Add changelog

changelog.d/18944.misc

@@ -0,0 +1 @@
+Introduce `Clock.call_when_running(...)` to wrap startup code in a logcontext, ensuring we can identify which server generated the logs.

changelog.d/18945.misc

@@ -0,0 +1 @@
+Introduce `Clock.add_system_event_trigger(...)` to wrap system event callback code in a logcontext, ensuring we can identify which server generated the logs.

scripts-dev/mypy_synapse_plugin.py

@@ -68,6 +68,18 @@ PROMETHEUS_METRIC_MISSING_FROM_LIST_TO_CHECK = ErrorCode(
     category="per-homeserver-tenant-metrics",
 )
 
+PREFER_SYNAPSE_CLOCK_CALL_WHEN_RUNNING = ErrorCode(
+    "prefer-synapse-clock-call-when-running",
+    "`synapse.util.Clock.call_when_running` should be used instead of `reactor.callWhenRunning`",
+    category="synapse-reactor-clock",
+)
+
+PREFER_SYNAPSE_CLOCK_ADD_SYSTEM_EVENT_TRIGGER = ErrorCode(
+    "prefer-synapse-clock-add-system-event-trigger",
+    "`synapse.util.Clock.add_system_event_trigger` should be used instead of `reactor.addSystemEventTrigger`",
+    category="synapse-reactor-clock",
+)
+
 
 class Sentinel(enum.Enum):
     # defining a sentinel in this way allows mypy to correctly handle the
@@ -229,9 +241,77 @@ class SynapsePlugin(Plugin):
         ):
             return check_is_cacheable_wrapper
 
+        if fullname in (
+            "twisted.internet.interfaces.IReactorCore.callWhenRunning",
+            "synapse.types.ISynapseThreadlessReactor.callWhenRunning",
+            "synapse.types.ISynapseReactor.callWhenRunning",
+        ):
+            return check_call_when_running
+
+        if fullname in (
+            "twisted.internet.interfaces.IReactorCore.addSystemEventTrigger",
+            "synapse.types.ISynapseThreadlessReactor.addSystemEventTrigger",
+            "synapse.types.ISynapseReactor.addSystemEventTrigger",
+        ):
+            return check_add_system_event_trigger
+
         return None
 
 
+def check_call_when_running(ctx: MethodSigContext) -> CallableType:
+    """
+    Ensure that the `reactor.callWhenRunning` callsites aren't used.
+
+    `synapse.util.Clock.call_when_running` should always be used instead of
+    `reactor.callWhenRunning`.
+
+    Since `reactor.callWhenRunning` is a reactor callback, the callback will start out
+    with the sentinel logcontext. `synapse.util.Clock` starts a default logcontext as we
+    want to know which server the logs came from.
+
+    Args:
+        ctx: The `FunctionSigContext` from mypy.
+    """
+    signature: CallableType = ctx.default_signature
+    ctx.api.fail(
+        (
+            "Expected all `reactor.callWhenRunning` calls to use `synapse.util.Clock.call_when_running` instead. "
+            "This is so all Synapse code runs with a logcontext as we want to know which server the logs came from."
+        ),
+        ctx.context,
+        code=PREFER_SYNAPSE_CLOCK_CALL_WHEN_RUNNING,
+    )
+
+    return signature
+
+
+def check_add_system_event_trigger(ctx: MethodSigContext) -> CallableType:
+    """
+    Ensure that the `reactor.addSystemEventTrigger` callsites aren't used.
+
+    `synapse.util.Clock.add_system_event_trigger` should always be used instead of
+    `reactor.addSystemEventTrigger`.
+
+    Since `reactor.addSystemEventTrigger` is a reactor callback, the callback will start out
+    with the sentinel logcontext. `synapse.util.Clock` starts a default logcontext as we
+    want to know which server the logs came from.
+
+    Args:
+        ctx: The `FunctionSigContext` from mypy.
+    """
+    signature: CallableType = ctx.default_signature
+    ctx.api.fail(
+        (
+            "Expected all `reactor.addSystemEventTrigger` calls to use `synapse.util.Clock.add_system_event_trigger` instead. "
+            "This is so all Synapse code runs with a logcontext as we want to know which server the logs came from."
+        ),
+        ctx.context,
+        code=PREFER_SYNAPSE_CLOCK_ADD_SYSTEM_EVENT_TRIGGER,
+    )
+
+    return signature
+
+
 def analyze_prometheus_metric_classes(ctx: ClassDefContext) -> None:
     """
     Cross-check the list of Prometheus metric classes against the

scripts-dev/sign_json.py

@@ -30,7 +30,7 @@ from signedjson.sign import sign_json
 
 from synapse.api.room_versions import KNOWN_ROOM_VERSIONS
 from synapse.crypto.event_signing import add_hashes_and_signatures
-from synapse.util import json_encoder
+from synapse.util.json import json_encoder
 
 
 def main() -> None:

synapse/_scripts/synapse_port_db.py

@@ -54,11 +54,11 @@ from twisted.internet import defer, reactor as reactor_
 from synapse.config.database import DatabaseConnectionConfig
 from synapse.config.homeserver import HomeServerConfig
 from synapse.logging.context import (
-    LoggingContext,
     make_deferred_yieldable,
     run_in_background,
 )
-from synapse.notifier import ReplicationNotifier
+from synapse.server import HomeServer
+from synapse.storage import DataStore
 from synapse.storage.database import DatabasePool, LoggingTransaction, make_conn
 from synapse.storage.databases.main import FilteringWorkerStore
 from synapse.storage.databases.main.account_data import AccountDataWorkerStore
@@ -98,8 +98,7 @@ from synapse.storage.databases.state.bg_updates import StateBackgroundUpdateStor
 from synapse.storage.engines import create_engine
 from synapse.storage.prepare_database import prepare_database
 from synapse.types import ISynapseReactor
-from synapse.util import SYNAPSE_VERSION, Clock
-from synapse.util.stringutils import random_string
+from synapse.util import SYNAPSE_VERSION
 
 # Cast safety: Twisted does some naughty magic which replaces the
 # twisted.internet.reactor module with a Reactor instance at runtime.
@@ -318,31 +317,16 @@ class Store(
         )
 
 
-class MockHomeserver:
+class MockHomeserver(HomeServer):
+    DATASTORE_CLASS = DataStore
+
     def __init__(self, config: HomeServerConfig):
-        self.clock = Clock(reactor)
-        self.config = config
-        self.hostname = config.server.server_name
-        self.version_string = SYNAPSE_VERSION
-        self.instance_id = random_string(5)
-
-    def get_clock(self) -> Clock:
-        return self.clock
-
-    def get_reactor(self) -> ISynapseReactor:
-        return reactor
-
-    def get_instance_id(self) -> str:
-        return self.instance_id
-
-    def get_instance_name(self) -> str:
-        return "master"
-
-    def should_send_federation(self) -> bool:
-        return False
-
-    def get_replication_notifier(self) -> ReplicationNotifier:
-        return ReplicationNotifier()
+        super().__init__(
+            hostname=config.server.server_name,
+            config=config,
+            reactor=reactor,
+            version_string=f"Synapse/{SYNAPSE_VERSION}",
+        )
 
 
 class Porter:
@@ -351,12 +335,12 @@ class Porter:
         sqlite_config: Dict[str, Any],
         progress: "Progress",
         batch_size: int,
-        hs_config: HomeServerConfig,
+        hs: HomeServer,
     ):
         self.sqlite_config = sqlite_config
         self.progress = progress
         self.batch_size = batch_size
-        self.hs_config = hs_config
+        self.hs = hs
 
     async def setup_table(self, table: str) -> Tuple[str, int, int, int, int]:
         if table in APPEND_ONLY_TABLES:
@@ -676,8 +660,7 @@ class Porter:
 
         engine = create_engine(db_config.config)
 
-        hs = MockHomeserver(self.hs_config)
-        server_name = hs.hostname
+        server_name = self.hs.hostname
 
         with make_conn(
             db_config=db_config,
@@ -688,16 +671,16 @@ class Porter:
             engine.check_database(
                 db_conn, allow_outdated_version=allow_outdated_version
             )
-            prepare_database(db_conn, engine, config=self.hs_config)
+            prepare_database(db_conn, engine, config=self.hs.config)
             # Type safety: ignore that we're using Mock homeservers here.
             store = Store(
                 DatabasePool(
-                    hs,  # type: ignore[arg-type]
+                    self.hs,
                     db_config,
                     engine,
                 ),
                 db_conn,
-                hs,  # type: ignore[arg-type]
+                self.hs,
             )
             db_conn.commit()
 
@@ -795,7 +778,7 @@ class Porter:
                 return
 
             self.postgres_store = self.build_db_store(
-                self.hs_config.database.get_single_database()
+                self.hs.config.database.get_single_database()
             )
 
             await self.remove_ignored_background_updates_from_database()
@@ -1584,6 +1567,8 @@ def main() -> None:
     config = HomeServerConfig()
     config.parse_config_dict(hs_config, "", "")
 
+    hs = MockHomeserver(config)
+
     def start(stdscr: Optional["curses.window"] = None) -> None:
         progress: Progress
         if stdscr:
@@ -1595,15 +1580,14 @@ def main() -> None:
             sqlite_config=sqlite_config,
             progress=progress,
             batch_size=args.batch_size,
-            hs_config=config,
+            hs=hs,
         )
 
