Learn how to use advanced events() operators and functions.

Event sets returned from events() queries support several types of operators and functions. You can combine, compare, and filter events sets. You can generate synthetic events sets, convert events sets to time series, and isolate or create individual events.

Event Set Combination Operators

You can combine two event sets using union, intersect, and the minus ()-) operator.

Union

The union operator returns all events that exist in either of the event sets. In its simplest form, this expression

events(type=maintenanceWindow) union events(name="test")

is equivalent to

events(type=maintenanceWindow or name="test")

Intersect

The intersect operator returns all events that exist in both of the event sets. This expression

events(type=maintenanceWindow) intersect events(name="test")

is equivalent to

events(type=maintenanceWindow and name="test")

Minus

The minus (-) operator returns the difference between two event sets. For example, events() - closed(events)) returns all ongoing events.

Event Set Comparison Operators

You can use Allen’s interval algebra operators to compare two event sets.

  • events(severity=severe) d since(1d) returns all events with severity severe that occurred in the last day.
  • events(severity=severe) - (events(severity=severe) d since(1d)) returns all events with severity severe that are older than one day.

Event Set Filtering Functions

You can use many of the event functions to filter events. For example, you can return all ongoing events or all closed events.

  • closed(<events>) - filters out all ongoing and future events, and returns only events that have ended and instantaneous events that occurred the past.

Synthetic Event Set Functions

Some events() functions return synthetic events. These events are displayed by the query, but not stored in Wavefront.

  • since(<events>) - Returns a synthetic event with the same start time as the input event and no end time (converts all events to ongoing).

    Events since

  • until(<events>) - Returns a synthetic event that starts at the beginning of Epoch time (Jan 1, 1970) and ends where the input event starts.

    Events until

  • after(<events>) - Returns a synthetic ongoing event that starts the moment the input event ends.

    Events after

Event Set to Time Series Conversion Functions

Some functions convert event sets to time series.

  • count(<events>) - Aggregates a set of events and converts the result to a single time series, where every data point represents the number of events that started at that time minus the number of events that ended at that time. Instantaneous events are represented as a single “0” value: 1 started minus 1 ended (instantaneous events are defined as events having their end time equal to their start time).

    Events count

  • ongoing(<events>) - Returns a continuous time series (values reported every second), representing the number of ongoing events at any given moment.

Single Event Functions

Some functions return a single event as opposed to a set of events. These functions either create a single synthetic event or isolate a single event from a series. All functions and operations that accept a set of events also accept a single event.

Isolation Functions

These functions isolate a single event from an event set. If multiple events match the condition, the result is non-deterministic, however, each of these functions always returns just one event.

  • first(<events>) - Returns a single event with the earliest start time.
  • last(<events>) - Returns a single event with the latest start time.
  • firstEnding(<events>) - Returns a single event with the earliest end time.
  • lastEnding(<events>) - Returns a single event with the latest end time.

Creation Functions

  • timespan(startTimestamp, endTimestamp) - creates a single synthetic event with the specified start and end timestamps. A timestamp can be expressed in epoch seconds or using a time expression such as “5 minutes ago”. For example, timespan("5 minutes ago", "2 minutes ago").

  • since(timeWindow) - creates a single synthetic event that started timeWindow ago and ended now. timeWindow can be specified in seconds, minutes, hours, days or weeks (e.g. 1s, 1m, 1h, 1d, 1w). If the time unit is not specified, the function uses minutes.