Clean up cached HTTP connections on shutdown.

src/allmydata/storage/http_client.py

@@ -310,6 +310,7 @@ class StorageClient(object):
     _base_url: DecodedURL
     _swissnum: bytes
     _treq: Union[treq, StubTreq, HTTPClient]
+    _pool: HTTPConnectionPool
     _clock: IReactorTime
 
     @classmethod
@@ -339,7 +340,7 @@ class StorageClient(object):
         )
 
         https_url = DecodedURL().replace(scheme="https", host=nurl.host, port=nurl.port)
-        return cls(https_url, swissnum, treq_client, reactor)
+        return cls(https_url, swissnum, treq_client, pool, reactor)
 
     def relative_url(self, path: str) -> DecodedURL:
         """Get a URL relative to the base URL."""
@@ -479,6 +480,10 @@ class StorageClient(object):
                 ).read()
                 raise ClientException(response.code, response.phrase, data)
 
+    def shutdown(self) -> Deferred:
+        """Shutdown any connections."""
+        return self._pool.closeCachedConnections()
+
 
 @define(hash=True)
 class StorageClientGeneral(object):

src/allmydata/storage_client.py

@@ -1271,6 +1271,11 @@ class HTTPNativeStorageServer(service.MultiService):
         if self._lc.running:
             self._lc.stop()
         self._failed_to_connect("shut down")
+
+        maybe_storage_server = self.get_storage_server()
+        if maybe_storage_server is not None:
+            result.addCallback(lambda _: maybe_storage_server._http_client.shutdown())
+
         return result