diff --git a/changelog.d/15891.feature b/changelog.d/15891.feature
new file mode 100644
index 0000000000..5024b5adc4
--- /dev/null
+++ b/changelog.d/15891.feature
@@ -0,0 +1 @@
+Implements a task scheduler for resumable potentially long running tasks.
diff --git a/synapse/app/generic_worker.py b/synapse/app/generic_worker.py
index dc79efcc14..d25e3548e0 100644
--- a/synapse/app/generic_worker.py
+++ b/synapse/app/generic_worker.py
@@ -91,6 +91,7 @@ from synapse.storage.databases.main.state import StateGroupWorkerStore
from synapse.storage.databases.main.stats import StatsStore
from synapse.storage.databases.main.stream import StreamWorkerStore
from synapse.storage.databases.main.tags import TagsWorkerStore
+from synapse.storage.databases.main.task_scheduler import TaskSchedulerWorkerStore
from synapse.storage.databases.main.transactions import TransactionWorkerStore
from synapse.storage.databases.main.ui_auth import UIAuthWorkerStore
from synapse.storage.databases.main.user_directory import UserDirectoryStore
@@ -144,6 +145,7 @@ class GenericWorkerStore(
TransactionWorkerStore,
LockStore,
SessionStore,
+ TaskSchedulerWorkerStore,
):
# Properties that multiple storage classes define. Tell mypy what the
# expected type is.
diff --git a/synapse/server.py b/synapse/server.py
index e753ff0377..7cdd3ea3c2 100644
--- a/synapse/server.py
+++ b/synapse/server.py
@@ -142,6 +142,7 @@ from synapse.util.distributor import Distributor
from synapse.util.macaroons import MacaroonGenerator
from synapse.util.ratelimitutils import FederationRateLimiter
from synapse.util.stringutils import random_string
+from synapse.util.task_scheduler import TaskScheduler
logger = logging.getLogger(__name__)
@@ -360,6 +361,7 @@ class HomeServer(metaclass=abc.ABCMeta):
"""
for i in self.REQUIRED_ON_BACKGROUND_TASK_STARTUP:
getattr(self, "get_" + i + "_handler")()
+ self.get_task_scheduler()
def get_reactor(self) -> ISynapseReactor:
"""
@@ -912,6 +914,9 @@ class HomeServer(metaclass=abc.ABCMeta):
"""Usage metrics shared between phone home stats and the prometheus exporter."""
return CommonUsageMetricsManager(self)
- @cache_in_self
def get_worker_locks_handler(self) -> WorkerLocksHandler:
return WorkerLocksHandler(self)
+
+ @cache_in_self
+ def get_task_scheduler(self) -> TaskScheduler:
+ return TaskScheduler(self)
diff --git a/synapse/storage/databases/main/__init__.py b/synapse/storage/databases/main/__init__.py
index e17f25e87a..a85633efcd 100644
--- a/synapse/storage/databases/main/__init__.py
+++ b/synapse/storage/databases/main/__init__.py
@@ -70,6 +70,7 @@ from .state import StateStore
from .stats import StatsStore
from .stream import StreamWorkerStore
from .tags import TagsStore
+from .task_scheduler import TaskSchedulerWorkerStore
from .transactions import TransactionWorkerStore
from .ui_auth import UIAuthStore
from .user_directory import UserDirectoryStore
@@ -127,6 +128,7 @@ class DataStore(
CacheInvalidationWorkerStore,
LockStore,
SessionStore,
+ TaskSchedulerWorkerStore,
):
def __init__(
self,
diff --git a/synapse/storage/databases/main/task_scheduler.py b/synapse/storage/databases/main/task_scheduler.py
new file mode 100644
index 0000000000..1fb3180c3c
--- /dev/null
+++ b/synapse/storage/databases/main/task_scheduler.py
@@ -0,0 +1,202 @@
+# Copyright 2023 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from typing import TYPE_CHECKING, Any, Dict, List, Optional
+
+from synapse.storage._base import SQLBaseStore, db_to_json
+from synapse.storage.database import (
+ DatabasePool,
+ LoggingDatabaseConnection,
+ LoggingTransaction,
+ make_in_list_sql_clause,
+)
+from synapse.types import JsonDict, JsonMapping, ScheduledTask, TaskStatus
+from synapse.util import json_encoder
+
+if TYPE_CHECKING:
+ from synapse.server import HomeServer
+
+
+class TaskSchedulerWorkerStore(SQLBaseStore):
+ def __init__(
+ self,
+ database: DatabasePool,
+ db_conn: LoggingDatabaseConnection,
+ hs: "HomeServer",
+ ):
+ super().__init__(database, db_conn, hs)
+
+ @staticmethod
+ def _convert_row_to_task(row: Dict[str, Any]) -> ScheduledTask:
+ row["status"] = TaskStatus(row["status"])
+ if row["params"] is not None:
+ row["params"] = db_to_json(row["params"])
+ if row["result"] is not None:
+ row["result"] = db_to_json(row["result"])
+ return ScheduledTask(**row)
+
+ async def get_scheduled_tasks(
+ self,
+ *,
+ actions: Optional[List[str]] = None,
+ resource_id: Optional[str] = None,
+ statuses: Optional[List[TaskStatus]] = None,
+ max_timestamp: Optional[int] = None,
+ ) -> List[ScheduledTask]:
+ """Get a list of scheduled tasks from the DB.
+
+ Args:
+ actions: Limit the returned tasks to those specific action names
+ resource_id: Limit the returned tasks to the specific resource id, if specified
+ statuses: Limit the returned tasks to the specific statuses
+ max_timestamp: Limit the returned tasks to the ones that have
+ a timestamp inferior to the specified one
+
+ Returns: a list of `ScheduledTask`, ordered by increasing timestamps
+ """
+
+ def get_scheduled_tasks_txn(txn: LoggingTransaction) -> List[Dict[str, Any]]:
+ clauses: List[str] = []
+ args: List[Any] = []
+ if resource_id:
+ clauses.append("resource_id = ?")
+ args.append(resource_id)
+ if actions is not None:
+ clause, temp_args = make_in_list_sql_clause(
+ txn.database_engine, "action", actions
+ )
+ clauses.append(clause)
+ args.extend(temp_args)
+ if statuses is not None:
+ clause, temp_args = make_in_list_sql_clause(
+ txn.database_engine, "status", statuses
+ )
+ clauses.append(clause)
+ args.extend(temp_args)
+ if max_timestamp is not None:
+ clauses.append("timestamp <= ?")
+ args.append(max_timestamp)
+
+ sql = "SELECT * FROM scheduled_tasks"
+ if clauses:
+ sql = sql + " WHERE " + " AND ".join(clauses)
+
+ sql = sql + "ORDER BY timestamp"
+
+ txn.execute(sql, args)
+ return self.db_pool.cursor_to_dict(txn)
+
+ rows = await self.db_pool.runInteraction(
+ "get_scheduled_tasks", get_scheduled_tasks_txn
+ )
+ return [TaskSchedulerWorkerStore._convert_row_to_task(row) for row in rows]
+
+ async def insert_scheduled_task(self, task: ScheduledTask) -> None:
+ """Insert a specified `ScheduledTask` in the DB.
+
+ Args:
+ task: the `ScheduledTask` to insert
+ """
+ await self.db_pool.simple_insert(
+ "scheduled_tasks",
+ {
+ "id": task.id,
+ "action": task.action,
+ "status": task.status,
+ "timestamp": task.timestamp,
+ "resource_id": task.resource_id,
+ "params": None
+ if task.params is None
+ else json_encoder.encode(task.params),
+ "result": None
+ if task.result is None
+ else json_encoder.encode(task.result),
+ "error": task.error,
+ },
+ desc="insert_scheduled_task",
+ )
+
+ async def update_scheduled_task(
+ self,
+ id: str,
+ timestamp: int,
+ *,
+ status: Optional[TaskStatus] = None,
+ result: Optional[JsonMapping] = None,
+ error: Optional[str] = None,
+ ) -> bool:
+ """Update a scheduled task in the DB with some new value(s).
