16-VIP 配置
VIP配置可以采用两种方式，一种为通过keepalived的方式管理虚拟IP的浮动，另一种为通过脚本方式手动摘除的方式。
1．keepalived方式管理虚拟IP
keepalived配置步骤如下。
（1）下载集群心跳软件keepalived，并进行安装：
wget http://www.keepalived.org/software/keepalived-1.2.1.tar.gz
tar zxvf keepalived-1.2.1.tar.gz
cd keepalived-1.2.1
./configure --prefix=/usr/local/keepalived
--with-kernel-dir=/usr/src/kernels/2.6.18-164.el5-i686/
make && make install
cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/rc.d/init.d/
cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
mkdir /etc/keepalived
cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/
cp /usr/local/keepalived/sbin/keepalived /usr/sbin/
（2）配置keepalived的配置文件。
在ip81上设置：
[root@ip81 tools]# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
notification_email {
}
notification_email_from [email protected]
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id MySQL-ha
}
vrrp_instance VI_1 {
state BACKUP
interface eth0
virtual_router_id 51
priority 150
advert_int 1
nopreempt
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.7.201/23
}}
注意黑体部分的代码，其中 router_id MySQL-ha 表示设定 keepalived 组的名称，将192.168.7.201/23这个 IP绑定到 ip81主机 interface eth0上，并且设置了状态为backup模式，将 keepalived的模式设置为非抢占模式（nopreempt），priority 150优先级别设置为 150。
在候选主ip83上设置：
[root@ip83 ~]# cat /etc/keepalived/keepalived.conf
onfiguration File for keepalived
global_defs {
notification_email {
}
notification_email_from [email protected]
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id MySQL-ha
}
vrrp_instance VI_1 {
state BACKUP
interface eth0
virtual_router_id 51
priority 120
advert_int 1
nopreempt
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.7.201/23
}
}
注意黑体部分的代码，其中 router_id MySQL-ha表示设定 keepalived组的名称，并且设置了状态为backup模式，将 keepalived的模式设置为非抢占模式（nopreempt），priority 120优先级别设置为120。
（3）启动keepalived服务。
在ip81上启动keepalived服务：
[root@ip81 tools]# service keepalived start
[root@ip81 tools]# tail -f /var/log/messages
Jul 19 18:10:13 ip81 Keepalived_vrrp: Registering Kernel netlink reflector
Jul 19 18:10:13 ip81 Keepalived_vrrp: Registering Kernel netlink command channel
Jul 19 18:10:13 ip81 Keepalived: Starting VRRP child process, pid=18426
Jul 19 18:10:13 ip81 Keepalived_healthcheckers:Using LinkWatch kernel netlink reflector...
Jul 19 18:10:13 ip81 Keepalived_vrrp: Registering gratutious ARP shared channel
Jul 19 18:10:13 ip81 Keepalived_vrrp: Opening file '/etc/keepalived/keepalived.conf'.
Jul 19 18:10:13 ip81 Keepalived_vrrp: Configuration is using : 35902 Bytes
Jul 19 18:10:13 ip81 Keepalived_vrrp: Using LinkWatch kernel netlink reflector...
Jul 19 18:10:13 ip81 Keepalived_vrrp: VRRP_Instance(VI_1) Entering BACKUP STATE
Jul 19 18:10:13 ip81 Keepalived_vrrp: VRRP sockpool:[ifindex(2), proto(112), fd(10,11)]
Jul 19 18:10:16 ip81 Keepalived_vrrp: VRRP_Instance(VI_1) Transition to MASTER STATE
Jul 19 18:10:17 ip81 Keepalived_vrrp: VRRP_Instance(VI_1) Entering MASTER STATE
Jul 19 18:10:17 ip81 Keepalived_vrrp: VRRP_Instance(VI_1) setting protocol VIPs.
Jul 19 18:10:17 ip81 Keepalived_healthcheckers: Netlink reflector reports IP 192.168. 7.188 added
Jul 19 18:10:17 ip81 Keepalived_vrrp: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 192.168.7.188
Jul 19 18:10:17 ip81 Keepalived_vrrp: Netlink reflector reports IP 192.168.7.201 added
Jul 19 18:10:17 ip81 avahi-daemon[2799]: Registering new address record for 192.168.7.201 on eth0.
