Convert delete room admin API to async endpoint (#11223)

Signed-off-by: Dirk Klimpel dirk@klimpel.org

changelog.d/11223.feature

@@ -0,0 +1 @@
+Add a new version of delete room admin API `DELETE /_synapse/admin/v2/rooms/<room_id>` to run it in background. Contributed by @dklimpel.

docs/admin_api/purge_history_api.md

@@ -70,6 +70,8 @@ This API returns a JSON body like the following:
 
 The status will be one of `active`, `complete`, or `failed`.
 
+If `status` is `failed` there will be a string `error` with the error message.
+
 ## Reclaim disk space (Postgres)
 
 To reclaim the disk space and return it to the operating system, you need to run

docs/admin_api/rooms.md

@@ -4,6 +4,9 @@
 - [Room Members API](#room-members-api)
 - [Room State API](#room-state-api)
 - [Delete Room API](#delete-room-api)
+  * [Version 1 (old version)](#version-1-old-version)
+  * [Version 2 (new version)](#version-2-new-version)
+  * [Status of deleting rooms](#status-of-deleting-rooms)
   * [Undoing room shutdowns](#undoing-room-shutdowns)
 - [Make Room Admin API](#make-room-admin-api)
 - [Forward Extremities Admin API](#forward-extremities-admin-api)
@@ -397,10 +400,10 @@ as room administrator and will contain a message explaining what happened. Users
 to the new room will have power level `-10` by default, and thus be unable to speak.
 
 If `block` is `true`, users will be prevented from joining the old room.
-This option can also be used to pre-emptively block a room, even if it's unknown
-to this homeserver. In this case, the room will be blocked, and no further action
-will be taken. If `block` is `false`, attempting to delete an unknown room is
-invalid and will be rejected as a bad request.
+This option can in [Version 1](#version-1-old-version) also be used to pre-emptively
+block a room, even if it's unknown to this homeserver. In this case, the room will be
+blocked, and no further action will be taken. If `block` is `false`, attempting to
+delete an unknown room is invalid and will be rejected as a bad request.
 
 This API will remove all trace of the old room from your database after removing
 all local users. If `purge` is `true` (the default), all traces of the old room will
@@ -412,6 +415,17 @@ several minutes or longer.
 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.
 
+To use it, you will need to authenticate by providing an ``access_token`` for a
+server admin: see [Admin API](../usage/administration/admin_api).
+
+## Version 1 (old version)
+
+This version works synchronously. That means you only get the response once the server has
+finished the action, which may take a long time. If you request the same action
+a second time, and the server has not finished the first one, the second request will block.
+This is fixed in version 2 of this API. The parameters are the same in both APIs.
+This API will become deprecated in the future.
+
 The API is:
 
 ```
@@ -430,9 +444,6 @@ with a body of:
 }
 ```
 
-To use it, you will need to authenticate by providing an ``access_token`` for a
-server admin: see [Admin API](../usage/administration/admin_api).
-
 A response body like the following is returned:
 
 ```json
@@ -449,6 +460,44 @@ A response body like the following is returned:
 }
 ```
 
+The parameters and response values have the same format as
+[version 2](#version-2-new-version) of the API.
+
+## Version 2 (new version)
+
+**Note**: This API is new, experimental and "subject to change".
+
+This version works asynchronously, meaning you get the response from server immediately
+while the server works on that task in background. You can then request the status of the action
+to check if it has completed.
+
+The API is:
+
+```
+DELETE /_synapse/admin/v2/rooms/<room_id>
+```
+
+with a body of:
+
+```json
+{
+    "new_room_user_id": "@someuser:example.com",
+    "room_name": "Content Violation Notification",
+    "message": "Bad Room has been shutdown due to content violations on this server. Please review our Terms of Service.",
+    "block": true,
+    "purge": true
+}
+```
+
+The API starts the shut down and purge running, and returns immediately with a JSON body with
+a purge id:
+
+```json
+{
+    "delete_id": "<opaque id>"
+}
+```
+
 **Parameters**
 
