PHP-FPM and Nginx 502 Bad Gateway

Question

Configuration   Ubuntu Server 11 10 64 bit Amazon AWS  Ec2  hosted on the cloud t1 micro instance   Before I write anything else  I d like to state that I ve checked both nginx 502 bad gateway and Nginx   PHP-FPM 502 Bad Gateway threads  which unfortunately haven t helped me in this regard   The issue appears to be rather common  a misconfiguration of nginx or php-fpm can lead to a 502 Bad Gateway error  which is something that I haven t been able to get rid of  Note that this appears even when I go to my domain root  without specifying any particular directory    I m running an Amazon EC2 webserver  with port 9000 enabled  port 80 open  etc   The question in particular is  how can I get rid of this nasty error  Or  better yet  how can I get php5-fpm to actually work   What I Have Attempted so Far  Mostly consistent editing of configuration files  notably php-fpm conf and nginx conf   i  php-fpm conf  I ve added the following  which hasn t quite helped much                   Fpm Start                   pm start servers   20  pm min spare servers   5  pm max spare servers   35   Now  afterward I tried including my configuration files   include  etc php5 fpm   conf  Which only screwed me even further   Full Configuration                          FPM Configuration                            All relative paths in this configuration file are relative to PHP s install   prefix   usr   This prefix can be dynamicaly changed by using the    -p  argument from the command line     Include one or more files  If glob 3  exists  it is used to include a bunch of   files from a glob 3  pattern  This directive can be used everywhere in the   file    Relative path can also be used  They will be prefixed by     - the global prefix if it s been set  -p arguement     -  usr otherwise  include  etc php5 fpm   conf                       Global Options                        global    Pid file   Note  the default prefix is  var   Default Value  none pid    var run php5-fpm pid    Error log 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    If this number of child processes exit with SIGSEGV or SIGBUS within the time   interval set by emergency restart interval then FPM will restart  A value   of  0  means  Off     Default Value  0  emergency restart threshold   0    Interval of time used by emergency restart interval to determine when    a graceful restart will be initiated   This can be useful to work around   accidental corruptions in an accelerator s shared memory    Available Units  s econds   m inutes   h ours   or d ays    Default Unit  seconds   Default Value  0 emergency restart interval   0    Time limit for child processes to wait for a reaction on signals from master    Available units  s econds   m inutes   h ours   or d ays    Default Unit  seconds   Default Value  0  process control timeout   0    Send FPM to background  Set to  no  to keep FPM in foreground for debugging    Default Value  yes daemonize   no                  Fpm Start                   pm start servers   20  pm min spare servers   5  pm max spare servers   35                         Pool Definitions                            Multiple pools of child processes may be started with different listening   ports and different management options   The name of the pool will be   used in logs and stats  There is no limitation on the number of pools which   FPM can handle  Your system will tell you anyway       To configure the pools it is recommended to have one  conf file per   pool in the following directory  include  etc php5 fpm pool d   conf   ii  nginx conf  In all honesty this configuration is a smattering of a few websites I ve visited  but I can tell you that before this 502 Bad Gateway business  the server was running fine  without PHP working  Period     The issue primarily lies in the fact that something is terribly  terribly wrong  And now  when I try to do a service php5-fpm restart  it hangs in what I m guessing is an infinite loop or something  which I can t even CTRL-C out of   Full Configuration  user www-data  worker processes 1  pid  var run nginx pid   events       worker connections 64        multi accept on     http                 Basic Settings             sendfile on      tcp nopush off      tcp nodelay on      keepalive timeout 65      types hash max size 2048        server tokens off         server names hash bucket size 64        server name in redirect off       include  etc nginx mime types      default type application octet-stream                Logging Settings             access log  var log nginx access log      error log  var log nginx error log                Gzip Settings             gzip on      gzip disable  msie6          gzip vary on        gzip proxied any        gzip comp level 6        gzip buffers 16 8k        gzip http version 1 1        gzip types text plain text css application json application x-javascript text xml application xml application xml rss text javascript                Virtual Host Configs             include  etc nginx conf d   conf      include  etc nginx sites-enabled         server           listen 80          server name ec2-xx-xx-xx-xx compute-x amazonaws com           location         php                     root    home wayvac public              fastcgi pass   unix  var run php5-fpm pid                 fastcgi pass   127 0 0 1 9000   Un-comment this and comment  fastcgi pass   unix  var run php-fpm php-fpm sock   if you are not using php-fpm              fastcgi index  index php              set  document root2  document root              if   document root2                                         set  document root2  1 2                if   document root2                                         set  document root2  1 2                if   document root2                                         set  document root2  1 2                if   document root2                                         set  document root2  1 2                if   document root2                                         set  document root2  1 2                fastcgi split path info       php                    fastcgi param   SCRIPT FILENAME  document root2 fastcgi script name              fastcgi param   PATH INFO    fastcgi path info              fastcgi param   PATH TRANSLATED  document root2 fastcgi path info              include fastcgi params              fastcgi param  DOCUMENT ROOT       document root2                            access log  var log nginx access log          error log  var log nginx error log           location                 root  home wayvac public                 index index html index htm index php                     location         ico css js gif jpe g png                   Some basic cache-control for static files to be sent to the browser             expires max              add header Pragma public              add header Cache-Control  public  must-revalidate  proxy-revalidate                       include drop conf           include php conf

User · Answer

I ve also found this error can be caused when writing json encoded   data to MySQL  To get around it I base64 encode   the JSON  Please not that when decoded  the JSON encoding can change values  Nb  24 can become 24 00

User · Answer

In your NGINX vhost file  in location block which processes your PHP files  usually location     php     through FastCGI  make sure you have next lines    proxy buffer size          128k  proxy buffers              4 256k  proxy busy buffers size    256k  fastcgi buffer size        16k  fastcgi buffers            4 16k    After that don t forget to restart fpm and nginx      Additional    NGINX vhost paths    etc nginx sites-enabled  - Linux   usr local etc nginx sites-enabled   - Mac   Restart NGINX     sudo service nginx restart - Linux brew service restart nginx - Mac   Restart FPM    Determine fpm process name    - systemctl list-unit-files   grep fpm - Linux  - brew services list   grep php - Mac  and then restart it with     sudo service  lt service-name gt  restart - Linux brew services restart  lt service-name gt  - Mac

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I m very late to this game  but my problem started when I upgraded php on my server   I was able to just remove the  socket file and restart my services   Then  everything worked   Not sure why it made a difference  since the file is size 0 and the ownership and permissions are the same  but it worked

User · Answer

Don t forget that php-fpm is a service  After installing it  make sure you start it     service php-fpm start   chkconfig php-fpm on

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Maybe this answer will help   nginx error connect to php5-fpm sock failed  13  Permission denied   The solution was to replace www-data with nginx in  var www php fpm pool d www conf  And respectively modify the socket credentials     sudo chmod nginx nginx  var run php php7 2-fpm sock

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If you met the problem after upgrading php-fpm like me  try this  open  etc php5 fpm pool d www conf uncomment the following lines   listen owner   www-data listen group   www-data listen mode   0666   then restart php-fpm

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Before messing with Nginx config  try to disable ChromePHP first  1 - Open app config config dev yml 2 - Comment these lines  chromephp      type    chromephp     level   info  ChromePHP pack the debug info json-encoded in the X-ChromePhp-Data header  which is too big for the default config of nginx with fastcgi

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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 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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You should see the error log  By default  its location is in  var log nginx error log  In my case  502 get way because of   GET  app dev php HTTP 1 1   upstream   fastcgi   unix  run php php7 0-fpm sock    host   symfony2 local  2016 05 25 11 57 28  error  22889 22889   3 upstream sent too big header while reading response header from upstream  client  127 0 0 1  server  symfony2 local  request   GET  app dev php HTTP 1 1   upstream   fastcgi   unix  run php php7 0-fpm sock    host   symfony2 local  2016 05 25 11 57 29  error  22889 22889   3 upstream sent too big header while reading response header from upstream  client  127 0 0 1  server  symfony2 local  request   GET  app dev php HTTP 1 1   upstream   fastcgi   unix  run php php7 0-fpm sock    host   symfony2 local  2016 05 25 11 57 29  error  22889 22889   3 upstream sent too big header while reading response header from upstream  client  127 0 0 1  server  symfony2 local  request   GET  app dev php HTTP 1 1   upstream   fastcgi   unix  run php php7 0-fpm sock    host   symfony2 local    When we know exactly what is wrong  then fix it  For these error  just modify the buffer   fastcgi buffers 16 512k   fastcgi buffer size 512k

