data-missing

• Route: write-events
• Description: data is missing: expected a JSON object
• Details: event, the place of the event in its list, counting from 0.

Why It Happens#

Every event carries its payload in data, which is a JSON object, see CloudEvents. The database reports this error when an event of a write leaves out data. An event that has nothing to say beyond its subject and type still needs data, as an empty object.

A typical cause is a serializer that leaves out empty fields, and with them the data of an event that has none. A data of null, or of another JSON type than an object, such as a string, does not get this far: the database rejects the request with 400 Bad Request, see Requests.

How to Fix It#

Send data with every event, as {} where the event carries nothing, and make your serializer keep it. Sending the same request again fails the same way, since the error depends on the request alone.

Example#

For a write whose first event leaves out its data, EventSourcingDB answers with this error, as a line of the stream, and then ends the stream with its end item:

{
  "type": "error",
  "data": {
    "code": "https://docs.eventsourcingdb.io/errors/data-missing",
    "description": "data is missing: expected a JSON object",
    "details": {
      "event": 0
    }
  }
}