The following content is now out of date, since an update in early 2014 replaced the scripts in {{{/var/xdrago/}}}, see Upgrade to BOA-2.2.3 Stable Edition ticket:721, this wiki pages was created on ticket:670#comment:22.

For up to date documentation see wiki:PuffinServer#LoadSpikes

== BOA Load Spikes ==

The server has been suffering from load spikes which cause the site to be unresponsive for clients, you can see the current status via the [https://penguin.transitionnetwork.org/munin/transitionnetwork.org/puffin.transitionnetwork.org/load.html puffin Munin load graph], note the Max values for the last day, week, month and year.

'''When the load hits 23.28 robots are served 403 Forbidden responses and when the load hits 86.64 maintenance tasks are killed and when the load hits 113.28 the server terminates until the 5 min load average falls below 93.30.'''

The [ticket:563#second.sh default thresholds] have been changed as they were causing [ticket:555 the shut to shutdown for 15 min at a time] far too often, the [ticket:555#comment:124 current values] were applied on [ticket:555#comment:126 23rd October 2013].

The server has 14 CPU cores, see [https://en.wikipedia.org/wiki/Load_average#Unix-style_load_calculation Unix-style load calculation], the current thresholds are generated from these variables in {{{/root/.barracuda.cnf}}}, the commented out values are the default ones:

{{{
#_LOAD_LIMIT_ONE=1444
#_LOAD_LIMIT_TWO=888
_LOAD_LIMIT_ONE=8664
_LOAD_LIMIT_TWO=5328
}}}

These variables are used by the {{{/var/xdrago/second.sh}}} script, which is run every minute via cron and has a internal loop which causes it to run 5 times, waiting 10 seconds between each run, and it has the following variables in it (these have been [ticket:555#comment:126 edited from their default values]):

{{{
ONEX_LOAD=`awk '{print $1*100}' /proc/loadavg`
FIVX_LOAD=`awk '{print $2*100}' /proc/loadavg`
CTL_ONEX_SPIDER_LOAD=2328
CTL_FIVX_SPIDER_LOAD=2328
CTL_ONEX_LOAD=8664
CTL_FIVX_LOAD=5328
CTL_ONEX_LOAD_CRIT=11328
CTL_FIVX_LOAD_CRIT=9330
}}}

These values translate to the following loads for comparison to the Munin graphs:

* ONEX_LOAD: load average over the last minute times 100
* FIVX_LOAD: load average over the last 5 minutes times 100
* CTL_ONEX_SPIDER_LOAD: 23.28
* CTL_FIVX_SPIDER_LOAD: 23.28
* CTL_ONEX_LOAD: 86.64
* CTL_FIVX_LOAD: 53.28
* CTL_ONEX_LOAD_CRIT: 113.28
* CTL_FIVX_LOAD_CRIT: 93.30

And the logic, translated into english, is:

1. If the load average over the last minute is greater than 23.28 and less than 86.64 and the nginx high load config isn't in use then start to use it.
2. Else if the load average over the last 5 mins is greater than 23.28 and less than 53.28 and the nginx high load config isn't in use then start to use it.
3. Else if the load average over the last minute is less than 23.28 and the the load average over the last 5 mins is less than 23.28 and the nginx high load config is in use then stop using it.

1. If the load average over the last minute is greater than 132.16 and if {{{/var/run/boa_run.pid}}} exists, wait a second, if not kill some maintenance jobs:  {{{killall -9 php drush.php wget}}}
2. Else if the load average over the last 5 mins is greater than 108.85 and if {{{/var/run/boa_run.pid}}} exists, wait a second, if not kill some maintenance jobs: {{{killall -9 php drush.php wget}}}

1. If the load average over the last minute is greater than 101.08 then kill the web server, {{{killall -9 nginx}}} and {{{killall -9 php-fpm php-cgi}}}
2. Else if the load average over the last 5 mins is greater than 62.16 then kill the web server, {{{killall -9 nginx}}} and {{{killall -9 php-fpm php-cgi}}}
3. Else restart all the services via {{{/var/xdrago/proc_num_ctrl.cgi}}}

Tickets generated in relation to these issues include:

* ticket:483 	Nginx 502 Bad Gateway Errors with BOA
* ticket:543 	Puffin Load Spike
* ticket:552 	Puffin Downtime 23rd May 2013
* ticket:554 	Site slow down and MySQL load increase
* ticket:555 	Load spikes causing the TN site to be stopped for 15 min at a time
* ticket:563 	503 Errors
* ticket:569 	403s served to editors, admin very slow
* ticket:576 	Site down

A total of 77.5 hours was spent on the tickets listed above, the final one was closed on 15th December 2013 and the total time was added up, see ticket:555#comment:132.

== xdrago shell script changes ==

To disable the clobbering of log files two shell scripts need editing and some lines commenting out (see ticket:555#comment:22):

{{{
vim /var/xdrago/clear.sh
:1,$s/^echo rotate/# echo rotate/g
}}}

To adjust the restarting of nginx and the killing of nginx and php-fpm under heave loads edit {{{/var/xdrago/second.sh}}} changing these values (see ticket:563#comment:9 and ticket:555#comment:52 and ticket:555#comment:124):

{{{
CTL_ONEX_SPIDER_LOAD=2716
CTL_FIVX_SPIDER_LOAD=2716
CTL_ONEX_LOAD=10108
CTL_FIVX_LOAD=6216
CTL_ONEX_LOAD_CRIT=13216
CTL_FIVX_LOAD_CRIT=10885
}}}

There is a copy of {{{second.sh}}} in {{{/root}}} so after an upgrade do:

{{{
cp /root/second.sh /var/xdrago/
}}}