+
+ Args:
+ id: id of the `ScheduledTask` to update
+ timestamp: new timestamp of the task
+ status: new status of the task
+ result: new result of the task
+ error: new error of the task
+
+ Returns: `False` if no matching row was found, `True` otherwise
+ """
+ updatevalues: JsonDict = {"timestamp": timestamp}
+ if status is not None:
+ updatevalues["status"] = status
+ if result is not None:
+ updatevalues["result"] = json_encoder.encode(result)
+ if error is not None:
+ updatevalues["error"] = error
+ nb_rows = await self.db_pool.simple_update(
+ "scheduled_tasks",
+ {"id": id},
+ updatevalues,
+ desc="update_scheduled_task",
+ )
+ return nb_rows > 0
+
+ async def get_scheduled_task(self, id: str) -> Optional[ScheduledTask]:
+ """Get a specific `ScheduledTask` from its id.
+
+ Args:
+ id: the id of the task to retrieve
+
+ Returns: the task if available, `None` otherwise
+ """
+ row = await self.db_pool.simple_select_one(
+ table="scheduled_tasks",
+ keyvalues={"id": id},
+ retcols=(
+ "id",
+ "action",
+ "status",
+ "timestamp",
+ "resource_id",
+ "params",
+ "result",
+ "error",
+ ),
+ allow_none=True,
+ desc="get_scheduled_task",
+ )
+
+ return TaskSchedulerWorkerStore._convert_row_to_task(row) if row else None
+
+ async def delete_scheduled_task(self, id: str) -> None:
+ """Delete a specific task from its id.
+
+ Args:
+ id: the id of the task to delete
+ """
+ await self.db_pool.simple_delete(
+ "scheduled_tasks",
+ keyvalues={"id": id},
+ desc="delete_scheduled_task",
+ )
diff --git a/synapse/storage/schema/__init__.py b/synapse/storage/schema/__init__.py
index 7de9949a5b..649d3c8e9f 100644
--- a/synapse/storage/schema/__init__.py
+++ b/synapse/storage/schema/__init__.py
@@ -113,6 +113,7 @@ Changes in SCHEMA_VERSION = 79
Changes in SCHEMA_VERSION = 80
- The event_txn_id_device_id is always written to for new events.
+ - Add tables for the task scheduler.
"""
diff --git a/synapse/storage/schema/main/delta/80/02_scheduled_tasks.sql b/synapse/storage/schema/main/delta/80/02_scheduled_tasks.sql
new file mode 100644
index 0000000000..286d109ed7
--- /dev/null
+++ b/synapse/storage/schema/main/delta/80/02_scheduled_tasks.sql
@@ -0,0 +1,28 @@
+/* Copyright 2023 The Matrix.org Foundation C.I.C
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+-- cf ScheduledTask docstring for the meaning of the fields.
+CREATE TABLE IF NOT EXISTS scheduled_tasks(
+ id TEXT PRIMARY KEY,
+ action TEXT NOT NULL,
+ status TEXT NOT NULL,
+ timestamp BIGINT NOT NULL,
+ resource_id TEXT,
+ params TEXT,
+ result TEXT,
+ error TEXT
+);
+
+CREATE INDEX IF NOT EXISTS scheduled_tasks_status ON scheduled_tasks(status);
diff --git a/synapse/types/__init__.py b/synapse/types/__init__.py
index 073f682aca..e750417189 100644
--- a/synapse/types/__init__.py
+++ b/synapse/types/__init__.py
@@ -15,6 +15,7 @@
import abc
import re
import string
+from enum import Enum
from typing import (
TYPE_CHECKING,
AbstractSet,
@@ -969,3 +970,41 @@ class UserProfile(TypedDict):
class RetentionPolicy:
min_lifetime: Optional[int] = None
max_lifetime: Optional[int] = None
+
+
+class TaskStatus(str, Enum):
+ """Status of a scheduled task"""
+
+ # Task is scheduled but not active
+ SCHEDULED = "scheduled"
+ # Task is active and probably running, and if not
+ # will be run on next scheduler loop run
+ ACTIVE = "active"
+ # Task has completed successfully
+ COMPLETE = "complete"
+ # Task is over and either returned a failed status, or had an exception
+ FAILED = "failed"
+
+
+@attr.s(auto_attribs=True, frozen=True, slots=True)
+class ScheduledTask:
+ """Description of a scheduled task"""
+
+ # Id used to identify the task
+ id: str
+ # Name of the action to be run by this task
+ action: str
+ # Current status of this task
+ status: TaskStatus
+ # If the status is SCHEDULED then this represents when it should be launched,
+ # otherwise it represents the last time this task got a change of state.
