Implements a task scheduler for resumable potentially long running tasks (#15891)

Author: Mathieu Velten

changelog.d/15891.feature

@@ -0,0 +1 @@
+Implements a task scheduler for	resumable potentially long running tasks.

synapse/app/generic_worker.py

@@ -91,6 +91,7 @@
 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.

synapse/server.py

@@ -142,6 +142,7 @@
 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 @@ def setup_background_tasks(self) -> None:
         """
         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 @@ def get_common_usage_metrics_manager(self) -> CommonUsageMetricsManager:
         """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)

synapse/storage/databases/main/__init__.py

@@ -70,6 +70,7 @@
 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,

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",
+        )

synapse/storage/schema/__init__.py

@@ -113,6 +113,7 @@
 
 Changes in SCHEMA_VERSION = 80
     - The event_txn_id_device_id is always written to for new events.
+    - Add tables for the task scheduler.
 """
 
 

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);

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]