Allow background tasks to be run on a separate worker.

changelog.d/8369.feature

@@ -0,0 +1 @@
+Allow running background tasks in a separate worker process.

synapse/app/generic_worker.py

@@ -885,6 +885,7 @@ def start(config_options):
     # For backwards compatibility let any of the old app names.
     assert config.worker_app in (
         "synapse.app.appservice",
+        "synapse.app.background_worker",
         "synapse.app.client_reader",
         "synapse.app.event_creator",
         "synapse.app.federation_reader",
@@ -961,6 +962,22 @@ def start(config_options):
         # For other worker types we force this to off.
         config.worker.send_federation = False
 
+    if config.worker_app == "synapse.app.background_worker":
+        if config.worker.run_background_tasks:
+            sys.stderr.write(
+                "\nThe run_background_tasks must be disabled in the main synapse process"
+                "\nbefore they can be run in a separate worker."
+                "\nPlease add ``run_background_tasks: false`` to the main config"
+                "\n"
+            )
+            sys.exit(1)
+
+            # Force the background tasks to start since they will be disabled in the main config
+            config.worker.run_background_tasks = True
+        else:
+            # For other worker types we force this to off.
+            config.worker.run_background_tasks = False
+
     synapse.events.USE_FROZEN_DICTS = config.use_frozen_dicts
 
     hs = GenericWorkerServer(

synapse/app/homeserver.py

@@ -620,16 +620,18 @@ def generate_user_daily_visit_stats():
     # Rather than update on per session basis, batch up the requests.
     # If you increase the loop period, the accuracy of user_daily_visits
     # table will decrease
-    clock.looping_call(generate_user_daily_visit_stats, 5 * 60 * 1000)
+    if hs.config.run_background_tasks:
+        clock.looping_call(generate_user_daily_visit_stats, 5 * 60 * 1000)
 
     # monthly active user limiting functionality
     def reap_monthly_active_users():
         return run_as_background_process(
             "reap_monthly_active_users", hs.get_datastore().reap_monthly_active_users
         )
 
-    clock.looping_call(reap_monthly_active_users, 1000 * 60 * 60)
-    reap_monthly_active_users()
+    if hs.config.run_background_tasks:
+        clock.looping_call(reap_monthly_active_users, 1000 * 60 * 60)
+        reap_monthly_active_users()
 
     async def generate_monthly_active_users():
         current_mau_count = 0
@@ -656,11 +658,13 @@ def start_generate_monthly_active_users():
         )
 
     start_generate_monthly_active_users()
-    if hs.config.limit_usage_by_mau or hs.config.mau_stats_only:
+    if hs.config.run_background_tasks and (
+        hs.config.limit_usage_by_mau or hs.config.mau_stats_only
+    ):
         clock.looping_call(start_generate_monthly_active_users, 5 * 60 * 1000)
     # End of monthly active user settings
 
-    if hs.config.report_stats:
+    if hs.config.run_background_tasks and hs.config.report_stats:
         logger.info("Scheduling stats reporting for 3 hour intervals")
         clock.looping_call(start_phone_stats_home, 3 * 60 * 60 * 1000)
 

synapse/config/workers.py

@@ -132,6 +132,16 @@ def read_config(self, config, **kwargs):
 
         self.events_shard_config = ShardedWorkerHandlingConfig(self.writers.events)
 
+        # Whether this worker should run background tasks or not.
+        #
+        # As a note for developers, the background tasks guarded by this should
+        # be able to run on only a single instance (meaning that they don't
+        # depend on any in-memory state of a particular worker).
+        #
+        # Effort is not made to ensure only a single instance of these tasks is
+        # running.
+        self.run_background_tasks = config.get("run_background_tasks", True)
+
     def generate_config_section(self, config_dir_path, server_name, **kwargs):
         return """\
         ## Workers ##

synapse/handlers/account_validity.py

@@ -42,6 +42,7 @@ def __init__(self, hs):
         if (
             self._account_validity.enabled
             and self._account_validity.renew_by_email_enabled
+            and hs.config.run_background_tasks
         ):
             # Don't do email-specific configuration if renewal by email is disabled.
             self._template_html = self.config.account_validity_template_html

synapse/handlers/auth.py

@@ -203,7 +203,7 @@ def __init__(self, hs):
         self._clock = self.hs.get_clock()
 
