subject-missing

• Routes: write-events, read-events, observe-events, and read-subjects
• Description: subject is missing: expected a slash-separated path such as '/books/42'
• Details: When writing events, event or precondition, the place of the event or the precondition in its list, counting from 0. On the other routes, none; details is an empty object.

Why It Happens#

Every event has a subject, and reading events, observing them, and reading subjects start from one. The database reports this error when subject is left out or is an empty string: at the top level of a read, an observation, or a listing of subjects, in an event of a write, or in the payload of an isSubjectPristine, isSubjectPopulated, or isSubjectOnEventId precondition.

A typical cause is a read that leaves out the subject to get every event. That takes the root subject / with recursive set, see Reading All Events. A fromLatestEvent without its subject is reported as from-latest-event-incomplete instead.

How to Fix It#

Send the subject as a slash-separated path, such as /books/42, or as / together with recursive to cover every subject. Sending the same request again fails the same way, since the error depends on the request alone.

Example#

For a write whose second event leaves out its subject, 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/subject-missing",
    "description": "subject is missing: expected a slash-separated path such as '/books/42'",
    "details": {
      "event": 1
    }
  }
}