Payload versions and raw JSON

type Versioned interface {
  SchemaVersion() int
}

A message payload type implements Versioned and can be encoded as JSON. Its schema version is stored with each produced message. A consumer instance processes messages matching the version declared by its payload type.

Define a payload

Use a value receiver that returns a constant of at least 1.

type PaymentRequestedV1 struct {
  OrderId string `json:"order_id"`
}

func (p PaymentRequestedV1) SchemaVersion() int { return 1 }

Declare a new version for incompatible payload changes, such as removing or renaming a field or changing its type. The payload version is separate from the database schema version managed by migrations.

RawPayload

type RawPayload []byte

Use RawPayload for administrative reads that should preserve stored JSON without decoding it into an application struct. It implements JSON marshal and unmarshal methods and returns 0 from SchemaVersion.

payments := client.Stream[sqlstreams.RawPayload]("payments.requested")
stream, err := payments.Get(ctx)
if err != nil {
  return err
}
if stream != nil {
  fmt.Println(stream.Id, stream.Name)
}

This example uses an initialized client to inspect the payments.requested stream.

Related topics

• Produce a message — Payload validation and message production.
• Register a consumer group — Consumer payload requirements.
• Streams and messages — How payloads and message metadata are stored.