cluster preempt

Function

The cluster preempt command enables the preemption function of a cluster business group.

The undo cluster preempt command disables the function.

Format

cluster preempt

undo cluster preempt

Parameters

None

Views

System view

Default Level

2: Configuration level

Usage Guidelines

By default, the function is enabled.

Usage Scenario

After the function is enabled, the original business master preempts the master state after recovering from a fault. After the function is disabled, the original business master preempts the master state only when its health is higher than that of the current business master. In specific scenarios, for example, if you want the network to be stable and do not want frequent traffic switching, you can disable preemption function.

Table 1 lists the elected business masters in a business group when the preemption function is enabled and disabled.

**Table 1** Business master election results
Business Group Information	Elected Business Master (Preemption Enabled)	Elected Business Master (Preemption Disabled)
Normal business group information Device A (health: 10000; priority: 100) Device B (health: 10000; priority: 90) Device C (health: 10000; priority: 80)	Device A	Device A
Business group information when device A fails Device A (health: 9998; priority: 100) Device B (health: 10000; priority: 90) Device C (health: 10000; priority: 80)	Device B	Device B
Business group information when device A recovers Device A (health: 10000; priority: 100) Device B (health: 10000; priority: 90) Device C (health: 10000; priority: 80)	Device A	Device B

After the preemption function is disabled, it can still be triggered in the following situations:

The health rating of the original business master device is restored to be greater than that of the current business master device.
The administrator disables the cluster function for the original business master device and adds it to the cluster again.
The original business master device completes the upgrade operation.
The administrator changes the shared key of the original business master device and adds it to the cluster again.
The original business master device is added to the cluster again over 24 hours after it is removed from the cluster.
In a scenario with the same health rating, the administrator changes the priority of the original business master device to be higher than that of the current business master device.

Precautions

Even if the preemption function of a business group is disabled, the status of the devices in the business group will be ranked again if a new device is added to the cluster or the priorities of devices are changed.

Disabling the preemption function and then enabling it do not trigger the change of the business master.

Example

# Enable the preemption function of a business group.

<sysname> system-view
[sysname] cluster preempt