nginx 502 bad gateway

Question

I get a 502 Bad Gateway with nginx when using spawn fcgi to spawn php5-cgi   I use this to span an instance on server start using the following line in rc local   usr bin spawn-fcgi -a 127 0 0 1 -p 9000 -u www-data -g www-data -f  usr bin php5-cgi -P  var run fastcgi-php pid   presumably I m getting the error because the spawn-fcgi   php5-cgi dies and there is nothing listening there anymore to parse php   I get nothing in the logs that I can see anywhere  I m out of ideas  and new to this setup with nginx

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When I did sudo  etc init d php-fpm start I got the following error   Starting php-fpm   28-Mar-2013 16 18 16  ERROR   pool www  cannot get uid for user  apache    I guess  etc php-fpm d www conf needs to know the user that the webserver is running as and assumes it s apache when  for nginx  it s actually nginx  and needs to be changed

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I had the same problem while setting up an Ubuntu server  Turns out I was having the problem due to incorrect permissions on socket file   If you are having the problem due to a permission problem  you can uncomment the following lines from   etc php5 fpm pool d www conf  listen owner   www-data listen group   www-data listen mode   0660   Alternatively  although I wouldn t recommend  you can give read and write permissions to all groups by using the following command   sudo chmod go rw  var run php5-fpm sock

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You have to match the settings for PHP-FPM and Nginx to communicate over sockets or TCP    So go to  etc php5 fpm pool d www conf and look for this line   listen    var run php5-fpm sock   Then go to  etc nginx nginx conf  Look for this    upstream php       server unix  var run php5-fpm socket      Match those values and you should be all set

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Try disabling the xcache or apc modules   Seems to cause a problem with some versions are saving objects to a session variable

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If you re on Ubuntu  and all of the above has failed you  AppArmor is most likely to blame    Here is a good guide how to fix it  https   www digitalocean com community tutorials how-to-create-an-apparmor-profile-for-nginx-on-ubuntu-14-04  Long story short    vi  etc apparmor d nginx   Or   sudo aa-complain nginx sudo service nginx restart   See everything working nicely    then  sudo aa-logprof   I still had problems with Nginx not being able to read error log  even though it had all the permissions possible  including in Apparomor  I m guessing it s got something to do with the order of the entries  or some interaction with Passenger or PHP-Fpm    I ve run out of time to troubleshoot this and have gone back to Apache for now   Apache performs much better too FYI     AppArmor just lets Nginx do whatever it wants if you just remove the profile    rm  etc apparmor d nginx  service apparmor reload   Shockingly  but hardly surprising  a lot of posts on fixing Nginx errors resorts to completely disabling SELinux or removing AppArmor  That s a bad idea because you lose protection from a whole lot of software  Just removing the Nginx profile is a better way to troubleshoot your config files  Once you know that the problem isn t in your Nginx config files  you can take the time to create a proper AppArmor profile    Without an AppArmor profile  especially if you run something like Passenger too  I give your server about a month to get backdoored

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Similar setup here and looks like it was just a bug in my code   At the start of my app I looked for the offending URL and this worked  echo   lt html gt test lt  html gt    exit      In my case  turns out the problem was an uninitialized variable that only failed under peculiar circumstances

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You can make nginx ignore client aborts using   location       proxy ignore client abort on

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change  fastcgi pass    unix  var run php-fpm sock    to  fastcgi pass    unix  var run php5-fpm sock

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I executed my localhost and the page displayed the 502 bad gateway message  This helped me    Edit  etc php5 fpm pool d www conf Change listen    var run php5-fpm sock to listen   127 0 0 1 9000 Ensure the location is set properly in nginx conf  Run sudo service php5-fpm restart   Maybe it will help you   Source from  http   wildlyinaccurate com solving-502-bad-gateway-with-nginx-php-fpm

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The 502 error appears because nginx cannot hand off to php5-cgi   You can try reconfiguring php5-cgi to use unix sockets as opposed to tcp    then adjust the server config to point to the socket instead of the tcp       ps auxww   grep php5-cgi  -- is the process running    netstat -an   grep 9000   is the port open

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If running a linux server  make sure that your IPTABLES configuration is correct   Execute sudo iptables -L -n   you will recieve a listing of your open ports  If there is not an Iptables Rule to open the port serving the fcgi script you will receive a 502 error  The Iptables Rule which opens the correct port must be listed before any rule which categorically rejects all packets  i e  a rule of the form  REJECT ALL -- 0 0 0 0 0 0 0 0 0 0 reject-with icmp-port-unreachable or similar   On my configuration  to properly open the port  I had to execute this command  assume my fcgi server is running at port 4567    sudo iptables -I INPUT 1 -p tcp --dport 4567 -j ACCEPT   WARNING  This will open port 4567 to the whole world   So it might be better to do something like this      sudo iptables-save  gt  gt  backup iptables    sudo iptables -D INPUT 1  Delete the previously entered rule    sudo iptables -I INPUT 1 -p tcp --dport 8080 -s localhost -j ACCEPT   Add new rule   Doing this removed the 502 error for me

User · Answer

For me the error was in default file of Nginx located at  etc nginx sites-available default  I noticed the version of php-fpm used was 7 0 and the php version i downloaded was 7 2 I simply changed the version to 7 2 and it worked   fastcgi pass unix  var run php php7 0-fpm sock

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Hope this tip will save someone else s life  In my case the problem was that I ran out of memory  but only slightly  was hard to think about it  Wasted 3hrs on that  I recommend running   sudo htop   or  sudo free -m      along with running problematic requests on the server to see if your memory doesn t run out  And if it does like in my case  you need to create a swap file  unless you already have one    I have followed this tutorial to create swap file on Ubuntu Server 14 04 and it worked just fine  http   www cyberciti biz faq ubuntu-linux-create-add-swap-file

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Go to  etc php5 fpm pool d www conf and if you are using sockets or this line is uncommented   listen    var run php5-fpm sock   Set couple of other values too -  listen owner   www-data listen group   www-data listen mode   0660   Don t forget to restart php-fpm and nginx  Make sure you are using the same nginx owner and group name

[php] nginx 502 bad gateway

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