Official specification: https://github.com/cloudevents/spec

Types: Integer, String, Binary, Map, Time, URI, Any (can be any of Integer, String, Binary or Map)

An event is a collection of named attributes of the above types:

  • Required: type(String), specversion(String), source(URI), id(String)

  • Optional: time(Time), schemaurl(URI), contenttype(String), data(Any)

  • Custom Extensions: defined by an application

The data attribute carries the "payload" of the event. The other attributes are context (metadata). The abstract event definition is independent of the format or transport binding used to serialize and deliver them.

Format

Serialize a complete event (context+data) as a sequence of bytes (e.g. JSON, Protocol buffer). Each format is identified by a media type like application/cloudEvents+json, application/cloudEvents+proto

Transport binding

Map an event to/from a message defined by some transport (e.g. HTTP, AMQP, MQTT). Bindings can support one or both of the following modes:

Structured

The complete event structure (context + data) is serialized using a known format and stored as the message body. The format media type is stored as message meta-data.

Binary

The binary data value becomes the message body. Context attributes (including contenttype) are stored as message meta-data ("headers", "annotations", "properties" or similar). The receiver can access the binary data and context attributes directly, without decoding a format envelope.

Note
 The format media type is separate from the event’s contenttype. For example an event with contenttype = text/xml could be encoded as application/cloudEvents+json The receiver decodes the event as JSON, but treats the data attribute as XML.

MQTT 3.1.1 transport binding

Structured JSON only. MQTT PUBLISH payload is an application/cloudEvents+json format event. That’s all folks.

MQTT 5.0 transport binding

Structured

MQTT Content Type is an application/cloudEvents+ format. No Content Type means application/cloudEvents+json (MQTT 3.1.1 compatible).

Binary

  • contenttype== MQTT Content Type property (must not be empty or start with application/cloudEvents)

  • data == MQTT binary payload

  • Context attributes == MQTT User Properties with the same names

AMQP Message mapping

Structured

AMQP content-type is an application/cloudEvents+ format. No content-type means application/cloudEvents+json.

Binary

  • contenttype == AMQP content-type (must not be empty or start with application/cloudEvents)

  • data == AMQP body (single data section)

  • Context attributes == AMQP application-properties, attribute names prefixed with cloudEvents: