Add some background update admin APIs (#11263)

Fixes #11259

2 files changed, 85 insertions, 0 deletions

diff --git a/docs/SUMMARY.md b/docs/SUMMARY.md
index 35412ea92c..04320ab07b 100644
--- a/docs/SUMMARY.md
+++ b/docs/SUMMARY.md
@@ -51,6 +51,7 @@
   - [Administration](usage/administration/README.md)
     - [Admin API](usage/administration/admin_api/README.md)
       - [Account Validity](admin_api/account_validity.md)
+      - [Background Updates](usage/administration/admin_api/background_updates.md)
       - [Delete Group](admin_api/delete_group.md)
       - [Event Reports](admin_api/event_reports.md)
       - [Media](admin_api/media_admin_api.md)
diff --git a/docs/usage/administration/admin_api/background_updates.md b/docs/usage/administration/admin_api/background_updates.md
new file mode 100644
index 0000000000..b36d7fe398
--- /dev/null
+++ b/docs/usage/administration/admin_api/background_updates.md
@@ -0,0 +1,84 @@
+# 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:
+
+```json
+{
+    "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 allow 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:
+
+```json
+{
+    "enabled": false
+}
+```
+
+`enabled` sets whether the background updates are enabled or disabled.
+
+The API returns the `enabled` param.
+
+```json
+{
+    "enabled": false
+}
+```
+
+There is also a `GET` version which returns the `enabled` state.