Windows development - connection fails sometimes with `urllib3` error on page load

Describe the bug In Windows development, pages sometimes randomly fail to load in the frontend and produce urllib3 errors in the backend.

To Reproduce Steps to reproduce the behavior (if you get lucky, you’ll run into the bug):

1. Run the start script
2. Navigate to localhost:8181
3. Click “LIBRARY”
4. See error (if you’re lucky)

Observed behavior Orange error is raised in the frontend. Various urllib3 errors are raised in console. Logs added below.

Expected behavior All pages should load completely without errors in Windows devservers.

Desktop:

• OS: Windows WSL1 and WSL2

Additional context Issue encountered in #12190.

Console logs On WSL1 (cc @MohdImran001):

WARNING  2021-03-22 11:43:20,920 base.py:281] PUT http://localhost:9200/collections [status:N/A request:10.007s]
Traceback (most recent call last):
  File "/home/skull/opensource/oppia/third_party/python_libs/elasticsearch/connection/http_urllib3.py", line 246, in perform_request
    method, url, body, retries=Retry(False), headers=request_headers, **kw
  File "/home/skull/opensource/oppia/third_party/python_libs/urllib3/connectionpool.py", line 727, in urlopen
    method, url, error=e, _pool=self, _stacktrace=sys.exc_info()[2]
  File "/home/skull/opensource/oppia/third_party/python_libs/urllib3/util/retry.py", line 386, in increment
    raise six.reraise(type(error), error, _stacktrace)
  File "/home/skull/opensource/oppia/third_party/python_libs/urllib3/connectionpool.py", line 677, in urlopen
    chunked=chunked,
  File "/home/skull/opensource/oppia/third_party/python_libs/urllib3/connectionpool.py", line 428, in _make_request
    self._raise_timeout(err=e, url=url, timeout_value=read_timeout)
  File "/home/skull/opensource/oppia/third_party/python_libs/urllib3/connectionpool.py", line 336, in _raise_timeout
    self, url, "Read timed out. (read timeout=%s)" % timeout_value
ReadTimeoutError: HTTPConnectionPool(host='localhost', port=9200): Read timed out. (read timeout=10)
ERROR    2021-03-22 11:43:21,079 base.py:464] Traceback (most recent call last):
  File "/home/skull/opensource/oppia/third_party/python_libs/webapp2.py", line 604, in dispatch
    return method(*args, **kwargs)
  File "/home/skull/opensource/oppia/core/controllers/acl_decorators.py", line 86, in test_can_access
    return handler(self, *args, **kwargs)
  File "/home/skull/opensource/oppia/core/controllers/library.py", line 121, in get
    constants.DEFAULT_LANGUAGE_CODE])
INFO     2021-03-22 11:43:21,177 module.py:865] default: "GET /libraryindexhandler HTTP/1.1" 500 168
  File "/home/skull/opensource/oppia/core/domain/summary_services.py", line 494, in get_library_groups
    '', group['search_categories'], language_codes, 8)[0]
  File "/home/skull/opensource/oppia/core/domain/search_services.py", line 247, in search_collections
    offset=offset, size=size, ids_only=True)
  File "/home/skull/opensource/oppia/core/platform/search/elastic_search_services.py", line 222, in search
    _create_index(index_name)
  File "/home/skull/opensource/oppia/core/platform/search/elastic_search_services.py", line 48, in _create_index
    ES.indices.create(index_name)
  File "/home/skull/opensource/oppia/third_party/python_libs/elasticsearch/client/utils.py", line 152, in _wrapped
    return func(*args, params=params, headers=headers, **kwargs)
  File "/home/skull/opensource/oppia/third_party/python_libs/elasticsearch/client/indices.py", line 124, in create
    "PUT", _make_path(index), params=params, headers=headers, body=body
  File "/home/skull/opensource/oppia/third_party/python_libs/elasticsearch/transport.py", line 392, in perform_request
    raise e
ConnectionTimeout: ConnectionTimeout caused by - ReadTimeoutError(HTTPConnectionPool(host='localhost', port=9200): Read timed out. (read timeout=10))

ERROR    2021-03-22 11:43:21,080 base.py:474] Exception raised: ConnectionTimeout caused by - ReadTimeoutError(HTTPConnectionPool(host='localhost', port=9200): Read timed out. (read timeout=10))

On WSL2:

WARNING  2021-03-23 03:28:07,371 base.py:281] POST http://localhost:9200/collections/_search?from=0&size=9 [status:N/A request:0.001s]
Traceback (most recent call last):
  File "/home/eric/opensource/oppia/third_party/python_libs/elasticsearch/connection/http_urllib3.py", line 246, in perform_request
    method, url, body, retries=Retry(False), headers=request_headers, **kw
  File "/home/eric/opensource/oppia/third_party/python_libs/urllib3/connectionpool.py", line 727, in urlopen
    method, url, error=e, _pool=self, _stacktrace=sys.exc_info()[2]
  File "/home/eric/opensource/oppia/third_party/python_libs/urllib3/util/retry.py", line 386, in increment
    raise six.reraise(type(error), error, _stacktrace)
  File "/home/eric/opensource/oppia/third_party/python_libs/urllib3/connectionpool.py", line 677, in urlopen
    chunked=chunked,
  File "/home/eric/opensource/oppia/third_party/python_libs/urllib3/connectionpool.py", line 392, in _make_request
    conn.request(method, url, **httplib_request_kw)
  File "/home/eric/opensource/oppia_tools/google-cloud-sdk-304.0.0/google-cloud-sdk/platform/google_appengine/google/appengine/dist27/python_std_lib/httplib.py", line 1055, in request
    self._send_request(method, url, body, headers)
  File "/home/eric/opensource/oppia_tools/google-cloud-sdk-304.0.0/google-cloud-sdk/platform/google_appengine/google/appengine/dist27/python_std_lib/httplib.py", line 1095, in _send_request
    self.endheaders(body)
  File "/home/eric/opensource/oppia_tools/google-cloud-sdk-304.0.0/google-cloud-sdk/platform/google_appengine/google/appengine/dist27/python_std_lib/httplib.py", line 1051, in endheaders
    self._send_output(message_body)
  File "/home/eric/opensource/oppia_tools/google-cloud-sdk-304.0.0/google-cloud-sdk/platform/google_appengine/google/appengine/dist27/python_std_lib/httplib.py", line 895, in _send_output
    self.send(msg)
  File "/home/eric/opensource/oppia_tools/google-cloud-sdk-304.0.0/google-cloud-sdk/platform/google_appengine/google/appengine/dist27/python_std_lib/httplib.py", line 857, in send
    self.connect()
  File "/home/eric/opensource/oppia/third_party/python_libs/urllib3/connection.py", line 187, in connect
    conn = self._new_conn()
  File "/home/eric/opensource/oppia/third_party/python_libs/urllib3/connection.py", line 172, in _new_conn
    self, "Failed to establish a new connection: %s" % e
NewConnectionError: <urllib3.connection.HTTPConnection object at 0x7f4311f11d90>: Failed to establish a new connection: [Errno 111] Connection refused

[SAEb-ai]

@MohdImran001 No, not till now.

[SAEb-ai]

@EricZLou PTAL (#12108) . I think this error has also been reproduced on CircleCI.