 The following parameters should be set in the URL:
@@ -470,7 +519,8 @@ The following JSON body parameters are available:
                is not permitted and rooms in violation will be blocked.`
 * `block` - Optional. If set to `true`, this room will be added to a blocking list,
             preventing future attempts to join the room. Rooms can be blocked
-            even if they're not yet known to the homeserver. Defaults to `false`.
+            even if they're not yet known to the homeserver (only with
+            [Version 1](#version-1-old-version) of the API). Defaults to `false`.
 * `purge` - Optional. If set to `true`, it will remove all traces of the room from your database.
             Defaults to `true`.
 * `force_purge` - Optional, and ignored unless `purge` is `true`. If set to `true`, it
@@ -480,17 +530,124 @@ The following JSON body parameters are available:
 
 The JSON body must not be empty. The body must be at least `{}`.
 
-**Response**
+## Status of deleting rooms
 
-The following fields are returned in the JSON response body:
+**Note**: This API is new, experimental and "subject to change".
+
+It is possible to query the status of the background task for deleting rooms.
+The status can be queried up to 24 hours after completion of the task,
+or until Synapse is restarted (whichever happens first).
+
+### Query by `room_id`
 
-* `kicked_users` - An array of users (`user_id`) that were kicked.
-* `failed_to_kick_users` - An array of users (`user_id`) that that were not kicked.
-* `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, or `null` if
-                  no such room was created.
+With this API you can get the status of all active deletion tasks, and all those completed in the last 24h,
+for the given `room_id`.
+
+The API is:
+
+```
+GET /_synapse/admin/v2/rooms/<room_id>/delete_status
+```
+
+A response body like the following is returned:
+
+```json
+{
+    "results": [
+        {
+            "delete_id": "delete_id1",
+            "status": "failed",
+            "error": "error message",
+            "shutdown_room": {
+                "kicked_users": [],
+                "failed_to_kick_users": [],
+                "local_aliases": [],
+                "new_room_id": null
+            }
+        }, {
+            "delete_id": "delete_id2",
+            "status": "purging",
+            "shutdown_room": {
+                "kicked_users": [
+                    "@foobar:example.com"
+                ],
+                "failed_to_kick_users": [],
+                "local_aliases": [
+                    "#badroom:example.com",
+                    "#evilsaloon:example.com"
+                ],
+                "new_room_id": "!newroomid:example.com"
+            }
+        }
+    ]
+}
+```
+
+**Parameters**
+
+The following parameters should be set in the URL:
+
+* `room_id` - The ID of the room.
+
+### Query by `delete_id`
+
+With this API you can get the status of one specific task by `delete_id`.
+
+The API is:
+
+```
+GET /_synapse/admin/v2/rooms/delete_status/<delete_id>
+```
+
+A response body like the following is returned:
+
+```json
+{
+    "status": "purging",
+    "shutdown_room": {
+        "kicked_users": [
+            "@foobar:example.com"
+        ],
+        "failed_to_kick_users": [],
+        "local_aliases": [
+            "#badroom:example.com",
+            "#evilsaloon:example.com"
+        ],
+        "new_room_id": "!newroomid:example.com"
+    }
+}
+```
+
+**Parameters**
+
+The following parameters should be set in the URL:
+
+* `delete_id` - The ID for this delete.
+
+### Response
+
+The following fields are returned in the JSON response body:
 
+- `results` - An array of objects, each containing information about one task.
+  This field is omitted from the result when you query by `delete_id`.
+  Task objects contain the following fields:
+  - `delete_id` - The ID for this purge if you query by `room_id`.
+  - `status` - The status will be one of:
+    - `shutting_down` - The process is removing users from the room.
+    - `purging` - The process is purging the room and event data from database.
+    - `complete` - The process has completed successfully.
+    - `failed` - The process is aborted, an error has occurred.
+  - `error` - A string that shows an error message if `status` is `failed`.
+    Otherwise this field is hidden.
+  - `shutdown_room` - An object containing information about the result of shutting down the room.
+    *Note:* The result is shown after removing the room members.
+    The delete process can still be running. Please pay attention to the `status`.
+    - `kicked_users` - An array of users (`user_id`) that were kicked.
+    - `failed_to_kick_users` - An array of users (`user_id`) that that were not kicked.
+    - `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, or `null` if
+      no such room was created.
 
