Confluent Schema Registry REST API cheatsheet

The Schema Registry support a REST API for finding out information about the schemas within it. Here’s a quick cheatsheat with REST calls that I often use.

Note	If you’re connecting to Schema Registry on Confluent Cloud then you need to specify your Schema Registry API key and secret as authentication in the HTTP request: `curl -u API_KEY:API_SECRET https://yourcluster_here.gcp.confluent.cloud/subjects/`

List 'subjects' (topics)

$ curl -s "http://localhost:8081/subjects/"
["COMP_WATCH_BY_EMP_ID_T-value"]⏎

List schema for given ID

$ curl -s "http://localhost:8081/schemas/ids/1"
{"schema":"{\"type\":\"record\",\"name\":\"KsqlDataSourceSchema\",\"namespace\":\"io.confluent.ksql.avro_schemas\",\"fields\":[{\"name\":\"EMP_ID\",\"type\":[\"null\",\"string\"],\"default\":null},{\"name\":\"EMP_NAME\",\"type\":[\"null\",\"string\"],\"default\":null},{\"name\":\"EMP_KEY\",\"type\":[\"null\",\"string\"],\"default\":null},{\"name\":\"MACADDR\",\"type\":[\"null\",\"string\"],\"default\":null}]}"}⏎

List latest schema for given subject

$ curl -s "http://localhost:8081/subjects/COMP_WATCH_BY_EMP_ID_T-value/versions/latest"|jq '.'
{
  "subject": "COMP_WATCH_BY_EMP_ID_T-value",
  "version": 1,
  "id": 1,
  "schema": "{\"type\":\"record\",\"name\":\"KsqlDataSourceSchema\",\"namespace\":\"io.confluent.ksql.avro_schemas\",\"fields\":[{\"name\":\"EMP_ID\",\"type\":[\"null\",\"string\"],\"default\":null},{\"name\":\"EMP_NAME\",\"type\":[\"null\",\"string\"],\"default\":null},{\"name\":\"EMP_KEY\",\"type\":[\"null\",\"string\"],\"default\":null},{\"name\":\"MACADDR\",\"type\":[\"null\",\"string\"],\"default\":null}]}"
}

List schema for given subject and version

$ curl -s "http://localhost:8081/subjects/COMP_WATCH_BY_EMP_ID_T-value/versions/1"|jq '.'
{
  "subject": "COMP_WATCH_BY_EMP_ID_T-value",
  "version": 1,
  "id": 1,
  "schema": "{\"type\":\"record\",\"name\":\"KsqlDataSourceSchema\",\"namespace\":\"io.confluent.ksql.avro_schemas\",\"fields\":[{\"name\":\"EMP_ID\",\"type\":[\"null\",\"string\"],\"default\":null},{\"name\":\"EMP_NAME\",\"type\":[\"null\",\"string\"],\"default\":null},{\"name\":\"EMP_KEY\",\"type\":[\"null\",\"string\"],\"default\":null},{\"name\":\"MACADDR\",\"type\":[\"null\",\"string\"],\"default\":null}]}"
}

List versions for given subject

$ curl -s "http://localhost:8081/subjects/COMP_WATCH_BY_EMP_ID_T-value/versions/"
[1]⏎

Use jq to reformat the schema JSON:

$ curl -s "http://localhost:8081/subjects/COMP_WATCH_BY_EMP_ID_T-value/versions/1"|jq '.schema|fromjson'
{
  "type": "record",
  "name": "KsqlDataSourceSchema",
  "namespace": "io.confluent.ksql.avro_schemas",
  "fields": [
    {
      "name": "EMP_ID",
      "type": [
        "null",
        "string"
      ],
      "default": null
    },
    {
      "name": "EMP_NAME",
      "type": [
        "null",
        "string"
      ],
      "default": null
    },
    {
      "name": "EMP_KEY",
      "type": [
        "null",
        "string"
      ],
      "default": null
    },
    {
      "name": "MACADDR",
      "type": [
        "null",
        "string"
      ],
      "default": null
    }
  ]
}

Use jq to show schema for columns matching a given name pattern

$ curl -s "http://localhost:8081/subjects/oracle-04-NUM_TEST-value/versions/latest"|jq '.schema|fromjson.fields[] | select (.name | contains("AMOUNT"))'
{
  "name": "AMOUNT_01",
  "type": [
    "null",
    "double"
  ],
  "default": null
}
{
  "name": "AMOUNT_02",
  "type": [
    "null",
    "double"
  ],
  "default": null
}
{
  "name": "AMOUNT_03",
  "type": [
    "null",
    "int"
  ],
  "default": null
}
{
  "name": "AMOUNT_04",
  "type": [
    "null",
    "double"
  ],
  "default": null
}
{
  "name": "AMOUNT_05",
  "type": [
    "null",
    "double"
  ],
  "default": null
}
{
  "name": "AMOUNT_06",
  "type": [
    "null",
    "double"
  ],
  "default": null
}
{
  "name": "AMOUNT_07",
  "type": [
    "null",
    "double"
  ],
  "default": null
}

echo '{
    "type": "record",
    "name": "myrecord",
    "fields": [
        {
            "name": "tags",
            "type": {
                "type": "map",
                "values": "string"
            }
        },
        {
            "name": "AVG_NOISE_FLOOR_DBM",
            "type": [
                "null",
                "double"
            ],
            "default": null
        },
        {
            "name": "OFDM_ANI_LEVEL_ADJUSTED",
            "type": [
                "null",
                "int"
            ],
            "default": null
        }
    ]
}' | \
    jq '. | {schema: tojson}' | \
    curl -X POST http://localhost:8081/subjects/sonos_metrics_avro_01-value/versions \
         -H "Content-Type:application/json" \
         -d @-

jq '. | {schema: tojson}' /tmp/example.avsc  | \
    curl -X POST http://localhost:8081/subjects/my_schema_01-value/versions \
         -H "Content-Type:application/json" \
         -d @-

Robin Moffatt

Robin Moffatt works on the DevRel team at Confluent. He likes writing about himself in the third person, eating good breakfasts, and drinking good beer.