Avro format enconding

I would like to propose an official Avro encoding schema to be supported by CloudEvents.

I’ve seen a lot of uses cases, in special here in my current project, with Apache Kafka and the many of them were using Avro as the format. Inspired by this Gist (thanks @rbramley), the following schema could be the first draft:

{
  "namespace":"io.cloudevents",
  "type":"record",
  "name":"CloudEvent",
  "version": "1",
  "doc": "CloudEvents Spec for Avro format encoding (the version is just for the schema itself)",
  "fields":[
    {
      "name":"specversion",
      "type":"string"
    },
    {
      "name":"type",
      "type":"string"
    },
    {
      "name":"source",
      "type":"string"
    },
    {
      "name":"id",
      "type":"string",
    },
    {
      "name":"time",
      "type":[
        "null",
        "int"
      ],
      "logicalType": "date"
    },
    {
      "name":"schemaurl",
      "type":[
        "null",
        "string"
      ]
    },
    {
      "name":"contenttype",
      "type":[
        "null",
        "string"
      ]
    },
    {
      "name":"data",
      "type":[
        "null",
        "string"
      ]
    },
    {
      "name":"extensions",
      "type":[
        "null",
        {
          "type":"map",
          "values":[
            "string",
            "int",
            "long",
            "float",
            "double",
            "boolean",
            "bytes"
          ]
        }
      ]
    },
  ]
}

• Official Avro spec available here

Extensions

To define a top-level extension (like below) is not allowed by Avro spec for avsc, because we do not have the feature for dynamic fields like JSON. Because of this, you will see the extension attribute to the example above.

...
    "comexampleextension1" : "value",
    "comexampleextension2" : {
        "othervalue": 5
    }
...

For that, we may employ Avro spec for ìdl that is a higher-level language for authoring Avro schemas.

• Official Avro IDL docs available here

Special Types

What I mean with special types, logical types in JSON Schema, are: uri-reference. We do not have this type in Avro.

For that, again, we may employ Avro IDL.

[gunnarmorling]

Ha, came here to file a feature request for Avro myself, it’s there already 😃 I’m not sure where things stand with that format spec, but I’ll be happy to help out with it.

[clemensv]

That’s a great idea. Avro and CBOR are the two extra encodings which I’d love to see.

@duglin this would be a different event format, not a different transport.

I’m in favor. Who writes the spec.