Use a larger, dedicated threadpool for media sending (#17564)

changelog.d/17564.misc

@@ -0,0 +1 @@
+Speed up responding to media requests.

synapse/media/_base.py

@@ -51,15 +51,15 @@ from synapse.api.errors import Codes, cs_error
 from synapse.http.server import finish_request, respond_with_json
 from synapse.http.site import SynapseRequest
 from synapse.logging.context import (
-    defer_to_thread,
+    defer_to_threadpool,
     make_deferred_yieldable,
     run_in_background,
 )
-from synapse.types import ISynapseReactor
 from synapse.util import Clock
 from synapse.util.stringutils import is_ascii
 
 if TYPE_CHECKING:
+    from synapse.server import HomeServer
     from synapse.storage.databases.main.media_repository import LocalMedia
 
 
@@ -132,6 +132,7 @@ def respond_404(request: SynapseRequest) -> None:
 
 
 async def respond_with_file(
+    hs: "HomeServer",
     request: SynapseRequest,
     media_type: str,
     file_path: str,
@@ -148,7 +149,7 @@ async def respond_with_file(
         add_file_headers(request, media_type, file_size, upload_name)
 
         with open(file_path, "rb") as f:
-            await ThreadedFileSender(request.reactor).beginFileTransfer(f, request)
+            await ThreadedFileSender(hs).beginFileTransfer(f, request)
 
         finish_request(request)
     else:
@@ -632,8 +633,9 @@ class ThreadedFileSender:
     # read.
     TIMEOUT_SECONDS = 90.0
 
-    def __init__(self, reactor: ISynapseReactor) -> None:
-        self.reactor = reactor
+    def __init__(self, hs: "HomeServer") -> None:
+        self.reactor = hs.get_reactor()
+        self.thread_pool = hs.get_media_sender_thread_pool()
 
         self.file: Optional[BinaryIO] = None
         self.deferred: "Deferred[None]" = Deferred()
@@ -661,7 +663,12 @@ class ThreadedFileSender:
 
         # We set the wakeup signal as we should start producing immediately.
         self.wakeup_event.set()
-        run_in_background(defer_to_thread, self.reactor, self._on_thread_read_loop)
+        run_in_background(
+            defer_to_threadpool,
+            self.reactor,
+            self.thread_pool,
+            self._on_thread_read_loop,
+        )
 
         return make_deferred_yieldable(self.deferred)
 

synapse/media/media_storage.py

@@ -57,7 +57,7 @@ from synapse.media._base import ThreadedFileSender
 from synapse.util import Clock
 from synapse.util.file_consumer import BackgroundFileConsumer
 
-from ..types import ISynapseReactor, JsonDict
+from ..types import JsonDict
 from ._base import FileInfo, Responder
 from .filepath import MediaFilePaths
 
@@ -209,7 +209,7 @@ class MediaStorage:
             local_path = os.path.join(self.local_media_directory, path)
             if os.path.exists(local_path):
                 logger.debug("responding with local file %s", local_path)
-                return FileResponder(self.reactor, open(local_path, "rb"))
+                return FileResponder(self.hs, open(local_path, "rb"))
             logger.debug("local file %s did not exist", local_path)
 
         for provider in self.storage_providers:
@@ -332,14 +332,12 @@ class FileResponder(Responder):
             is closed when finished streaming.
     """
 
-    def __init__(self, reactor: ISynapseReactor, open_file: BinaryIO):
-        self.reactor = reactor
+    def __init__(self, hs: "HomeServer", open_file: BinaryIO):
+        self.hs = hs
         self.open_file = open_file
 
     def write_to_consumer(self, consumer: IConsumer) -> Deferred:
-        return ThreadedFileSender(self.reactor).beginFileTransfer(
-            self.open_file, consumer
-        )
+        return ThreadedFileSender(self.hs).beginFileTransfer(self.open_file, consumer)
 
     def __exit__(
         self,

synapse/media/storage_provider.py

@@ -178,7 +178,7 @@ class FileStorageProviderBackend(StorageProvider):
 
         backup_fname = os.path.join(self.base_directory, path)
         if os.path.isfile(backup_fname):
-            return FileResponder(self.reactor, open(backup_fname, "rb"))
+            return FileResponder(self.hs, open(backup_fname, "rb"))
 
         return None
 

synapse/media/thumbnailer.py

@@ -374,11 +374,11 @@ class ThumbnailProvider:
                 await respond_with_multipart_responder(
                     self.hs.get_clock(),
                     request,
-                    FileResponder(self.reactor, open(file_path, "rb")),
+                    FileResponder(self.hs, open(file_path, "rb")),
                     media_info,
                 )
             else:
-                await respond_with_file(request, desired_type, file_path)
+                await respond_with_file(self.hs, request, desired_type, file_path)
         else:
             logger.warning("Failed to generate thumbnail")
             raise SynapseError(400, "Failed to generate thumbnail.")
@@ -456,7 +456,7 @@ class ThumbnailProvider:
         )
 
         if file_path:
-            await respond_with_file(request, desired_type, file_path)
+            await respond_with_file(self.hs, request, desired_type, file_path)
         else:
             logger.warning("Failed to generate thumbnail")
             raise SynapseError(400, "Failed to generate thumbnail.")

synapse/server.py

@@ -34,6 +34,7 @@ from typing_extensions import TypeAlias
 
 from twisted.internet.interfaces import IOpenSSLContextFactory
 from twisted.internet.tcp import Port
+from twisted.python.threadpool import ThreadPool
 from twisted.web.iweb import IPolicyForHTTPS
 from twisted.web.resource import Resource
 
@@ -941,3 +942,21 @@ class HomeServer(metaclass=abc.ABCMeta):
     @cache_in_self
     def get_task_scheduler(self) -> TaskScheduler:
         return TaskScheduler(self)
+
+    @cache_in_self
+    def get_media_sender_thread_pool(self) -> ThreadPool:
+        """Fetch the threadpool used to read files when responding to media
+        download requests."""
+
+        # We can choose a large threadpool size as these threads predominately
+        # do IO rather than CPU work.
+        media_threadpool = ThreadPool(
+            name="media_threadpool", minthreads=1, maxthreads=50
+        )
+
+        media_threadpool.start()
+        self.get_reactor().addSystemEventTrigger(
+            "during", "shutdown", media_threadpool.stop
+        )
+
+        return media_threadpool

tests/server.py

@@ -1166,6 +1166,12 @@ def setup_test_homeserver(
 
     hs.get_auth_handler().validate_hash = validate_hash  # type: ignore[assignment]
 
+    # We need to replace the media threadpool with the fake test threadpool.
+    def thread_pool() -> threadpool.ThreadPool:
+        return reactor.getThreadPool()
+
+    hs.get_media_sender_thread_pool = thread_pool  # type: ignore[method-assign]
+
     # Load any configured modules into the homeserver
     module_api = hs.get_module_api()
     for module, module_config in hs.config.modules.loaded_modules: