db2haip

db2 HADR – highly available virtual ip address manager script

The concept is, that for each HADR pair we assign a virtual ip address, which is needed to be registered to DNS or clients' host files. The client applications connect to the virtual ip.

The scripts are needed to be run as root (or a user, which is able to use the ip a add/delete commands and also needs to be able to run a db2 select command to get information of db2 hadr status.

The script – quite simple – checks if a server is a HADR Primary. If so it assigns the virtual ip to the host, if not, then it removes ip from the host.

This settings must be implemented on both the primary and standby server. The settings need to be the very similar (or the same in some cases) on both the systems

Steps to set up:

• Create a timer service at operating system level (as root)

• file path and name: /etc/systemd/system/db2haip.timer
• file content as below
• you may adjust the OnCalendar line to change the default every minute value to a longer one (00 means every minute)

[Unit]
Description=Timer service for the db2haip service
Requires=db2haip.service

[Timer]
Unit=db2haip.service
OnCalendar=*-*-* *:*:00
AccuracySec=1s

[Install]
WantedBy=timers.target

• Create service unit file

• file path and name: /etc/system/system/db2haip.service
• file content as below
• may be the script location is not perfect and may be adjusted (ExecStart)

[Unit]
Description=Service assigns Virtual IP to the db2 HADR primary system
Wants=myMonitor.timer

[Service]
Type=oneshot
ExecStart=/root/db2haip.sh

[Install]
WantedBy=multi-user.target

• Create the worker script

• file path and name: /root/db2haip.sh – as in the service file
• file content as below
• please adjust the static variables, like virtual address, mask and network device

#!/bin/bash

# static data
VIP=10.0.2.100
VNM=24
DEV=enp0s3

#dynamic data
HADR_ROLE=$(su - db2inst1 -c 'db2 connect to sample > /dev/null; db2 -x select HADR_ROLE from table \(mon_get_hadr\(-2\)\)' | tr -d [:space:])
echo HADR_ROLE: $HADR_ROLE
IPAS=$(ip a s | grep $VIP)
echo $IPAS


if [ "$HADR_ROLE" == "PRIMARY" ]; then
  echo assign vip
  if [ -z "$IPAS" ]; then
    ip a add $VIP/$VNM dev $DEV
    echo vip added
  else
    echo vip already assigned
  fi
else
  echo remove vip
  if [ -z "$IPAS" ]; then
    echo vip is not assigned, no need to remove
  else
    ip a delete $VIP/$VNM dev $DEV
    echo vip removed
  fi
fi

• Make the worker script executable: chmod +x /root/db2haip.sh

• Start the timer service systemctl start myMonitor.service

• Enable the timer service systemctl enable myMonitor.service

• You may montor the service log using the below command: journalctl -S today -f -u myMonitor.service