+ # In milliseconds since epoch in system time timezone, usually UTC.
+ timestamp: int
+ # Optionally bind a task to some resource id for easy retrieval
+ resource_id: Optional[str]
+ # Optional parameters that will be passed to the function ran by the task
+ params: Optional[JsonMapping]
+ # Optional result that can be updated by the running task
+ result: Optional[JsonMapping]
+ # Optional error that should be assigned a value when the status is FAILED
+ error: Optional[str]
diff --git a/synapse/util/task_scheduler.py b/synapse/util/task_scheduler.py
new file mode 100644
index 0000000000..773a8327f6
--- /dev/null
+++ b/synapse/util/task_scheduler.py
@@ -0,0 +1,364 @@
+# Copyright 2023 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import logging
+from typing import TYPE_CHECKING, Awaitable, Callable, Dict, List, Optional, Set, Tuple
+
+from prometheus_client import Gauge
+
+from twisted.python.failure import Failure
+
+from synapse.metrics.background_process_metrics import run_as_background_process
+from synapse.types import JsonMapping, ScheduledTask, TaskStatus
+from synapse.util.stringutils import random_string
+
+if TYPE_CHECKING:
+ from synapse.server import HomeServer
+
+logger = logging.getLogger(__name__)
+
+
+running_tasks_gauge = Gauge(
+ "synapse_scheduler_running_tasks",
+ "The number of concurrent running tasks handled by the TaskScheduler",
+)
+
+
+class TaskScheduler:
+ """
+ This is a simple task sheduler aimed at resumable tasks: usually we use `run_in_background`
+ to launch a background task, or Twisted `deferLater` if we want to do so later on.
+
+ The problem with that is that the tasks will just stop and never be resumed if synapse
+ is stopped for whatever reason.
+
+ How this works:
+ - A function mapped to a named action should first be registered with `register_action`.
+ This function will be called when trying to resuming tasks after a synapse shutdown,
+ so this registration should happen when synapse is initialised, NOT right before scheduling
+ a task.
+ - A task can then be launched using this named action with `schedule_task`. A `params` dict
+ can be passed, and it will be available to the registered function when launched. This task
+ can be launch either now-ish, or later on by giving a `timestamp` parameter.
+
+ The function may call `update_task` at any time to update the `result` of the task,
+ and this can be used to resume the task at a specific point and/or to convey a result to
+ the code launching the task.
+ You can also specify the `result` (and/or an `error`) when returning from the function.
+
+ The reconciliation loop runs every 5 mns, so this is not a precise scheduler. When wanting
+ to launch now, the launch will still not happen before the next loop run.
+
+ Tasks will be run on the worker specified with `run_background_tasks_on` config,
+ or the main one by default.
+ There is a limit of 10 concurrent tasks, so tasks may be delayed if the pool is already
+ full. In this regard, please take great care that scheduled tasks can actually finished.
+ For now there is no mechanism to stop a running task if it is stuck.
+ """
+
+ # Precision of the scheduler, evaluation of tasks to run will only happen
+ # every `SCHEDULE_INTERVAL_MS` ms
+ SCHEDULE_INTERVAL_MS = 1 * 60 * 1000 # 1mn
+ # Time before a complete or failed task is deleted from the DB
+ KEEP_TASKS_FOR_MS = 7 * 24 * 60 * 60 * 1000 # 1 week
+ # Maximum number of tasks that can run at the same time
+ MAX_CONCURRENT_RUNNING_TASKS = 10
+ # Time from the last task update after which we will log a warning
+ LAST_UPDATE_BEFORE_WARNING_MS = 24 * 60 * 60 * 1000 # 24hrs
+
+ def __init__(self, hs: "HomeServer"):
+ self._store = hs.get_datastores().main
+ self._clock = hs.get_clock()
+ self._running_tasks: Set[str] = set()
+ # A map between action names and their registered function
+ self._actions: Dict[
+ str,
+ Callable[
+ [ScheduledTask, bool],
+ Awaitable[Tuple[TaskStatus, Optional[JsonMapping], Optional[str]]],
+ ],
+ ] = {}
+ self._run_background_tasks = hs.config.worker.run_background_tasks
+
+ if self._run_background_tasks:
+ self._clock.looping_call(
+ run_as_background_process,
+ TaskScheduler.SCHEDULE_INTERVAL_MS,
+ "handle_scheduled_tasks",
+ self._handle_scheduled_tasks,
+ )
+
+ def register_action(
+ self,
+ function: Callable[
+ [ScheduledTask, bool],
+ Awaitable[Tuple[TaskStatus, Optional[JsonMapping], Optional[str]]],
+ ],
+ action_name: str,
+ ) -> None:
+ """Register a function to be executed when an action is scheduled with
+ the specified action name.