         # Expire old UI auth sessions after a period of time.
-        if hs.config.worker_app is None:
+        if hs.config.run_background_tasks:
             self._clock.looping_call(
                 run_as_background_process,
                 5 * 60 * 1000,

synapse/handlers/deactivate_account.py

@@ -42,7 +42,7 @@ def __init__(self, hs):
 
         # Start the user parter loop so it can resume parting users from rooms where
         # it left off (if it has work left to do).
-        if hs.config.worker_app is None:
+        if hs.config.run_background_tasks:
             hs.get_reactor().callWhenRunning(self._start_user_parting)
 
         self._account_validity_enabled = hs.config.account_validity.enabled

synapse/handlers/device.py

@@ -522,12 +522,13 @@ def __init__(self, hs, device_handler):
 
         # Attempt to resync out of sync device lists every 30s.
         self._resync_retry_in_progress = False
-        self.clock.looping_call(
-            run_as_background_process,
-            30 * 1000,
-            func=self._maybe_retry_device_resync,
-            desc="_maybe_retry_device_resync",
-        )
+        if hs.config.run_background_tasks:
+            self.clock.looping_call(
+                run_as_background_process,
+                30 * 1000,
+                func=self._maybe_retry_device_resync,
+                desc="_maybe_retry_device_resync",
+            )
 
     @trace
     async def incoming_device_list_update(self, origin, edu_content):

synapse/handlers/message.py

@@ -413,7 +413,7 @@ def __init__(self, hs: "HomeServer"):
             self._consent_uri_builder = ConsentURIBuilder(self.config)
 
         if (
-            not self.config.worker_app
+            self.config.run_background_tasks
             and self.config.cleanup_extremities_with_dummy_events
         ):
             self.clock.looping_call(

synapse/handlers/pagination.py

@@ -92,7 +92,7 @@ def __init__(self, hs: "HomeServer"):
         self._retention_allowed_lifetime_min = hs.config.retention_allowed_lifetime_min
         self._retention_allowed_lifetime_max = hs.config.retention_allowed_lifetime_max
 
-        if hs.config.retention_enabled:
+        if hs.config.run_background_tasks and hs.config.retention_enabled:
             # Run the purge jobs described in the configuration file.
             for job in hs.config.retention_purge_jobs:
                 logger.info("Setting up purge job with config: %s", job)

synapse/handlers/profile.py

@@ -371,11 +371,10 @@ class MasterProfileHandler(BaseProfileHandler):
     def __init__(self, hs):
         super().__init__(hs)
 
-        assert hs.config.worker_app is None
-
-        self.clock.looping_call(
-            self._start_update_remote_profile_cache, self.PROFILE_UPDATE_MS
-        )
+        if hs.config.run_background_tasks:
+            self.clock.looping_call(
+                self._start_update_remote_profile_cache, self.PROFILE_UPDATE_MS
+            )
 
     def _start_update_remote_profile_cache(self):
         return run_as_background_process(

synapse/handlers/stats.py

@@ -49,7 +49,7 @@ def __init__(self, hs):
         # Guard to ensure we only process deltas one at a time
         self._is_processing = False
 
-        if hs.config.stats_enabled:
+        if self.stats_enabled and hs.config.run_background_tasks:
             self.notifier.add_replication_callback(self.notify_new_event)
 
             # We kick this off so that we don't have to wait for a change before

synapse/storage/databases/main/censor_events.py

@@ -40,7 +40,10 @@ def _censor_redactions():
                 "_censor_redactions", self._censor_redactions
             )
 
-        if self.hs.config.redaction_retention_period is not None:
+        if (
+            self.hs.config.run_background_tasks
+            and self.hs.config.redaction_retention_period is not None
+        ):
             hs.get_clock().looping_call(_censor_redactions, 5 * 60 * 1000)
 
     async def _censor_redactions(self):

synapse/storage/databases/main/client_ips.py

@@ -372,7 +372,7 @@ def __init__(self, database: DatabasePool, db_conn, hs):
             "before", "shutdown", self._update_client_ips_batch
         )
 
