Corosync and pacemaker clusters allow two machines to share a high availability address. Each machine has its own normal IP address used to administer the machine. There is then a third "service" IP address that MySQL clients connect to. This normally runs on the primary machine as an IP alias eth0:0. The backup machine then monitors the health of the primary machine, and if it crashes the backup takes over the service IP address, again as eth0:0. Each machine monitors the other through the network.
Install corosync and pacemaker
Do the steps below on both machines. First, install the packages:
Debian / Ubuntu:
- apt-get install ntp
- [If the above fails, try apt-get install chrony instead]
- apt-get install pacemaker crmsh
- systemctl enable corosync.service
- systemctl enable pacemaker.service
Devuan Ascii and later:
- apt-get install ntp
- [If the above fails, try apt-get install chrony instead]
- apt-get install pacemaker crmsh
- update-rc.d corosync defaults
- update-rc.d pacemaker defaults
Devuan Jessie:
Edit /etc/apt/sources.list and add the following lines:
- deb http://auto.mirror.devuan.org/merged jessie-backports main
- deb-src http://auto.mirror.devuan.org/merged jessie-backports main
Then do:
- apt-get install ntp
- [If the above fails, try apt-get install chrony instead]
- apt-get install pacemaker crmsh -t jessie-backports
- update-rc.d corosync defaults
- update-rc.d pacemaker defaults
CentOS 6:
- cd /etc/yum.repos.d
- wget https://download.opensuse.org/repositories/network:ha-clustering:Stable/CentOS_CentOS-6/network:ha-clustering:Stable.repo
- yum -y install ntp
- yum -y install pacemaker crmsh
- chkconfig corosync on
- chkconfig pacemaker on
CentOS 7:
- cd /etc/yum.repos.d
- wget https://download.opensuse.org/repositories/network:ha-clustering:Stable/CentOS_CentOS-7/network:ha-clustering:Stable.repo
- yum -y install ntp
- yum -y install pacemaker crmsh
- systemctl enable corosync.service
- systemctl enable pacemaker.service
CentOS 8:
- cd /etc/yum.repos.d
- wget https://download.opensuse.org/repositories/network:ha-clustering:Stable/CentOS_CentOS-7/network:ha-clustering:Stable.repo
- dnf -y install chrony
- dnf -y install pacemaker corosync
- dnf -y install crmsh
- systemctl enable corosync.service
- systemctl enable pacemaker.service
On machines running Rocky Linux:
- dnf config-manager --set-enabled HighAvailability
- dnf -y install chrony
- dnf -y install pacemaker pcs
- systemctl enable corosync.service
- systemctl enable pacemaker.service
Others:
- yum -y install ntp
- [If the above fails, try yum -y install chrony instead]
- yum -y install pacemaker crmsh
- update-rc.d corosync defaults
- update-rc.d pacemaker defaults
Configure corosync and pacemaker
Verify that the directory /var/log/corosync has been created on both machines. If not, then do:
- mkdir /var/log/corosync
Do the steps below on the primary node only:
Debian / Ubuntu / Devuan:
- apt-get install haveged
- corosync-keygen
- apt-get remove --purge haveged
- scp /etc/corosync/authkey username@<ip address of the secondary node>:/etc/corosync/.
Others:
- yum install haveged
- corosync-keygen
- yum remove haveged
- scp /etc/corosync/authkey username@<ip address of the secondary node>:/etc/corosync/.
Do the steps below on the secondary node only:
- chown root: /etc/corosync/authkey
- chmod 400 /etc/corosync/authkey
On both nodes do:
- cp /opt/enswitch/current/install/etc/corosync/corosync.conf /etc/corosync/corosync.conf
- mkdir /etc/corosync/service.d
- ln -s /opt/enswitch/current/etc/corosync/service.d/pcmk /etc/corosync/service.d/pcmk
- ln -s /opt/enswitch/current/etc/corosync/corosync /etc/default/corosync
- vi /etc/corosync/corosync.conf
Edit /etc/corosync/corosync.conf as follows:
- Set the first IP address of your network in bindnetaddr under interface, under totem.
- Set the IP addresses of the primary and secondary node under nodelist.
- Set the hostnames of the primary and secondary node under nodelist.
On both nodes start the corosync and pacemaker services (or restart them if they are already started):
- service corosync start
- service pacemaker start
On only one of the nodes check whether there are any resources already configured by default:
- crm status
If there are these must be removed:
- crm resource stop <resource name>
- crm configure delete <resource name>
On only one of the nodes run:
- crm configure property stonith-enabled=false
- crm configure property no-quorum-policy=ignore
To add the floating IP resource where MySQL will be listening on run on either one of the nodes the following command after replacing the IP address and netmask with the appropriate values:
- crm configure primitive ip ocf:heartbeat:IPaddr2 params ip=192.168.1.1 cidr_netmask="24" op monitor interval="30s"