 ## Undoing room deletions
 

synapse/handlers/pagination.py

@@ -13,7 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import logging
-from typing import TYPE_CHECKING, Any, Dict, Optional, Set
+from typing import TYPE_CHECKING, Any, Collection, Dict, List, Optional, Set
 
 import attr
 
@@ -22,7 +22,7 @@ from twisted.python.failure import Failure
 from synapse.api.constants import EventTypes, Membership
 from synapse.api.errors import SynapseError
 from synapse.api.filtering import Filter
-from synapse.logging.context import run_in_background
+from synapse.handlers.room import ShutdownRoomResponse
 from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.storage.state import StateFilter
 from synapse.streams.config import PaginationConfig
@@ -56,11 +56,62 @@ class PurgeStatus:
         STATUS_FAILED: "failed",
     }
 
+    # Save the error message if an error occurs
+    error: str = ""
+
     # Tracks whether this request has completed. One of STATUS_{ACTIVE,COMPLETE,FAILED}.
     status: int = STATUS_ACTIVE
 
     def asdict(self) -> JsonDict:
-        return {"status": PurgeStatus.STATUS_TEXT[self.status]}
+        ret = {"status": PurgeStatus.STATUS_TEXT[self.status]}
+        if self.error:
+            ret["error"] = self.error
+        return ret
+
+
+@attr.s(slots=True, auto_attribs=True)
+class DeleteStatus:
+    """Object tracking the status of a delete room request
+
+    This class contains information on the progress of a delete room request, for
+    return by get_delete_status.
+    """
+
+    STATUS_PURGING = 0
+    STATUS_COMPLETE = 1
+    STATUS_FAILED = 2
+    STATUS_SHUTTING_DOWN = 3
+
+    STATUS_TEXT = {
+        STATUS_PURGING: "purging",
+        STATUS_COMPLETE: "complete",
+        STATUS_FAILED: "failed",
+        STATUS_SHUTTING_DOWN: "shutting_down",
+    }
+
+    # Tracks whether this request has completed.
+    # One of STATUS_{PURGING,COMPLETE,FAILED,SHUTTING_DOWN}.
+    status: int = STATUS_PURGING
+
+    # Save the error message if an error occurs
+    error: str = ""
+
+    # Saves the result of an action to give it back to REST API
+    shutdown_room: ShutdownRoomResponse = {
+        "kicked_users": [],
+        "failed_to_kick_users": [],
+        "local_aliases": [],
+        "new_room_id": None,
+    }
+
+    def asdict(self) -> JsonDict:
+        ret = {
+            "status": DeleteStatus.STATUS_TEXT[self.status],
+            "shutdown_room": self.shutdown_room,
+        }
+        if self.error:
+            ret["error"] = self.error
+        return ret
 
 
 class PaginationHandler:
@@ -70,6 +121,9 @@ class PaginationHandler:
     paginating during a purge.
     """
 
