502 Error Issue

[Miguel Clara]

On June 24, 2015 11:45:38 AM GMT+01:00, "mudgil.gaurav" <nginx-forum at nginx.us> wrote:
>Hi All,
>
>We recently migrated from apache to nginx.
>
>OS - CetnOS 6
>Nginx - 1.62 (4 CPU 8 GB RAM)
>PHP-FPM (php 5.4.37) (4 CPU 8 GB RAM)
>APC (Code Cache APC 3.1.13  beta)
>Memcache (data cache)
>
>I have upstream of 4 php servers for php-fpm service. 
>
>I am facing two issues:
>
>1. I am getting 502 status code in access log means nginx generating
>502 bad
>gateway error
>
>2. Randomly connections got pile up on nginx up to 2500 and on php-fpm
>servers we do not see any load in top only 1-2 process seems to be
>running
>during that time and without taking any restart after 2-3 minutes it
>starts
>working normally and connections goes down to normal without taking any
>restart.
>
>
>Please check nginx configuration in-line
>
>user  nguser;
>worker_processes  4;
>
>pid        /var/run/nginx.pid;
>worker_rlimit_nofile 70000;
>
>events {
>    worker_connections 1024;
>    multi_accept on;
>    use epoll;
>}
>
>http {
>    ##
>    # Basic Settings
>    ##
>
>    sendfile on;
>    tcp_nopush on;
>    tcp_nodelay on;
>    keepalive_requests 1000;
>    keepalive_timeout 65;
>    send_timeout 15;
>    types_hash_max_size 2048;
>    server_tokens off;
>    client_max_body_size 50M;
>    client_body_buffer_size 1m;
>    client_body_timeout 15;
>    client_header_timeout 15;
>    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 on;
>
>    access_log /var/log/nginx/access.log combined;
>    #error_log /dev/null crit;
>    error_log /var/log/nginx/error.log error;
>
>
>    #gzip  on;
>    gzip on;
>    gzip_static on;
>    gzip_disable "msie6";
>    gzip_vary on;
>    gzip_proxied any;
>    gzip_comp_level 6;
>    gzip_min_length 512;
>    gzip_buffers 16 8k;
>    gzip_http_version 1.1;
>    gzip_types text/css text/javascript text/xml text/plain
>text/x-component
>    application/javascript application/x-javascript application/json
>    application/xml  application/rss+xml font/truetype
>application/x-font-ttf
>    font/opentype application/vnd.ms-fontobject image/svg+xml;
>
>    open_file_cache max=2000 inactive=20s;
>    open_file_cache_valid 60s;
>    open_file_cache_min_uses 5;
>    open_file_cache_errors off;
>
>    fastcgi_buffers 256 16k;
>    fastcgi_buffer_size 128k;
>    fastcgi_busy_buffers_size 256k;
>    fastcgi_temp_file_write_size 256k;
>    fastcgi_connect_timeout 300;
>    fastcgi_send_timeout 300;
>    fastcgi_read_timeout 300;
>    fastcgi_intercept_errors on;
>reset_timedout_connection on;
>
>    upstream fastcgiservers {
>        least_conn;
>        server xxx.xxx.xx.xx:9000;
>        server xxx.xxx.xx.xx:9000;
>        server xxx.xxx.xx.xx:9000;
>        server xxx.xxx.xx.xx:9000;
>       }
>
>    include /etc/nginx/conf.d/*.conf;
>    include /etc/nginx/sites-enabled/*;
>}
>
>location ~ \.php$ {
>        try_files $uri =404;
>        include fastcgi_params;
>        fastcgi_pass fastcgiservers;
>        fastcgi_index index.php;
>      fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
>    }
>
>---------------------------------------------------------PHP-FPM
>Settings
>------------------------------------------------------------------
>
>pm.max_children = 150
>pm.start_servers = 90
>pm.min_spare_servers = 70
>pm.max_spare_servers = 100
>pm.max_requests = 1500
>

php logs would be useful but I can notice at least that the value for pm.max_requests is too low. I've made the same mistake in the first times I've setup php-fpm servers, IMHO you should defiantly set a value, but such a low values means php respaws a lot in a very short period of time... I would recommend something higher that 10000... 

Also I've been having better results with ondemand  but that might be related to a lot of different things, but you might also give it a try if you like.

hope this helps 

>Any help or suggestion would be greatly appreciated.
>
>Thanks
>
>Posted at Nginx Forum:
>http://forum.nginx.org/read.php?2,259833,259833#msg-259833
>
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