HeaderToValue

Example

To extract message headers in an event record into the record value, configure the HeaderToValue SMT in the Kafka Connect configuration for a connector. You can configure the transformation to either remove the original headers or to copy them. To remove header fields from the record, configure the SMT to use the move operations. To retain the header fields in the original record, configure the SMT to use the copy operation. For example, to remove the headers event_timestamp and key from an event message, add the following lines to your connector configuration:

transforms=moveHeadersToValue
transforms.moveHeadersToValue.type=io.debezium.transforms.HeaderToValue
transforms.moveHeadersToValue.headers=event_timestamp,key
transforms.moveHeadersToValue.fields=timestamp,source.id
transforms.moveHeadersToValue.operation=move

The following example shows the headers and values of an event record before and after the transformation is applied.

Example 1. Effect of applying the HeaderToValue SMT

Event record before it is processed by the HeaderToValue transformation

• Header before the SMT processes the event record

{
    "header_x": 0,
    "event_timestamp": 1626102708861,
    "key": 100,
}

• Value before the SMT processes the event record

  {
          "before": null,
          "after": {
              "id": 1,
              "first_name": "Anne",
              "last_name": "Kretchmar",
              "email": "annek@noanswer.org"
          },
          "source": {
              "version": "2.1.3.Final",
              "connector": "postgresql",
              "name": "PostgreSQL_server",
              "ts_ms": 1559033904863,
              "snapshot": true,
              "db": "postgres",
              "sequence": "[\"24023119\",\"24023128\"]"
              "schema": "public",
              "table": "customers",
              "txId": 555,
              "lsn": 24023128,
              "xmin": null
          },
          "op": "c",
          "ts_ms": 1559033904863
      }

Event record after it is processed by the HeaderToValue transformation

• Header after the SMT removes the specified field

{
    "header_x": 0
}

• Value after the SMT moves header fields into the value

  {
          "before": null,
          "after": {
              "id": 1,
              "first_name": "Anne",
              "last_name": "Kretchmar",
              "email": "annek@noanswer.org"
          },
          "source": {
              "version": "2.1.3.Final",
              "connector": "postgresql",
              "name": "PostgreSQL_server",
              "ts_ms": 1559033904863,
              "snapshot": true,
              "db": "postgres",
              "sequence": "[\"24023119\",\"24023128\"]"
              "schema": "public",
              "table": "customers",
              "txId": 555,
              "lsn": 24023128,
              "xmin": null,
              "id": 100
          },
          "op": "c",
          "ts_ms": 1559033904863,
          "event_timestamp": 1626102708861
      }

Configuration options

The following table lists the configuration options that you can use with the HeaderToValue SMT.