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SystemController is Reactor's own controller to publish memory and CPU usage for the host system to a single entity for access by automations and the dashboard. It also publishes the "Sun Information" entity (capability suninfo, canonical ID reactor_system>sun); see below.

The update_interval value is the time (in milliseconds) between updates to the system data entity. The default is 60000, which is 60 seconds (one minute), and there should be little cause to change it.

The protect_controller_group flag (boolean) determines whether the controller's default group exists or not. Since SystemController publishes only one entity, it's a bit of a waste to have it in a group by itself, so by default, SystemController will remove the one-member group. However, there are cases, such as on the dashboard, where having the group can aid navigation and access to the entity. To address this need when it arises, protect_controller_group can be set to true.

The report_volumes key may, optionally, define an array objects describing zero or more storage volumes to be monitored for available space. If not set, Reactor base directory, logs directory, and storage directory will be monitored. Monitored volumes/directories will present as additional attributes in the reactor_system>system entity. Each volume will have a reactor_system.volume_<id> attribute, where <id> is the identifier associated with the volume (explained shortly). Custom configuration of volumes looks like this:

  # other controllers and config redacted for clarity
  - id: reactor_system
    enabled: true
    implementation: SystemController
    name: Reactor System
        - id: root
          path: /
          critical: 10%
        - id: home
          path: /home
          critical: 5%

In the above example configuration, the directories (presumably mount points for volumes) / and /home are monitored, and assigned IDs root and home respectively. The reactor_system.system entity will have attributes reactor_system.volume_root and reactor_system.volume_home, the value of each being an array of four elements: the free space of the volume (in KB), the total space of the volume (in KB), the percentage of free space (expressed as fractional 0.0 to 1.0), and the path monitored. In addition, because each of these contains the optional critical key and value, additional boolean attributes reactor_system.volume_critical_root and reactor_system.volume_critical_home will be present and true if the free space of the volume is less than the configured critical value (which may be given as a percentage as shown, or a fixed number of KB).

Alert Information

The alert information on the reactor_system.system entity provides triggerable information about system alerts:

  • alert_count - the number of active alerts; updated whenever the alerts list changes; 0 means there are no active alerts.
  • alert_severity - the severity of the most severe alert (0=error, 1=warning, 2=notice).
  • alert_last - the timestamp of the most recent alert; this moves forward in time only, that is, clearing the most recent alert does not reset this value backwards to the timestamp of the then-remaining most recent alert. In effect, it does not change unless there is a new alert, making it easier to detect new alerts in conditions.
  • alerts - the current list of active alerts (an array of objects), for use in expressions. The published object fields are id, severity (0-2), message (string), timestamp (Epoch milliseconds), level_name (string), repeat (integer). If an alert is repeated (i.e. an alert is generated with the same text and severity as an active prior alert), it is not entered in the array as a new element; the existing element will have its timestamp and repeat (counter) updated.

There are also actions available to clear all alerts (reactor_system.clear_alerts), or just one (by its ID, reactor_system.clear_alert).

Sun Information

SystemController publishes a Sun Information (reactor_system>sun) entity that provides information about the current day's sunrise and sunset times, and the current sun position. The following attributes are published in the suninfo capability of this entity:

sunrise, sunset

The time of local sunrise and sunset.

_dawn, _dusk

The alternate dawn and dusk times, also referred to as twilight hours.


The time of solar noon, where the sun is at its highest point in the sky.


The length of the current day in hours.

elevation and azimuth

The elevation and azimuth establish the current position of the sun in the sky. The elevation is the angle, in degrees, above the horizon, while the azimuth is the compass angle (from North, clockwise) of the sun. This attribute is updated on the configured interval of the SystemController (default: 60 seconds, see above).


A simple string indicating "day" or "night", where "day" is the period where the sun is above the horizon.

DEPRECATION NOTICE: sun_angle attribute

The sun_angle attribute is a simplified representation of the sun position relative to its daily min and max, but it has turned out to be not very useful, and for users more then a few degrees from the equator, it has nothing to do with reality. It is therefore deprecated and will be removed from a future release. Its replacement is elevation.

All times are reported in integer milliseconds since midnight, January 1, 1970 UTC (the Unix Epoch). These are compatible with all date/time functions in expressions.

In the extreme latitudes at particular times of year, the sun does not rise or set. During these periods, all sunrise/sunset/dawn/dusk values will be null; sun_angle will be null; and daylength will be 0 or 24 and period will show an unchanging night or day as conditions require. If you live in these latitudes and are creating conditions based on these values, be aware of these special conditions and values and make sure you take them into account in your logic.

Updated: 2021-Dec-21