+
+ Actions need to be registered as early as possible so that a resumed action
+ can find its matching function. It's usually better to NOT do that right before
+ calling `schedule_task` but rather in an `__init__` method.
+
+ Args:
+ function: The function to be executed for this action. The parameters
+ passed to the function when launched are the `ScheduledTask` being run,
+ and a `first_launch` boolean to signal if it's a resumed task or the first
+ launch of it. The function should return a tuple of new `status`, `result`
+ and `error` as specified in `ScheduledTask`.
+ action_name: The name of the action to be associated with the function
+ """
+ self._actions[action_name] = function
+
+ async def schedule_task(
+ self,
+ action: str,
+ *,
+ resource_id: Optional[str] = None,
+ timestamp: Optional[int] = None,
+ params: Optional[JsonMapping] = None,
+ ) -> str:
+ """Schedule a new potentially resumable task. A function matching the specified
+ `action` should have been previously registered with `register_action`.
+
+ Args:
+ action: the name of a previously registered action
+ resource_id: a task can be associated with a resource id to facilitate
+ getting all tasks associated with a specific resource
+ timestamp: if `None`, the task will be launched as soon as possible, otherwise it
+ will be launch as soon as possible after the `timestamp` value.
+ Note that this scheduler is not meant to be precise, and the scheduling
+ could be delayed if too many tasks are already running
+ params: a set of parameters that can be easily accessed from inside the
+ executed function
+
+ Returns:
+ The id of the scheduled task
+ """
+ if action not in self._actions:
+ raise Exception(
+ f"No function associated with action {action} of the scheduled task"
+ )
+
+ if timestamp is None or timestamp < self._clock.time_msec():
+ timestamp = self._clock.time_msec()
+
+ task = ScheduledTask(
+ random_string(16),
+ action,
+ TaskStatus.SCHEDULED,
+ timestamp,
+ resource_id,
+ params,
+ result=None,
+ error=None,
+ )
+ await self._store.insert_scheduled_task(task)
+
+ return task.id
+
+ async def update_task(
+ self,
+ id: str,
+ *,
+ timestamp: Optional[int] = None,
+ status: Optional[TaskStatus] = None,
+ result: Optional[JsonMapping] = None,
+ error: Optional[str] = None,
+ ) -> bool:
+ """Update some task associated values. This is exposed publically so it can
+ be used inside task functions, mainly to update the result and be able to
+ resume a task at a specific step after a restart of synapse.
+
+ It can also be used to stage a task, by setting the `status` to `SCHEDULED` with
+ a new timestamp.
+
+ The `status` can only be set to `ACTIVE` or `SCHEDULED`, `COMPLETE` and `FAILED`
+ are terminal status and can only be set by returning it in the function.
+
+ Args:
+ id: the id of the task to update
+ timestamp: useful to schedule a new stage of the task at a later date
+ status: the new `TaskStatus` of the task
+ result: the new result of the task
+ error: the new error of the task
+ """
+ if status == TaskStatus.COMPLETE or status == TaskStatus.FAILED:
+ raise Exception(
+ "update_task can't be called with a FAILED or COMPLETE status"
+ )
+
+ if timestamp is None:
+ timestamp = self._clock.time_msec()
+ return await self._store.update_scheduled_task(
+ id,
+ timestamp,
+ status=status,
+ result=result,
+ error=error,
+ )
+
+ async def get_task(self, id: str) -> Optional[ScheduledTask]:
+ """Get a specific task description by id.
+
+ Args:
+ id: the id of the task to retrieve
+
+ Returns:
+ The task information or `None` if it doesn't exist or it has
+ already been removed because it's too old.
