Instead of a simple list of disabled plugins, hosts and host groups can
now control whether plugins are enabled or disabled using the
`collectd_plugins` map. The map keys are plugin names, and the values
are booleans indicating if the plugin is enabled.
Using this mechanism, some plugins can be disabled by default (e.g. the
*md* plugin), and enabling them per host or per host group is simpler.
The *unixsock* plugin for *collectd* provides a socket-based interface
that other software can use to communicate with *collectd*. Notably,
this can be used to publish custom values, query existing values, and
flush caches.
The socket is created at `/run/collectd/socket`. The `/run/collectd`
directory is managed by systemd; it will be created automatically when
the service starts and cleaned up when it stops.
The `collectd_df` variable can be used to configure the *df* plugin for
collectd. It should contain a map on key-value pairs that correspond
exactly to the plugin's configuration options.
The *collectd* role, with its corresponding `collectd.yml` playbook,
installs *collectd* onto the managed node and manages basic
configuration for it. By default, it will enable several plugins,
including the `network` plugin. The `collectd_disable_plugins` variable
can be set to a list names of plugins that should NOT be enabled.
The default configuration for the `network` plugin instructs *collectd*
to send metrics to the default IPv6 multicast group. Any host that has
joined this group and is listening on the specified UDP port (default
25826) can receive the data. This allows for nearly zero configuration,
as the configuration does not need to be updated if the name or IP
address of the receiver changes.
This configuration is ready to be deployed without any variable changes
to all Pyrocufflink servers. Once *collectd* is running on the servers,
we can set up a *collectd* instance to receive the data and store them
in a time series database (i.e. Prometheus).
Dustin