keepalived集群高可用
keepalived是基于vrrp的实现，最初为ipvs提供高可用功能，同时能够检测后端realserver的健康状态，此后又为其他的服务提供高可用功能，它可以调用外部脚本，监控资源状态，从而进行故障转移，比较适用于节点比较少，不使用共享存储等情况下；相对于heartbeat以及corosync和RHCS来说，算是一种轻量级的高可用解决方案。
keepalived包含2个主要组件，一个组件负责VRRP协议的实现和管理，一个负责对资源进行监控；运行VRRP的主机在主机之间发送组播信息，用以通告自身的优先级、以及其他属性，主机的优先级范围从0-255, 0表示不参与选举，255表示最高优先级，优先级高的会成为MASTER，在MASTER上启动VIP和VMAC，所有发送到VIP的数据包，由MASTER进行处理，当MASTER出现故障或资源出现问题，会停止发送心跳信息或降低自身优先级，当BACKUP主机发现自己的优先级高于对方或检测不到对方时，会将自己提升为MASTER，当原先的MASTER恢复时，默认可以把MASTER抢回去，可以配置不抢占。
在CentOS 6.4上有keepalived的rpm包，直接安装就可以
[root@node4 ~]# yum -yinstall keepalived
Installed:
keepalived.x86_64 0:1.2.7-3.el6
Dependency Installed:
lm_sensors-libs.x86_64 0:3.1.1-17.el6 net-snmp-libs.x86_64 1:5.5-44.el6
配置文件在/etc/keepalived/keepalived.conf，服务启动脚本是/etc/init.d/keepalived
[root@node4 keepalived]#cat keepalived.conf
! Configuration File forkeepalived
global_defs {
notification_email {
[email protected]用以定义状态切换时邮件通知对象，可写多行（个）
}
smtp_server 192.168.200.1 SMTP服务器地址
smtp_connect_timeout 30连接超时时长
router_id LVS_DEVEL VRRP主机标识
vrrp_scriptchk_state_down {
script "[[ -f /etc/keepalived/down ]]"自定义一个检测条件，如果存在此文件
interval 1检测间隔为1s
weight -10 weight 减去10；
}
}
vrrp_instanceVI_1 {定义一个VRRP实例
state MASTER状态为MASTER
interface eth0在eth0上监听VIP
virtual_router_id 10 定义所属的组，同一个组中的主机必须相同；
priority 100优先级
advert_int 1通告间隔（advertising interval）
authentication {认证
auth_type PASS类型
auth_pass 1111密码
}
virtual_ipaddress {
172.16.1.250 定义VIP
}
track_script {
chk_state_down
}
}
virtual_server172.16.1.10080 {
delay_loop 6
lb_algo rr
lb_kind NAT
nat_mask 255.255.255.0
persistence_timeout 50
protocol TCP
real_server 172.16.1.2 80 {
weight 1
HTTP_GET {检测后端realserver的方式为GET
url {
path /
state_code 200 检测报文头部的状态码为200
}
connect_timeout 3检测超时时间为3s
nb_get_retry 3重试的次数为3次
delay_before_retry 3重试的间隔
}
}
}
定义主机发生状态变化时，发送邮件通知
首先定义一个脚本：
#!/bin/bash
#
vip=172.16.1.100
contact='root@localhost'
notify (){
mailsubject="`hostname` became to $1 , $vip floated."
mailbody="`date +"%F %T"`: vrrp status changed.`hostname` became $1"
echo $mailbody | mail -s "$mailsubject" $contact
}
case $1in
master)
notify master ;;
backup)
notify backup;;
fault)
notify fault ;;
*)
echo "Usage: `basename $0` {master|backup|fault}"
exit 1;;
esac
编辑配置文件：
vrrp_instance Instance1 {
state MASTER
interface eth0
virtual_router_id 10
priority 100
advert_int 1
authentication {
auth_type PASS
auth_pass 1119
}
virtual_ipaddress {
172.16.1.100
}
track_script {
chk_state_down
}
notify_master"/etc/keepalived/nofity.sh master"
notify_backup"/etc/keepalived/nofity.sh backup"
notify_fault"/etc/keepalived/nofity.sh fault"
}
[root@node4 keepalived]#cat keepalived.conf
! Configuration File forkeepalived
global_defs {
notification_email {
root@localhost
}
notification_email_from [email protected]
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id Node4.magedu.com
}
vrrp_scriptchk_state_down {
script "[[ -f /etc/keepalived/down]] && exit 1 || exit 0"
interval 1
weight -10
}
vrrp_instance Instance1 {
state MASTER
interface eth0
virtual_router_id 10
priority 100
advert_int 1
authentication {
auth_type PASS
auth_pass 1119
}
virtual_ipaddress {
172.16.1.100
}
track_script {
chk_state_down
}
notify_master"/etc/keepalived/notify.sh master"
notify_backup"/etc/keepalived/notify.sh backup"
notify_fault"/etc/keepalived/notify.sh fault"
}
virtual_server172.16.1.100 80 {
delay_loop 6
lb_algo rr
lb_kind NAT
nat_mask 255.255.255.0
persistence_timeout 50
protocol TCP
real_server 172.16.1.3 80 {
weight 1
HTTP_GET {
url {
path /
state_code 200
}
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
}
}
real_server 172.16.1.2 80 {
weight 1
HTTP_GET {
url {
path /
status_code 200
}
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
}
}
}
}
如果检测成功就会自动生成ipvs规则
[root@node5 keepalived]#ipvsadm -L -n
IP Virtual Server version1.2.1 (size=4096)
Prot LocalAddress:PortScheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 172.16.1.100:80 rr persistent 50
-> 172.16.1.2:80 Masq 1 0 0
-> 172.16.1.3:80 Masq 1 0 0
当有一个real server失效以后，会自动修改规则：
[root@node5 keepalived]#ipvsadm -L -n
IP Virtual Server version1.2.1 (size=4096)
Prot LocalAddress:PortScheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 172.16.1.100:80 rr persistent 50
-> 172.16.1.3:80 Masq 1 0 0
[root@node5 keepalived]#tail /var/log/messages
Sep 25 04:22:20 node5Keepalived_vrrp[16223]: VRRP_Instance(Instance1) Sending gratuitous ARPs oneth0 for 172.16.1.100
Sep 25 04:22:25 node5Keepalived_vrrp[16223]: VRRP_Instance(Instance1) Sending gratuitous ARPs oneth0 for 172.16.1.100
Sep 25 04:22:28 node5Keepalived_vrrp[16223]: VRRP_Instance(Instance1) Received higher prio advert
Sep 25 04:22:28 node5Keepalived_vrrp[16223]: VRRP_Instance(Instance1) Entering BACKUP STATE
Sep 25 04:22:28 node5Keepalived_vrrp[16223]: VRRP_Instance(Instance1) removing protocol VIPs.