         @defer.inlineCallbacks
         def run() -> Generator["defer.Deferred[Any]", Any, None]:
-            with LoggingContext("synapse_port_db_run"):
-                yield defer.ensureDeferred(porter.run())
+            yield defer.ensureDeferred(porter.run())
 
-        reactor.callWhenRunning(run)
+        hs.get_clock().call_when_running(run)
 
         reactor.run()
 

synapse/_scripts/update_synapse_database.py

@@ -74,7 +74,7 @@ def run_background_updates(hs: HomeServer) -> None:
             )
         )
 
-    reactor.callWhenRunning(run)
+    hs.get_clock().call_when_running(run)
 
     reactor.run()
 

synapse/api/auth/mas.py

@@ -43,9 +43,9 @@ from synapse.logging.opentracing import (
 from synapse.metrics import SERVER_NAME_LABEL
 from synapse.synapse_rust.http_client import HttpClient
 from synapse.types import JsonDict, Requester, UserID, create_requester
-from synapse.util import json_decoder
 from synapse.util.caches.cached_call import RetryOnExceptionCachedCall
 from synapse.util.caches.response_cache import ResponseCache, ResponseCacheContext
+from synapse.util.json import json_decoder
 
 from . import introspection_response_timer
 

synapse/api/auth/msc3861_delegated.py

@@ -48,9 +48,9 @@ from synapse.logging.opentracing import (
 from synapse.metrics import SERVER_NAME_LABEL
 from synapse.synapse_rust.http_client import HttpClient
 from synapse.types import Requester, UserID, create_requester
-from synapse.util import json_decoder
 from synapse.util.caches.cached_call import RetryOnExceptionCachedCall
 from synapse.util.caches.response_cache import ResponseCache, ResponseCacheContext
+from synapse.util.json import json_decoder
 
 from . import introspection_response_timer
 

synapse/api/errors.py

@@ -30,7 +30,7 @@ from typing import Any, Dict, List, Optional, Union
 
 from twisted.web import http
 
-from synapse.util import json_decoder
+from synapse.util.json import json_decoder
 
 if typing.TYPE_CHECKING:
     from synapse.config.homeserver import HomeServerConfig

synapse/api/ratelimiting.py

@@ -26,7 +26,7 @@ from synapse.api.errors import LimitExceededError
 from synapse.config.ratelimiting import RatelimitSettings
 from synapse.storage.databases.main import DataStore
 from synapse.types import Requester
-from synapse.util import Clock
+from synapse.util.clock import Clock
 
 if TYPE_CHECKING:
     # To avoid circular imports:

synapse/app/_base.py

@@ -241,7 +241,7 @@ def redirect_stdio_to_logs() -> None:
 
 
 def register_start(
-    cb: Callable[P, Awaitable], *args: P.args, **kwargs: P.kwargs
+    hs: "HomeServer", cb: Callable[P, Awaitable], *args: P.args, **kwargs: P.kwargs
 ) -> None:
     """Register a callback with the reactor, to be called once it is running
 
@@ -278,7 +278,8 @@ def register_start(
             # on as normal.
             os._exit(1)
 
-    reactor.callWhenRunning(lambda: defer.ensureDeferred(wrapper()))
+    clock = hs.get_clock()
+    clock.call_when_running(lambda: defer.ensureDeferred(wrapper()))
 
 
 def listen_metrics(bind_addresses: StrCollection, port: int) -> None:
@@ -517,7 +518,9 @@ async def start(hs: "HomeServer") -> None:
     # numbers of DNS requests don't starve out other users of the threadpool.
     resolver_threadpool = ThreadPool(name="gai_resolver")
     resolver_threadpool.start()
-    reactor.addSystemEventTrigger("during", "shutdown", resolver_threadpool.stop)
+    hs.get_clock().add_system_event_trigger(
+        "during", "shutdown", resolver_threadpool.stop
+    )
     reactor.installNameResolver(
         GAIResolver(reactor, getThreadPool=lambda: resolver_threadpool)
     )
@@ -604,7 +607,7 @@ async def start(hs: "HomeServer") -> None:
             logger.info("Shutting down...")
 
     # Log when we start the shut down process.
-    hs.get_reactor().addSystemEventTrigger("before", "shutdown", log_shutdown)
+    hs.get_clock().add_system_event_trigger("before", "shutdown", log_shutdown)
 
     setup_sentry(hs)
     setup_sdnotify(hs)
@@ -719,7 +722,7 @@ def setup_sdnotify(hs: "HomeServer") -> None:
     # we're not using systemd.
     sdnotify(b"READY=1\nMAINPID=%i" % (os.getpid(),))
 
-    hs.get_reactor().addSystemEventTrigger(
+    hs.get_clock().add_system_event_trigger(
         "before", "shutdown", sdnotify, b"STOPPING=1"
     )
 

synapse/app/generic_worker.py

@@ -356,11 +356,9 @@ def start(config_options: List[str]) -> None:
         handle_startup_exception(e)
 
     async def start() -> None:
-        # Re-establish log context now that we're back from the reactor
-        with LoggingContext("start"):
-            await _base.start(hs)
+        await _base.start(hs)
 
-    register_start(start)
+    register_start(hs, start)
 
     # redirect stdio to the logs, if configured.
     if not hs.config.logging.no_redirect_stdio:

synapse/app/homeserver.py

@@ -377,19 +377,17 @@ def setup(config_options: List[str]) -> SynapseHomeServer:
         handle_startup_exception(e)
 
     async def start() -> None:
-        # Re-establish log context now that we're back from the reactor
-        with LoggingContext("start"):
-            # Load the OIDC provider metadatas, if OIDC is enabled.
-            if hs.config.oidc.oidc_enabled:
-                oidc = hs.get_oidc_handler()
-                # Loading the provider metadata also ensures the provider config is valid.
-                await oidc.load_metadata()
+        # Load the OIDC provider metadatas, if OIDC is enabled.
+        if hs.config.oidc.oidc_enabled:
+            oidc = hs.get_oidc_handler()
+            # Loading the provider metadata also ensures the provider config is valid.
+            await oidc.load_metadata()
 
-            await _base.start(hs)
+        await _base.start(hs)
 
-            hs.get_datastores().main.db_pool.updates.start_doing_background_updates()
+        hs.get_datastores().main.db_pool.updates.start_doing_background_updates()
 
-    register_start(start)
+    register_start(hs, start)
 
     return hs
 

synapse/appservice/scheduler.py

@@ -84,7 +84,7 @@ from synapse.logging.context import run_in_background
 from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.storage.databases.main import DataStore
 from synapse.types import DeviceListUpdates, JsonMapping
-from synapse.util import Clock
+from synapse.util.clock import Clock
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer

synapse/events/builder.py

@@ -38,7 +38,7 @@ from synapse.storage.databases.main import DataStore
 from synapse.synapse_rust.events import EventInternalMetadata
 from synapse.types import EventID, JsonDict, StrCollection
 from synapse.types.state import StateFilter
-from synapse.util import Clock
+from synapse.util.clock import Clock
 from synapse.util.stringutils import random_string
 
 if TYPE_CHECKING:

synapse/federation/sender/__init__.py

@@ -178,7 +178,7 @@ from synapse.types import (
     StrCollection,
     get_domain_from_id,
 )
-from synapse.util import Clock
+from synapse.util.clock import Clock
 from synapse.util.metrics import Measure
 from synapse.util.retryutils import filter_destinations_by_retry_limiter
 

synapse/federation/sender/transaction_manager.py

@@ -36,7 +36,7 @@ from synapse.logging.opentracing import (
 )
 from synapse.metrics import SERVER_NAME_LABEL
 from synapse.types import JsonDict
-from synapse.util import json_decoder
+from synapse.util.json import json_decoder
 from synapse.util.metrics import measure_func
 
 if TYPE_CHECKING:

synapse/handlers/deactivate_account.py

@@ -62,7 +62,7 @@ class DeactivateAccountHandler:
         # 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.worker_app is None:
-            hs.get_reactor().callWhenRunning(self._start_user_parting)
+            hs.get_clock().call_when_running(self._start_user_parting)
         else:
             self._notify_account_deactivated_client = (
                 ReplicationNotifyAccountDeactivatedServlet.make_client(hs)

synapse/handlers/device.py

@@ -1002,7 +1002,7 @@ class DeviceWriterHandler(DeviceHandler):
         # rolling-restarting Synapse.
         if self._is_main_device_list_writer:
             # On start up check if there are any updates pending.
-            hs.get_reactor().callWhenRunning(self._handle_new_device_update_async)
+            hs.get_clock().call_when_running(self._handle_new_device_update_async)
             self.device_list_updater = DeviceListUpdater(hs, self)
             hs.get_federation_registry().register_edu_handler(
                 EduTypes.DEVICE_LIST_UPDATE,

synapse/handlers/devicemessage.py

@@ -34,7 +34,7 @@ from synapse.logging.opentracing import (
     set_tag,
 )
 from synapse.types import JsonDict, Requester, StreamKeyType, UserID, get_domain_from_id
-from synapse.util import json_encoder
+from synapse.util.json import json_encoder
 from synapse.util.stringutils import random_string
 
 if TYPE_CHECKING:

synapse/handlers/e2e_keys.py

@@ -44,9 +44,9 @@ from synapse.types import (
     get_domain_from_id,
     get_verify_key_from_cross_signing_key,
 )
-from synapse.util import json_decoder
 from synapse.util.async_helpers import Linearizer, concurrently_execute
 from synapse.util.cancellation import cancellable
+from synapse.util.json import json_decoder
 from synapse.util.retryutils import (
     NotRetryingDestination,
     filter_destinations_by_retry_limiter,

synapse/handlers/identity.py

@@ -39,8 +39,8 @@ from synapse.http import RequestTimedOutError
 from synapse.http.client import SimpleHttpClient
 from synapse.http.site import SynapseRequest
 from synapse.types import JsonDict, Requester
-from synapse.util import json_decoder
 from synapse.util.hash import sha256_and_url_safe_base64
+from synapse.util.json import json_decoder
 from synapse.util.stringutils import (
     assert_valid_client_secret,
     random_string,

synapse/handlers/message.py

@@ -81,9 +81,10 @@ from synapse.types import (
     create_requester,
 )
 from synapse.types.state import StateFilter
-from synapse.util import json_decoder, json_encoder, log_failure, unwrapFirstError
+from synapse.util import log_failure, unwrapFirstError
 from synapse.util.async_helpers import Linearizer, gather_results
 from synapse.util.caches.expiringcache import ExpiringCache
+from synapse.util.json import json_decoder, json_encoder
 from synapse.util.metrics import measure_func
 from synapse.visibility import get_effective_room_visibility_from_state
 

synapse/handlers/oidc.py

@@ -67,8 +67,9 @@ from synapse.http.site import SynapseRequest
 from synapse.logging.context import make_deferred_yieldable
 from synapse.module_api import ModuleApi
 from synapse.types import JsonDict, UserID, map_username_to_mxid_localpart
-from synapse.util import Clock, json_decoder
 from synapse.util.caches.cached_call import RetryOnExceptionCachedCall
+from synapse.util.clock import Clock
+from synapse.util.json import json_decoder
 from synapse.util.macaroons import MacaroonGenerator, OidcSessionData
 from synapse.util.templates import _localpart_from_email_filter
 

synapse/handlers/presence.py

@@ -541,7 +541,7 @@ class WorkerPresenceHandler(BasePresenceHandler):
             self.send_stop_syncing, UPDATE_SYNCING_USERS_MS
         )
 
-        hs.get_reactor().addSystemEventTrigger(
+        hs.get_clock().add_system_event_trigger(
             "before",
             "shutdown",
             run_as_background_process,
@@ -842,7 +842,7 @@ class PresenceHandler(BasePresenceHandler):
         # have not yet been persisted
         self.unpersisted_users_changes: Set[str] = set()
 
-        hs.get_reactor().addSystemEventTrigger(
+        hs.get_clock().add_system_event_trigger(
             "before",
             "shutdown",
             run_as_background_process,

synapse/handlers/ui_auth/checkers.py

@@ -27,7 +27,7 @@ from twisted.web.client import PartialDownloadError
 
 from synapse.api.constants import LoginType
 from synapse.api.errors import Codes, LoginError, SynapseError
-from synapse.util import json_decoder
+from synapse.util.json import json_decoder
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer

synapse/http/client.py

@@ -87,8 +87,8 @@ from synapse.logging.context import make_deferred_yieldable, run_in_background
 from synapse.logging.opentracing import set_tag, start_active_span, tags
 from synapse.metrics import SERVER_NAME_LABEL
 from synapse.types import ISynapseReactor, StrSequence
-from synapse.util import json_decoder
 from synapse.util.async_helpers import timeout_deferred
+from synapse.util.json import json_decoder
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer

synapse/http/federation/matrix_federation_agent.py

@@ -49,7 +49,7 @@ from synapse.http.federation.well_known_resolver import WellKnownResolver
 from synapse.http.proxyagent import ProxyAgent
 from synapse.logging.context import make_deferred_yieldable, run_in_background
 from synapse.types import ISynapseReactor
-from synapse.util import Clock
+from synapse.util.clock import Clock
 
 logger = logging.getLogger(__name__)
 

synapse/http/federation/well_known_resolver.py

@@ -27,7 +27,6 @@ from typing import Callable, Dict, Optional, Tuple
 import attr
 
 from twisted.internet import defer
-from twisted.internet.interfaces import IReactorTime
 from twisted.web.client import RedirectAgent
 from twisted.web.http import stringToDatetime
 from twisted.web.http_headers import Headers
@@ -35,8 +34,10 @@ from twisted.web.iweb import IAgent, IResponse
 
 from synapse.http.client import BodyExceededMaxSize, read_body_with_max_size
 from synapse.logging.context import make_deferred_yieldable
-from synapse.util import Clock, json_decoder
+from synapse.types import ISynapseThreadlessReactor
 from synapse.util.caches.ttlcache import TTLCache
+from synapse.util.clock import Clock
+from synapse.util.json import json_decoder
 from synapse.util.metrics import Measure
 
 # period to cache .well-known results for by default
@@ -88,7 +89,7 @@ class WellKnownResolver:
     def __init__(
         self,
         server_name: str,
-        reactor: IReactorTime,
+        reactor: ISynapseThreadlessReactor,
         agent: IAgent,
         user_agent: bytes,
         well_known_cache: Optional[TTLCache[bytes, Optional[bytes]]] = None,

synapse/http/matrixfederationclient.py

@@ -89,8 +89,8 @@ from synapse.logging.context import make_deferred_yieldable, run_in_background
 from synapse.logging.opentracing import set_tag, start_active_span, tags
 from synapse.metrics import SERVER_NAME_LABEL
 from synapse.types import JsonDict
-from synapse.util import json_decoder
 from synapse.util.async_helpers import AwakenableSleeper, Linearizer, timeout_deferred
+from synapse.util.json import json_decoder
 from synapse.util.metrics import Measure
 from synapse.util.stringutils import parse_and_validate_server_name
 

synapse/http/server.py

@@ -52,10 +52,11 @@ from zope.interface import implementer
 
 from twisted.internet import defer, interfaces, reactor
 from twisted.internet.defer import CancelledError
-from twisted.internet.interfaces import IReactorTime
 from twisted.python import failure
 from twisted.web import resource
 
+from synapse.types import ISynapseThreadlessReactor
+
 try:
     from twisted.web.pages import notFound
 except ImportError:
@@ -77,10 +78,11 @@ from synapse.api.errors import (
 from synapse.config.homeserver import HomeServerConfig
 from synapse.logging.context import defer_to_thread, preserve_fn, run_in_background
 from synapse.logging.opentracing import active_span, start_active_span, trace_servlet
-from synapse.util import Clock, json_encoder
 from synapse.util.caches import intern_dict
 from synapse.util.cancellation import is_function_cancellable
+from synapse.util.clock import Clock
 from synapse.util.iterutils import chunk_seq
+from synapse.util.json import json_encoder
 
 if TYPE_CHECKING:
     import opentracing
@@ -410,7 +412,7 @@ class DirectServeJsonResource(_AsyncResource):
         clock: Optional[Clock] = None,
     ):
         if clock is None:
-            clock = Clock(cast(IReactorTime, reactor))
+            clock = Clock(cast(ISynapseThreadlessReactor, reactor))
 
         super().__init__(clock, extract_context)
         self.canonical_json = canonical_json
@@ -589,7 +591,7 @@ class DirectServeHtmlResource(_AsyncResource):
         clock: Optional[Clock] = None,
     ):
         if clock is None:
-            clock = Clock(cast(IReactorTime, reactor))
+            clock = Clock(cast(ISynapseThreadlessReactor, reactor))
 
         super().__init__(clock, extract_context)
 

synapse/http/servlet.py

@@ -51,7 +51,7 @@ from synapse.api.errors import Codes, SynapseError
 from synapse.http import redact_uri
 from synapse.http.server import HttpServer
 from synapse.types import JsonDict, RoomAlias, RoomID, StrCollection
-from synapse.util import json_decoder
+from synapse.util.json import json_decoder
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer

synapse/logging/handlers.py

@@ -60,8 +60,18 @@ class PeriodicallyFlushingMemoryHandler(MemoryHandler):
         else:
             reactor_to_use = reactor
 
-        # call our hook when the reactor start up
-        reactor_to_use.callWhenRunning(on_reactor_running)
+        # Call our hook when the reactor start up
+        #
+        # type-ignore: Ideally, we'd use `Clock.call_when_running(...)`, but
+        # `PeriodicallyFlushingMemoryHandler` is instantiated via Python logging
+        # configuration, so it's not straightforward to pass in the homeserver's clock
+        # (and we don't want to burden other peoples logging config with the details).
+        #
+        # The important reason why we want to use `Clock.call_when_running` is so that
+        # the callback runs with a logcontext as we want to know which server the logs
+        # came from. But since we don't log anything in the callback, it's safe to
+        # ignore the lint here.
+        reactor_to_use.callWhenRunning(on_reactor_running)  # type: ignore[prefer-synapse-clock-call-when-running]
 
     def shouldFlush(self, record: LogRecord) -> bool:
         """

synapse/logging/opentracing.py

@@ -204,7 +204,7 @@ from twisted.web.http import Request
 from twisted.web.http_headers import Headers
 
 from synapse.config import ConfigError
-from synapse.util import json_decoder, json_encoder
+from synapse.util.json import json_decoder, json_encoder
 
 if TYPE_CHECKING:
     from synapse.http.site import SynapseRequest

synapse/media/_base.py

@@ -54,8 +54,8 @@ from synapse.logging.context import (
     make_deferred_yieldable,
     run_in_background,
 )
-from synapse.util import Clock
 from synapse.util.async_helpers import DeferredEvent
+from synapse.util.clock import Clock
 from synapse.util.stringutils import is_ascii
 
