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;
    }
}

Answer 1

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.

Answer 2

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.

Answer 3

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 .

Answer 4

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 <service-name> restart - Linux
• brew services restart <service-name> - Mac

Answer 5

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/

Answer 6

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