Remove BackgroundSocket wrapper, use IOPubThread directly

ipykernel/inprocess/ipkernel.py

@@ -15,7 +15,7 @@
 from ipykernel.jsonutil import json_clean
 from ipykernel.zmqshell import ZMQInteractiveShell
 
-from ..iostream import BackgroundSocket, IOPubThread, OutStream
+from ..iostream import IOPubThread, OutStream
 from .constants import INPROCESS_KEY
 from .socket import DummySocket
 
@@ -60,11 +60,11 @@ def _default_iopub_thread(self):
         thread.start()
         return thread
 
-    iopub_socket: BackgroundSocket = Instance(BackgroundSocket)  # type:ignore[assignment]
+    iopub_socket: IOPubThread = Instance(IOPubThread)  # type:ignore[assignment]
 
     @default("iopub_socket")
     def _default_iopub_socket(self):
-        return self.iopub_thread.background_socket
+        return self.iopub_thread
 
     stdin_socket = Instance(DummySocket, ())
 
@@ -133,9 +133,9 @@ def _redirected_io(self):
 
     def _io_dispatch(self, change):
         """Called when a message is sent to the IO socket."""
-        assert self.iopub_socket.io_thread is not None
+        assert self.iopub_socket is not None
         assert self.session is not None
-        _ident, msg = self.session.recv(self.iopub_socket.io_thread.socket, copy=False)
+        _ident, msg = self.session.recv(self.iopub_socket.socket, copy=False)
         for frontend in self.frontends:
             assert frontend is not None
             frontend.iopub_channel.call_handlers(msg)

ipykernel/iostream.py

@@ -42,9 +42,6 @@ class IOPubThread:
     """An object for sending IOPub messages in a background thread
 
     Prevents a blocking main thread from delaying output from threads.
-
-    IOPubThread(pub_socket).background_socket is a Socket-API-providing object
-    whose IO is always run in a thread.
     """
 
     def __init__(self, socket, pipe=False, session=False):
@@ -61,7 +58,6 @@ def __init__(self, socket, pipe=False, session=False):
         self.socket = socket
         self.session = session
         self._stopped = False
-        self.background_socket = BackgroundSocket(self)
         self._master_pid = os.getpid()
         self._pipe_flag = pipe
         self.io_loop = IOLoop(make_current=False)
@@ -340,6 +336,10 @@ def schedule(self, f):
         else:
             f()
 
+    def send(self, msg, *args, **kwargs):
+        """Send a message to the socket."""
+        return self.send_multipart([msg], *args, **kwargs)
+
     def send_multipart(self, *args, **kwargs):
         """send_multipart schedules actual zmq send in my thread.
 
@@ -367,57 +367,6 @@ def _really_send(self, msg, *args, **kwargs):
             ctx.term()
 
 
-class BackgroundSocket:
-    """Wrapper around IOPub thread that provides zmq send[_multipart]"""
-
-    io_thread = None
-
-    def __init__(self, io_thread):
-        """Initialize the socket."""
-        self.io_thread = io_thread
-
-    def __getattr__(self, attr):
-        """Wrap socket attr access for backward-compatibility"""
-        if attr.startswith("__") and attr.endswith("__"):
-            # don't wrap magic methods
-            super().__getattr__(attr)  # type:ignore[misc]
-        assert self.io_thread is not None
-        if hasattr(self.io_thread.socket, attr):
-            warnings.warn(
-                f"Accessing zmq Socket attribute {attr} on BackgroundSocket"
-                f" is deprecated since ipykernel 4.3.0"
-                f" use .io_thread.socket.{attr}",
-                DeprecationWarning,
-                stacklevel=2,
-            )
-            return getattr(self.io_thread.socket, attr)
-        return super().__getattr__(attr)  # type:ignore[misc]
-
-    def __setattr__(self, attr, value):
-        """Set an attribute on the socket."""
-        if attr == "io_thread" or (attr.startswith("__") and attr.endswith("__")):
-            super().__setattr__(attr, value)
-        else:
-            warnings.warn(
-                f"Setting zmq Socket attribute {attr} on BackgroundSocket"
-                f" is deprecated since ipykernel 4.3.0"
-                f" use .io_thread.socket.{attr}",
-                DeprecationWarning,
-                stacklevel=2,
-            )
-            assert self.io_thread is not None
-            setattr(self.io_thread.socket, attr, value)
-
-    def send(self, msg, *args, **kwargs):
-        """Send a message to the socket."""
-        return self.send_multipart([msg], *args, **kwargs)
-
-    def send_multipart(self, *args, **kwargs):
-        """Schedule send in IO thread"""
-        assert self.io_thread is not None
-        return self.io_thread.send_multipart(*args, **kwargs)
-
-
 class OutStream(TextIOBase):
     """A file like object that publishes the stream to a 0MQ PUB socket.
 

ipykernel/kernelapp.py

@@ -384,8 +384,7 @@ def init_iopub(self, context):
         self.configure_tornado_logger()
         self.iopub_thread = IOPubThread(self.iopub_socket, pipe=True, session=self.session)
         self.iopub_thread.start()
-        # backward-compat: wrap iopub socket API in background thread
-        self.iopub_socket = self.iopub_thread.background_socket
+        self.iopub_socket = self.iopub_thread
 
     def init_heartbeat(self):
         """start the heart beating"""

tests/test_io.py

@@ -14,7 +14,7 @@
 import zmq
 from jupyter_client.session import Session
 
-from ipykernel.iostream import MASTER, BackgroundSocket, IOPubThread, OutStream
+from ipykernel.iostream import MASTER, IOPubThread, OutStream
 
 
 @pytest.fixture()
@@ -81,15 +81,8 @@ def test_io_thread(iopub_thread):
     thread._really_send(None)
 
 
-def test_background_socket(iopub_thread):
-    sock = BackgroundSocket(iopub_thread)
-    assert sock.__class__ == BackgroundSocket
-    with warnings.catch_warnings():
-        warnings.simplefilter("ignore", DeprecationWarning)
-        sock.linger = 101
-        assert iopub_thread.socket.linger == 101
-    assert sock.io_thread == iopub_thread
-    sock.send(b"hi")
+def test_iopub_thread_send(iopub_thread):
+    iopub_thread.send(b"hi")
 
 
 def test_outstream(iopub_thread):