+    # when to remove a completed deletion/purge from the results map
+    CLEAR_PURGE_AFTER_MS = 1000 * 3600 * 24  # 24 hours
+
     def __init__(self, hs: "HomeServer"):
         self.hs = hs
         self.auth = hs.get_auth()
@@ -78,11 +132,18 @@ class PaginationHandler:
         self.state_store = self.storage.state
         self.clock = hs.get_clock()
         self._server_name = hs.hostname
+        self._room_shutdown_handler = hs.get_room_shutdown_handler()
 
         self.pagination_lock = ReadWriteLock()
+        # IDs of rooms in which there currently an active purge *or delete* operation.
         self._purges_in_progress_by_room: Set[str] = set()
         # map from purge id to PurgeStatus
         self._purges_by_id: Dict[str, PurgeStatus] = {}
+        # map from purge id to DeleteStatus
+        self._delete_by_id: Dict[str, DeleteStatus] = {}
+        # map from room id to delete ids
+        # Dict[`room_id`, List[`delete_id`]]
+        self._delete_by_room: Dict[str, List[str]] = {}
         self._event_serializer = hs.get_event_client_serializer()
 
         self._retention_default_max_lifetime = (
@@ -265,8 +326,13 @@ class PaginationHandler:
         logger.info("[purge] starting purge_id %s", purge_id)
 
         self._purges_by_id[purge_id] = PurgeStatus()
-        run_in_background(
-            self._purge_history, purge_id, room_id, token, delete_local_events
+        run_as_background_process(
+            "purge_history",
+            self._purge_history,
+            purge_id,
+            room_id,
+            token,
+            delete_local_events,
         )
         return purge_id
 
@@ -276,7 +342,7 @@ class PaginationHandler:
         """Carry out a history purge on a room.
 
         Args:
-            purge_id: The id for this purge
+            purge_id: The ID for this purge.
             room_id: The room to purge from
             token: topological token to delete events before
             delete_local_events: True to delete local events as well as remote ones
@@ -295,6 +361,7 @@ class PaginationHandler:
                 "[purge] failed", exc_info=(f.type, f.value, f.getTracebackObject())  # type: ignore
             )
             self._purges_by_id[purge_id].status = PurgeStatus.STATUS_FAILED
+            self._purges_by_id[purge_id].error = f.getErrorMessage()
         finally:
             self._purges_in_progress_by_room.discard(room_id)
 
@@ -302,7 +369,9 @@ class PaginationHandler:
             def clear_purge() -> None:
                 del self._purges_by_id[purge_id]
 
-            self.hs.get_reactor().callLater(24 * 3600, clear_purge)
+            self.hs.get_reactor().callLater(
+                PaginationHandler.CLEAR_PURGE_AFTER_MS / 1000, clear_purge
+            )
 
     def get_purge_status(self, purge_id: str) -> Optional[PurgeStatus]:
         """Get the current status of an active purge
@@ -312,8 +381,25 @@ class PaginationHandler:
         """
         return self._purges_by_id.get(purge_id)
 
+    def get_delete_status(self, delete_id: str) -> Optional[DeleteStatus]:
+        """Get the current status of an active deleting
+
+        Args:
+            delete_id: delete_id returned by start_shutdown_and_purge_room
+        """
+        return self._delete_by_id.get(delete_id)
+
+    def get_delete_ids_by_room(self, room_id: str) -> Optional[Collection[str]]:
+        """Get all active delete ids by room
+
+        Args:
+            room_id: room_id that is deleted
+        """
+        return self._delete_by_room.get(room_id)
+
     async def purge_room(self, room_id: str, force: bool = False) -> None:
         """Purge the given room from the database.
+        This function is part the delete room v1 API.
 
         Args:
             room_id: room to be purged
@@ -472,3 +558,192 @@ class PaginationHandler:
             )
 
