Temporarily reduce scheduled task load

- reduce hardcoded task parallelism
- add hardcoded post task sleep

Author: Fizzadar

synapse/util/task_scheduler.py

@@ -100,12 +100,14 @@ class TaskScheduler:
     # 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 = 5
+    MAX_CONCURRENT_RUNNING_TASKS = 1  # Beep: temporarily changed from 5
     # Time from the last task update after which we will log a warning
     LAST_UPDATE_BEFORE_WARNING_MS = 24 * 60 * 60 * 1000  # 24hrs
     # Report a running task's status and usage every so often.
     OCCASIONAL_REPORT_INTERVAL_MS = 5 * 60 * 1000  # 5 minutes
 
+    SLEEP_AFTER_TASK_S = 1
+
     def __init__(self, hs: "HomeServer"):
         self._hs = hs
         self.server_name = (
@@ -456,6 +458,10 @@ async def wrapper() -> None:
                     result = None
                     error = f.getErrorMessage()
 
+                # Beep: sleep before we remove/complete the running task
+                if TaskScheduler.SLEEP_AFTER_TASK_S > 0:
+                    await self._clock.sleep(TaskScheduler.SLEEP_AFTER_TASK_S)
+
                 await self._store.update_scheduled_task(
                     task.id,
                     self._clock.time_msec(),