client: prepare merge of ConnectionPool inside Application

neo/client/pool.py

-#
-# Copyright (C) 2006-2017  Nexedi SA
-#
-# This program is free software; you can redistribute it and/or
-# modify it under the terms of the GNU General Public License
-# as published by the Free Software Foundation; either version 2
-# of the License, or (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-
-import random, time
-from neo.lib import logging
-from neo.lib.locking import Lock
-from neo.lib.protocol import NodeTypes, Packets
-from neo.lib.connection import MTClientConnection, ConnectionClosed
-from neo.lib.exception import NodeNotReady
-from .exception import NEOPrimaryMasterLost
-
-# How long before we might retry a connection to a node to which connection
-# failed in the past.
-MAX_FAILURE_AGE = 600
-
-
-class ConnectionPool(object):
-    """This class manages a pool of connections to storage nodes."""
-    # XXX: This is not a pool anymore.
-
-    def __init__(self, app):
-        self.app = app
-        # Define a lock in order to create one connection to
-        # a storage node at a time to avoid multiple connections
-        # to the same node.
-        self._lock = Lock()
-        self.node_failure_dict = {}
-
-    def _initNodeConnection(self, node):
-        """Init a connection to a given storage node."""
-        app = self.app
-        if app.master_conn is None:
-            raise NEOPrimaryMasterLost
-        conn = MTClientConnection(app, app.storage_event_handler, node,
-                                  dispatcher=app.dispatcher)
-        p = Packets.RequestIdentification(NodeTypes.CLIENT,
-            app.uuid, None, app.name, (), app.id_timestamp)
-        try:
-            app._ask(conn, p, handler=app.storage_bootstrap_handler)
-        except ConnectionClosed:
-            logging.error('Connection to %r failed', node)
-        except NodeNotReady:
-            logging.info('%r not ready', node)
-        else:
-            logging.info('Connected %r', node)
-            # Make sure this node will be considered for the next reads
-            # even if there was a previous recent failure.
-            self.node_failure_dict.pop(node.getUUID(), None)
-            return conn
-        self.node_failure_dict[node.getUUID()] = time.time() + MAX_FAILURE_AGE
-
-    def getCellSortKey(self, cell, random=random.random):
-        # Prefer a node that didn't fail recently.
-        failure = self.node_failure_dict.get(cell.getUUID())
-        if failure:
-            if time.time() < failure:
-                # Or order by date of connection failure.
-                return failure
-            # Do not use 'del' statement: we didn't lock, so another
-            # thread might have removed uuid from node_failure_dict.
-            self.node_failure_dict.pop(cell.getUUID(), None)
-        # A random one, connected or not, is a trivial and quite efficient way
-        # to distribute the load evenly. On write accesses, a client connects
-        # to all nodes of touched cells, but before that, or if a client is
-        # specialized to only do read-only accesses, it should not limit
-        # itself to only use the first connected nodes.
-        return random()
-
-    def getConnForNode(self, node):
-        """Return a locked connection object to a given node
-        If no connection exists, create a new one"""
-        conn = node._connection # XXX
-        if node.isRunning() if conn is None else not node._identified:
-            with self._lock:
-                conn = node._connection # XXX
-                if conn is None:
-                    return self._initNodeConnection(node)
-        return conn
-
-    def closeAll(self):
-        with self._lock:
-            for node in self.app.nm.getStorageList():
-                conn = node._connection # XXX
-                if conn is not None:
-                    conn.setReconnectionNoDelay()
-                    conn.close()