Deprecate Shutdown Room and Purge Room Admin API (#8829)

Deprecate both APIs in favour of the Delete Room API.

Related: #8663 and #8810

3 files changed, 47 insertions, 9 deletions

diff --git a/docs/admin_api/purge_room.md b/docs/admin_api/purge_room.md
index ae01a543c6..54fea2db6d 100644
--- a/docs/admin_api/purge_room.md
+++ b/docs/admin_api/purge_room.md
@@ -1,12 +1,13 @@
-Purge room API
-==============
+Deprecated: Purge room API
+==========================
+
+**The old Purge room API is deprecated and will be removed in a future release.
+See the new [Delete Room API](rooms.md#delete-room-api) for more details.**
 
 This API will remove all trace of a room from your database.
 
 All local users must have left the room before it can be removed.
 
-See also: [Delete Room API](rooms.md#delete-room-api)
-
 The API is:
 
 ```
diff --git a/docs/admin_api/rooms.md b/docs/admin_api/rooms.md
index 004a802e17..3ac21b5cae 100644
--- a/docs/admin_api/rooms.md
+++ b/docs/admin_api/rooms.md
@@ -1,3 +1,14 @@
+# Contents
+- [List Room API](#list-room-api)
+  * [Parameters](#parameters)
+  * [Usage](#usage)
+- [Room Details API](#room-details-api)
+- [Room Members API](#room-members-api)
+- [Delete Room API](#delete-room-api)
+  * [Parameters](#parameters-1)
+  * [Response](#response)
+  * [Undoing room shutdowns](#undoing-room-shutdowns)
+
 # List Room API
 
 The List Room admin API allows server admins to get a list of rooms on their
@@ -357,8 +368,6 @@ Response:
 
 The Delete Room admin API allows server admins to remove rooms from server
 and block these rooms.
-It is a combination and improvement of "[Shutdown room](shutdown_room.md)"
-and "[Purge room](purge_room.md)" API.
 
 Shuts down a room. Moves all local users and room aliases automatically to a
 new room if `new_room_user_id` is set. Otherwise local users only
@@ -455,3 +464,30 @@ The following fields are returned in the JSON response body:
 * `local_aliases` - An array of strings representing the local aliases that were migrated from
                     the old room to the new.
 * `new_room_id` - A string representing the room ID of the new room.
+
+## Undoing room shutdowns
+
+*Note*: This guide may be outdated by the time you read it. By nature of room shutdowns being performed at the database level,
+the structure can and does change without notice.
+
+First, it's important to understand that a room shutdown is very destructive. Undoing a shutdown is not as simple as pretending it
+never happened - work has to be done to move forward instead of resetting the past. In fact, in some cases it might not be possible
+to recover at all:
+
+* If the room was invite-only, your users will need to be re-invited.
+* If the room no longer has any members at all, it'll be impossible to rejoin.
+* The first user to rejoin will have to do so via an alias on a different server.
+
+With all that being said, if you still want to try and recover the room:
+
+1. For safety reasons, shut down Synapse.
+2. In the database, run `DELETE FROM blocked_rooms WHERE room_id = '!example:example.org';`
+   * For caution: it's recommended to run this in a transaction: `BEGIN; DELETE ...;`, verify you got 1 result, then `COMMIT;`.
+   * The room ID is the same one supplied to the shutdown room API, not the Content Violation room.
+3. Restart Synapse.
+
+You will have to manually handle, if you so choose, the following:
+
+* Aliases that would have been redirected to the Content Violation room.
+* Users that would have been booted from the room (and will have been force-joined to the Content Violation room).
+* Removal of the Content Violation room if desired.
\ No newline at end of file
diff --git a/docs/admin_api/shutdown_room.md b/docs/admin_api/shutdown_room.md
index 9b1cb1c184..856a629487 100644
--- a/docs/admin_api/shutdown_room.md
+++ b/docs/admin_api/shutdown_room.md
@@ -1,4 +1,7 @@
-# Shutdown room API
+# Deprecated: Shutdown room API
+
+**The old Shutdown room API is deprecated and will be removed in a future release.
+See the new [Delete Room API](rooms.md#delete-room-api) for more details.**
 
 Shuts down a room, preventing new joins and moves local users and room aliases automatically
 to a new room. The new room will be created with the user specified by the
@@ -10,8 +13,6 @@ disallow any further invites or joins.
 The local server will only have the power to move local user and room aliases to
 the new room. Users on other servers will be unaffected.
 
-See also: [Delete Room API](rooms.md#delete-room-api)
-
 ## API
 
 You will need to authenticate with an access token for an admin user.