use 127.0.0.1 instead of localhost

localhost can cause some issues on badly behaved or misconfigured systems,
and 127 seems simpler.

jupyterhub/app.py

@@ -50,7 +50,7 @@ from ._data import DATA_FILES_PATH
 from .log import CoroutineLogFormatter, log_request
 from .traitlets import URLPrefix, Command
 from .utils import (
-    url_path_join, localhost,
+    url_path_join,
     ISO8601_ms, ISO8601_s,
 )
 # classes for config
@@ -260,7 +260,7 @@ class JupyterHub(Application):
             token = orm.new_token()
         return token
     
-    proxy_api_ip = Unicode(localhost(), config=True,
+    proxy_api_ip = Unicode('127.0.0.1', config=True,
         help="The ip for the proxy API handlers"
     )
     proxy_api_port = Integer(config=True,
@@ -272,7 +272,7 @@ class JupyterHub(Application):
     hub_port = Integer(8081, config=True,
         help="The port for this process"
     )
-    hub_ip = Unicode(localhost(), config=True,
+    hub_ip = Unicode('127.0.0.1', config=True,
         help="The ip for this process"
     )
     

jupyterhub/orm.py

@@ -26,7 +26,7 @@ from sqlalchemy import create_engine
 
 from .utils import (
     random_port, url_path_join, wait_for_server, wait_for_http_server,
-    new_token, hash_token, compare_token, localhost,
+    new_token, hash_token, compare_token,
 )
 
 
@@ -78,7 +78,7 @@ class Server(Base):
         ip = self.ip
         if ip in {'', '0.0.0.0'}:
             # when listening on all interfaces, connect to localhost
-            ip = localhost()
+            ip = '127.0.0.1'
         return "{proto}://{ip}:{port}".format(
             proto=self.proto,
             ip=ip,
@@ -100,7 +100,7 @@ class Server(Base):
         since it can be non-connectable value, such as '', meaning all interfaces.
         """
         if self.ip in {'', '0.0.0.0'}:
-            return self.url.replace('localhost', self.ip or '*', 1)
+            return self.url.replace('127.0.0.1', self.ip or '*', 1)
         return self.url
     
     @gen.coroutine
@@ -109,12 +109,12 @@ class Server(Base):
         if http:
             yield wait_for_http_server(self.url, timeout=timeout)
         else:
-            yield wait_for_server(self.ip or localhost(), self.port, timeout=timeout)
+            yield wait_for_server(self.ip or '127.0.0.1', self.port, timeout=timeout)
     
     def is_up(self):
         """Is the server accepting connections?"""
         try:
-            socket.create_connection((self.ip or localhost(), self.port))
+            socket.create_connection((self.ip or '127.0.0.1', self.port))
         except socket.error as e:
             if e.errno == errno.ENETUNREACH:
                 try:

jupyterhub/spawner.py

@@ -22,7 +22,7 @@ from traitlets import (
 )
 
 from .traitlets import Command
-from .utils import random_port, localhost
+from .utils import random_port
 
 class Spawner(LoggingConfigurable):
     """Base class for spawning single-user notebook servers.
@@ -41,7 +41,7 @@ class Spawner(LoggingConfigurable):
     hub = Any()
     authenticator = Any()
     api_token = Unicode()
-    ip = Unicode(localhost(), config=True,
+    ip = Unicode('127.0.0.1', config=True,
         help="The IP address (or hostname) the single-user server should listen on"
     )
     start_timeout = Integer(60, config=True,

jupyterhub/tests/mocking.py

@@ -17,7 +17,6 @@ from ..spawner import LocalProcessSpawner
 from ..app import JupyterHub
 from ..auth import PAMAuthenticator
 from .. import orm
-from ..utils import localhost
 
 from pamela import PAMError
 
@@ -111,7 +110,7 @@ class MockHub(JupyterHub):
     db_file = None
     
     def _ip_default(self):
-        return localhost()
+        return '127.0.0.1'
     
     def _authenticator_class_default(self):
         return MockPAMAuthenticator

jupyterhub/tests/test_orm.py

@@ -20,7 +20,7 @@ def test_server(db):
     assert server.proto == 'http'
     assert isinstance(server.port, int)
     assert isinstance(server.cookie_name, str)
-    assert server.host == 'http://localhost:%i' % server.port
+    assert server.host == 'http://127.0.0.1:%i' % server.port
     assert server.url == server.host + '/'
     assert server.bind_url == 'http://*:%i/' % server.port
     server.ip = '127.0.0.1'

jupyterhub/tests/test_spawner.py

@@ -45,7 +45,7 @@ def new_spawner(db, **kwargs):
 def test_spawner(db, io_loop):
     spawner = new_spawner(db)
     io_loop.run_sync(spawner.start)
-    assert spawner.user.server.ip == 'localhost'
+    assert spawner.user.server.ip == '127.0.0.1'
     
     # wait for the process to get to the while True: loop
     time.sleep(1)
@@ -59,7 +59,7 @@ def test_spawner(db, io_loop):
 def test_single_user_spawner(db, io_loop):
     spawner = new_spawner(db, cmd=['jupyterhub-singleuser'])
     io_loop.run_sync(spawner.start)
-    assert spawner.user.server.ip == 'localhost'
+    assert spawner.user.server.ip == '127.0.0.1'
     # wait for http server to come up,
     # checking for early termination every 1s
     def wait():

jupyterhub/utils.py

@@ -195,35 +195,3 @@ def url_path_join(*pieces):
 
     return result
 
-def localhost():
-    """Return localhost or 127.0.0.1"""
-    if hasattr(localhost, '_localhost'):
-        return localhost._localhost
-    binder = connector = None
-    try:
-        binder = socket.socket()
-        binder.bind(('localhost', 0))
-        binder.listen(1)
-        port = binder.getsockname()[1]
-        def accept():
-            try:
-                conn, addr = binder.accept()
-            except ConnectionAbortedError:
-                pass
-            else:
-                conn.close()
-        t = Thread(target=accept)
-        t.start()
-        connector = socket.create_connection(('localhost', port), timeout=10)
-        t.join(timeout=10)
-    except (socket.error, socket.gaierror) as e:
-        warnings.warn("localhost doesn't appear to work, using 127.0.0.1\n%s" % e, RuntimeWarning)
-        localhost._localhost = '127.0.0.1'
-    else:
-        localhost._localhost = 'localhost'
-    finally:
-        if binder:
-            binder.close()
-        if connector:
-            connector.close()
-    return localhost._localhost