With an MQ Queue Manager Group on DataPower, how is the backup MQ Queue Manager selected when the primary MQ Queue Manager is down?
Resolving the problem
An MQ Queue Manager Group enables automatic failover between queue managers when the current primary queue manager becomes unavailable.
If multiple backup queue managers are defined, the MQ Queue Manager Group object will select an available queue manager from one or more backup MQ queue managers as the primary queue manager.
When the original primary queue manager returns to service, the appliance reassigns this queue manager to its former role. Hence, it will preempt current primary queue manager when new transactions arrive.
The primary queue manager will have the highest preempt priority, it always becomes primary queue manager when it is available. If more than one backup queue manager has been defined, selection will depend upon which one is the last one returning to service.
For example, assuming the following MQ Queue Manager Group configuration:
Primary Queue Manager:
queue manager A
Backup Queue Managers:
queue manager B,
queue manager C,
queue manager D
(1) If the current primary queue manager down is caused by an event such as network down, queue manager down in MQ server, etc., then MQ Queue Manager Group object will search in the order in which the queue managers are listed as backup queue managers.
In the example above, if the primary queue manager A is down due to MQ server down, then queue manager B will become primary queue manager. If queue manager B is also down, then queue manager C will become primary queue manager and so on.
(2) If the current primary queue manager is down due to disablement of the queue manager object, then MQ queue manager group object will select the first available queue manager from the backup queue managers as primary queue manager.
In the example above, when queue manager A is disabled, then MQ queue manager group will select queue manager B, or queue manager C, or queue manager D. It will not follow the order in the list. It depends on queue manager object status, first available will be selected first.
In above situations (1) and (2), whenever Primary Queue Manager A returns to service, it will preempt to become primary queue manager.
If A remains down, the last queue manager in backup list returning to service will be the primary queue manager. For example if queue managers return to service in order of B, D, C. Then queue manger C will become the primary queue manager because it is the last one to become available.