Jul 19 18:10:22 ip81 Keepalived_vrrp: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 192.168.7.201
通过输出可以看到虚拟IP（192.168.7.201）已经绑定到ip81的eth0网卡上了。
（4）查看绑定情况。
在ip81上查看IP地址绑定情况：
[root@ip81 mysqlhome]# ip addr
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast qlen 1000
link/ether 00:11:43:de:78:78 brd ff:ff:ff:ff:ff:ff
inet 192.168.7.81/23 brd 192.168.7.255 scope global eth0
inet 192.168.7.201/23 scope global secondary eth0
inet6 fe80::211:43ff:fede:7878/64 scope link
valid_lft forever preferred_lft forever
从keepalived 的输出信息和系统的网卡信息可以看到，虚拟IP（192.168.7.201）已经添加成功。在ip83上：
[root@ip83 ~]# service keepalived start
[root@ip83 ~]# tail -f /var/log/messages
Jul 19 18:15:36 ip83 Keepalived_vrrp: Registering Kernel netlink reflector
Jul 19 18:15:36 ip83 Keepalived_vrrp: Registering Kernel netlink command channel
Jul 19 18:15:36 ip83 Keepalived_vrrp: Registering gratutious ARP shared channel
Jul 19 18:15:36 ip83 Keepalived_vrrp: Opening file '/etc/keepalived/keepalived.conf'.
Jul 19 18:15:36 ip83 Keepalived_healthcheckers: Using LinkWatch kernel netlink reflector...
Jul 19 18:15:36 ip83 Keepalived_vrrp: Configuration is using : 35910 Bytes
Jul 19 18:15:36 ip83 Keepalived: Starting VRRP child process, pid=9505
Jul 19 18:15:36 ip83 Keepalived_vrrp: Using LinkWatch kernel netlink reflector...
Jul 19 18:15:36 ip83 Keepalived_vrrp: VRRP_Instance(VI_1) Entering BACKUP STATE
Jul 19 18:15:36 ip83 Keepalived_vrrp: VRRP sockpool: [ifindex(2), proto(112), fd(10,11)]
从上面的输出可以看到keepalived已经配置成功。
注意：这里ip81和ip83都要设置为BACKUP模式。在keepalived中有2种模式，分别是master-->backup模式和backup-->backup模式，这两种模式分别有什么区别呢？
在 master-->backup 模式下，一旦主库宕掉，虚拟 IP 会自动漂移到从库，当主库修复后， keepalived 启动后，还会把虚拟 IP 抢过来，即使你设置 nopreempt（不抢占）的方式抢占 IP的动作也会发生。在backup-->backup模式下，当主库宕掉后虚拟IP会自动漂移到从库上，当原主恢复之后重启keepalived服务，并不会抢占新主的虚拟IP，即使是优先级高于从库的优先级别，也不会抢占IP。为了减少IP的漂移次数，生产中我们通常是把修复好的主库当作新主库的备库。
keepalived还存在一种脑裂状况，当主从间网络出现问题，这时主库会持有虚拟IP不变，从库失去和主库的联系后，从库也会抢夺IP（即便你采用backup-->backup非抢占模式），这样造成的后果是主从数据库都持有虚拟IP。于是造成IP冲突，业务也会受到影响，因此在网络不是很好的状况下，强烈不建议采用keepavlived服务。
（5）MHA引入keepalived。
那么如何才能把keepalived服务引入MHA呢？很简单，只需修改切换时触发的脚本文件master_ip_failover即可，在该脚本中添加在master发生宕机时对keepalived的处理。
使用vi编辑MHA切换时调用的配置文件master_ip_failover：
vi /usr/local/bin/master_ip_failover
!/usr/bin/env perl
Copyright (C) 2011 DeNA Co.,Ltd.
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, write to the Free Software
Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
Note: This is a sample script and is not complete. Modify the script based on your environment.
use strict;
use warnings FATAL => 'all';
use Getopt::Long;
use MHA::DBHelper;
my (
$command, $ssh_user, $orig_master_host, $orig_master_ip,
$orig_master_port, $new_master_host, $new_master_ip, $new_master_port,
$user, $password
);
GetOptions(
'command=s' => \$command,
'ssh_user=s' => \$ssh_user,
'orig_master_host=s' => \$orig_master_host,
'orig_master_ip=s' => \$orig_master_ip,
'orig_master_port=i' => \$orig_master_port,
'new_master_host=s' => \$new_master_host,
'new_master_ip=s' => \$new_master_ip,
'new_master_port=i' => \$new_master_port,
'user=s' => \$user,
'password=s' => \$password,
);
exit &main();
sub main {
if ( $command eq "stop" || $command eq "stopssh" ) {
$orig_master_host, $orig_master_ip, $orig_master_port are passed.
If you manage master ip address at global catalog database,
invalidate orig_master_ip here.
my $exit_code = 1;
eval {
updating global catalog, etc
$exit_code = 0;
};
if ($@) {
warn "Got Error: $@\n";
exit $exit_code;
}
exit $exit_code;
}
elsif ( $command eq "start" ) {
all arguments are passed.
If you manage master ip address at global catalog database,
activate new_master_ip here.
