# Background Updates - Synapse

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# Background Updates API

This API allows a server administrator to manage the background updates being run against the database.

## Status

This API gets the current status of the background updates.

The API is:

    GET /_synapse/admin/v1/background_updates/status

Returning:

    {
        "enabled": true,
        "current_updates": {
            "<db_name>": {
                "name": "<background_update_name>",
                "total_item_count": 50,
                "total_duration_ms": 10000.0,
                "average_items_per_ms": 2.2,
            },
        }
    }

`enabled` whether the background updates are enabled or disabled.

`db_name` the database name (usually Synapse is configured with a single database named ‘master’).

For each update:

`name` the name of the update. `total_item_count` total number of “items” processed (the meaning of ‘items’ depends on the update in question). `total_duration_ms` how long the background process has been running, not including time spent sleeping. `average_items_per_ms` how many items are processed per millisecond based on an exponential average.

## Enabled

This API allows pausing background updates.

Background updates should not be paused for significant periods of time, as this can affect the performance of Synapse.

Note: This won’t persist over restarts.

Note: This won’t cancel any update query that is currently running. This is usually fine since most queries are short lived, except for `CREATE INDEX` background updates which won’t be cancelled once started.

The API is:

    POST /_synapse/admin/v1/background_updates/enabled

with the following body:

    {
        "enabled": false
    }

`enabled` sets whether the background updates are enabled or disabled.

The API returns the `enabled` param.

    {
        "enabled": false
    }

There is also a `GET` version which returns the `enabled` state.

## Run

This API schedules a specific background update to run. The job starts immediately after calling the API.

The API is:

    POST /_synapse/admin/v1/background_updates/start_job

with the following body:

    {
        "job_name": "populate_stats_process_rooms"
    }

The following JSON body parameters are available:

- `job_name` - A string which job to run. Valid values are:
  - `populate_stats_process_rooms` - Recalculate the stats for all rooms.
  - `regenerate_directory` - Recalculate the user directory if it is stale or out of sync.
  - `event_resign` - Re-sign all locally-sent events with the current signing key. This is useful after rotating the server’s signing key to ensure all historical events are signed with the new key. Optional additional parameters:
    - `old_key` - Only re-sign events whose signature verifies against this key. Format: `"ed25519:key_id base64_public_key"` (e.g. `"ed25519:my_old_key XGX0JRS2Af3be3knz2fBiRbApjm2Dh61gXDJA8kcJNI"`).
    - `before_ts` - Only re-sign events with a `received_ts` less than this value (milliseconds since the epoch).