+ """
+ return await self._store.get_scheduled_task(id)
+
+ async def get_tasks(
+ self,
+ *,
+ actions: Optional[List[str]] = None,
+ resource_id: Optional[str] = None,
+ statuses: Optional[List[TaskStatus]] = None,
+ max_timestamp: Optional[int] = None,
+ ) -> List[ScheduledTask]:
+ """Get a list of tasks. Returns all the tasks if no args is provided.
+
+ If an arg is `None` all tasks matching the other args will be selected.
+ If an arg is an empty list, the corresponding value of the task needs
+ to be `None` to be selected.
+
+ Args:
+ actions: Limit the returned tasks to those specific action names
+ resource_id: Limit the returned tasks to the specific resource id, if specified
+ statuses: Limit the returned tasks to the specific statuses
+ max_timestamp: Limit the returned tasks to the ones that have
+ a timestamp inferior to the specified one
+
+ Returns
+ A list of `ScheduledTask`, ordered by increasing timestamps
+ """
+ return await self._store.get_scheduled_tasks(
+ actions=actions,
+ resource_id=resource_id,
+ statuses=statuses,
+ max_timestamp=max_timestamp,
+ )
+
+ async def delete_task(self, id: str) -> None:
+ """Delete a task. Running tasks can't be deleted.
+
+ Can only be called from the worker handling the task scheduling.
+
+ Args:
+ id: id of the task to delete
+ """
+ if self.task_is_running(id):
+ raise Exception(f"Task {id} is currently running and can't be deleted")
+ await self._store.delete_scheduled_task(id)
+
+ def task_is_running(self, id: str) -> bool:
+ """Check if a task is currently running.
+
+ Can only be called from the worker handling the task scheduling.
+
+ Args:
+ id: id of the task to check
+ """
+ assert self._run_background_tasks
+ return id in self._running_tasks
+
+ async def _handle_scheduled_tasks(self) -> None:
+ """Main loop taking care of launching tasks and cleaning up old ones."""
+ await self._launch_scheduled_tasks()
+ await self._clean_scheduled_tasks()
+
+ async def _launch_scheduled_tasks(self) -> None:
+ """Retrieve and launch scheduled tasks that should be running at that time."""
+ for task in await self.get_tasks(statuses=[TaskStatus.ACTIVE]):
+ if not self.task_is_running(task.id):
+ if (
+ len(self._running_tasks)
+ < TaskScheduler.MAX_CONCURRENT_RUNNING_TASKS
+ ):
+ await self._launch_task(task, first_launch=False)
+ else:
+ if (
+ self._clock.time_msec()
+ > task.timestamp + TaskScheduler.LAST_UPDATE_BEFORE_WARNING_MS
+ ):
+ logger.warn(
+ f"Task {task.id} (action {task.action}) has seen no update for more than 24h and may be stuck"
+ )
+ for task in await self.get_tasks(
+ statuses=[TaskStatus.SCHEDULED], max_timestamp=self._clock.time_msec()
+ ):
+ if (
+ not self.task_is_running(task.id)
+ and len(self._running_tasks)
+ < TaskScheduler.MAX_CONCURRENT_RUNNING_TASKS
+ ):
+ await self._launch_task(task, first_launch=True)
+
+ running_tasks_gauge.set(len(self._running_tasks))
+
+ async def _clean_scheduled_tasks(self) -> None:
+ """Clean old complete or failed jobs to avoid clutter the DB."""
+ for task in await self._store.get_scheduled_tasks(
+ statuses=[TaskStatus.FAILED, TaskStatus.COMPLETE]
+ ):
+ # FAILED and COMPLETE tasks should never be running
+ assert not self.task_is_running(task.id)
+ if (
+ self._clock.time_msec()
+ > task.timestamp + TaskScheduler.KEEP_TASKS_FOR_MS
+ ):
+ await self._store.delete_scheduled_task(task.id)
+
+ async def _launch_task(self, task: ScheduledTask, first_launch: bool) -> None:
+ """Launch a scheduled task now.
