root 500 0 Oct 8 18:14 dmesg
drwx------ 2 root root 4.0K Oct 8 18:14 httpd
drwxr-xr-x 2 root root 4.0K Oct 8 19:08 php-fpm
-rw-rw---- 1 mysql root 2.3K Oct 9 12:38 mysqld.log
-rw------- 1 root root 9.2K Oct 26 10:48 yum.log
-rw------- 1 root utmp 94K Nov 7 22:59 btmp
drwxr-xr-x 2 root root 4.0K Nov 8 00:00 sa
-rw------- 1 root root 269K Nov 8 21:39 messages
-rw------- 1 root root 110K Nov 8 23:08 secure
-rw-rw-r-- 1 root utmp 43K Nov 8 23:08 wtmp
-rw-r--r-- 1 root root 144K Nov 8 23:08 lastlog
-rw------- 1 root root 69K Nov 8 23:08 lfd.log
-rw------- 1 root root 332K Nov 8 23:08 maillog
-rw------- 1 root 500 1.6M Nov 8 23:10 cron

For PHP-FPM error log:
Code (Text):

tail -10 /var/log/php-fpm/www-error.log

and/or
Code (Text):

/var/log/php-fpm/www-php.error.log

For MySQL / MariaDB error log:
Code (Text):

tail -10 /var/log/mysqld.log

For CSF firewall LFD log:
Code (Text):

tail -10 /var/log/lfd.log

For Mail log:
Code (Text):

tail -10 /var/log/maillog

For Cron job logs:
Code (Text):

tail -10 /var/log/cron

How to edit php.ini and php-fpm configuration files ?

Centmin Mod install created command short cuts outlined here to allow you to quickly edit your /usr/local/lib/php.ini file and your /usr/local/etc/php-fpm.conf file. Full list of command shortcuts below:

• Edit php.ini = phpedit ( /usr/local/lib/php.ini )
• Edit my.cnf = mycnf ( /etc/my.cnf )
• Edit php-fpm.conf = fpmconf ( /usr/local/etc/php-fpm.conf )
• Edit nginx.conf = nginxconf ( /usr/local/nginx/conf/nginx.conf )
• Edit (nginx) virtual.conf = vhostconf - only edits /usr/local/nginx/conf/conf.d/virtual.conf not the additional vhost domain.com.conf files added later
• Edit (nginx) php.conf = phpinc ( /usr/local/nginx/conf/php.conf )
• Edit (nginx) drop.conf = dropinc ( /usr/local/nginx/conf/drop.conf )
• Edit (nginx) staticfiles.conf = statfilesinc ( /usr/local/nginx/conf/staticfiles.conf )
• nginx stop/start/restart = ngxstop/ngxstart/ngxrestart
• php-fpm stop/start/restart = fpmstop/fpmstart/fpmrestart
• mysql stop/start/restart = mysqlstop/mysqlstart/mysqlrestart
• nginx + php-fpm stop/start/restart = npstop/npstart/nprestart
• memcached stop/start/restart =memcachedstop/memcachedstart/memcachedrestart
• csf stop/start/restart = csfstop/csfstart/csfrestart

Troubleshooting Tools

However, there's many linux tools and scripts that can help you figure out what was causing the load issues and when.

Tools and commands you will want to read up on and learn for basic system admin tasks and troubleshooting.

• 20 Command Line Tools to Monitor Linux Performance
• 13 Linux Performance Monitoring Tools - Part 2
• 80 Linux Monitoring Tools for SysAdmins - Server Density Blog
• Amazing ! 25 Linux Performance Monitoring Tools
• 20 Linux System Monitoring Tools Every SysAdmin Should Know
• My mysqlmymonlite.sh script can help with that mysqlmymonlite.sh Addon | Centmin Mod Community README text file has instructions for setting up a cronjob to email you reports i.e. every 10/15min or every hour.

Notes:

• Centmin Mod already installed Glances tool. It can be invoked from SSH command glances or top2. Official Glances site at nicolargo.github.io/glances/ and documentation here.

However, Centmin Mod users are free to help each other out and ask questions or give answers on this community forum. My hopes are that this community forum evolves so that more veteran long time Centmin Mod users help new Centmin Mod users out

 

what version of PHP ?

Code:

php -v

extensions loaded ?

Code:

php --ini
php -m

 

php-fpm is segmentation faulting (segfaults) so need to found out why but that's up to you to troubleshoot i.e. doing straces on php processes etc

Code:

exited on signal 11 (SIGSEGV)

I don't provide support for that as Centmin Mod is provided as is, Google might help see php+strace and php-fpm+segfaults

could be APC Cache, so if you don't use APC Cache for data caching, can try centmin.sh menu option 12 submenu option 1 to install Zend Opcache instead of APC Cache

Code:

--------------------------------------------------------
Centmin Mod 1.2.3-eva2000.08 - http://centminmod.com
--------------------------------------------------------
                   Centmin Mod Menu                 
--------------------------------------------------------
1).  Centmin Install
2).  Add Nginx vhost domain
3).  NSD setup domain name DNS
4).  Nginx Upgrade / Downgrade
5).  PHP Upgrade / Downgrade
6).  XCache Re-install
7).  APC Cache Re-install
8).  XCache Install
9).  APC Cache Install
10). Memcached Server Re-install
11). MariaDB 5.2, 5.5, 10, 10.1 Upgrade Sub-Menu
12). Zend OpCache Install/Re-install
13). Install ioping.sh vbtechsupport.com/1239/
14). SELinux disable
15). Install/Re-install ImageMagick PHP Extension
16). Change SSHD Port Number
17). Multi-thread compression: pigz,pbzip2,lbzip2,p7zip etc
18). Suhosin PHP Extension install
19). Install FFMPEG and FFMPEG PHP Extension
20). NSD Re-install
21). Update - Nginx + PHP-FPM + Siege
22). Add Wordpress Nginx vhost + WP Super Cache
23). Update Centmin Mod Code Base
24). Exit
--------------------------------------------------------
Enter option [ 1 - 24 ] 12
--------------------------------------------------------

--------------------------------------------------------
        Zend OpCache Sub-Menu            
--------------------------------------------------------
1). Install Zend OpCache for PHP <5.5 or <5.6
2). Reinstall Zend OpCache for PHP <5.5 or <5.6
3). Back to Main menu
--------------------------------------------------------
Enter option [ 1 - 3 ] 

Code:

 php -v
PHP 5.4.42 (cli) (built: Jun 17 2015 08:11:45)
Copyright (c) 1997-2014 The PHP Group
Zend Engine v2.4.0, Copyright (c) 1998-2014 Zend Technologies
    with Zend OPcache v7.0.5, Copyright (c) 1999-2015, by Zend Technologies

 

centos 6.6 already fixed CVE-2011-1720 in backported postfix 2.6.6-4

Don't think it's related as I have including this forum, 40+ servers running Centmin Mod LEMP stack with postfix 2.6.6-6 latest available and with problems with smtp sending from local, mandril, amazon ses smtps.

Code:

yum list postfix -q                  
Installed Packages
postfix.x86_64                                              2:2.6.6-6.el6_5                                               @bas

But yeah Nginx and PHP-FPM upgrades you should keep on top of