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#!/usr/bin/python
# 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 Library General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
# Copyright 2003 Jack Neely, NC State University
# Here we define a base class for failover methods. The idea here is that each
# failover method uses a class derived from the base class so yum only has to
# worry about calling get_serverurl() and server_failed() and these classes will
# figure out which URL to cough up based on the failover method.
"""Classes for handling failovers for server URLs."""
import random
class baseFailOverMethod:
"""A base class to provide a failover to switch to a new server if
the current one fails.
"""
def __init__(self, repo):
self.repo = repo
self.failures = 0
def get_serverurl(self, i=None):
"""Return a server URL based on this failover method, or None
if there is a complete failure. This method should always be
used to translate an index into a URL, as this object may
change how indexes map.
:param i: if given, this is the index of the server URL to
return, instead of using the failures counter
:return: the next server URL
"""
return None
def server_failed(self):
"""Notify the failover method that the current server has
failed.
"""
self.failures = self.failures + 1
def reset(self, i=0):
"""Reset the failures counter to the given index.
:param i: the index to reset the failures counter to
"""
self.failures = i
def get_index(self):
"""Return the current number of failures, which is also the
current index into the list of URLs that this object
represents. :fun:`get_serverurl` should always be used to
translate an index into a URL, as this object may change how
indexes map.
:return: the current number of failures, which is also the
current index
"""
return self.failures
def len(self):
"""Return the total number of URLs available to cycle through
in this object.
:return: the total number of URLs available
"""
return len(self.repo.urls)
class priority(baseFailOverMethod):
"""A class to provide a failover to switch to a new server
if the current one fails. This classes chooses the next server
based on the first success in the list of servers.
"""
def get_serverurl(self, i=None):
"""Return the next successful server URL in the list, or None
if there is a complete failure. This method should always be
used to translate an index into a URL, as this object may
change how indexes map.
:param i: if given, this is the index of the server URL to
return, instead of using the failures counter
:return: the next server URL
"""
if i == None:
index = self.failures
else:
index = i
if index >= len(self.repo.urls):
return None
return self.repo.urls[index]
class roundRobin(baseFailOverMethod):
"""A class to provide a failover to switch to a new server
if the current one fails. When an object of this class is
created, it selects a random place in the list of URLs to begin
with, then each time :func:`get_serveurl` is called, the next URL
in the list is returned, cycling back to the beginning of the list
after the end is reached.
"""
def __init__(self, repo):
baseFailOverMethod.__init__(self, repo)
random.seed()
self.offset = random.randint(0, 37)
def get_serverurl(self, i=None):
"""Return the next successful server URL in the list, using
the round robin scheme, or None if there is a complete
failure. This method should always be used to translate an
index into a URL, as this object may change how indexes map.
:param i: if given, this is the index of the server URL to
return, instead of using the failures counter
:return: the next server URL
"""
if i == None:
index = self.failures
else:
index = i
if index >= len(self.repo.urls):
return None
rr = (index + self.offset) % len(self.repo.urls)
return self.repo.urls[rr]
# SDG