+
+ Args:
+ task: the task to launch
+ first_launch: `True` if it's the first time is launched, `False` otherwise
+ """
+ assert task.action in self._actions
+
+ function = self._actions[task.action]
+
+ async def wrapper() -> None:
+ try:
+ (status, result, error) = await function(task, first_launch)
+ except Exception:
+ f = Failure()
+ logger.error(
+ f"scheduled task {task.id} failed",
+ exc_info=(f.type, f.value, f.getTracebackObject()),
+ )
+ status = TaskStatus.FAILED
+ result = None
+ error = f.getErrorMessage()
+
+ await self._store.update_scheduled_task(
+ task.id,
+ self._clock.time_msec(),
+ status=status,
+ result=result,
+ error=error,
+ )
+ self._running_tasks.remove(task.id)
+
+ self._running_tasks.add(task.id)
+ await self.update_task(task.id, status=TaskStatus.ACTIVE)
+ description = f"{task.id}-{task.action}"
+ run_as_background_process(description, wrapper)
diff --git a/tests/util/test_task_scheduler.py b/tests/util/test_task_scheduler.py
new file mode 100644
index 0000000000..3a97559bf0
--- /dev/null
+++ b/tests/util/test_task_scheduler.py
@@ -0,0 +1,186 @@
+# Copyright 2023 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from typing import Optional, Tuple
+
+from twisted.internet.task import deferLater
+from twisted.test.proto_helpers import MemoryReactor
+
+from synapse.server import HomeServer
+from synapse.types import JsonMapping, ScheduledTask, TaskStatus
+from synapse.util import Clock
+from synapse.util.task_scheduler import TaskScheduler
+
+from tests import unittest
+
+
+class TestTaskScheduler(unittest.HomeserverTestCase):
+ def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
+ self.task_scheduler = hs.get_task_scheduler()
+ self.task_scheduler.register_action(self._test_task, "_test_task")
+ self.task_scheduler.register_action(self._sleeping_task, "_sleeping_task")
+ self.task_scheduler.register_action(self._raising_task, "_raising_task")
+ self.task_scheduler.register_action(self._resumable_task, "_resumable_task")
+
+ async def _test_task(
+ self, task: ScheduledTask, first_launch: bool
+ ) -> Tuple[TaskStatus, Optional[JsonMapping], Optional[str]]:
+ # This test task will copy the parameters to the result
+ result = None
+ if task.params:
+ result = task.params
+ return (TaskStatus.COMPLETE, result, None)
+
+ def test_schedule_task(self) -> None:
+ """Schedule a task in the future with some parameters to be copied as a result and check it executed correctly.
+ Also check that it get removed after `KEEP_TASKS_FOR_MS`."""
+ timestamp = self.clock.time_msec() + 30 * 1000
+ task_id = self.get_success(
+ self.task_scheduler.schedule_task(
+ "_test_task",
+ timestamp=timestamp,
+ params={"val": 1},
+ )
+ )
+
+ task = self.get_success(self.task_scheduler.get_task(task_id))
+ assert task is not None
+ self.assertEqual(task.status, TaskStatus.SCHEDULED)
+ self.assertIsNone(task.result)
+
+ # The timestamp being 30s after now the task should been executed
+ # after the first scheduling loop is run
+ self.reactor.advance(TaskScheduler.SCHEDULE_INTERVAL_MS / 1000)
+
+ task = self.get_success(self.task_scheduler.get_task(task_id))
+ assert task is not None
+ self.assertEqual(task.status, TaskStatus.COMPLETE)
+ assert task.result is not None
+ # The passed parameter should have been copied to the result
+ self.assertTrue(task.result.get("val") == 1)
+
+ # Let's wait for the complete task to be deleted and hence unavailable
+ self.reactor.advance((TaskScheduler.KEEP_TASKS_FOR_MS / 1000) + 1)
+
+ task = self.get_success(self.task_scheduler.get_task(task_id))
+ self.assertIsNone(task)
+
+ async def _sleeping_task(
+ self, task: ScheduledTask, first_launch: bool
+ ) -> Tuple[TaskStatus, Optional[JsonMapping], Optional[str]]:
+ # Sleep for a second
+ await deferLater(self.reactor, 1, lambda: None)
+ return TaskStatus.COMPLETE, None, None
+
+ def test_schedule_lot_of_tasks(self) -> None:
+ """Schedule more than `TaskScheduler.MAX_CONCURRENT_RUNNING_TASKS` tasks and check the behavior."""