User · Answer

For anyone else struggling to get to the bottom of this  I tried adjusting timeouts as suggested as I didn t want to stop using Unix sockets   after lots of troubleshooting and not much to go on I found that this issue was being caused by the APC extension that I d enabled in php-fpm a few months back  Disabling this extension resolved the intermittent 502 errors  easiest way to do this was by commenting out the following line     extension   apc so   This did the trick for me

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If anyone finds this page by encountering the same problem I had  I found the answer here   For those of you who can t be bothered to click and work it out for themselves        The Condition   Ubuntu or Debian server with NGINX and PHP 5 3 works fine but upgrading PHP to 5 4 gives 502 Bad Gateway errors  Looking for services running on port 9000  typically running netstat -lp or similar  returns nothing   The fix   Open  etc php5 fpm pool d www conf and make a note of the  listen  parameter  in my case  var run php5-fpm sock      The address on which to accept FastCGI requests    Valid syntaxes are       ip add re ss port     - to listen on a TCP socket to a specific address on                              a specific port       port                  - to listen on a TCP socket to all addresses on a                              specific port        path to unix socket  - to listen on a unix socket    Note  This value is mandatory  listen    var run php5-fpm sock   and replace the fastcgi pass variable in your vhost with the location you just noted   So this sample symfony2 configuration  taken from here        pass the PHP scripts to FastCGI server listening on 127 0 0 1 9000   location      app app dev   php            fastcgi pass   127 0 0 1 9000      fastcgi split path info       php             include fastcgi params      fastcgi param  SCRIPT FILENAME     document root fastcgi script name      fastcgi param  HTTPS              off        becomes this       pass the PHP scripts to FastCGI server at  var run php5-fpm sock   location      app app dev   php            fastcgi pass unix  var run php5-fpm sock      fastcgi split path info       php             include fastcgi params      fastcgi param  SCRIPT FILENAME     document root fastcgi script name      fastcgi param  HTTPS              off        Then restart nginx   sudo  etc init d nginx restart   Note  replace      app app dev   php        with     index  php        if you re not on SF2    Hope this saves someone a little bit of time     Edit  Of course  you could change the listen    var run php5-fpm sock to listen   127 0 0 1 9000 in  etc php5 fpm pool d www conf then restart php5-fpm  which would save you from having to change your vhosts   but you have to assume they changed php5-fpm to run through a socket rather than listening on port 9000 for a reason   Edit2  If you re still experiencing 502 error see this answer

User · Answer

Try setting these values  it solves problem in fast-cgi  fastcgi buffer size 16k  fastcgi buffers 4 16k

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All right after trying every solution on the web I ended up figuare out the issue using very simple method   first I cheked php-fpm err log   cat  var log php5-fpm log    and the most repeated error was     WARNING   pool www  server reached pm max children setting  5   consider raising it     I edit PHP-fpm pools setting   nano  etc php5 fpm pool d www conf   I chenged This Line   pm max children   5   To new Value   pm max children   10   BTW I m using low end VPS with 128MB ram As everyone else I was thinkin redusing pm max children will make my server run faster consume less memory   but the setting we using were too low tho even start PHP-fpm process   I hope this help others since I found this after 24 hour testing and failing   ever my webhost support were not able to solve the issue

User · Answer

I made all this similar tweaks  but from time to time I was getting 501 502 errors  daily    This are my settings on  etc php5 fpm pool d www conf to avoid 501 and 502 nginx errors    The server has 16Gb RAM  This configuration is for a 8Gb RAM server so     sudo nano  etc php5 fpm pool d www conf   then set the following values for  pm max children   70 pm start servers   20 pm min spare servers   20 pm max spare servers   35 pm max requests   500   After this changes restart php-fpm  sudo service php-fpm restart

User · Answer

The port was changed to 9001 in 5 4  just changing the port from 9000 to 9001 in the nginx conf and in php-fpm configuration worked for me

[nginx] PHP-FPM and Nginx: 502 Bad Gateway

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