         return chunk
+
+    async def _shutdown_and_purge_room(
+        self,
+        delete_id: str,
+        room_id: str,
+        requester_user_id: str,
+        new_room_user_id: Optional[str] = None,
+        new_room_name: Optional[str] = None,
+        message: Optional[str] = None,
+        block: bool = False,
+        purge: bool = True,
+        force_purge: bool = False,
+    ) -> None:
+        """
+        Shuts down and purges a room.
+
+        See `RoomShutdownHandler.shutdown_room` for details of creation of the new room
+
+        Args:
+            delete_id: The ID for this delete.
+            room_id: The ID of the room to shut down.
+            requester_user_id:
+                User who requested the action. Will be recorded as putting the room on the
+                blocking list.
+            new_room_user_id:
+                If set, a new room will be created with this user ID
+                as the creator and admin, and all users in the old room will be
+                moved into that room. If not set, no new room will be created
+                and the users will just be removed from the old room.
+            new_room_name:
+                A string representing the name of the room that new users will
+                be invited to. Defaults to `Content Violation Notification`
+            message:
+                A string containing the first message that will be sent as
+                `new_room_user_id` in the new room. Ideally this will clearly
+                convey why the original room was shut down.
+                Defaults to `Sharing illegal content on this server is not
+                permitted and rooms in violation will be blocked.`
+            block:
+                If set to `true`, this room will be added to a blocking list,
+                preventing future attempts to join the room. Defaults to `false`.
+            purge:
+                If set to `true`, purge the given room from the database.
+            force_purge:
+                If set to `true`, the room will be purged from database
+                also if it fails to remove some users from room.
+
+        Saves a `RoomShutdownHandler.ShutdownRoomResponse` in `DeleteStatus`:
+        """
+
+        self._purges_in_progress_by_room.add(room_id)
+        try:
+            with await self.pagination_lock.write(room_id):
+                self._delete_by_id[delete_id].status = DeleteStatus.STATUS_SHUTTING_DOWN
+                self._delete_by_id[
+                    delete_id
+                ].shutdown_room = await self._room_shutdown_handler.shutdown_room(
+                    room_id=room_id,
+                    requester_user_id=requester_user_id,
+                    new_room_user_id=new_room_user_id,
+                    new_room_name=new_room_name,
+                    message=message,
+                    block=block,
+                )
+                self._delete_by_id[delete_id].status = DeleteStatus.STATUS_PURGING
+
+                if purge:
+                    logger.info("starting purge room_id %s", room_id)
+
+                    # first check that we have no users in this room
+                    if not force_purge:
+                        joined = await self.store.is_host_joined(
+                            room_id, self._server_name
+                        )
+                        if joined:
+                            raise SynapseError(
+                                400, "Users are still joined to this room"
+                            )
+
+                    await self.storage.purge_events.purge_room(room_id)
+
+            logger.info("complete")
+            self._delete_by_id[delete_id].status = DeleteStatus.STATUS_COMPLETE
+        except Exception:
+            f = Failure()
+            logger.error(
+                "failed",
+                exc_info=(f.type, f.value, f.getTracebackObject()),  # type: ignore
+            )
+            self._delete_by_id[delete_id].status = DeleteStatus.STATUS_FAILED
+            self._delete_by_id[delete_id].error = f.getErrorMessage()
+        finally:
+            self._purges_in_progress_by_room.discard(room_id)
+
+            # remove the delete from the list 24 hours after it completes
+            def clear_delete() -> None:
+                del self._delete_by_id[delete_id]
+                self._delete_by_room[room_id].remove(delete_id)
+                if not self._delete_by_room[room_id]:
+                    del self._delete_by_room[room_id]
+
+            self.hs.get_reactor().callLater(
+                PaginationHandler.CLEAR_PURGE_AFTER_MS / 1000, clear_delete
+            )
+
+    def start_shutdown_and_purge_room(
+        self,
+        room_id: str,
+        requester_user_id: str,
+        new_room_user_id: Optional[str] = None,
+        new_room_name: Optional[str] = None,
+        message: Optional[str] = None,
+        block: bool = False,
+        purge: bool = True,
+        force_purge: bool = False,
+    ) -> str:
+        """Start off shut down and purge on a room.
+
+        Args:
+            room_id: The ID of the room to shut down.
+            requester_user_id:
+                User who requested the action and put the room on the
+                blocking list.
+            new_room_user_id:
+                If set, a new room will be created with this user ID
+                as the creator and admin, and all users in the old room will be
+                moved into that room. If not set, no new room will be created
+                and the users will just be removed from the old room.
+            new_room_name:
+                A string representing the name of the room that new users will
+                be invited to. Defaults to `Content Violation Notification`
+            message:
+                A string containing the first message that will be sent as
+                `new_room_user_id` in the new room. Ideally this will clearly
+                convey why the original room was shut down.
+                Defaults to `Sharing illegal content on this server is not
+                permitted and rooms in violation will be blocked.`
+            block:
+                If set to `true`, this room will be added to a blocking list,
+                preventing future attempts to join the room. Defaults to `false`.
+            purge:
+                If set to `true`, purge the given room from the database.
+            force_purge:
+                If set to `true`, the room will be purged from database
+                also if it fails to remove some users from room.
+
+        Returns:
+            unique ID for this delete transaction.
+        """
+        if room_id in self._purges_in_progress_by_room:
+            raise SynapseError(
+                400, "History purge already in progress for %s" % (room_id,)
+            )
+
+        # This check is double to `RoomShutdownHandler.shutdown_room`
+        # But here the requester get a direct response / error with HTTP request
+        # and do not have to check the purge status
+        if new_room_user_id is not None:
+            if not self.hs.is_mine_id(new_room_user_id):
+                raise SynapseError(
+                    400, "User must be our own: %s" % (new_room_user_id,)
+                )
+
+        delete_id = random_string(16)
+
+        # we log the delete_id here so that it can be tied back to the
+        # request id in the log lines.
+        logger.info(
+            "starting shutdown room_id %s with delete_id %s",
+            room_id,
+            delete_id,
+        )
+
+        self._delete_by_id[delete_id] = DeleteStatus()
+        self._delete_by_room.setdefault(room_id, []).append(delete_id)
+        run_as_background_process(
+            "shutdown_and_purge_room",
+            self._shutdown_and_purge_room,
+            delete_id,
+            room_id,
+            requester_user_id,
+            new_room_user_id,
+            new_room_name,
+            message,
+            block,
+            purge,
+            force_purge,
+        )
+        return delete_id