+ timestamp = self.clock.time_msec() + 30 * 1000
+ task_ids = []
+ for i in range(TaskScheduler.MAX_CONCURRENT_RUNNING_TASKS + 1):
+ task_ids.append(
+ self.get_success(
+ self.task_scheduler.schedule_task(
+ "_sleeping_task",
+ timestamp=timestamp,
+ params={"val": i},
+ )
+ )
+ )
+
+ # The timestamp being 30s after now the task should been executed
+ # after the first scheduling loop is run
+ self.reactor.advance((TaskScheduler.SCHEDULE_INTERVAL_MS / 1000))
+
+ # This is to give the time to the sleeping tasks to finish
+ self.reactor.advance(1)
+
+ # Check that only MAX_CONCURRENT_RUNNING_TASKS tasks has run and that one
+ # is still scheduled.
+ tasks = [
+ self.get_success(self.task_scheduler.get_task(task_id))
+ for task_id in task_ids
+ ]
+
+ self.assertEquals(
+ len(
+ [t for t in tasks if t is not None and t.status == TaskStatus.COMPLETE]
+ ),
+ TaskScheduler.MAX_CONCURRENT_RUNNING_TASKS,
+ )
+
+ scheduled_tasks = [
+ t for t in tasks if t is not None and t.status == TaskStatus.SCHEDULED
+ ]
+ self.assertEquals(len(scheduled_tasks), 1)
+
+ self.reactor.advance((TaskScheduler.SCHEDULE_INTERVAL_MS / 1000))
+ self.reactor.advance(1)
+
+ # Check that the last task has been properly executed after the next scheduler loop run
+ prev_scheduled_task = self.get_success(
+ self.task_scheduler.get_task(scheduled_tasks[0].id)
+ )
+ assert prev_scheduled_task is not None
+ self.assertEquals(
+ prev_scheduled_task.status,
+ TaskStatus.COMPLETE,
+ )
+
+ async def _raising_task(
+ self, task: ScheduledTask, first_launch: bool
+ ) -> Tuple[TaskStatus, Optional[JsonMapping], Optional[str]]:
+ raise Exception("raising")
+
+ def test_schedule_raising_task(self) -> None:
+ """Schedule a task raising an exception and check it runs to failure and report exception content."""
+ task_id = self.get_success(self.task_scheduler.schedule_task("_raising_task"))
+
+ self.reactor.advance((TaskScheduler.SCHEDULE_INTERVAL_MS / 1000))
+
+ task = self.get_success(self.task_scheduler.get_task(task_id))
+ assert task is not None
+ self.assertEqual(task.status, TaskStatus.FAILED)
+ self.assertEqual(task.error, "raising")
+
+ async def _resumable_task(
+ self, task: ScheduledTask, first_launch: bool
+ ) -> Tuple[TaskStatus, Optional[JsonMapping], Optional[str]]:
+ if task.result and "in_progress" in task.result:
+ return TaskStatus.COMPLETE, {"success": True}, None
+ else:
+ await self.task_scheduler.update_task(task.id, result={"in_progress": True})
+ # Await forever to simulate an aborted task because of a restart
+ await deferLater(self.reactor, 2**16, lambda: None)
+ # This should never been called
+ return TaskStatus.ACTIVE, None, None
+
+ def test_schedule_resumable_task(self) -> None:
+ """Schedule a resumable task and check that it gets properly resumed and complete after simulating a synapse restart."""
+ task_id = self.get_success(self.task_scheduler.schedule_task("_resumable_task"))
+
+ self.reactor.advance((TaskScheduler.SCHEDULE_INTERVAL_MS / 1000))
+
+ task = self.get_success(self.task_scheduler.get_task(task_id))
+ assert task is not None
+ self.assertEqual(task.status, TaskStatus.ACTIVE)
+
+ # Simulate a synapse restart by emptying the list of running tasks
+ self.task_scheduler._running_tasks = set()
+ self.reactor.advance((TaskScheduler.SCHEDULE_INTERVAL_MS / 1000))
+
+ task = self.get_success(self.task_scheduler.get_task(task_id))
+ assert task is not None
+ self.assertEqual(task.status, TaskStatus.COMPLETE)
+ assert task.result is not None
+ self.assertTrue(task.result.get("success"))
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