Article From:https://www.cnblogs.com/heiguu/p/9969180.html
Contents
- keepalived
- I. Introduction of keepalive:
- 2. The Working Principle of Keeping alive
- 3. Configuration of keepalive
- IV. Testing (DS1 master, DS2 auxiliary)
- 1、DS1On-line
- 2、Close DS1 keepalive service
- DS1Journal
- 3、When the DS1 main service was opened again, the service was not stopped, and DS1 took over the service again.
- 4、Online servers can’t let primary and secondary servers switch back and forth, so the preemptive mode should be turned on. The primary priority is greater than the secondary priority, so that the secondary service can take over when the primary service is down.
- Examples are as follows:
keepalived
I. Introduction of keepalive:
KeepalivedThe software was originally designed for LVS load balancing software to manage and monitor the status of each service node in the LVS cluster system. Later, the VRRP function was added to realize high availability. Therefore, Keepalived can not only manage LVS software, but also serve as other clothes.High availability solution software for business (e.g. Nginx, Haproxy, MySQL, etc.).
KeepalivedThe function is to detect the status of the server. If a web server goes down or fails, Keepalived will detect and remove the failed server from the system. At the same time, other servers will be used to replace the server. When the server is working properly, KeepalIved automatically adds servers to the server cluster. All these tasks are automatically completed without manual intervention. What we need to do manually is to repair the failed servers.
Therefore, Keepalived not only has the function of configuring and managing LVS, but also has the function of checking the health of the nodes under LVS. On the other hand, it can also realize the high availability of system network services.
2. The Working Principle of Keeping alive
At work, the primary node sends packets, and the standby node receives packets. When the standby node can not receive the data packets sent by the primary node, it starts the takeover program to take over the open source of the primary node. Standby nodes can be multiple, through priority election, but the general Keepalived system operation and maintenance work is a pair.
KeepalivedHigh-availability pairs communicate with each other through VRRP. VRRP defines the backup through election mechanism. The priority of the backup is higher than that of the backup. Therefore, the backup node will take over the resources of the main node when the backup node is hung up, and then the backup node will take over the resources of the main node.Replacement of the main node to provide services to the outside world.
Between Keepalived service pairs, only the main server will send VRRP broadcast packets all the time, telling the standby that it is still alive. At this time, the standby will not occupy the gun. When the main is unavailable, that is, when the standby can not listen to the broadcast packets sent by the main server, it will start relevant services to take over resources to ensure business continuity.Sex. The fastest takeover speed can be less than 1 second.
3. Configuration of keepalive
Preparing four virtual machines (two DS and two RS)
Two DS terminal configurations
yum -y install keepalived #Install keepalive
yum -y install ipvsadm #Install ipvsadm
yum -y install httpd #Install httpd
Modify configuration file
vim /etc/keepalived/keepalived.conf
! Configuration File for keepalived
#Global configuration
global_defs {
notification_email {
}
}
# VRRPTo configure
vrrp_instance VI_1 {
state MASTER #Role Type MASTER | BACKUP
interface ens33 #NIC name
virtual_router_id 51 #Virtual routing ID (need to be consistent with BACKUP)
priority 100 #priority
advert_int 1 #No one second to check once.
#nopreempt #Non preemptive mode
authentication {
auth_type PASS #Authentication type
auth_pass 1111 #Authentication password
}
virtual_ipaddress {
192.168.88.250 #Virtual IP (VIP)
}
}
#LVSTo configure
virtual_server 192.168.88.250 80 {
delay_loop 3 #Interval of health examination
lb_algo rr #Load Balancing Scheduling Algorithms
lb_kind DR #Load Balancing Forwarding Rules
protocol TCP #Agreement
real_server 192.168.88.50 80 { #IP and port number of real_server to monitor
weight 1 #weight
TCP_CHECK { #Checking based on TCP protocol
connect_timeout 3 #Connection time timeout
retry 3 #Reconnection times
delay_before_retry 3 #Reconnect interval
}
}
real_server 192.168.88.51 80 {
weight 1
TCP_CHECK {
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
}
}
}
DS1Configuration (192.168.88.49)
#Start service
systemctl start keepalived.service
systemctl start ipvsadm.service
systemctl start httpd.service
ifconfig ens33:0 192.168.88.250 broadcast 192.168.88.250 netmask 255.255.255.255 up
route add -host 192.168.88.250 dev ens33
DS2Configuration (192.168.88.48)
#Start service
systemctl start keepalived.service
systemctl start ipvsadm.service
systemctl start httpd.service
ifconfig ens33:0 192.168.88.250 broadcast 192.168.88.250 netmask 255.255.255.255 up
route add -host 192.168.88.250 dev ens33:0
RS1Configuration (192.168.88.50)
yum -y install httpd
systemctl start httpd.service
ifconfig lo:0 192.168.88.250 broadcast 192.168.88.250 netmask 255.255.255.255 up
route add -host 192.168.88.250 dev lo:0
echo “1”>/proc/sys/net/ipv4/conf/lo/arp_ignore
echo “2”>/proc/sys/net/ipv4/conf/lo/arp_announce
echo “1”>/proc/sys/net/ipv4/conf/all/arp_ignore
echo “2”>/proc/sys/net/ipv4/conf/all/arp_announce
RS2Configuration (192.168.88.51)
yum -y install httpd
systemctl start httpd.service
ifconfig lo:0 192.168.88.250 broadcast 192.168.88.250 netmask 255.255.255.255 up
route add -host 192.168.88.250 dev lo:0
echo “1”>/proc/sys/net/ipv4/conf/lo/arp_ignore
echo “2”>/proc/sys/net/ipv4/conf/lo/arp_announce
echo “1”>/proc/sys/net/ipv4/conf/all/arp_ignore
echo “2”>/proc/sys/net/ipv4/conf/all/arp_announce
IV. Testing (DS1 master, DS2 auxiliary)
1、DS1On-line
Testing on Windows Command Line
View status on DS1
2、Close DS1 keepalive service
DS1Journal
DS2Journal
Continue to test on the Windows command line (the service is still running, indicating that DS2 has taken over the DS1 service)
Re DS2 view status
3、When the DS1 main service was opened again, the service was not stopped, and DS1 took over the service again.
4、Online servers can’t let primary and secondary servers switch back and forth, so the preemptive mode should be turned on. The primary priority is greater than the secondary priority, so that the secondary service can take over when the primary service is down.
Examples are as follows:
DS1 vim /etc/keepalived/keepalived.conf
priority 100 #priority
#nopreempt #Non preemptive mode
DS2 vim /etc/keepalived/keepalived.conf
Stop DS1 Service DS2 and take over
Restart DS1 service, this time DS1 has no service, or DS2 is taking over the service, test:
DS1
DS2
Link of this Article: Keepalived achieve high availability of services