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Step 1

The Active cluster node sends a heartbeat by updating a timestamp in the database.

The heartbeat interval is 10 seconds. It can be adjusted with the 'Heartbeat' parameter:

[controller]
; The frequency at which the heartbeat will be updated
Heartbeat = 10s

Step 2

All Passive cluster nodes check the Active cluster node's timestamp to determine if it is current.

This check runs every 20 seconds. It can be adjusted with the 'HeartbeatCheck' parameter:

[controller]
; The heartbeat to determine if this instance will be probed
HeartbeatCheck = 20s

Step 3

If a Passive cluster node determines that the Active cluster node's timestamp is stale, failover occurs: the Passive cluster node changes the mode of the Active cluster node to Offline and takes over as the Active cluster node. If more than one cluster node is operating in Passive mode, the first cluster node eligible to become Active that determines that the Active cluster node is not running becomes the Active cluster node. A stale cluster node is one whose timestamp is older than 5 minutes.

It can be adjusted with the 'Deadline' parameter:

[controller]
; The deadline to determine if this instance will be active
Deadline = 5m

What To Do If a Failover Occurs

A Passive cluster node taking over as an Active cluster node is referred to as failover. If failover occurs, the event is invisible unless you are using the Active cluster node in a browser.

If you are using the Active cluster node in a browser and the cluster node fails, you will receive a browser error. In this case, take the following steps to continue working:


Step 1

Access the new Active cluster node in your browser. 

This can be achieved by selecting the appropriate service in that UDMG Admin UI login page, provided that each UDMG Server instance is defined as a dedicated login service.

Step 2

If you were adding, deleting, or updating records at the time of the failure, check the record you were working on. Any data you had not yet saved will be lost.


Viewing Cluster Node Status

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