add server hook "on_starting" to allow socket patching to allow gevent worker reloading.

examples/example_gevent_reloader.py

@@ -3,6 +3,11 @@ import os
 import signal
 import sys
 
+def on_starting(server):
+    # use server hook to patch socket to allow worker reloading
+    from gevent import monkey
+    monkey.patch_socket()
+
 def when_ready(server):
     def monitor():
         modify_times = {}

gunicorn/arbiter.py

@@ -109,6 +109,7 @@ class Arbiter(object):
         """\
         Initialize the arbiter. Start listening and set pidfile if needed.
         """
+        self.cfg.on_starting(self)
         self.pid = os.getpid()
         self.init_signals()
         if not self.LISTENER:

gunicorn/config.py

@@ -703,3 +703,19 @@ class WorkerExit(Setting):
         The callable needs to accept two instance variables for the Arbiter and
         the just-exited Worker.
         """
+
+class OnStarting(Setting):
+    name = "on_starting"
+    section = "Server Hooks"
+    validator = validate_callable(1)
+    type = "callable"
+    def def_on_starting(server):
+        pass
+    def_on_starting = staticmethod(def_on_starting)
+    default = def_on_starting
+    desc = """\
+        Called just before the master process is initialized.
+        
+        The callable needs to accept a single instance variable for the Arbiter.
+        """
+