PYTHON-525 Remove "force" param for Pool.get_socket().

MongoReplicaSetClient's old monitor used "force" to get a socket even when the
pool had reached its max size. This was so complicated and bug-prone that I
prohibited it in the Server Discovery And Monitoring Spec: monitors use
dedicated sockets now instead of sharing a pool with the application.

pymongo/pool.py

@@ -148,7 +148,6 @@ class SocketInfo(object):
         self.authset = set()
         self.closed = False
         self.last_checkout = time.time()
-        self.forced = False
         self.pool_ref = weakref.ref(pool)
 
         # The pool's pool_id changes with each reset() so we can close sockets
@@ -434,7 +433,7 @@ class Pool:
         sock.settimeout(self.opts.socket_timeout)
         return SocketInfo(sock, self, hostname)
 
-    def get_socket(self, all_credentials, force=False):
+    def get_socket(self, all_credentials):
         """Get a socket from the pool.
 
         Returns a :class:`SocketInfo` object wrapping a connected
@@ -443,12 +442,10 @@ class Pool:
 
         :Parameters:
           - `all_credentials`: dict, maps auth source to MongoCredential.
-          - `force`: optional boolean, forces a connection to be returned
-              without blocking, even if `max_size` has been reached.
         """
         # First get a socket, then attempt authentication. Simplifies
         # semaphore management in the face of network errors during auth.
-        sock_info = self._get_socket_no_auth(force)
+        sock_info = self._get_socket_no_auth()
         try:
             sock_info.check_auth(all_credentials)
             return sock_info
@@ -456,7 +453,7 @@ class Pool:
             self.maybe_return_socket(sock_info)
             raise
 
-    def _get_socket_no_auth(self, force):
+    def _get_socket_no_auth(self):
         # We use the pid here to avoid issues with fork / multiprocessing.
         # See test.test_client:TestClient.test_fork for an example of
         # what could go wrong otherwise
@@ -474,16 +471,8 @@ class Pool:
             checked_sock.last_checkout = time.time()
             return checked_sock
 
-        forced = False
-        # We're not in a request, just get any free socket or create one
-        if force:
-            # If we're doing an internal operation, attempt to play nicely with
-            # max_size, but if there is no open "slot" force the connection
-            # and mark it as forced so we don't release the semaphore without
-            # having acquired it for this socket.
-            if not self._socket_semaphore.acquire(False):
-                forced = True
-        elif not self._socket_semaphore.acquire(
+        # We're not in a request, just get any free socket or create one.
+        if not self._socket_semaphore.acquire(
                 True, self.opts.wait_queue_timeout):
             self._raise_wait_queue_timeout()
 
@@ -504,16 +493,13 @@ class Pool:
             if from_pool:
                 sock_info = self._check(sock_info)
 
-            sock_info.forced = forced
-
             if req_state == NO_SOCKET_YET:
                 # start_request has been called but we haven't assigned a
                 # socket to the request yet. Let's use this socket for this
                 # request until end_request.
                 self._set_request_state(sock_info)
         except:
-            if not forced:
-                self._socket_semaphore.release()
+            self._socket_semaphore.release()
             raise
 
         sock_info.last_checkout = time.time()
@@ -552,14 +538,11 @@ class Pool:
             return
 
         if self.pid != os.getpid():
-            if not sock_info.forced:
-                self._socket_semaphore.release()
+            self._socket_semaphore.release()
             self.reset()
         else:
             if sock_info.closed:
-                if sock_info.forced:
-                    sock_info.forced = False
-                elif sock_info != self._get_request_state():
+                if sock_info != self._get_request_state():
                     self._socket_semaphore.release()
                 return
 
@@ -582,10 +565,7 @@ class Pool:
         finally:
             self.lock.release()
 
-        if sock_info.forced:
-            sock_info.forced = False
-        else:
-            self._socket_semaphore.release()
+        self._socket_semaphore.release()
 
     def _check(self, sock_info):
         """This side-effecty function checks if this pool has been reset since

test/pymongo_mocks.py

@@ -38,7 +38,7 @@ class MockPool(Pool):
         Pool.__init__(self,
             (default_host, default_port), PoolOptions(connect_timeout=20))
 
-    def get_socket(self, all_credentials, force=False):
+    def get_socket(self, all_credentials):
         client = self.client
         host_and_port = '%s:%s' % (self.mock_host, self.mock_port)
         if host_and_port in client.mock_down_hosts:
@@ -49,7 +49,7 @@ class MockPool(Pool):
             + client.mock_members
             + client.mock_mongoses), "bad host: %s" % host_and_port
 
-        sock_info = Pool.get_socket(self, all_credentials, force)
+        sock_info = Pool.get_socket(self, all_credentials)
         sock_info.mock_host = self.mock_host
         sock_info.mock_port = self.mock_port
         return sock_info