Andre-487 Andre-487 - 10 months ago 68
PHP Question

Error 502 in nginx + php5-fpm

I have some error with subj. Server doesn't high loaded: ~15% CPU, there are several Gb of memory, HDD is not buisy. But error 502 throws approximately in 3% of cases.

Programs: Debian 6, nginx/0.7.62, php5-fpm (5.3.3-1).

In error.log of nginx is this error:

connect() to unix:/var/run/php5-fpm.sock failed

State of php5-fpm usually like this:

accepted conn: 41680
pool: www
process manager: dynamic
idle processes: 258
active processes: 1
total processes: 259

I think, this mean loading is not high.

I have increased backlog params: in sysctl - net.core.somaxconn = 5000, in php-fpm pool - listen.backlog = 5000. No effect.

I quote a configuration:


user www-data;
worker_processes 8;
timer_resolution 100ms;
worker_rlimit_nofile 20240;
worker_priority -5;

error_log /var/log/nginx/error.log;
pid /var/run/;

events {
worker_connections 2048;
use epoll;
# multi_accept on;

http {
include /etc/nginx/mime.types;

access_log /var/log/nginx/access.log;

sendfile on;
tcp_nopush on;

#keepalive_timeout 0;
keepalive_timeout 65;
tcp_nodelay on;

gzip on;
gzip_min_length 1100;
gzip_buffers 64 8k;
gzip_comp_level 3;
gzip_http_version 1.1;
gzip_proxied any;
gzip_types text/plain application/xml application/x-javascript text/css;
gzip_disable "MSIE [1-6]\.(?!.*SV1)";

include /etc/nginx/conf.d/*.conf;
include /etc/nginx/sites-enabled/*;

client_max_body_size 100M;
server_tokens off;


fastcgi_pass unix:/var/run/php5-fpm.sock;
fastcgi_index index.php;
fastcgi_param SCRIPT_FILENAME $document_root/$fastcgi_script_name;
fastcgi_buffers 256 128k;
#fastcgi_buffer_size 16k;
#fastcgi_busy_buffers_size 256k;
fastcgi_connect_timeout 300s;
fastcgi_send_timeout 300s;
fastcgi_read_timeout 300s;
include fastcgi_params;

php-fpm pool

listen = /var/run/php5-fpm.sock
listen.backlog = 5000
listen.owner = www-data = www-data
listen.mode = 0666
user = www-data
group = www-data
pm = dynamic
pm.max_children = 1024
pm.start_servers = 64
pm.min_spare_servers = 64
pm.max_spare_servers = 128
pm.max_requests = 32000
pm.status_path = /system/php5-fpm-status
slowlog = /var/www/log/php-fpm.log.slow
chdir = /var/www

What can I do to optimize this system and make this use all server resources?

PS. I'm sorry, my english is bad.

Answer Source

The issue is socket itself, its problems on high-load cases is well-known. Please consider using TCP\IP connection instead of unix socket, for that you need to make these changes:

  • in php-fpm pool configuration replace listen = /var/run/php5-fpm.sock with listen =
  • in /etc/nginx/php_location replace fastcgi_pass unix:/var/run/php5-fpm.sock; with fastcgi_pass;