Events Events are central to the operation of the Horizon platform, so it’s critical to have a firm grasp of this topic. Whenever something in Horizon appears to work by magic, it’s probably events working behind the curtain. Anatomy of an Event Events are structured historical records of things that happen in Horizon and the nodes, interfaces, and services it manages. Every event has a number of fixed fields and zero or more parameters. Mandatory Fields UEI (Unique Event Identifier) A string uniquely identifying the event’s type. UEIs are typically formatted in the style of a URI, but the only requirement is that they start with the string uei.. Event Label A short, static label summarizing the gist of all instances of this event. Description A long-form description of all instances of this event. Log Message A long-form log message describing this event, optionally including expansions of fields and parameters so that the value is tailored to the event at hand. Severity A severity for this event type. Possible values range from Cleared to Critical. Event ID A numeric identifier used to look up a specific event in the Horizon system. Notable Optional Fields Operator Instruction A set of instructions for an operator to respond appropriately to an event of this type. Alarm Data If this field is provided for an event, Horizon will create, update, or clear alarms for events of that type according to the alarm-data specifics. Stress Testing Sources of Events