Confluent Schema Registry: POST simple JSON schema with object having single property

Question

OS:  Ubuntu 18.x
docker image (from dockerhub.com, as of 2020-09-25):  confluentinc/cp-schema-registry:latest

I am exploring the HTTP API for the Confluent Schema Registry. First off, is there a definitive assertion somewhere about what version of the JSON Schema definition the registry assumes? For now, I am assuming Draft v7.0. More broadly, I believe the API that returns supported schema should list versions. Eg, instead of:

$ curl -X GET http://localhost:8081/schemas/types
["JSON","PROTOBUF","AVRO"]

you would have:

$ curl -X GET http://localhost:8081/schemas/types
[{"flavor": "JSON", "version": "7.0"}, {"flavor": "PROTOBUF", "version": "1.2"}, {"flavor": "AVRO", "version": "3.5"}]

so at least programmers would know for sure what the Schema Registry assumes.

This issue aside, I cannot seem to POST a rather trivial JSON schema to the registry:

$ curl -X POST -H "Content-Type: application/vnd.schemaregistry.v1+json" --data '{ "schema": "{ \"type\": \"object\", \"properties\": { \"f1\": { \"type\": \"string\" } } }" }' http://localhost:8081/subjects/mytest-value/versions
{"error_code":42201,"message":"Either the input schema or one its references is invalid"}

Here I am POSTing the schema to the mytest subject. The schema, incidentally, I scraped from Confluent documentation, and then escaped it accordingly.

Can you tell why this schema is not POSTing to the registry? And more generally, can I assume full support for Draft v7.0 of the JSON Schema definition?

Answer 1

You need to pass the schemaType flag. "If no schemaType is supplied, schemaType is assumed to be AVRO." https://docs.confluent.io/current/schema-registry/develop/api.html#post--subjects-(string-%20subject)-versions:

'{"schemaType":"JSON","schema":"{\"type\":\"object\",\"fields\":[{\"name\":\"f1\",\"type\":\"string\"}]}"}'

I agree that output of the supported versions would be helpful.