synapse/handlers/room.py

@@ -1279,6 +1279,17 @@ class RoomEventSource(EventSource[RoomStreamToken, EventBase]):
 
 
 class ShutdownRoomResponse(TypedDict):
+    """
+    Attributes:
+        kicked_users: An array of users (`user_id`) that were kicked.
+        failed_to_kick_users:
+            An array of users (`user_id`) that that were not kicked.
+        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.
+    """
+
     kicked_users: List[str]
     failed_to_kick_users: List[str]
     local_aliases: List[str]
@@ -1286,7 +1297,6 @@ class ShutdownRoomResponse(TypedDict):
 
 
 class RoomShutdownHandler:
-
     DEFAULT_MESSAGE = (
         "Sharing illegal content on this server is not permitted and rooms in"
         " violation will be blocked."
@@ -1299,7 +1309,6 @@ class RoomShutdownHandler:
         self._room_creation_handler = hs.get_room_creation_handler()
         self._replication = hs.get_replication_data_handler()
         self.event_creation_handler = hs.get_event_creation_handler()
-        self.state = hs.get_state_handler()
         self.store = hs.get_datastore()
 
     async def shutdown_room(

synapse/rest/admin/__init__.py

@@ -46,6 +46,8 @@ from synapse.rest.admin.registration_tokens import (
     RegistrationTokenRestServlet,
 )
 from synapse.rest.admin.rooms import (
+    DeleteRoomStatusByDeleteIdRestServlet,
+    DeleteRoomStatusByRoomIdRestServlet,
     ForwardExtremitiesRestServlet,
     JoinRoomAliasServlet,
     ListRoomRestServlet,
@@ -53,6 +55,7 @@ from synapse.rest.admin.rooms import (
     RoomEventContextServlet,
     RoomMembersRestServlet,
     RoomRestServlet,
+    RoomRestV2Servlet,
     RoomStateRestServlet,
 )
 from synapse.rest.admin.server_notice_servlet import SendServerNoticeServlet
@@ -223,7 +226,10 @@ def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
     ListRoomRestServlet(hs).register(http_server)
     RoomStateRestServlet(hs).register(http_server)
     RoomRestServlet(hs).register(http_server)
+    RoomRestV2Servlet(hs).register(http_server)
     RoomMembersRestServlet(hs).register(http_server)
+    DeleteRoomStatusByDeleteIdRestServlet(hs).register(http_server)
+    DeleteRoomStatusByRoomIdRestServlet(hs).register(http_server)
     JoinRoomAliasServlet(hs).register(http_server)
     VersionServlet(hs).register(http_server)
     UserAdminServlet(hs).register(http_server)

