Using Failover Manager with Virtual IP Addresses

Failover Manager uses the efm_address script to assign or release a virtual IP address.

Please note: Virtual IP addresses are not supported by many cloud providers. In those environments, another mechanism should be used (such as an Elastic IP Address on AWS), which can be changed when needed by a fencing or post-promotion script.

By default, the script resides in:

/usr/edb/efm-4.0/bin/efm_address

Use the following command variations to assign or release an IPv4 or IPv6 IP address.

To assign a virtual IPv4 IP address:

# efm_address add4 <interface_name> <IPv4_addr>/<prefix>

To assign a virtual IPv6 IP address:

# efm_address add6 <interface_name> <IPv6_addr>/<prefix>

To release a virtual address:

# efm_address del <interface_name> <IP_address/prefix>

Where:

<interface_name> matches the name specified in the virtual.ip.interface property in the cluster properties file.

<IPv4_addr> or <IPv6_addr> matches the value specified in the virtual.ip property in the cluster properties file.

prefix matches the value specified in the virtual.ip.prefix property in the cluster properties file.

For more information about properties that describe a virtual IP address, see The Cluster Properties File.

You must invoke the efm_address script as the root user. The efm user is created during the installation, and is granted privileges in the sudoers file to run the efm_address script. For more information about the sudoers file, see Extending Failover Manager Permissions.

Please note: : If a VIP address (or any address other than the bind.address) is assigned to a node, the operating system can choose the source address used when contacting the database. Be sure that you modify the pg_hba.conf file on all monitored databases to allow contact from all addresses within your replication scenario.

Testing the VIP

When using a virtual IP (VIP) address with Failover Manager, it is important to test the VIP functionality manually before starting failover manager. This will catch any network-related issues before they cause a problem during an actual failover. The following steps test the actions that Failover Manager will take. The example uses the following property values:

virtual.ip=172.24.38.239
virtual.ip.interface=eth0
virtual.ip.prefix=24
ping.server.command=/bin/ping -q -c3 -w5

Please note: : The virtual.ip.prefix specifies the number of significant bits in the virtual Ip address.

When instructed to ping the VIP from a node, use the command defined by the ping.server.command property.

1. Ping the VIP from all nodes to confirm that the address is not already in use:

# /bin/ping -q -c3 -w5 172.24.38.239
PING 172.24.38.239 (172.24.38.239) 56(84) bytes of data.
--- 172.24.38.239 ping statistics ---
4 packets transmitted, 0 received, +3 errors, 100% packet loss,
 time 3000ms

You should see 100% packet loss.

2. Run the efm_address add4 command on the Primary node to assign the VIP and then confirm with ip address:

# efm_address add4 eth0 172.24.38.239/24
# ip address
<output truncated>
eth0 Link encap:Ethernet HWaddr 36:AA:A4:F4:1C:40
inet addr:172.24.38.239 Bcast:172.24.38.255
...

3. Ping the VIP from the other nodes to verify that they can reach the VIP:

# /bin/ping -q -c3 -w5 172.24.38.239
PING 172.24.38.239 (172.24.38.239) 56(84) bytes of data.
--- 172.24.38.239 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 1999ms
rtt min/avg/max/mdev = 0.023/0.025/0.029/0.006 ms

You should see no packet loss.

4. Use the efm_address del command to release the address on the primary node and confirm the node has been released with ip address:

# efm_address del eth0 172.24.38.239/24
# ip address
eth0 Link encap:Ethernet HWaddr 22:00:0A:89:02:8E
inet addr:10.137.2.142 Bcast:10.137.2.191
...

The output from this step should not show an eth0 interface

5. Repeat step 3, this time verifying that the Standby and Witness do not see the VIP in use:

# /bin/ping -q -c3 -w5 172.24.38.239
PING 172.24.38.239 (172.24.38.239) 56(84) bytes of data.
--- 172.24.38.239 ping statistics ---
4 packets transmitted, 0 received, +3 errors, 100% packet loss,
 time 3000ms

You should see 100% packet loss. Repeat this step on all nodes.

6. Repeat step 2 on all Standby nodes to assign the VIP to every node. You can ping the VIP from any node to verify that it is in use.

# efm_address add4 eth0 172.24.38.239/24
# ip address
<output truncated>
eth0 Link encap:Ethernet HWaddr 36:AA:A4:F4:1C:40
inet addr:172.24.38.239 Bcast:172.24.38.255
...

After the test steps above, release the VIP from any non-Primary node before attempting to start Failover Manager.

Please note: : The network interface used for the VIP does not have to be the same interface used for the Failover Manager agent’s bind.address value. The primary agent will drop the VIP as needed during a failover, and Failover Manager will verify that the VIP is no longer available before promoting a standby. A failure of the bind address network will lead to primary isolation and failover.

If the VIP uses a different interface, you may encounter a timing condition where the rest of the cluster checks for a reachable VIP before the primary agent has dropped it. In this case, EFM will retry the VIP check for the number of seconds specified in the node.timeout property to help ensure that a failover happens as expected.