-        if self.user_ips_max_age:
+        if hs.config.run_background_tasks and self.user_ips_max_age:
             self._clock.looping_call(self._prune_old_user_ips, 5 * 1000)
 
     async def insert_client_ip(

synapse/storage/databases/main/devices.py

@@ -834,7 +834,10 @@ def __init__(self, database: DatabasePool, db_conn, hs):
             name="device_id_exists", keylen=2, max_entries=10000
         )
 
-        self._clock.looping_call(self._prune_old_outbound_device_pokes, 60 * 60 * 1000)
+        if hs.config.run_background_tasks:
+            self._clock.looping_call(
+                self._prune_old_outbound_device_pokes, 60 * 60 * 1000
+            )
 
     async def store_device(
         self, user_id: str, device_id: str, initial_device_display_name: str

synapse/storage/databases/main/event_federation.py

@@ -606,9 +606,10 @@ def __init__(self, database: DatabasePool, db_conn, hs):
             self.EVENT_AUTH_STATE_ONLY, self._background_delete_non_state_event_auth
         )
 
-        hs.get_clock().looping_call(
-            self._delete_old_forward_extrem_cache, 60 * 60 * 1000
-        )
+        if hs.config.run_background_tasks:
+            hs.get_clock().looping_call(
+                self._delete_old_forward_extrem_cache, 60 * 60 * 1000
+            )
 
     def _delete_old_forward_extrem_cache(self):
         def _delete_old_forward_extrem_cache_txn(txn):

synapse/storage/databases/main/event_push_actions.py

@@ -679,9 +679,10 @@ def __init__(self, database: DatabasePool, db_conn, hs):
         )
 
         self._doing_notif_rotation = False
-        self._rotate_notif_loop = self._clock.looping_call(
-            self._start_rotate_notifs, 30 * 60 * 1000
-        )
+        if hs.config.run_background_tasks:
+            self._rotate_notif_loop = self._clock.looping_call(
+                self._start_rotate_notifs, 30 * 60 * 1000
+            )
 
     async def get_push_actions_for_user(
         self, user_id, before=None, limit=50, only_highlight=False
@@ -741,7 +742,7 @@ def _remove_old_push_actions_before_txn(
         users can still get a list of recent highlights.
 
         Args:
-            txn: The transcation
+            txn: The transaction
             room_id: Room ID to delete from
             user_id: user ID to delete for
             stream_ordering: The lowest stream ordering which will

synapse/storage/databases/main/metrics.py

@@ -52,7 +52,8 @@ def read_forward_extremities():
                 "read_forward_extremities", self._read_forward_extremities
             )
 
-        hs.get_clock().looping_call(read_forward_extremities, 60 * 60 * 1000)
+        if hs.config.run_background_tasks:
+            hs.get_clock().looping_call(read_forward_extremities, 60 * 60 * 1000)
 
     async def _read_forward_extremities(self):
         def fetch(txn):

synapse/storage/databases/main/registration.py

@@ -914,7 +914,8 @@ def start_cull():
                 self.cull_expired_threepid_validation_tokens,
             )
 
-        hs.get_clock().looping_call(start_cull, THIRTY_MINUTES_IN_MS)
+        if hs.config.run_background_tasks:
+            hs.get_clock().looping_call(start_cull, THIRTY_MINUTES_IN_MS)
 
     async def add_access_token_to_user(
         self,

synapse/storage/databases/main/roommember.py

@@ -69,7 +69,10 @@ def __init__(self, database: DatabasePool, db_conn, hs):
         self._check_safe_current_state_events_membership_updated_txn(txn)
         txn.close()
 
-        if self.hs.config.metrics_flags.known_servers:
+        if (
+            self.hs.config.run_background_tasks
+            and self.hs.config.metrics_flags.known_servers
+        ):
             self._known_servers_count = 1
             self.hs.get_clock().looping_call(
                 run_as_background_process,

synapse/storage/databases/main/transactions.py

@@ -50,7 +50,8 @@ class TransactionStore(SQLBaseStore):
     def __init__(self, database: DatabasePool, db_conn, hs):
         super().__init__(database, db_conn, hs)
 
-        self._clock.looping_call(self._start_cleanup_transactions, 30 * 60 * 1000)
+        if hs.config.run_background_tasks:
+            self._clock.looping_call(self._start_cleanup_transactions, 30 * 60 * 1000)
 
         self._destination_retry_cache = ExpiringCache(
             cache_name="get_destination_retry_timings",