 if TYPE_CHECKING:

synapse/media/media_storage.py

@@ -55,7 +55,7 @@ from synapse.api.errors import NotFoundError
 from synapse.logging.context import defer_to_thread, run_in_background
 from synapse.logging.opentracing import start_active_span, trace, trace_with_opname
 from synapse.media._base import ThreadedFileSender
-from synapse.util import Clock
+from synapse.util.clock import Clock
 from synapse.util.file_consumer import BackgroundFileConsumer
 
 from ..types import JsonDict

synapse/media/oembed.py

@@ -27,7 +27,7 @@ import attr
 
 from synapse.media.preview_html import parse_html_description
 from synapse.types import JsonDict
-from synapse.util import json_decoder
+from synapse.util.json import json_decoder
 
 if TYPE_CHECKING:
     from lxml import etree

synapse/media/url_previewer.py

@@ -46,9 +46,9 @@ from synapse.media.oembed import OEmbedProvider
 from synapse.media.preview_html import decode_body, parse_html_to_open_graph
 from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.types import JsonDict, UserID
-from synapse.util import json_encoder
 from synapse.util.async_helpers import ObservableDeferred
 from synapse.util.caches.expiringcache import ExpiringCache
+from synapse.util.json import json_encoder
 from synapse.util.stringutils import random_string
 
 if TYPE_CHECKING:

synapse/module_api/__init__.py

@@ -158,9 +158,9 @@ from synapse.types import (
     create_requester,
 )
 from synapse.types.state import StateFilter
-from synapse.util import Clock
 from synapse.util.async_helpers import maybe_awaitable
 from synapse.util.caches.descriptors import CachedFunction, cached as _cached
+from synapse.util.clock import Clock
 from synapse.util.frozenutils import freeze
 
 if TYPE_CHECKING:

synapse/replication/tcp/commands.py

@@ -29,7 +29,7 @@ import logging
 from typing import List, Optional, Tuple, Type, TypeVar
 
 from synapse.replication.tcp.streams._base import StreamRow
-from synapse.util import json_decoder, json_encoder
+from synapse.util.json import json_decoder, json_encoder
 
 logger = logging.getLogger(__name__)
 

synapse/replication/tcp/external_cache.py

@@ -27,7 +27,7 @@ from prometheus_client import Counter, Histogram
 from synapse.logging import opentracing
 from synapse.logging.context import make_deferred_yieldable
 from synapse.metrics import SERVER_NAME_LABEL
-from synapse.util import json_decoder, json_encoder
+from synapse.util.json import json_decoder, json_encoder
 
 if TYPE_CHECKING:
     from txredisapi import ConnectionHandler

synapse/replication/tcp/protocol.py

@@ -55,7 +55,7 @@ from synapse.replication.tcp.commands import (
     ServerCommand,
     parse_command_from_line,
 )
-from synapse.util import Clock
+from synapse.util.clock import Clock
 from synapse.util.stringutils import random_string
 
 if TYPE_CHECKING:

synapse/rest/client/sync.py

@@ -58,8 +58,8 @@ from synapse.logging.opentracing import log_kv, set_tag, trace_with_opname
 from synapse.rest.admin.experimental_features import ExperimentalFeature
 from synapse.types import JsonDict, Requester, SlidingSyncStreamToken, StreamToken
 from synapse.types.rest.client import SlidingSyncBody
-from synapse.util import json_decoder
 from synapse.util.caches.lrucache import LruCache
+from synapse.util.json import json_decoder
 
 from ._base import client_patterns, set_timeline_upper_limit
 

synapse/rest/key/v2/remote_key_resource.py

@@ -38,8 +38,8 @@ from synapse.http.servlet import (
 from synapse.storage.keys import FetchKeyResultForRemote
 from synapse.types import JsonDict
 from synapse.types.rest import RequestBodyModel
-from synapse.util import json_decoder
 from synapse.util.async_helpers import yieldable_gather_results
+from synapse.util.json import json_decoder
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer

synapse/rest/well_known.py

@@ -28,7 +28,7 @@ from synapse.api.errors import NotFoundError
 from synapse.http.server import DirectServeJsonResource
 from synapse.http.site import SynapseRequest
 from synapse.types import JsonDict
-from synapse.util import json_encoder
+from synapse.util.json import json_encoder
 from synapse.util.stringutils import parse_server_name
 
 if TYPE_CHECKING:

synapse/server.py

@@ -156,7 +156,7 @@ from synapse.storage.controllers import StorageControllers
 from synapse.streams.events import EventSources
 from synapse.synapse_rust.rendezvous import RendezvousHandler
 from synapse.types import DomainSpecificString, ISynapseReactor
-from synapse.util import Clock
+from synapse.util.clock import Clock
 from synapse.util.distributor import Distributor
 from synapse.util.macaroons import MacaroonGenerator
 from synapse.util.ratelimitutils import FederationRateLimiter
@@ -1007,7 +1007,7 @@ class HomeServer(metaclass=abc.ABCMeta):
         )
 
         media_threadpool.start()
-        self.get_reactor().addSystemEventTrigger(
+        self.get_clock().add_system_event_trigger(
             "during", "shutdown", media_threadpool.stop
         )
 

synapse/storage/_base.py

@@ -29,8 +29,8 @@ from synapse.storage.database import (
     make_in_list_sql_clause,  # noqa: F401
 )
 from synapse.types import get_domain_from_id
-from synapse.util import json_decoder
 from synapse.util.caches.descriptors import CachedFunction
+from synapse.util.json import json_decoder
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer

synapse/storage/background_updates.py

@@ -45,7 +45,8 @@ from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.storage.engines import PostgresEngine
 from synapse.storage.types import Connection, Cursor
 from synapse.types import JsonDict, StrCollection
-from synapse.util import Clock, json_encoder
+from synapse.util.clock import Clock
+from synapse.util.json import json_encoder
 
 from . import engines
 

synapse/storage/databases/main/account_data.py

@@ -48,9 +48,9 @@ from synapse.storage.databases.main.push_rule import PushRulesWorkerStore
 from synapse.storage.invite_rule import InviteRulesConfig
 from synapse.storage.util.id_generators import MultiWriterIdGenerator
 from synapse.types import JsonDict, JsonMapping
-from synapse.util import json_encoder
 from synapse.util.caches.descriptors import cached
 from synapse.util.caches.stream_change_cache import StreamChangeCache
+from synapse.util.json import json_encoder
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer

synapse/storage/databases/main/appservice.py

@@ -42,8 +42,8 @@ from synapse.storage.databases.main.roommember import RoomMemberWorkerStore
 from synapse.storage.types import Cursor
 from synapse.storage.util.sequence import build_sequence_generator
 from synapse.types import DeviceListUpdates, JsonMapping
-from synapse.util import json_encoder
 from synapse.util.caches.descriptors import _CacheContext, cached
+from synapse.util.json import json_encoder
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer

synapse/storage/databases/main/censor_events.py

@@ -32,7 +32,7 @@ from synapse.storage.database import (
 )
 from synapse.storage.databases.main.cache import CacheInvalidationWorkerStore
 from synapse.storage.databases.main.events_worker import EventsWorkerStore
-from synapse.util import json_encoder
+from synapse.util.json import json_encoder
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer

synapse/storage/databases/main/client_ips.py

@@ -455,7 +455,7 @@ class ClientIpWorkerStore(ClientIpBackgroundUpdateStore, MonthlyActiveUsersWorke
             self._client_ip_looper = self._clock.looping_call(
                 self._update_client_ips_batch, 5 * 1000
             )
-            self.hs.get_reactor().addSystemEventTrigger(
+            self.hs.get_clock().add_system_event_trigger(
                 "before", "shutdown", self._update_client_ips_batch
             )
 

synapse/storage/databases/main/delayed_events.py

@@ -22,7 +22,8 @@ from synapse.storage._base import SQLBaseStore, db_to_json
 from synapse.storage.database import LoggingTransaction, StoreError
 from synapse.storage.engines import PostgresEngine
 from synapse.types import JsonDict, RoomID
-from synapse.util import json_encoder, stringutils as stringutils
+from synapse.util import stringutils
+from synapse.util.json import json_encoder
 
 logger = logging.getLogger(__name__)
 

synapse/storage/databases/main/deviceinbox.py

@@ -53,10 +53,11 @@ from synapse.storage.database import (
 )
 from synapse.storage.util.id_generators import MultiWriterIdGenerator
 from synapse.types import JsonDict, StrCollection
-from synapse.util import Duration, json_encoder
+from synapse.util import Duration
 from synapse.util.caches.expiringcache import ExpiringCache
 from synapse.util.caches.stream_change_cache import StreamChangeCache
 from synapse.util.iterutils import batch_iter
+from synapse.util.json import json_encoder
 from synapse.util.stringutils import parse_and_validate_server_name
 
 if TYPE_CHECKING:

synapse/storage/databases/main/devices.py

@@ -64,11 +64,11 @@ from synapse.types import (
     StrCollection,
     get_verify_key_from_cross_signing_key,
 )
-from synapse.util import json_decoder, json_encoder
 from synapse.util.caches.descriptors import cached, cachedList
 from synapse.util.caches.stream_change_cache import StreamChangeCache
 from synapse.util.cancellation import cancellable
 from synapse.util.iterutils import batch_iter
+from synapse.util.json import json_decoder, json_encoder
 from synapse.util.stringutils import shortstr
 
 if TYPE_CHECKING:

synapse/storage/databases/main/e2e_room_keys.py

@@ -41,7 +41,7 @@ from synapse.storage.database import (
     LoggingTransaction,
 )
 from synapse.types import JsonDict, JsonSerializable, StreamKeyType
-from synapse.util import json_encoder
+from synapse.util.json import json_encoder
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer

synapse/storage/databases/main/end_to_end_keys.py

@@ -61,10 +61,10 @@ from synapse.storage.databases.main.cache import CacheInvalidationWorkerStore
 from synapse.storage.engines import PostgresEngine
 from synapse.storage.util.id_generators import MultiWriterIdGenerator
 from synapse.types import JsonDict, JsonMapping, MultiWriterStreamToken
-from synapse.util import json_decoder, json_encoder
 from synapse.util.caches.descriptors import cached, cachedList
 from synapse.util.cancellation import cancellable
 from synapse.util.iterutils import batch_iter
+from synapse.util.json import json_decoder, json_encoder
 
 if TYPE_CHECKING:
     from synapse.handlers.e2e_keys import SignatureListItem

synapse/storage/databases/main/event_federation.py

@@ -59,11 +59,11 @@ from synapse.storage.databases.main.events_worker import EventsWorkerStore
 from synapse.storage.databases.main.signatures import SignatureWorkerStore
 from synapse.storage.engines import PostgresEngine, Sqlite3Engine
 from synapse.types import JsonDict, StrCollection
-from synapse.util import json_encoder
 from synapse.util.caches.descriptors import cached
 from synapse.util.caches.lrucache import LruCache
 from synapse.util.cancellation import cancellable
 from synapse.util.iterutils import batch_iter
+from synapse.util.json import json_encoder
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer

synapse/storage/databases/main/event_push_actions.py

@@ -107,8 +107,8 @@ from synapse.storage.database import (
 from synapse.storage.databases.main.receipts import ReceiptsWorkerStore
 from synapse.storage.databases.main.stream import StreamWorkerStore
 from synapse.types import JsonDict, StrCollection
-from synapse.util import json_encoder
 from synapse.util.caches.descriptors import cached
+from synapse.util.json import json_encoder
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer

synapse/storage/databases/main/events.py

@@ -83,9 +83,9 @@ from synapse.types import (
 )
 from synapse.types.handlers import SLIDING_SYNC_DEFAULT_BUMP_EVENT_TYPES
 from synapse.types.state import StateFilter
-from synapse.util import json_encoder
 from synapse.util.events import get_plain_text_topic_from_event_content
 from synapse.util.iterutils import batch_iter, sorted_topologically
+from synapse.util.json import json_encoder
 from synapse.util.stringutils import non_null_str_or_none
 
 if TYPE_CHECKING:

synapse/storage/databases/main/events_bg_updates.py

@@ -58,8 +58,8 @@ from synapse.types import JsonDict, RoomStreamToken, StateMap, StrCollection
 from synapse.types.handlers import SLIDING_SYNC_DEFAULT_BUMP_EVENT_TYPES
 from synapse.types.state import StateFilter
 from synapse.types.storage import _BackgroundUpdates
-from synapse.util import json_encoder
 from synapse.util.iterutils import batch_iter
+from synapse.util.json import json_encoder
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer

synapse/storage/databases/main/lock.py

@@ -38,7 +38,7 @@ from synapse.storage.database import (
     LoggingTransaction,
 )
 from synapse.types import ISynapseReactor
-from synapse.util import Clock
+from synapse.util.clock import Clock
 from synapse.util.stringutils import random_string
 
 if TYPE_CHECKING:
@@ -99,7 +99,7 @@ class LockStore(SQLBaseStore):
         # lead to a race, as we may drop the lock while we are still processing.
         # However, a) it should be a small window, b) the lock is best effort
         # anyway and c) we want to really avoid leaking locks when we restart.
-        hs.get_reactor().addSystemEventTrigger(
+        hs.get_clock().add_system_event_trigger(
             "before",
             "shutdown",
             self._on_shutdown,

synapse/storage/databases/main/push_rule.py

@@ -56,10 +56,11 @@ from synapse.storage.push_rule import InconsistentRuleException, RuleNotFoundExc
 from synapse.storage.util.id_generators import IdGenerator, MultiWriterIdGenerator
 from synapse.synapse_rust.push import FilteredPushRules, PushRule, PushRules
 from synapse.types import JsonDict
-from synapse.util import json_encoder, unwrapFirstError
+from synapse.util import unwrapFirstError
 from synapse.util.async_helpers import gather_results
 from synapse.util.caches.descriptors import cached, cachedList
 from synapse.util.caches.stream_change_cache import StreamChangeCache
+from synapse.util.json import json_encoder
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer

synapse/storage/databases/main/pusher.py

@@ -42,8 +42,8 @@ from synapse.storage.database import (
 )
 from synapse.storage.util.id_generators import MultiWriterIdGenerator
 from synapse.types import JsonDict
-from synapse.util import json_encoder
 from synapse.util.caches.descriptors import cached
+from synapse.util.json import json_encoder
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer

synapse/storage/databases/main/receipts.py

@@ -55,10 +55,10 @@ from synapse.types import (
     PersistedPosition,
     StrCollection,
 )
-from synapse.util import json_encoder
 from synapse.util.caches.descriptors import cached, cachedList
 from synapse.util.caches.stream_change_cache import StreamChangeCache
 from synapse.util.iterutils import batch_iter
+from synapse.util.json import json_encoder
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer

synapse/storage/databases/main/room.py

@@ -65,8 +65,8 @@ from synapse.storage.databases.main.cache import CacheInvalidationWorkerStore
 from synapse.storage.types import Cursor
 from synapse.storage.util.id_generators import IdGenerator, MultiWriterIdGenerator
 from synapse.types import JsonDict, RetentionPolicy, StrCollection, ThirdPartyInstanceID
-from synapse.util import json_encoder
 from synapse.util.caches.descriptors import cached, cachedList
+from synapse.util.json import json_encoder
 from synapse.util.stringutils import MXC_REGEX
 
 if TYPE_CHECKING:

synapse/storage/databases/main/session.py

@@ -30,7 +30,7 @@ from synapse.storage.database import (
     LoggingTransaction,
 )
 from synapse.types import JsonDict
-from synapse.util import json_encoder
+from synapse.util.json import json_encoder
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer

synapse/storage/databases/main/sliding_sync.py

@@ -35,8 +35,8 @@ from synapse.types.handlers.sliding_sync import (
     RoomStatusMap,
     RoomSyncConfig,
 )
-from synapse.util import json_encoder
 from synapse.util.caches.descriptors import cached
+from synapse.util.json import json_encoder
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer

synapse/storage/databases/main/tags.py

@@ -30,8 +30,8 @@ from synapse.storage.database import LoggingTransaction
 from synapse.storage.databases.main.account_data import AccountDataWorkerStore
 from synapse.storage.util.id_generators import AbstractStreamIdGenerator
 from synapse.types import JsonDict, JsonMapping
-from synapse.util import json_encoder
 from synapse.util.caches.descriptors import cached
+from synapse.util.json import json_encoder
 
 logger = logging.getLogger(__name__)
 

synapse/storage/databases/main/task_scheduler.py

@@ -29,7 +29,7 @@ from synapse.storage.database import (
     make_in_list_sql_clause,
 )
 from synapse.types import JsonDict, JsonMapping, ScheduledTask, TaskStatus
-from synapse.util import json_encoder
+from synapse.util.json import json_encoder
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer

synapse/storage/databases/main/ui_auth.py

@@ -27,7 +27,8 @@ from synapse.api.errors import StoreError
 from synapse.storage._base import SQLBaseStore, db_to_json
 from synapse.storage.database import LoggingTransaction
 from synapse.types import JsonDict
-from synapse.util import json_encoder, stringutils
+from synapse.util import stringutils
+from synapse.util.json import json_encoder
 
 
 @attr.s(slots=True, auto_attribs=True)

synapse/types/__init__.py

@@ -116,13 +116,27 @@ StrSequence = Union[Tuple[str, ...], List[str]]
 
 # Note that this seems to require inheriting *directly* from Interface in order
 # for mypy-zope to realize it is an interface.
-class ISynapseReactor(
+class ISynapseThreadlessReactor(
     IReactorTCP,
     IReactorSSL,
     IReactorUNIX,
     IReactorPluggableNameResolver,
     IReactorTime,
     IReactorCore,
+    Interface,
+):
+    """
+    The interfaces necessary for Synapse to function (without threads).
+
+    Helpful because we use `twisted.internet.testing.MemoryReactorClock` in tests which
+    doesn't implement `IReactorThreads`.
+    """
+
+
+# Note that this seems to require inheriting *directly* from Interface in order
+# for mypy-zope to realize it is an interface.
+class ISynapseReactor(
+    ISynapseThreadlessReactor,
     IReactorThreads,
     Interface,
 ):

synapse/util/__init__.py

@@ -20,12 +20,9 @@
 #
 
 import collections.abc
-import json
 import logging
 import typing
 from typing import (
-    Any,
-    Callable,
     Dict,
     Iterator,
     Mapping,
@@ -36,17 +33,11 @@ from typing import (
 )
 
 import attr
-from immutabledict import immutabledict
 from matrix_common.versionstring import get_distribution_version_string
-from typing_extensions import ParamSpec
 
-from twisted.internet import defer, task
-from twisted.internet.interfaces import IDelayedCall, IReactorTime
-from twisted.internet.task import LoopingCall
+from twisted.internet import defer
 from twisted.python.failure import Failure
 
-from synapse.logging import context
-
 if typing.TYPE_CHECKING:
     pass
 
@@ -62,41 +53,6 @@ class Duration:
     DAY_MS = 24 * HOUR_MS
 
 
-def _reject_invalid_json(val: Any) -> None:
-    """Do not allow Infinity, -Infinity, or NaN values in JSON."""
-    raise ValueError("Invalid JSON value: '%s'" % val)
-
-
-def _handle_immutabledict(obj: Any) -> Dict[Any, Any]:
-    """Helper for json_encoder. Makes immutabledicts serializable by returning
-    the underlying dict
-    """
-    if type(obj) is immutabledict:
-        # fishing the protected dict out of the object is a bit nasty,
-        # but we don't really want the overhead of copying the dict.
-        try:
-            # Safety: we catch the AttributeError immediately below.
-            return obj._dict
-        except AttributeError:
-            # If all else fails, resort to making a copy of the immutabledict
-            return dict(obj)
-    raise TypeError(
-        "Object of type %s is not JSON serializable" % obj.__class__.__name__
-    )
-
-
-# A custom JSON encoder which:
-#   * handles immutabledicts
-#   * produces valid JSON (no NaNs etc)
-#   * reduces redundant whitespace
-json_encoder = json.JSONEncoder(
-    allow_nan=False, separators=(",", ":"), default=_handle_immutabledict
-)
-
-# Create a custom decoder to reject Python extensions to JSON.
-json_decoder = json.JSONDecoder(parse_constant=_reject_invalid_json)
-
-
 def unwrapFirstError(failure: Failure) -> Failure:
     # Deprecated: you probably just want to catch defer.FirstError and reraise
     # the subFailure's value, which will do a better job of preserving stacktraces.
@@ -105,129 +61,6 @@ def unwrapFirstError(failure: Failure) -> Failure:
     return failure.value.subFailure
 
 
-P = ParamSpec("P")
-
-
-@attr.s(slots=True)
-class Clock:
-    """
-    A Clock wraps a Twisted reactor and provides utilities on top of it.
-
-    Args:
-        reactor: The Twisted reactor to use.
-    """
-
-    _reactor: IReactorTime = attr.ib()
-
-    async def sleep(self, seconds: float) -> None:
-        d: defer.Deferred[float] = defer.Deferred()
-        with context.PreserveLoggingContext():
-            self._reactor.callLater(seconds, d.callback, seconds)
-            await d
-
-    def time(self) -> float:
-        """Returns the current system time in seconds since epoch."""
-        return self._reactor.seconds()
-
-    def time_msec(self) -> int:
-        """Returns the current system time in milliseconds since epoch."""
-        return int(self.time() * 1000)
-
-    def looping_call(
-        self,
-        f: Callable[P, object],
-        msec: float,
-        *args: P.args,
-        **kwargs: P.kwargs,
-    ) -> LoopingCall:
-        """Call a function repeatedly.
-
-        Waits `msec` initially before calling `f` for the first time.
-
-        If the function given to `looping_call` returns an awaitable/deferred, the next
-        call isn't scheduled until after the returned awaitable has finished. We get
-        this functionality thanks to this function being a thin wrapper around
-        `twisted.internet.task.LoopingCall`.
-
-        Note that the function will be called with no logcontext, so if it is anything
-        other than trivial, you probably want to wrap it in run_as_background_process.
-
-        Args:
-            f: The function to call repeatedly.
-            msec: How long to wait between calls in milliseconds.
-            *args: Positional arguments to pass to function.
-            **kwargs: Key arguments to pass to function.
-        """
-        return self._looping_call_common(f, msec, False, *args, **kwargs)
-
-    def looping_call_now(
-        self,
-        f: Callable[P, object],
-        msec: float,
-        *args: P.args,
-        **kwargs: P.kwargs,
-    ) -> LoopingCall:
-        """Call a function immediately, and then repeatedly thereafter.
-
-        As with `looping_call`: subsequent calls are not scheduled until after the
-        the Awaitable returned by a previous call has finished.
-
-        Also as with `looping_call`: the function is called with no logcontext and
-        you probably want to wrap it in `run_as_background_process`.
-
-        Args:
-            f: The function to call repeatedly.
-            msec: How long to wait between calls in milliseconds.
-            *args: Positional arguments to pass to function.
-            **kwargs: Key arguments to pass to function.
-        """
-        return self._looping_call_common(f, msec, True, *args, **kwargs)
-
-    def _looping_call_common(
-        self,
-        f: Callable[P, object],
-        msec: float,
-        now: bool,
-        *args: P.args,
-        **kwargs: P.kwargs,
-    ) -> LoopingCall:
-        """Common functionality for `looping_call` and `looping_call_now`"""
-        call = task.LoopingCall(f, *args, **kwargs)
-        call.clock = self._reactor
-        d = call.start(msec / 1000.0, now=now)
-        d.addErrback(log_failure, "Looping call died", consumeErrors=False)
-        return call
-
-    def call_later(
-        self, delay: float, callback: Callable, *args: Any, **kwargs: Any
-    ) -> IDelayedCall:
-        """Call something later
-
-        Note that the function will be called with no logcontext, so if it is anything
-        other than trivial, you probably want to wrap it in run_as_background_process.
-
-        Args:
-            delay: How long to wait in seconds.
-            callback: Function to call
-            *args: Postional arguments to pass to function.
-            **kwargs: Key arguments to pass to function.
-        """
-
-        def wrapped_callback(*args: Any, **kwargs: Any) -> None:
-            with context.PreserveLoggingContext():
-                callback(*args, **kwargs)
-
-        with context.PreserveLoggingContext():
-            return self._reactor.callLater(delay, wrapped_callback, *args, **kwargs)
-
-    def cancel_call_later(self, timer: IDelayedCall, ignore_errs: bool = False) -> None:
-        try:
-            timer.cancel()
-        except Exception:
-            if not ignore_errs:
-                raise
-
-
 def log_failure(
     failure: Failure, msg: str, consumeErrors: bool = True
 ) -> Optional[Failure]:

synapse/util/async_helpers.py

@@ -65,7 +65,8 @@ from synapse.logging.context import (
     run_coroutine_in_background,
     run_in_background,
 )
-from synapse.util import Clock
+from synapse.types import ISynapseThreadlessReactor
+from synapse.util.clock import Clock
 
 logger = logging.getLogger(__name__)
 
@@ -566,7 +567,7 @@ class Linearizer:
         if not clock:
             from twisted.internet import reactor
 
-            clock = Clock(cast(IReactorTime, reactor))
+            clock = Clock(cast(ISynapseThreadlessReactor, reactor))
         self._clock = clock
         self.max_count = max_count
 

synapse/util/batching_queue.py

@@ -39,7 +39,7 @@ from twisted.internet import defer
 from synapse.logging.context import PreserveLoggingContext, make_deferred_yieldable
 from synapse.metrics import SERVER_NAME_LABEL
 from synapse.metrics.background_process_metrics import run_as_background_process
-from synapse.util import Clock
+from synapse.util.clock import Clock
 
 logger = logging.getLogger(__name__)
 

synapse/util/caches/expiringcache.py

@@ -29,8 +29,8 @@ from twisted.internet import defer
 
 from synapse.config import cache as cache_config
 from synapse.metrics.background_process_metrics import run_as_background_process
-from synapse.util import Clock
 from synapse.util.caches import EvictionReason, register_cache
+from synapse.util.clock import Clock
 
 logger = logging.getLogger(__name__)
 

synapse/util/caches/lrucache.py

@@ -46,20 +46,21 @@ from typing import (
 )
 
 from twisted.internet import defer, reactor
-from twisted.internet.interfaces import IReactorTime
 
 from synapse.config import cache as cache_config
 from synapse.metrics.background_process_metrics import (
     run_as_background_process,
 )
 from synapse.metrics.jemalloc import get_jemalloc_stats
-from synapse.util import Clock, caches
+from synapse.types import ISynapseThreadlessReactor
+from synapse.util import caches
 from synapse.util.caches import CacheMetric, EvictionReason, register_cache
 from synapse.util.caches.treecache import (
     TreeCache,
     iterate_tree_cache_entry,
     iterate_tree_cache_items,
 )
+from synapse.util.clock import Clock
 from synapse.util.linked_list import ListNode
 
 if TYPE_CHECKING:
@@ -496,7 +497,7 @@ class LruCache(Generic[KT, VT]):
         # Default `clock` to something sensible. Note that we rename it to
         # `real_clock` so that mypy doesn't think its still `Optional`.
         if clock is None:
-            real_clock = Clock(cast(IReactorTime, reactor))
+            real_clock = Clock(cast(ISynapseThreadlessReactor, reactor))
         else:
             real_clock = clock
 

synapse/util/caches/response_cache.py

@@ -41,9 +41,9 @@ from synapse.logging.opentracing import (
     start_active_span,
     start_active_span_follows_from,
 )
-from synapse.util import Clock
 from synapse.util.async_helpers import AbstractObservableDeferred, ObservableDeferred
 from synapse.util.caches import EvictionReason, register_cache
+from synapse.util.clock import Clock
 
 logger = logging.getLogger(__name__)
 

synapse/util/clock.py

@@ -0,0 +1,264 @@
+#
+# This file is licensed under the Affero General Public License (AGPL) version 3.
+#
+# Copyright (C) 2025 New Vector, Ltd
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+#
+# See the GNU Affero General Public License for more details:
+# <https://www.gnu.org/licenses/agpl_3.0.html>.
+#
+#
+
+
+from typing import (
+    Any,
+    Callable,
+)
+
+import attr
+from typing_extensions import ParamSpec
+
+from twisted.internet import defer, task
+from twisted.internet.interfaces import IDelayedCall
+from twisted.internet.task import LoopingCall
+
+from synapse.logging import context
+from synapse.types import ISynapseThreadlessReactor
+from synapse.util import log_failure
+
+P = ParamSpec("P")
+
+
+@attr.s(slots=True)
+class Clock:
+    """
+    A Clock wraps a Twisted reactor and provides utilities on top of it.
+
+    Args:
+        reactor: The Twisted reactor to use.
+    """
+
+    _reactor: ISynapseThreadlessReactor = attr.ib()
+
+    async def sleep(self, seconds: float) -> None:
+        d: defer.Deferred[float] = defer.Deferred()
+        with context.PreserveLoggingContext():
+            self._reactor.callLater(seconds, d.callback, seconds)
+            await d
+
+    def time(self) -> float:
+        """Returns the current system time in seconds since epoch."""
+        return self._reactor.seconds()
+
+    def time_msec(self) -> int:
+        """Returns the current system time in milliseconds since epoch."""
+        return int(self.time() * 1000)
+
+    def looping_call(
+        self,
+        f: Callable[P, object],
+        msec: float,
+        *args: P.args,
+        **kwargs: P.kwargs,
+    ) -> LoopingCall:
+        """Call a function repeatedly.
+
+        Waits `msec` initially before calling `f` for the first time.
+
+        If the function given to `looping_call` returns an awaitable/deferred, the next
+        call isn't scheduled until after the returned awaitable has finished. We get
+        this functionality thanks to this function being a thin wrapper around
+        `twisted.internet.task.LoopingCall`.
+
+        Note that the function will be called with no logcontext, so if it is anything
+        other than trivial, you probably want to wrap it in run_as_background_process.
+
+        Args:
+            f: The function to call repeatedly.
+            msec: How long to wait between calls in milliseconds.
+            *args: Positional arguments to pass to function.
+            **kwargs: Key arguments to pass to function.
+        """
+        return self._looping_call_common(f, msec, False, *args, **kwargs)
+
+    def looping_call_now(
+        self,
+        f: Callable[P, object],
+        msec: float,
+        *args: P.args,
+        **kwargs: P.kwargs,
+    ) -> LoopingCall:
+        """Call a function immediately, and then repeatedly thereafter.
+
+        As with `looping_call`: subsequent calls are not scheduled until after the
+        the Awaitable returned by a previous call has finished.
+
+        Also as with `looping_call`: the function is called with no logcontext and
+        you probably want to wrap it in `run_as_background_process`.
+
+        Args:
+            f: The function to call repeatedly.
+            msec: How long to wait between calls in milliseconds.
+            *args: Positional arguments to pass to function.
+            **kwargs: Key arguments to pass to function.
+        """
+        return self._looping_call_common(f, msec, True, *args, **kwargs)
+
+    def _looping_call_common(
+        self,
+        f: Callable[P, object],
+        msec: float,
+        now: bool,
+        *args: P.args,
+        **kwargs: P.kwargs,
+    ) -> LoopingCall:
+        """Common functionality for `looping_call` and `looping_call_now`"""
+        call = task.LoopingCall(f, *args, **kwargs)
+        call.clock = self._reactor
+        d = call.start(msec / 1000.0, now=now)
+        d.addErrback(log_failure, "Looping call died", consumeErrors=False)
+        return call
+
+    def call_later(
+        self, delay: float, callback: Callable, *args: Any, **kwargs: Any
+    ) -> IDelayedCall:
+        """Call something later
+
+        Note that the function will be called with no logcontext, so if it is anything
+        other than trivial, you probably want to wrap it in run_as_background_process.
+
+        Args:
+            delay: How long to wait in seconds.
+            callback: Function to call
+            *args: Postional arguments to pass to function.
+            **kwargs: Key arguments to pass to function.
+        """
+
+        def wrapped_callback(*args: Any, **kwargs: Any) -> None:
+            with context.PreserveLoggingContext():
+                callback(*args, **kwargs)
+
+        with context.PreserveLoggingContext():
+            return self._reactor.callLater(delay, wrapped_callback, *args, **kwargs)
+
+    def cancel_call_later(self, timer: IDelayedCall, ignore_errs: bool = False) -> None:
+        try:
+            timer.cancel()
+        except Exception:
+            if not ignore_errs:
+                raise
+
+    def call_when_running(
+        self,
+        callback: Callable[P, object],
+        *args: P.args,
+        **kwargs: P.kwargs,
+    ) -> None:
+        """
+        Call a function when the reactor is running.
+
+        If the reactor has not started, the callable will be scheduled to run when it
+        does start. Otherwise, the callable will be invoked immediately.
+
+        Args:
+            callback: Function to call
+            *args: Postional arguments to pass to function.
+            **kwargs: Key arguments to pass to function.
+        """
+
+        def wrapped_callback(*args: Any, **kwargs: Any) -> None:
+            # Since this callback can be invoked immediately if the reactor is already
+            # running, we can't always assume that we're running in the sentinel
+            # logcontext (i.e. we can't assert that we're in the sentinel context like
+            # we can in other methods).
+            #
+            # We will only be running in the sentinel logcontext if the reactor was not
+            # running when `call_when_running` was invoked and later starts up.
+            #
+            # assert context.current_context() is context.SENTINEL_CONTEXT
+
+            # Because this is a callback from the reactor, we will be using the
+            # `sentinel` log context at this point. We want the function to log with
+            # some logcontext as we want to know which server the logs came from.
+            #
+            # We use `PreserveLoggingContext` to prevent our new `call_when_running`
+            # logcontext from finishing as soon as we exit this function, in case `f`
+            # returns an awaitable/deferred which would continue running and may try to
+            # restore the `loop_call` context when it's done (because it's trying to
+            # adhere to the Synapse logcontext rules.)
+            #
+            # This also ensures that we return to the `sentinel` context when we exit
+            # this function and yield control back to the reactor to avoid leaking the
+            # current logcontext to the reactor (which would then get picked up and
+            # associated with the next thing the reactor does)
+            with context.PreserveLoggingContext(
+                context.LoggingContext("call_when_running")
+            ):
+                # We use `run_in_background` to reset the logcontext after `f` (or the
+                # awaitable returned by `f`) completes to avoid leaking the current
+                # logcontext to the reactor
+                context.run_in_background(callback, *args, **kwargs)
+
+        # We can ignore the lint here since this class is the one location
+        # callWhenRunning should be called.
+        self._reactor.callWhenRunning(wrapped_callback, *args, **kwargs)  # type: ignore[prefer-synapse-clock-call-when-running]
+
+    def add_system_event_trigger(
+        self,
+        phase: str,
+        event_type: str,
+        callback: Callable[P, object],
+        *args: P.args,
+        **kwargs: P.kwargs,
+    ) -> None:
+        """
+        Add a function to be called when a system event occurs.
+
+        Equivalent to `reactor.addSystemEventTrigger` (see the that docstring for more
+        details), but ensures that the callback is run in a logging context.
+
+        Args:
+            phase: a time to call the event -- either the string 'before', 'after', or
+                'during', describing when to call it relative to the event's execution.
+            eventType: this is a string describing the type of event.
+            callback: Function to call
+            *args: Postional arguments to pass to function.
+            **kwargs: Key arguments to pass to function.
+        """
+
+        def wrapped_callback(*args: Any, **kwargs: Any) -> None:
+            assert context.current_context() is context.SENTINEL_CONTEXT, (
+                "Expected `add_system_event_trigger` callback from the reactor to start with the sentinel logcontext "
+                f"but saw {context.current_context()}. In other words, another task shouldn't have "
+                "leaked their logcontext to us."
+            )
+
+            # Because this is a callback from the reactor, we will be using the
+            # `sentinel` log context at this point. We want the function to log with
+            # some logcontext as we want to know which server the logs came from.
+            #
+            # We use `PreserveLoggingContext` to prevent our new `system_event`
+            # logcontext from finishing as soon as we exit this function, in case `f`
+            # returns an awaitable/deferred which would continue running and may try to
+            # restore the `loop_call` context when it's done (because it's trying to
+            # adhere to the Synapse logcontext rules.)
+            #
+            # This also ensures that we return to the `sentinel` context when we exit
+            # this function and yield control back to the reactor to avoid leaking the
+            # current logcontext to the reactor (which would then get picked up and
+            # associated with the next thing the reactor does)
+            with context.PreserveLoggingContext(context.LoggingContext("system_event")):
+                # We use `run_in_background` to reset the logcontext after `f` (or the
+                # awaitable returned by `f`) completes to avoid leaking the current
+                # logcontext to the reactor
+                context.run_in_background(callback, *args, **kwargs)
+
+        # We can ignore the lint here since this class is the one location
+        # `addSystemEventTrigger` should be called.
+        self._reactor.addSystemEventTrigger(
+            phase, event_type, wrapped_callback, *args, **kwargs
+        )  # type: ignore[prefer-synapse-clock-add-system-event-trigger]

synapse/util/json.py

@@ -0,0 +1,57 @@
+#
+# This file is licensed under the Affero General Public License (AGPL) version 3.
+#
+# Copyright (C) 2025 New Vector, Ltd
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+#
+# See the GNU Affero General Public License for more details:
+# <https://www.gnu.org/licenses/agpl_3.0.html>.
+#
+#
+
+import json
+from typing import (
+    Any,
+    Dict,
+)
+
+from immutabledict import immutabledict
+
+
+def _reject_invalid_json(val: Any) -> None:
+    """Do not allow Infinity, -Infinity, or NaN values in JSON."""
+    raise ValueError("Invalid JSON value: '%s'" % val)
+
+
+def _handle_immutabledict(obj: Any) -> Dict[Any, Any]:
+    """Helper for json_encoder. Makes immutabledicts serializable by returning
+    the underlying dict
+    """
+    if type(obj) is immutabledict:
+        # fishing the protected dict out of the object is a bit nasty,
+        # but we don't really want the overhead of copying the dict.
+        try:
+            # Safety: we catch the AttributeError immediately below.
+            return obj._dict
+        except AttributeError:
+            # If all else fails, resort to making a copy of the immutabledict
+            return dict(obj)
+    raise TypeError(
+        "Object of type %s is not JSON serializable" % obj.__class__.__name__
+    )
+
+
+# A custom JSON encoder which:
+#   * handles immutabledicts
+#   * produces valid JSON (no NaNs etc)
+#   * reduces redundant whitespace
+json_encoder = json.JSONEncoder(
+    allow_nan=False, separators=(",", ":"), default=_handle_immutabledict
+)
+
+# Create a custom decoder to reject Python extensions to JSON.
+json_decoder = json.JSONDecoder(parse_constant=_reject_invalid_json)

synapse/util/macaroons.py

@@ -28,7 +28,8 @@ import attr
 import pymacaroons
 from pymacaroons.exceptions import MacaroonVerificationFailedException
 
-from synapse.util import Clock, stringutils
+from synapse.util import stringutils
+from synapse.util.clock import Clock
 
 MacaroonType = Literal["access", "delete_pusher", "session"]
 

synapse/util/metrics.py

@@ -42,7 +42,7 @@ from synapse.logging.context import (
     current_context,
 )
 from synapse.metrics import SERVER_NAME_LABEL, InFlightGauge
-from synapse.util import Clock
+from synapse.util.clock import Clock
 
 logger = logging.getLogger(__name__)
 

synapse/util/ratelimitutils.py

@@ -53,7 +53,7 @@ from synapse.logging.context import (
 )
 from synapse.logging.opentracing import start_active_span
 from synapse.metrics import SERVER_NAME_LABEL, Histogram, LaterGauge
-from synapse.util import Clock
+from synapse.util.clock import Clock
 
 if typing.TYPE_CHECKING:
     from contextlib import _GeneratorContextManager

synapse/util/retryutils.py

@@ -27,7 +27,7 @@ from synapse.api.errors import CodeMessageException
 from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.storage import DataStore
 from synapse.types import StrCollection
-from synapse.util import Clock
+from synapse.util.clock import Clock
 
 if TYPE_CHECKING:
     from synapse.notifier import Notifier

synapse/visibility.py

@@ -55,7 +55,7 @@ from synapse.types import (
     get_domain_from_id,
 )
 from synapse.types.state import StateFilter
-from synapse.util import Clock
+from synapse.util.clock import Clock
 
 logger = logging.getLogger(__name__)
 filtered_event_logger = logging.getLogger("synapse.visibility.filtered_event_debug")

synmark/__main__.py

@@ -62,7 +62,10 @@ def make_test(
                 return res
 
             d.addBoth(on_done)
-            reactor.callWhenRunning(lambda: d.callback(True))
+            # type-ignore: This is outside of Synapse (just a utility benchmark script)
+            # so we don't need to worry about  which server the logs are coming from
+            # (`Clock.call_when_running` manages the logcontext for us).
+            reactor.callWhenRunning(lambda: d.callback(True))  # type: ignore[prefer-synapse-clock-call-when-running]
             reactor.run()
 
         # mypy thinks this is an object for some reason.

synmark/suites/logging.py

@@ -37,7 +37,7 @@ from synapse.config.logger import _setup_stdlib_logging
 from synapse.logging import RemoteHandler
 from synapse.synapse_rust import reset_logging_config
 from synapse.types import ISynapseReactor
-from synapse.util import Clock
+from synapse.util.clock import Clock
 
 
 class LineCounter(LineOnlyReceiver):

tests/api/test_auth.py

@@ -39,7 +39,7 @@ from synapse.appservice import ApplicationService
 from synapse.server import HomeServer
 from synapse.storage.databases.main.registration import TokenLookupResult
 from synapse.types import Requester, UserID
-from synapse.util import Clock
+from synapse.util.clock import Clock
 
 from tests import unittest
 from tests.unittest import override_config

tests/api/test_filtering.py

@@ -33,7 +33,7 @@ from synapse.api.filtering import Filter
 from synapse.api.presence import UserPresenceState
 from synapse.server import HomeServer
 from synapse.types import JsonDict, UserID
-from synapse.util import Clock
+from synapse.util.clock import Clock
 from synapse.util.frozenutils import freeze
 
 from tests import unittest

tests/api/test_urls.py

@@ -17,7 +17,7 @@ from twisted.internet.testing import MemoryReactor
 
 from synapse.api.urls import LoginSSORedirectURIBuilder
 from synapse.server import HomeServer
-from synapse.util import Clock
+from synapse.util.clock import Clock
 
 from tests.unittest import HomeserverTestCase
 

tests/app/test_openid_listener.py

@@ -29,7 +29,7 @@ from synapse.app.homeserver import SynapseHomeServer
 from synapse.config.server import parse_listener_def
 from synapse.server import HomeServer
 from synapse.types import JsonDict
-from synapse.util import Clock
+from synapse.util.clock import Clock
 
 from tests.server import make_request
 from tests.unittest import HomeserverTestCase

tests/app/test_phone_stats_home.py

@@ -2,7 +2,7 @@ import synapse
 from synapse.app.phone_stats_home import start_phone_stats_home
 from synapse.rest.client import login, room
 from synapse.server import HomeServer
-from synapse.util import Clock
+from synapse.util.clock import Clock
 
 from tests.server import ThreadedMemoryReactorClock
 from tests.unittest import HomeserverTestCase

tests/appservice/test_api.py

@@ -26,7 +26,7 @@ from twisted.internet.testing import MemoryReactor
 from synapse.appservice import ApplicationService
 from synapse.server import HomeServer
 from synapse.types import JsonDict, UserID
-from synapse.util import Clock
+from synapse.util.clock import Clock
 
 from tests import unittest
 from tests.unittest import override_config

tests/appservice/test_scheduler.py

@@ -41,7 +41,7 @@ from synapse.events import EventBase
 from synapse.logging.context import make_deferred_yieldable
 from synapse.server import HomeServer
 from synapse.types import DeviceListUpdates, JsonDict
-from synapse.util import Clock
+from synapse.util.clock import Clock
 
 from tests import unittest
 

tests/config/test_room_directory.py

@@ -27,7 +27,7 @@ import synapse.rest.client.room
 from synapse.config._base import RootConfig
 from synapse.config.room_directory import RoomDirectoryConfig
 from synapse.server import HomeServer
-from synapse.util import Clock
+from synapse.util.clock import Clock
 
 from tests import unittest
 from tests.unittest import override_config

tests/crypto/test_keyring.py

@@ -49,7 +49,7 @@ from synapse.logging.context import (
 from synapse.server import HomeServer
 from synapse.storage.keys import FetchKeyResult
 from synapse.types import JsonDict
-from synapse.util import Clock
+from synapse.util.clock import Clock
 
 from tests import unittest
 from tests.unittest import logcontext_clean, override_config

tests/events/test_auto_accept_invites.py

@@ -41,7 +41,7 @@ from synapse.rest import admin
 from synapse.rest.client import login, room
 from synapse.server import HomeServer
 from synapse.types import StreamToken, UserID, UserInfo, create_requester
-from synapse.util import Clock
+from synapse.util.clock import Clock
 
 from tests.handlers.test_sync import generate_sync_config
 from tests.unittest import (

tests/events/test_presence_router.py

@@ -34,7 +34,7 @@ from synapse.rest import admin
 from synapse.rest.client import login, presence, room
 from synapse.server import HomeServer
 from synapse.types import JsonDict, StreamToken, create_requester
-from synapse.util import Clock
+from synapse.util.clock import Clock
 
 from tests.handlers.test_sync import SyncRequestKey, generate_sync_config
 from tests.unittest import (

tests/events/test_snapshot.py

@@ -26,7 +26,7 @@ from synapse.events.snapshot import EventContext
 from synapse.rest import admin
 from synapse.rest.client import login, room
 from synapse.server import HomeServer
-from synapse.util import Clock
+from synapse.util.clock import Clock
 
 from tests import unittest
 from tests.test_utils.event_injection import create_event

tests/federation/test_federation_catch_up.py

@@ -16,7 +16,7 @@ from synapse.rest import admin
 from synapse.rest.client import login, room
 from synapse.server import HomeServer
 from synapse.types import JsonDict
-from synapse.util import Clock
+from synapse.util.clock import Clock
 from synapse.util.retryutils import NotRetryingDestination
 
 from tests.test_utils import event_injection