502 Gateway Timeout with error exited on signal 7 (SIGBUS) after clearing cache (nginx with php5-fpm)

[degoya]

Hello,

i've got the problem when i load a page multiple times (i.E. 10 Tabs with
autoreload) only some of the pages load others get 502. it doesn't depend on
the content of the page. when i open the same page in all tabs it's the same
situation. about 3 out of 10 get 502 errors. 
The 502 Error comes direct when i force the autoload for all pages, so there
is no timeout causing the error because it only takes less that a second to
give the 502. I reconized that this only happens when the cache is cleared
in the cms and needs a rebuild on pageload. if the page is cached i don't
get any 502 errors anymore. When i disable the caching in modx backend i get
the same errors like manual clearing the cache.


installed on a openVZ VPS with 24GB Ram and 12 Cores also tested on a
physical machine with 32GB ram and 8 cores. both managed with ISPconfig3.

PHP 5.4.39-1~dotdeb.1 (fpm-fcgi) (built: Mar 22 2015 08:08:54)
nginx/1.6.2
mysql

The Page is done with Modx CMS Framework 2.3.3


Error Log:
2015/03/26 00:09:16 [error] 27345#0: *231 recv() failed (104: Connection
reset by peer) while reading response header from upstream, client:
178.203.23.132, ser$
2015/03/26 00:09:16 [error] 27345#0: *229 recv() failed (104: Connection
reset by peer) while reading response header from upstream, client:
178.203.23.132, ser$
2015/03/26 00:09:16 [error] 27345#0: *234 recv() failed (104: Connection
reset by peer) while reading response header from upstream, client:
178.203.23.132, ser$


PHP-FPM log
[25-Mar-2015 23:54:30.875237] DEBUG: pid 28694,
fpm_pctl_perform_idle_server_maintenance(), line 362: [pool web91] currently
0 active children, 6 spare children
[25-Mar-2015 23:54:30.875247] DEBUG: pid 28694,
fpm_pctl_perform_idle_server_maintenance(), line 379: [pool web32] currently
0 active children, 2 spare children, 2 running children. Spawning rate 1
[25-Mar-2015 23:54:30.875257] DEBUG: pid 28694,
fpm_pctl_perform_idle_server_maintenance(), line 379: [pool apps] currently
0 active children, 2 spare children,
2 running children. Spawning rate 1
[25-Mar-2015 23:54:31.398167] DEBUG: pid 28694, fpm_event_loop(), line 419:
event module triggered 1 events
[25-Mar-2015 23:54:31.487717] DEBUG: pid 28694, fpm_got_signal(), line 76:
received SIGCHLD
[25-Mar-2015 23:54:31.487757] WARNING: pid 28694, fpm_children_bury(), line
252: [pool web91] child 28735 exited on signal 7 (SIGBUS) after 57.721563
seconds from start
[25-Mar-2015 23:54:31.490246] NOTICE: pid 28694, fpm_children_make(), line
421: [pool web91] child 28783 started
[25-Mar-2015 23:54:31.490269] DEBUG: pid 28694, fpm_event_loop(), line 419:
event module triggered 1 events
[25-Mar-2015 23:54:31.587862] DEBUG: pid 28694, fpm_got_signal(), line 76:
received SIGCHLD
[25-Mar-2015 23:54:31.587906] WARNING: pid 28694, fpm_children_bury(), line
252: [pool web91] child 28740 exited on signal 7 (SIGBUS) after 47.234370
seconds from start
[25-Mar-2015 23:54:31.590430] NOTICE: pid 28694, fpm_children_make(), line
421: [pool web91] child 28784 started
[25-Mar-2015 23:54:31.590460] WARNING: pid 28694, fpm_children_bury(), line
252: [pool web91] child 28741 exited on signal 7 (SIGBUS) after 42.284682
seconds from start


nginx.conf
tcp_nopush on;
  tcp_nodelay on;
  types_hash_max_size 2048;
server_name_in_redirect off;
  include /etc/nginx/mime.types;
  default_type application/octet-stream;
  server_tokens  off;
  sendfile  on;
  keepalive_timeout  65;
  charset utf-8;
  client_max_body_size 64m;
  client_body_buffer_size 128k;
  client_body_timeout 300s;
  large_client_header_buffers 4 16k;
  server_names_hash_bucket_size 512;
  server_names_hash_max_size 2048;
  fastcgi_buffers 256 16k;
  fastcgi_buffer_size 128k;
  fastcgi_read_timeout 5m;
  fastcgi_max_temp_file_size 0;


php-fpm.conf
emergency_restart_threshold = 60
emergency_restart_interval = 1m
process_control_timeout = 60s
rlimit_files = 65536
rlimit_core = unlimited


anyone got a idea where to look for the source of the problem

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,257732,257732#msg-257732