From 1b974d0d048202da1f978849ba268d05ef9653b2 Mon Sep 17 00:00:00 2001
From: John Kirkham <jakirkham@gmail.com>
Date: Wed, 28 Jul 2021 15:49:28 -0700
Subject: [PATCH] Always cast frames to `memoryview`s

---
 distributed/comm/tcp.py | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/distributed/comm/tcp.py b/distributed/comm/tcp.py
index 7dfe78f5eb..e984b00dfc 100644
--- a/distributed/comm/tcp.py
+++ b/distributed/comm/tcp.py
@@ -271,10 +271,11 @@ async def write(self, msg, serializers=None, on_error="message"):
                     if stream._write_buffer is None:
                         raise StreamClosedError()
 
-                    if isinstance(each_frame, memoryview):
-                        # Make sure that `len(data) == data.nbytes`
-                        # See <https://github.com/tornadoweb/tornado/pull/2996>
-                        each_frame = each_frame.cast("B")
+                    each_frame = memoryview(each_frame)
+
+                    # Make sure that `len(data) == data.nbytes`
+                    # See <https://github.com/tornadoweb/tornado/pull/2996>
+                    each_frame = each_frame.cast("B")
 
                     stream._write_buffer.append(each_frame)
                     stream._total_write_index += each_frame_nbytes