synapse/rest/admin/rooms.py

@@ -34,7 +34,7 @@ from synapse.rest.admin._base import (
     assert_user_is_admin,
 )
 from synapse.storage.databases.main.room import RoomSortOrder
-from synapse.types import JsonDict, UserID, create_requester
+from synapse.types import JsonDict, RoomID, UserID, create_requester
 from synapse.util import json_decoder
 
 if TYPE_CHECKING:
@@ -46,6 +46,138 @@ if TYPE_CHECKING:
 logger = logging.getLogger(__name__)
 
 
+class RoomRestV2Servlet(RestServlet):
+    """Delete a room from server asynchronously with a background task.
+
+    It is a combination and improvement of shutdown and purge room.
+
+    Shuts down a room by removing all local users from the room.
+    Blocking all future invites and joins to the room is optional.
+
+    If desired any local aliases will be repointed to a new room
+    created by `new_room_user_id` and kicked users will be auto-
+    joined to the new room.
+
+    If 'purge' is true, it will remove all traces of a room from the database.
+    """
+
+    PATTERNS = admin_patterns("/rooms/(?P<room_id>[^/]+)$", "v2")
+
+    def __init__(self, hs: "HomeServer"):
+        self._auth = hs.get_auth()
+        self._store = hs.get_datastore()
+        self._pagination_handler = hs.get_pagination_handler()
+
+    async def on_DELETE(
+        self, request: SynapseRequest, room_id: str
+    ) -> Tuple[int, JsonDict]:
+
+        requester = await self._auth.get_user_by_req(request)
+        await assert_user_is_admin(self._auth, requester.user)
+
+        content = parse_json_object_from_request(request)
+
+        block = content.get("block", False)
+        if not isinstance(block, bool):
+            raise SynapseError(
+                HTTPStatus.BAD_REQUEST,
+                "Param 'block' must be a boolean, if given",
+                Codes.BAD_JSON,
+            )
+
+        purge = content.get("purge", True)
+        if not isinstance(purge, bool):
+            raise SynapseError(
+                HTTPStatus.BAD_REQUEST,
+                "Param 'purge' must be a boolean, if given",
+                Codes.BAD_JSON,
+            )
+
+        force_purge = content.get("force_purge", False)
+        if not isinstance(force_purge, bool):
+            raise SynapseError(
+                HTTPStatus.BAD_REQUEST,
+                "Param 'force_purge' must be a boolean, if given",
+                Codes.BAD_JSON,
+            )
+
+        if not RoomID.is_valid(room_id):
+            raise SynapseError(400, "%s is not a legal room ID" % (room_id,))
+
+        if not await self._store.get_room(room_id):
+            raise NotFoundError("Unknown room id %s" % (room_id,))
+
+        delete_id = self._pagination_handler.start_shutdown_and_purge_room(
+            room_id=room_id,
+            new_room_user_id=content.get("new_room_user_id"),
+            new_room_name=content.get("room_name"),
+            message=content.get("message"),
+            requester_user_id=requester.user.to_string(),
+            block=block,
+            purge=purge,
+            force_purge=force_purge,
+        )
+
+        return 200, {"delete_id": delete_id}
+
+
+class DeleteRoomStatusByRoomIdRestServlet(RestServlet):
+    """Get the status of the delete room background task."""
+
+    PATTERNS = admin_patterns("/rooms/(?P<room_id>[^/]+)/delete_status$", "v2")
+
+    def __init__(self, hs: "HomeServer"):
+        self._auth = hs.get_auth()
+        self._pagination_handler = hs.get_pagination_handler()
+
+    async def on_GET(
+        self, request: SynapseRequest, room_id: str
+    ) -> Tuple[int, JsonDict]:
+
+        await assert_requester_is_admin(self._auth, request)
+
+        if not RoomID.is_valid(room_id):
+            raise SynapseError(400, "%s is not a legal room ID" % (room_id,))
+
+        delete_ids = self._pagination_handler.get_delete_ids_by_room(room_id)
+        if delete_ids is None:
+            raise NotFoundError("No delete task for room_id '%s' found" % room_id)
+
+        response = []
+        for delete_id in delete_ids:
+            delete = self._pagination_handler.get_delete_status(delete_id)
+            if delete:
+                response += [
+                    {
+                        "delete_id": delete_id,
+                        **delete.asdict(),
+                    }
+                ]
+        return 200, {"results": cast(JsonDict, response)}
+
+
+class DeleteRoomStatusByDeleteIdRestServlet(RestServlet):
+    """Get the status of the delete room background task."""
+
+    PATTERNS = admin_patterns("/rooms/delete_status/(?P<delete_id>[^/]+)$", "v2")
+
+    def __init__(self, hs: "HomeServer"):
+        self._auth = hs.get_auth()
+        self._pagination_handler = hs.get_pagination_handler()
+
+    async def on_GET(
+        self, request: SynapseRequest, delete_id: str
+    ) -> Tuple[int, JsonDict]:
+
+        await assert_requester_is_admin(self._auth, request)
+
+        delete_status = self._pagination_handler.get_delete_status(delete_id)
+        if delete_status is None:
+            raise NotFoundError("delete id '%s' not found" % delete_id)
+
+        return 200, cast(JsonDict, delete_status.asdict())
+
+
 class ListRoomRestServlet(RestServlet):
     """
     List all rooms that are known to the homeserver. Results are returned

tests/rest/admin/test_admin.py

@@ -474,3 +474,51 @@ class QuarantineMediaTestCase(unittest.HomeserverTestCase):
                 % server_and_media_id_2
             ),
         )
+
+
+class PurgeHistoryTestCase(unittest.HomeserverTestCase):
+    servlets = [
+        synapse.rest.admin.register_servlets,
+        login.register_servlets,
+        room.register_servlets,
+    ]
+
+    def prepare(self, reactor, clock, hs):
+        self.admin_user = self.register_user("admin", "pass", admin=True)
+        self.admin_user_tok = self.login("admin", "pass")
+
+        self.other_user = self.register_user("user", "pass")
+        self.other_user_tok = self.login("user", "pass")
+
+        self.room_id = self.helper.create_room_as(
+            self.other_user, tok=self.other_user_tok
+        )
+        self.url = f"/_synapse/admin/v1/purge_history/{self.room_id}"
+        self.url_status = "/_synapse/admin/v1/purge_history_status/"
+
+    def test_purge_history(self):
+        """
+        Simple test of purge history API.
+        Test only that is is possible to call, get status 200 and purge_id.
+        """
+
+        channel = self.make_request(
+            "POST",
+            self.url,
+            content={"delete_local_events": True, "purge_up_to_ts": 0},
+            access_token=self.admin_user_tok,
+        )
+
+        self.assertEqual(200, channel.code, msg=channel.json_body)
+        self.assertIn("purge_id", channel.json_body)
+        purge_id = channel.json_body["purge_id"]
+
+        # get status
+        channel = self.make_request(
+            "GET",
+            self.url_status + purge_id,
+            access_token=self.admin_user_tok,
+        )
+
+        self.assertEqual(200, channel.code, msg=channel.json_body)
+        self.assertEqual("complete", channel.json_body["status"])