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2021/05/25 OpCache Observations

The new php_opc_apcu_ code carried over the warning limits of 50% for misses. On my shared server, I received alerts about every four hours, probably because the PHP or Apache processes were being restarted. However, I also noticed alerts on my Drupal test server. I increased opcache.force_restart_timeout from 180 to 600 which seemed to help, but periodically I still get repeated alerts that appear to start after a Drupal cron run (but not every run). I am capturing the list of cached files to see if I can determine the root cause.

2021/05/19 Unexplained Monitoring Gaps

I received an alert that my shared server was down on the 18th between 22:32 and 23:14 which obviously impacted munin. However, I also saw gaps in most (but not all) of the munin graphs for my AWS servers. The munin-update log showed the following error, repeated at 22:58:02, 23:03:01, and 23:08:02

2021/05/18 22:38:02 [ERROR] Error in node communication with localhost/127.0.0.1:4949: alarm 2021/05/18 22:38:02 [ERROR] Munin::Master::UpdateWorker<localhost;localhost> failed to connect to node

Internet searches tended to point to plugins timing out. My suspicion is that munin got hung trying to contact my shared server, causing most of the other plugins to timeout. I have not changed the default "global_timeout 900" and individual plugin "timeout 60" values.

2021/05/12 Overriding Limits

The warning and critical limits for php_opc_apcu_ cannot be changed via the configuration files in /etc/munin/plugin.conf - they must be changed in munin.conf using the format "<plugin_name>..warning ###" or "<plugin_name>..critical ###". There are some plugins that include support for warning/critical limits via environment variables. but php_opc_apcu_ only contains code to handle the env.url and env.ports environment variables.