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I have a Server running Apache/2.2.22 (Debian), PHP 5.6.17 as FPM and MySQL 5.6.25.

The project runs using a CMS called Redaxo (I don't think it's that important, but I'll tell ya anyway). In Redaxo there are some functions which take some time (e.g. deleting cache and rebuilding it takes 1-2 minutes). In this time, when other users come on the website FPM crashes with a 500 Internal Server Error and I have to reload the page multiple times until the Server Error disappears and the process is done.

I noticed that this only will happen if too many users are on the site on the same time and only when heavy operations are done.

10 users at the same time just surfing = No Problem
10 users at the same time just surfing, while cache deletion = 500 Error for everyone.

I checked this by disallowing the website for everyone except me (.htaccess deny/allow with ip). Then I did the heavy operation and had no problem. As soon as multiple people were on the site again, the problem was there again.

What could it be? What information do you need from me?

These values are set (not commented) in the php-fpm.conf

[global]
pid = /run/php5-fpm.pid
error_log = /var/log/php5-fpm.log
emergency_restart_threshold = 0
include=/etc/php5/fpm/pool.d/*.conf

These values are set (not commented) in the project specific fpm.conf

[projectname]
user = projectname
group = projectname

listen = /var/run/php5-fpm-projectname.sock
listen.owner = projectname
listen.group = projectname
listen.mode = 0660

pm = dynamic
pm.max_children = 150
pm.start_servers = 10
pm.min_spare_servers = 10
pm.max_spare_servers = 30

chdir = /

php_value[upload_max_filesize] = 128M
php_value[max_post_size] = 128M
php_value[max_execution_time] = 180
php_value[memory_limit] = 256M

The script when it fails does much with MySQL and File creation if it helps? But it's pretty big, so I'm not sure if I should post it here? Or if it is even the problem?

The apache error log says either this

[Tue Feb 09 10:54:01 2016] [error] [client {IP}] (104)Connection reset by peer: FastCGI: comm with server "/fcgi-bin-php5-fpm-projectnmae" aborted: read failed
[Tue Feb 09 10:54:01 2016] [error] [client {IP}] FastCGI: incomplete headers (0 bytes) received from server "/fcgi-bin-php5-fpm-projectnmae"

or this

[Tue Feb 09 11:00:46 2016] [error] [client {IP}] FastCGI: incomplete headers (0 bytes) received from server "/fcgi-bin-php5-fpm-projectname"
[Tue Feb 09 11:00:48 2016] [error] [client {IP}] (104)Connection reset by peer: FastCGI: comm with server "/fcgi-bin-php5-fpm-projectname" aborted: read failed

The fpm-log says the following. Always different timings of course

[10-Feb-2016 09:40:59] WARNING: [pool projectname] child 10970 exited on signal 7 (SIGBUS) after 50.186611 seconds from start
[10-Feb-2016 09:40:59] NOTICE: [pool projectname] child 11092 started

Sometimes there's a warning like this in it

[09-Feb-2016 11:00:41] WARNING: [pool projectname] seems busy (you may need to increase pm.start_servers, or pm.min/max_spare_servers), spawning 8 children, there are 0 idle, and 6 total children
[09-Feb-2016 11:00:42] WARNING: [pool projectname] seems busy (you may need to increase pm.start_servers, or pm.min/max_spare_servers), spawning 16 children, there are 0 idle, and 7 total children

1 Answer 1

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I've seen similiar errors before. Probably it's related to PHP cache modules. Try the following:

;php-fpm.conf:
pm.max_spare_servers = 30
pm.max_requests = 200
pm.start_servers = 30
;enable slowlog - it gives you readable stacktrace
slowlog = /var/log/php-fpm-slow.log
request_slowlog_timeout = 10s
listen.backlog = -1

Then check your PHP installation for cache modules. I've seen SIGBUS problems on installations with APC enabled. Try this for APC module:

#apc.ini
apc.stat = 0
#or disable it:
apc.enabled = 0
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  • 1
    Right, APC is crashy and mostly unmaintained and nobody should be using it. Feb 16, 2016 at 18:22
  • Hi, thanks for your answer, but we don't have any cache modules activated. Feb 18, 2016 at 15:09
  • Did you enable php-fpm slow log? Could you post the output of slow scripts?
    – anx
    Feb 18, 2016 at 16:04

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