# read-event-types

Lists **every event type** that the database knows, each with its **schema**, if it has one.

- **Route:** `QUERY /api/v2/data/read-event-types`
- **Category:** `data`
- **Authentication:** required, with the API token
- **Answer:** a stream of NDJSON

The database knows an **[event type](/docs/eventsourcingdb/event-types)** once an **event of the type has been written** or a **schema has been registered** for it. So an event type with a schema but **without any events** is listed as well, with `hasEvents` set to `false`. The listing shows the event types **as of the moment it starts**. The tutorial **[Listing Event Types](/learn/tutorials/first-steps-with-eventsourcingdb/listing-event-types)** walks through it step by step, and **[read-event-type](/docs/eventsourcingdb/api/read-event-type)** reads a single event type.

## Request

The route takes **no body**, and ignores one that is sent:

```shell
curl \
  -X QUERY \
  -H "authorization: Bearer secret" \
  http://localhost:3000/api/v2/data/read-event-types
```

## Answer

The answer is a **stream of items**, one per line. Each event type is an `eventType` item:

| Type | Data | When |
| --- | --- | --- |
| `eventType` | `type`, the event type; `hasEvents`, whether events of the type have been written; and `schema`, its schema, or `null` if it has none | For every event type that the database knows. |
| `error` | `code`, `description`, and `details` | When the listing cannot go on, see **[Errors](#errors)**. |
| `heartbeat` | empty | While nothing else is sent for a while, to keep the connection alive. |
| `end` | empty | Once, as the last item, when the stream ends cleanly. |

**Heartbeats and the `end` item** work as on every stream of the API, see **[Streams](/docs/eventsourcingdb/api#streams)**. A database that knows no event type answers with the `end` item alone.

For a database that holds events of the types `io.eventsourcingdb.library.book-acquired`, which has a schema, and `io.eventsourcingdb.library.book-borrowed`, which has none, and a schema for `io.eventsourcingdb.library.book-returned`, which has no events yet, the request above is answered with:

```json
{"type":"eventType","data":{"type":"io.eventsourcingdb.library.book-acquired","hasEvents":true,"schema":{"properties":{"author":{"type":"string"},"title":{"type":"string"}},"required":["title","author"],"type":"object"}}}
{"type":"eventType","data":{"type":"io.eventsourcingdb.library.book-borrowed","hasEvents":true,"schema":null}}
{"type":"eventType","data":{"type":"io.eventsourcingdb.library.book-returned","hasEvents":false,"schema":{"properties":{"returnedBy":{"type":"string"}},"required":["returnedBy"],"type":"object"}}}
{"type":"end","data":{}}
```

## Errors

The listing reports these errors as an `error` item, followed by the `end` item:

- **[`indexes-rebuilding`](/docs/eventsourcingdb/errors/indexes-rebuilding)**: The indexes that the listing needs are still being rebuilt after an upgrade.
- **[`restore-in-progress`](/docs/eventsourcingdb/errors/restore-in-progress)**: A restore is running as the listing starts, or begins while it runs, which refuses reads until it has finished.
- **[`file-unreadable`](/docs/eventsourcingdb/errors/file-unreadable)**: A file of the store that the listing needs is damaged, such as an events file whose checksum no longer matches.
- **[`store-failed`](/docs/eventsourcingdb/errors/store-failed)**: The store refuses reads for good, after a restore that could not empty it again.
- **[`server-shutting-down`](/docs/eventsourcingdb/errors/server-shutting-down)**: The server began to shut down while the listing was running. Before the stream begins, the server answers with `503` instead.

## Status Codes

Before the stream begins, the server answers with a status code other than `200` where it cannot take the request at all, as described in **[Errors](/docs/eventsourcingdb/api#errors)**:

- **`401`**: The API token is missing or wrong.
- **`429`**: Too many requests were sent, or the client already holds 256 open streams, see **[Rate Limiting](/docs/eventsourcingdb/rate-limiting)**; the answer says when to try again.
- **`500`**: The server failed unexpectedly before the stream began. Once it has begun, the stream breaks off without its `end` item instead.
- **`503`**: The server is shutting down.