常见负载均衡器禁(启)用成员汇总

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常见负载均衡器禁(启)用成员汇总

在我们日常运维工作中，经常会碰到负载均衡器后端应用代码更新、临时剔除后端服务器、排查一主机应用故障等，往往我们会选择比较粗鲁的做法，直接停止或重启应用服务，让负载均衡器探测服务不可用将其剔除。这样带来的坏处是用户与服务器已经建立的连接会被中止，开发人员无法对已经停止服务的主机进行调试。现介绍一种较为温柔的做法，即通过禁用/启用成员的方式来达到目的。本文针对目前最为流行的负载均衡器逐一进行介绍。包括LVS、Haproxy、F5在命令行模式下的实现(方便与其它管理平台对接，实现自动化维护)。当然，Haproxy与F5都提供了人性化管理界面，不过只依赖手工来进行操作。

一、LVS负载均衡器
原理
使用LVS自带的管理工具来实现。

环境说明
Disable VIP:192.168.100.11:80
Disable REAL SERVER:192.168.100.78

实施步骤
1、初始状态
[devuser@lvsserver ~]# ipvsadm -Ln

IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 192.168.100.11:80 rr persistent 60
-> 192.168.100.74:80 Route 3 462 464
-> 192.168.100.75:80 Route 3 420 440
-> 192.168.100.76:80 Route 3 431 400
-> 192.168.100.77:80 Route 3 430 432
-> 192.168.100.78:80 Route 3 435 438

复制代码2、禁用成员
[devuser@lvsserver ~]# ipvsadm -d -t 192.168.100.11:80 -r 192.168.100.78

3、当前状态
[devuser@lvsserver ~]# ipvsadm -Ln

IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 192.168.100.11:80 rr persistent 60
-> 192.168.100.74:80 Route 3 462 464
-> 192.168.100.75:80 Route 3 420 440
-> 192.168.100.76:80 Route 3 431 400
-> 192.168.100.77:80 Route 3 430 432

复制代码4、启用成员
[devuser@lvsserver ~]#ipvsadm -a -t 192.168.100.11:80 -r 192.168.100.78

5、当前状态
[devuser@lvsserver ~]# ipvsadm -Ln

IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 192.168.100.11:80 rr persistent 60
-> 192.168.100.74:80 Route 3 462 464
-> 192.168.100.75:80 Route 3 420 440
-> 192.168.100.76:80 Route 3 431 400
-> 192.168.100.77:80 Route 3 430 432
-> 192.168.100.78:80 Route 3 435 438

复制代码二、Haproxy负载均衡器
原理
使用Haproxy的socket admin通道来实现。

环境说明
Disable backend:test.tianya.cn
Disable REAL SERVER:192.168.100.78

实施步骤
1、修改haproxy.cfg配置
#vi /usr/local/haproxy/etc/haproxy.cfg
在global域添加socket admin支持并重启Haproxy服务

global
... ...
stats socket /usr/local/haproxy/HaproxySocket level admin
... ...
#service haproxy restart

复制代码2、安装socat(在任意的两个socket管道之间建立一个通道，在该通道中交换两端的数据。)

wget http://www.dest-unreach.org/socat/download/socat-2.0.0-b3.tar.gz
./configure --disable-fips
make;make install
注：disable OpenSSL FIPS support "--disable-fips"，在没有安装fips包的情况下make时会提示：

FIPSLD_CC=gcc fipsld -O -D_GNU_SOURCE -Wall -Wno-parentheses -DHAVE_CONFIG_H -I. -I. -c -o socat.o socat.c
/bin/sh: fipsld: command not found
make: *** [socat.o] Error 127
3、禁用成员

#echo "disable server test.tianya.cn/192.168.100.78" | socat stdio /usr/local/haproxy/HaproxySocket

复制代码

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4、启用成员

#echo "enable server test.tianya.cn/192.168.100.78" | socat stdio /usr/local/haproxy/HaproxySocket

复制代码

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三、F5-LTM负载均衡器[separator]
原理
使用F5-iControl开发包Pycontrol对F5设备进行管理。

环境说明
Disable POOL:test.tianya.cn
Disable SERVER:192.168.100.42:80 192.168.100.43:80 192.168.100.44:80

实施步骤
1、部署运行环境

#mkdir -p /home/install;cd /home/install

复制代码安装python环境(略)，要求py2.5或以上。
1.1、安装SUDS模块

#wget https://fedorahosted.org/release ... n-suds-0.3.8.tar.gz
#tar xvfz python-suds-0.3.8.tar.gz
#cd python-suds-0.3.8
#python setup.py install

