Merge pull request #2399 from pallets/no-keep-alive

disable keep-alive connections in dev server
pallets · Apr 25, 2022 · 53ba5f8 · 53ba5f8
2 parents 19323ef + 600a2b9
commit 53ba5f8
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diff --git a/CHANGES.rst b/CHANGES.rst
@@ -11,6 +11,9 @@ Unreleased
     ``<!doctype html>`` and ``<html lang=en>``. :issue:`2390`
 -   Fix ability to set some ``cache_control`` attributes to ``False``.
     :issue:`2379`
+-   Disable ``keep-alive`` connections in the development server, which
+    are not supported sufficiently by Python's ``http.server``.
+    :issue:`2397`
 
 
 Version 2.1.1

diff --git a/src/werkzeug/serving.py b/src/werkzeug/serving.py
@@ -271,18 +271,23 @@ def write(data: bytes) -> None:
                 # is the more conservative behavior and matches other
                 # parts of the code.
                 # https://httpwg.org/specs/rfc7230.html#rfc.section.3.3.1
-                if not (
-                    "content-length" in header_keys
-                    or environ["REQUEST_METHOD"] == "HEAD"
-                    or (100 <= code < 200)
-                    or code in {204, 304}
+                if (
+                    not (
+                        "content-length" in header_keys
+                        or environ["REQUEST_METHOD"] == "HEAD"
+                        or (100 <= code < 200)
+                        or code in {204, 304}
+                    )
+                    and self.protocol_version >= "HTTP/1.1"
                 ):
-                    if self.protocol_version >= "HTTP/1.1":
-                        chunk_response = True
-                        self.send_header("Transfer-Encoding", "chunked")
-                    else:
-                        self.send_header("Connection", "close")
-
+                    chunk_response = True
+                    self.send_header("Transfer-Encoding", "chunked")
+
+                # Always close the connection. This disables HTTP/1.1
+                # keep-alive connections. They aren't handled well by
+                # Python's http.server because it doesn't know how to
+                # drain the stream before the next request line.
+                self.send_header("Connection", "close")
                 self.end_headers()
 
             assert isinstance(data, bytes), "applications must write bytes"