Sep 25 04:22:28 node5Keepalived_healthcheckers[16222]: Netlink reflector reports IP 172.16.1.100removed
Sep 25 04:36:11 node5Keepalived_healthcheckers[16222]: Error connecting server [172.16.1.2]:80.
Sep 25 04:36:11 node5Keepalived_healthcheckers[16222]: Removing service [172.16.1.2]:80 from VS[172.16.1.100]:80
Sep 25 04:36:11 node5Keepalived_healthcheckers[16222]: Remote SMTP server [127.0.0.1]:25 connected.
Sep 25 04:36:11 node5Keepalived_healthcheckers[16222]: SMTP alert successfully sent.
# 如何对特定的服务实现高可用：
思路：
让vrrp_script 监控程序的运行状态，当服务停止时，降低优先级，优先级降低引起VRRP的状态切换，切换的同时，系统会发出邮件，管理员收到邮件后及时处理故障，启动服务后，优先级恢复到原来的值，根据实际情况配置preempt；如果不对故障进行处理那么当第二台设备也服务也停止了，整个系统将无法工作；
[root@node4keepalived]# cat keepalived.conf
!Configuration File for keepalived
global_defs {
notification_email {
root@localhost
}
notification_email_from [email protected]
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id Node4.magedu.com
}
vrrp_script chk_state_down {
script"[[ -f /etc/keepalived/down ]] && exit 1 || exit 0"
interval 1
weight-2
}
vrrp_script chk_httpd {
script"killall -0 httpd"
interval 1
fall 2
rise 1
weight-20
}
vrrp_instanceInstance1 {
state MASTER
interface eth0
virtual_router_id 10
priority 100
advert_int 1
authentication {
auth_type PASS
auth_pass 1119
}
virtual_ipaddress {
172.16.1.100
}
track_script {
chk_state_down
chk_httpd
}
notify_master "/etc/keepalived/notify.sh master"
notify_backup "/etc/keepalived/notify.sh backup"
notify_fault "/etc/keepalived/notify.sh fault"
}
[root@node4keepalived]# cat notify.sh
#!/bin/bash
vip=172.16.1.100
contact='root@localhost'
notify () {
mailsubject="`hostname` became to$1 , $vip floated."
mailbody="`date +"%F%T"`: vrrp status changed. `hostname` became $1"
echo $mailbody | mail -s"$mailsubject" $contact
}
case $1 in
master)
notify master
/etc/init.d/httpd start;;
backup)
notify backup
/etc/init.d/httpd stop;;
fault)
notify fault
/etc/init.d/httpd stop;;
*)
echo "Usage: `basename $0`{master|backup|fault}"
exit 1;;
esac
keepalived双主模型：
提供2个vrrp实例，2个vip；
vrrp_instance Instance1 {
state MASTER
interface eth0
virtual_router_id 10
priority 100
advert_int 1
authentication {
auth_type PASS
auth_pass 1119
}
virtual_ipaddress {
172.16.1.100
}
track_script {
chk_state_down
chk_httpd
}
notify_master"/etc/keepalived/notify.sh master"
notify_backup"/etc/keepalived/notify.sh backup"
notify_fault"/etc/keepalived/notify.sh fault"
}
vrrp_instance Instance2 {
state BACKUP
interface eth0
virtual_router_id 20
priority 95
advert_int 1
authentication {
auth_type PASS
auth_pass 2119
}
virtual_ipaddress {
172.16.1.101
}
track_script {
chk_state_down
chk_httpd
}
notify_master"/etc/keepalived/notify.sh master"
notify_backup"/etc/keepalived/notify.sh backup"
notify_fault"/etc/keepalived/notify.sh fault"
}
重启keepalived服务
# servicekeepalived restart
[root@node4 keepalived]#ip addr show
1: lo:<LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0:<BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen1000
link/ether 00:0c:29:85:22:ac brdff:ff:ff:ff:ff:ff
inet 172.16.1.4/16 brd 172.16.255.255 scopeglobal eth0
inet 172.16.1.100/32 scope global eth0
inet6 fe80::20c:29ff:fe85:22ac/64 scopelink
valid_lft forever preferred_lft forever
当另一台主机发生故障时：
[root@node4 keepalived]#ip addr show
1: lo:<LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0:<BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen1000
link/ether 00:0c:29:85:22:ac brdff:ff:ff:ff:ff:ff
inet 172.16.1.4/16 brd 172.16.255.255 scopeglobal eth0
inet 172.16.1.100/32 scope global eth0
inet 172.16.1.101/32 scope global eth0
inet6 fe80::20c:29ff:fe85:22ac/64 scopelink
valid_lft forever preferred_lft forever