复制代码1.2、安装PYCONTROL模块

#wget http://trungale.net/pycontrol.tar.gz
#tar xvfz pycontrol.tar.gz
#cd trunk
#python setup.py install

复制代码1.3、校验安装结果
#python

>>> import suds
>>> import pycontrol.pycontrol as pc
>>> suds.__version__
'0.4'
>>> suds.__build__
'GA R699-20100913'
>>> pc.__version__
'2.0.1'
>>> pc.__build__
'r83'
>>>

复制代码2、编写LB_member.py代码

# -*- coding: utf-8 -*-
"""
----------------------------------------------------------------------------
Disable/Enable F5-LTM POOL member
Name: LB_member.py
Author: Liu tian si
Email: liutiansi@gamil.com
Created: 2011/05/08
Version: 1.0
Blog: http://blog.liuts.com
Copyright: (c) 2011
----------------------------------------------------------------------------
"""
import sys
import time
import string
import pycontrol.pycontrol as pc
"""
----------------------------------------------------------------------------
F5-LTM Disable/Enable Pool member Class
----------------------------------------------------------------------------
__init__() -Initialization F5-BIG object
set_pool_member() -Initialization pool and member object
member_factory() -Create a pool member object (Common.IPPortDefinition)
session_state_factory() -Create a session state object (LocalLB.PoolMember.MemberSessionState)
disable_member() -Disable menber methods
enable_member() -Enable menber methods
----------------------------------------------------------------------------
"""
class F5_LB_menber():
def __init__(self,_hostname,_username,_password):
self.b = pc.BIGIP(
hostname = _hostname,
username = _username,
password = _password,
fromurl = True,
wsdls = ['LocalLB.PoolMember'])
self.sstate_seq = self.b.LocalLB.PoolMember.typefactory.create('LocalLB.PoolMember.MemberSessionStateSequence')
def set_pool_member(self,pool,members):
self.POOL=pool
self.members=members
self.sstate_seq.item = self.session_state_factory()
def member_factory(self, member):
ip,port = member.split(':')
pmem = self.b.LocalLB.PoolMember.typefactory.create('Common.IPPortDefinition')
pmem.address = ip
pmem.port = int(port)
return pmem
def session_state_factory(self):
session_states = []
for x in self.members:
sstate = self.b.LocalLB.PoolMember.typefactory.create('LocalLB.PoolMember.MemberSessionState')
sstate.member = self.member_factory(x)
session_states.append(sstate)
return session_states
def disable_member(self):
for x in self.sstate_seq.item:
x.session_state = 'STATE_DISABLED'
try:
self.b.LocalLB.PoolMember.set_session_enabled_state(pool_names =
[self.POOL], session_states = [self.sstate_seq])
except Exception, e:
print e
def enable_member(self):
for x in self.sstate_seq.item:
x.session_state = 'STATE_ENABLED'
try:
self.b.LocalLB.PoolMember.set_session_enabled_state(pool_names = [self.POOL],
session_states = [self.sstate_seq])
except Exception, e:
print e
if __name__ == "__main__":
if len(sys.argv) < 4:
print "Usage %s POOL MEMBER:port[,member1:80,member2:80,member3:80] enable|disable" % sys.argv[0]
print "Examples: python LB_member.py app.domain.com 192.168.0.10:80,192.168.0.11:80,192.168.0.12:80 disable"
sys.exit()
#F5 administrator info
hostname="192.168.100.2"
username="adminuser"
password="adminpass"
App=F5_LB_menber(hostname,username,password)
#init F5 pool and member
CommandParameters = sys.argv[1:]
pool=CommandParameters[0]
members=string.split(CommandParameters[1],',')
App.set_pool_member(pool,members)
if CommandParameters[2]=="enable":
App.enable_member()
elif CommandParameters[2]=="disable":
App.disable_member()
else:
print "opt parameters error!"
sys.exit()

复制代码3、源码分析：
3.1、创建一个池成员对象，将用户传入的成员列表转成规范的pool成员，见member_factory()方法;
3.2、创建一个会话状态对象，追加成员对象到会话状态当中，见session_state_factory()方法;
3.3、创建一个队列，将会话状态对象添加到队列子项中，同时修改所处状态，见__init__()、set_pool_member()、disable_member()/enable_member()方法。

4、禁用成员
#python LB_member.py test.tianya.cn 192.168.100.42:80,192.168.100.43:80,192.168.100.44:80 disable

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5、启用成员
#python LB_member.py test.tianya.cn 192.168.100.42:80,192.168.100.43:80,192.168.100.44:80 enable

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参考文章
http://devcentral.f5.com/wiki/default.aspx/iControl.CodeShare

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