Avro Schema Parser

An AsyncAPI schema parser for Avro 1.x schemas.

Installation

npm install @asyncapi/avro-schema-parser

Usage

const parser = require('@asyncapi/parser')
const avroSchemaParser = require('@asyncapi/avro-schema-parser')

parser.registerSchemaParser(avroSchemaParser);

const asyncapiWithAvro = `
asyncapi: 2.0.0
info:
  title: Example with Avro
  version: 0.1.0
channels:
  example:
    publish:
      message:
        schemaFormat: 'application/vnd.apache.avro;version=1.9.0'
        payload: # The following is an Avro schema in YAML format (JSON format is also supported)
          type: record
          name: User
          namespace: com.company
          doc: User information
          fields:
            - name: displayName
              type: string
            - name: email
              type: string
            - name: age
              type: int
`

await parser.parse(asyncapiWithAvro)

Usage with remote references

const parser = require('@asyncapi/parser')
const avroSchemaParser = require('@asyncapi/avro-schema-parser')

parser.registerSchemaParser(avroSchemaParser)

const asyncapiWithAvro = `
asyncapi: 2.0.0
info:
  title: Example with Avro
  version: 0.1.0
channels:
  example:
    publish:
      message:
        schemaFormat: 'application/vnd.apache.avro;version=1.9.0'
        payload:
          $ref: 'https://schemas.example.com/user'
`

await parser.parse(asyncapiWithAvro)

Usage with local references

const parser = require('@asyncapi/parser')
const avroSchemaParser = require('@asyncapi/avro-schema-parser')

parser.registerSchemaParser(avroSchemaParser)

const asyncapiWithAvro = `
asyncapi: 2.0.0
info:
  title: Example with Avro
  version: 0.1.0
channels:
  example:
    publish:
      message:
        schemaFormat: 'application/vnd.apache.avro;version=1.9.0'
        payload:
          $ref: 'local/path/to/file/user'
`

await parser.parse(asyncapiWithAvro)

Usage with Confluent Schema Registry

Create an API key

Copy the key and the secret

Use them on your AsyncAPI document

const parser = require('@asyncapi/parser')
const avroSchemaParser = require('@asyncapi/avro-schema-parser')

parser.registerSchemaParser(avroSchemaParser)

const asyncapiWithAvro = `
asyncapi: 2.0.0
info:
  title: Example with Avro
  version: 0.1.0
channels:
  example:
    publish:
      message:
        schemaFormat: 'application/vnd.apache.avro;version=1.9.0'
        payload:
          $ref: 'https://LY422RBU2HN6JQ5T:+f8wz9a0iM06AX7xfwbzSM9YPw/JIkr22Cvl5EKT5Hb1d/nz5nOpbXV/vZC+Iz5c@example.europe-west3.gcp.confluent.cloud/subjects/test/versions/1/schema'
`

await parser.parse(asyncapiWithAvro)

Features

Validation of Avro schemas

Avro schemas included in parsed AsyncAPI documents are validated using avsc. Invalid Avro schemas will cause the parse function to reject the promise, with an error that explains the problem.

const assert = require('assert');
const parser = require('@asyncapi/parser');
const avroSchemaParser = require('./index');

parser.registerSchemaParser(avroSchemaParser);

const asyncapiWithInvalidAvro = `
asyncapi: 2.0.0
info:
  title: Example with Avro
  version: 0.1.0
channels:
  example:
    publish:
      message:
        schemaFormat: 'application/vnd.apache.avro;version=1.9.0'
        payload:
          type: notAValidAvroType
`;

parser.parse(asyncapiWithInvalidAvro)
  .catch(err => {
    assert.strictEqual(err.message,
      'unknown type: "notAValidAvroType"');
  });

Support of required attributes

Required fields are fields with no default value and without the "null" union element.

Support for extra attributes on top of Avro specification

Additional attributes not defined in the Avro Specification are permitted and are treated as a metadata by the specification. To improve human readability of generated AsyncAPI documentation and to leverage more features from the JSON schema we included support for the extra attributes that can be added into Avro document.

List of all supported extra attributes

example - Can be used to define the example value from the business domain of given field. Value will be propagated into examples attribute of JSON schema and therefore will be picked for the generated "Example of payload" when using some AsyncAPI documentation generator.

For Number instances:

multipleOf - Can be used to define the multipleOf value of a numeric instance. The multipleOf MUST be a number, strictly greater than 0.
maximum - Can be used to define the maximum value of a numeric instance.
exclusiveMaximum - Can be used to define the exclusiveMaximum value of a numeric instance.
minimum - Can be used to define the minimum value of a numeric instance.
exclusiveMinimum - Can be used to define the exclusiveMinimum value of a numeric instance.

For String instances:

maxLength - Can be used to define the maxLength value of a string instance. The value of this keyword MUST be a non-negative integer.
minLength - Can be used to define the minLength value of a string instance. The value of this keyword MUST be a non-negative integer.
pattern - Can be used to define the pattern value of a string instance.

For Array instances:

maxItems - Can be used to define the maxItems value of a string instance. The value of this keyword MUST be a non-negative integer.
minItems - Can be used to define the minItems value of a string instance. The value of this keyword MUST be a non-negative integer.
uniqueItems - Can be used to define the uniqueItems value of a string instance. The value of this keyword MUST be a boolean.

Support for names and namespaces

If, at the top level of the Avro schema, the 'name' attribute is defined, it will be copied to the corresponding JSON schema's 'x-parser-schema-id' attribute. If the Avro schema also has the 'namespace' attribute defined, then that schema's fully qualified name will be put into that attribute. The fully qualified name is defined by the namespace, followed by a dot, followed by the name.

If there are two schemas that resolve to the same fully qualified name, only the last one will be returned by the parser. Make sure names of your schemas are unique.

If no name attribute is present, the 'x-parser-schema-id' will have a generated unique id with a name like 'anonymous-schema-1' generated by the main parser. 'x-parser-schema-id' is one of the custom extensions supported by the parser.

Limitations

Float and double-precision numbers

JSON numbers (RFC 4627, section 2.4) don't define any limit to the scale and/or precision of numbers. That said, we can enforce limits on int and long but we can't enforce them on float and double because they can't accurately be represented on JSON Schema.

Since we support extra attributes on field, you can set minimum and maximum attribute on float and double types to display number limits.

Hardcoded key and secret

This is not a limitation of this package per se but of the JSON Reference RFC. So far, you can only hardcode the values for key and secret on the $ref URL.

Contributors

Thanks goes to these wonderful people (emoji key):

_{Fran Méndez} 💻 🚧 👀 🤔	_{Lukasz Gornicki} 🚧 👀 🚇	_{Ludovic Dussart} 💻 🚧 👀	_{Dale Lane} 💻 🚧 👀	_Jonathan 💻	_{Radim Loskot} 💻	_{Michael Davis} 💻
_{Germán Schnyder} 💻