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events.md

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Semantic Conventions for Events

Status: Experimental

This document describes the characteristics of standalone Events that are represented in the data model by LogRecords.

Semantically, an Event is a named occurrence at an instant in time. It signals that "this thing happened at this time" and provides additional specifics about the occurrence. Examples of Events might include things like uncaught exceptions, button clicks, user logout, network connection severed, etc.

In OpenTelemetry, Events are implemented as a specific type of LogRecord that conforms to the conventions included here, and Events have their own API. The API abstracts away knowledge of LogRecord so that users only deal with Event semantics.

In addition to a required name, an Event may contain a payload of any type permitted by the LogRecord body. In its implementation, the Event payload will constitute the Body of the LogRecord. Like all other OpenTelemetry signals, an Event has optional attribute metadata that helps describe the event context.

Over time, some Events will be specified by OpenTelemetry and will have documented payload structure, field semantics, and stability and requirement levels. Other events may be user-defined and carry bespoke user semantics. When an Event name exists in the semantic conventions, its payload structure and semantics will also be defined.

The following semantic conventions for events are defined:

  • General: General semantic attributes that may be used in describing Events.
  • Exceptions: Semantic attributes that may be used in describing exceptions as events.

General event attributes

Events are recorded as LogRecords that are shaped in a special way: Event LogRecords MUST have the attribute event.name that uniquely identifies the event. Events with the same event.name are structurally similar to one another. Events may also have other LogRecord attributes.

When recording events from an existing system as OpenTelemetry Events, it is possible that the existing system does not have the equivalent of a name or requires multiple fields to identify the structure of the events. In such cases, OpenTelemetry recommends using a combination of one or more fields as the name such that the name identifies the event structurally. It is also recommended that the event names have low-cardinality, so care must be taken to use fields that identify the class of Events but not the instance of the Event.

Attribute Type Description Examples Requirement Level Stability
event.name string Identifies the class / type of event. [1] browser.mouse.click; device.app.lifecycle Required Experimental

[1]: Event names are subject to the same rules as attribute names. Notably, event names are namespaced to avoid collisions and provide a clean separation of semantics for events in separate domains like browser, mobile, and kubernetes.