You can also grant write access (create user, set read_only=0, etc) here.
my $exit_code = 10;
eval {
my $new_master_handler = new MHA::DBHelper();
args: hostname, port, user, password, raise_error_or_not
$new_master_handler->connect( $new_master_ip, $new_master_port, $user,
$password, 1 );
Set read_only=0 on the new master
$new_master_handler->disable_log_bin_local();
print "Set read_only=0 on the new master.\n";
$new_master_handler->disable_read_only();
Creating an app user on the new master
print "Creating app user on the new master..\n";
FIXME_xxx_create_user( $new_master_handler->{dbh} );
$new_master_handler->enable_log_bin_local();
$new_master_handler->disconnect();
Update master ip on the catalog database, etc
FIXME_xxx;
$cmd = 'ssh '.$ssh_user.'@'.$orig_master_ip.' \'./lvs-admin stop\'';
system($cmd);
$exit_code = 0;
};
if ($@) {
warn $@;
If you want to continue failover, exit 10.
exit $exit_code;
}
exit $exit_code;
}
elsif ( $command eq "status" ) {
do nothing
exit 0;
}
else {
&usage();
exit 1;
}
}
sub usage {
"Usage: master_ip_failover --command=start|stop|stopssh|status --ssh_user=s--orig_master_host=host --orig_master_ip=ip --orig_master_port=port --new_master_host=host--new_master_ip=ip --new_master_port=port --user=user --password=password\n";
}
上述黑体加粗部分即为添加的代码。在主库ip81上的根目录下编辑lvs-admin脚本：
case "$1" in
"stop")
echo;
echo "stop keepalived.....";
service keepalived stop
;;
"start")
echo
echo "start keepalive....."
service keepalived start
;;
*)
echo "please input you select!"
;;
esac
/usr/local/bin/master_ip_failover 添加内容的大体意思是，当主库数据库发生故障时刻，会触发MHA切换，MHA Manager会执行停掉主库上 keepalived服务，触发虚拟 IP漂移到备选从库，从而完成切换。
2．通过脚本的方式管理VIP
（1）修改触发故障切换脚本/usr/local/bin/master_ip_failover，修改内容如下：
!/usr/bin/env perl
use strict;
use warnings FATAL => 'all';
use Getopt::Long;
my (
$command, $ssh_user, $orig_master_host, $orig_master_ip,
$orig_master_port, $new_master_host, $new_master_ip, $new_master_port
);
my $vip = '192.168.7.201/23'; # Virtual IP
my $key = "2";
my $ssh_start_vip = "/sbin/ifconfig eth0:$key $vip";
my $ssh_stop_vip = "/sbin/ifconfig eth0:$key down";
GetOptions(
'command=s' => \$command,
'ssh_user=s' => \$ssh_user,
'orig_master_host=s' => \$orig_master_host,
'orig_master_ip=s' => \$orig_master_ip,
'orig_master_port=i' => \$orig_master_port,
'new_master_host=s' => \$new_master_host,
'new_master_ip=s' => \$new_master_ip,
'new_master_port=i' => \$new_master_port,
);
exit &main();
sub main {
if ( $command eq "stop" || $command eq "stopssh" ) {
$orig_master_host, $orig_master_ip, $orig_master_port are passed.
If you manage master ip address at global catalog database,
invalidate orig_master_ip here.
my $exit_code = 1;
eval {
print "Disabling the VIP on old master: $orig_master_host \n";
&stop_vip();
$exit_code = 0;
};
if ($@) {
warn "Got Error: $@\n";
exit $exit_code;
}
exit $exit_code;
}
elsif ( $command eq "start" ) {
all arguments are passed.
If you manage master ip address at global catalog database,
activate new_master_ip here.
You can also grant write access (create user, set read_only=0, etc) here.
my $exit_code = 10;
eval {
print "Enabling the VIP - $vip on the new master - $new_master_host \n";
&start_vip();
$exit_code = 0;
};
if ($@) {
warn $@;
exit $exit_code;
}
exit $exit_code;
}
elsif ( $command eq "status" ) {
print "Checking the Status of the script.. OK \n";
do nothing
exit 0;
}
else {
&usage();
exit 1;
}
}
A simple system call that enable the VIP on the new master
sub start_vip() {
ssh $ssh_user\@$new_master_host \" $ssh_start_vip \";
}
A simple system call that disable the VIP on the old_master
sub stop_vip() {
ssh $ssh_user\@$orig_master_host \" $ssh_stop_vip \";
}
sub usage {
"Usage: master_ip_failover --command=start|stop|stopssh|status --origmaster host=host --orig_master_ip=ip --orig_master_port=port --new_master_host=host --new_master_ip=ip--new_master_port=port\n";
}
为了防止脑裂情况的发生，这里将采用通过脚本的方式来管理虚拟IP，到此为止，基本上MHA 集群环境已经配置完毕，接下来我们将通过生产中的一些案例来看一下 MHA 到底是如何进行工作的。下面将从 MHA 自动 failover、手动 failover、在线切换三种方式来介绍 MHA的工作情况。