use a mock.patch instead of a raw socket in test_web_preload(_worker)

distributed/tests/test_preload.py

@@ -1,18 +1,16 @@
-import asyncio
 import os
 import re
 import shutil
-import socket
 import sys
 import tempfile
 from textwrap import dedent
+from unittest import mock
 
 import pytest
 
 import dask
 
 from distributed import Client, Nanny, Scheduler, Worker
-from distributed.compatibility import to_thread
 from distributed.utils_test import captured_logger, cluster, gen_cluster, gen_test
 
 PRELOAD_TEXT = """
@@ -157,38 +155,30 @@ async def test_preload_import_time(cleanup):
 
 @gen_test()
 async def test_web_preload():
-    def preload():
-        with server_sock.accept()[0] as client_sock, client_sock.makefile("rwb") as f:
-            assert f.readline() == b"GET /preload HTTP/1.1\r\n"
-            f.write(
-                b"HTTP/1.1 200 OK"
-                b"\r\nContent-Length: 53"
-                b"\r\n\r\n"
-                b"def dask_setup(dask_server):"
-                b"\n    dask_server.foo = 1"
-                b"\n"
-            )
-
-    async def test():
-        port = server_sock.getsockname()[1]
-        with captured_logger("distributed.preloading") as log:
-            async with Scheduler(
-                host="localhost",
-                preload=[f"http://127.0.0.1:{port}/preload"],
-            ) as s:
-                assert s.foo == 1
+    with mock.patch(
+        "urllib3.PoolManager.request",
+        **{
+            "return_value.data": b"def dask_setup(dask_server):"
+            b"\n    dask_server.foo = 1"
+            b"\n"
+        },
+    ) as request, captured_logger("distributed.preloading") as log:
+        async with Scheduler(
+            host="localhost", preload=["http://example.com/preload"]
+        ) as s:
+            assert s.foo == 1
         assert (
             re.match(
-                r"(?s).*Downloading preload at http://127.0.0.1:\d+/preload\n"
-                r".*Run preload setup function: http://127.0.0.1:\d+/preload\n"
+                r"(?s).*Downloading preload at http://example.com/preload\n"
+                r".*Run preload setup function: http://example.com/preload\n"
                 r".*",
                 log.getvalue(),
             )
             is not None
         )
-
-    with socket.create_server(("127.0.0.1", 0)) as server_sock:
-        await asyncio.gather(to_thread(preload), test())
+    assert request.mock_calls == [
+        mock.call(method="GET", url="http://example.com/preload", retries=mock.ANY)
+    ]
 
 
 @gen_cluster(nthreads=[])
@@ -213,28 +203,20 @@ async def test_scheduler_startup_nanny(s):
 
 @gen_test()
 async def test_web_preload_worker():
-    def preload():
-        with server_sock.accept()[0] as client_sock, client_sock.makefile("rwb") as f:
-            assert f.readline() == b"GET /preload HTTP/1.1\r\n"
-            f.write(
-                b"HTTP/1.1 200 OK"
-                b"\r\nContent-Length: 70"
-                b"\r\n\r\n"
-                b"import dask"
-                b'\ndask.config.set(scheduler_address="tcp://127.0.0.1:8786")'
-                b"\n"
-            )
-
-    async def test():
-        port = server_sock.getsockname()[1]
+    with mock.patch(
+        "urllib3.PoolManager.request",
+        **{
+            "return_value.data": b"import dask"
+            b'\ndask.config.set(scheduler_address="tcp://127.0.0.1:8786")'
+            b"\n"
+        },
+    ) as request:
         async with Scheduler(port=8786, host="localhost") as s:
-            async with Nanny(
-                preload_nanny=[f"http://127.0.0.1:{port}/preload"]
-            ) as nanny:
+            async with Nanny(preload_nanny=["http://example.com/preload"]) as nanny:
                 assert nanny.scheduler_addr == s.address
-
-    with socket.create_server(("127.0.0.1", 0)) as server_sock:
-        await asyncio.gather(to_thread(preload), test())
+    assert request.mock_calls == [
+        mock.call(method="GET", url="http://example.com/preload", retries=mock.ANY)
+    ]
 
 
 # This test is blocked on https://github.com/dask/distributed/issues/5819