Sun Microsystems
Products & Services
 
Support & Training
 
 

Previous Previous     Contents     Index     Next Next

Cluster Initialization Notifications

When neither node A nor B is currently running the Foundation Services, nodes A and B are out. When node A becomes the master node, a MASTER_ELECTED notification is sent to the registered applications and services. At cluster startup, this is the first step in the creation of a cluster. The notification sent for this scenario is shown in Table 6-5.

Table 6-5 A Master is Elected at Cluster Startup

Transition (node A, node B) Notifications Sent 
(out, out) --> (master, out)CMM_MASTER_ELECTED(A)

The following scenario describes the election of a qualified node to the vice-master role at cluster initialization. This takes place in one step, when the CMM_VICEMASTER_ELECTED notification is sent. The notification sent for this scenario is shown in Table 6-6.

Table 6-6 A New Node Joins the Cluster and Becomes Vice-Master

Transition (node A, node B) Notifications Sent 
(master, out) --> (master, vice-master)CMM_VICEMASTER_ELECTED (B)

The following scenario describes when a new node joins the cluster. This node does not take the master or vice-master role and could be a diskless node or a dataless node. The notification sent for this scenario is shown in Table 6-7. This scenario can occur at cluster initialization or when a new node is added to a running cluster.

Table 6-7 A New Node Joins the Cluster

Transition (node A, node B) Notifications Sent 
(master, out) --> (master, in)CMM_MEMBER_JOINED (B)

The following scenario describes the situation where a node that is in becomes vice-master. This scenario can occur if a node is in the cluster but does not immediately declare itself as master-eligible. When its eligibility to be a master node or a vice-master node is known, the node is elected vice-master. This scenario can also occur if a master-eligible node is disqualified. When the node is requalified, the node becomes that vice-master. The notification sent for this scenario is shown in Table 6-8.

Table 6-8 A Node is Elected Vice-Master

Transition (node A, node B) Notifications Sent 
(master, in) --> (master, vice-master)CMM_VICEMASTER_ELECTED (B)

Vice-Master Removal Notifications

Provided that there is a running vice-master node, if the master node stops being master because its role has been removed, there is a failover, as explained in Failover Notifications.

If the vice-master node stops being vice-master due to a failure, or because its role has been removed, there is no backup for the master node and the cluster loses its 2N redundancy.

If the vice-master role is removed because of a failure or by using the cmm_membership_remove() function, the notification is shown in Table 6-9.

Table 6-9 The Vice-Master Node Fails or the Vice-Master is Removed With the cmm_membership_remove() Function

Transition (node A, node B) Notifications Sent 
(master, vice-master) --> (master, out)CMM_VICEMASTER_DEMOTED (B) CMM_MEMBER_LEFT (B)

Vice-Master Excluded Notification

The vice-master node can be disqualified if you use the cmm_member_setqualif() function. The notification sent for this scenario is shown in Table 6-10.

Table 6-10 The Vice-Master is Disqualified with the cmm_member_setqualif() Function

Transition (node A, node B) Notifications Sent 
(master, vice-master) --> (master, in)CMM_VICEMASTER_DEMOTED (B)

For more information about disqualifying a node by using the cmm_member_setqualif() function, see Setting the Qualification of a Node. Care must be taken with the use of the cmm_member_setqualif() function. Do not trigger a failover. For more information, see Triggering a Failover by Using the cmm_member_setqualif()Function. See also the cmm_member_setqualif(3CMM) man page.

Peer Node Removal Notification

If a peer node other than the master or vice-master loses its role in the cluster, it becomes temporarily out of the cluster. This occurs if you use the cmm_membership_remove() function on the peer node. The notification sent in this scenario is shown in Table 6-11.

Table 6-11 A Node Other Than Master or Vice-Master is Removed From Cluster

Transition (node A, node B) Notifications Sent 
(master, in) --> (master, out)CMM_MEMBER_LEFT(B)

Master Node Excluded Notifications

If the master node fails, the node can be excluded from the cluster as described in Removing or Excluding a Node. The notification sent in this scenario is shown in Table 6-12.

Table 6-12 The Master Node is Excluded From Cluster

Transition (node A, node B) Notifications Sent 
(master, vice-master) --> (out, master)CMM_MEMBER_LEFT(A) CMM_MASTER_ELECTED(B)

Node Other Than Master Excluded Notification

If a node other than the master fails it can be excluded from the rest of the cluster as described in Removing or Excluding a Node. The notification sent is shown in Table 6-13.

Table 6-13 A Node Other Than Master is Excluded From Cluster

Transition (node A, node B) Notifications Sent 
(master, in) --> (master, out)CMM_MEMBER_LEFT(B)

The notification sent for this scenario can also be sent for a diskless node.

Switchover Notifications

A switchover is the scheduled transfer of the CMM_MASTER role from the master node to the vice-master node. A switchover is not a failure and does not change the qualification level of the master node. A switchover is not a persistent change. A switchover is usually triggered by the cluster administrator for the maintenance of a node. For more information about the maintenance of nodes, see "Starting and Stopping Services, Nodes, and Clusters" in the Netra High Availability Suite Foundation Services 2.1 6/03 Cluster Administration Guide.

The notifications sent in the case of a switchover from the master to the vice-master node, triggered by calling the cmm_mastership_release() function, are shown in Table 6-14.

Table 6-14 A Switchover Triggered by the cmm_mastership_release() Function

Transition (node A, node B) Notifications Sent 
(master, vice-master) --> (vice-master, master)CMM_MASTER_ELECTED (B) CMM_VICEMASTER_ELECTED (A)

For further information and an example that uses the cmm_mastership_release() function to trigger a switchover, see Triggering A Switchover.

Failover Notifications

A failover is the unscheduled transfer of the CMM_MASTER role from the master node to the vice-master node. A failover is a response to the removal or failure of the master node or disqualification of the master node. This section describes two failover scenarios:

Failover Due to the Removal or Failure of the Master Node

If master node is removed from the cluster by using the cmm_membership_remove() function, the node takes CMM_OUT_OF_CLUSTER role. This role indicates that the node is out of the cluster, but is configured to be in the cluster, and has access to cluster information. This is described in Membership Roles.

The notification sequence is the same, whether a master failover occurs because the master node fails or because the master role is removed. The master node is excluded from the cluster and the vice-master becomes the master. The notifications sent for this scenario are shown in Table 6-15.

Table 6-15 A Failover Due to the Removal or Failure of the Master Node

Transition (node A, node B) Notifications Sent 
(master, vice-master) --> (out, master)CMM_MASTER_DEMOTED (A) CMM_MEMBER_LEFT (A) CMM_MASTER_ELECTED (B)

The nhcmmd daemon issues notifications of this failover, described in Introduction to Change Notifications.

For an example of how to trigger a failover using thecmm_membership_remove() function, see Example 7-6.

Failover Due to Master Disqualification

In this scenario, the failover of the master node is due to the use of the cmm_member_setqualif() function. The master node is no longer able to be either master or vice-master, but is in the cluster as a peer node. The vice-master becomes the master node. Because there is no other master-eligible node to take the vice-master role, the cluster loses its 2N redundancy. The former master node must be requalified to restore 2N redundancy. The notifications sent for this scenario are shown in Table 6-16.

Table 6-16 A Failover Due to the Disqualification of the Master Node

Transition (node A, node B) Notifications Sent 
(master, vice-master) --> (in, master)CMM_MASTER_DEMOTED (A) CMM_MASTER_ELECTED (B)

The nhcmmd issues notifications of this failover, described in Introduction to Change Notifications.

The cmm_member_setqualif() function is used during the process of peer node reboot and is called from the node that is being rebooted by the service coordinating the node reboot.

For an example of how to trigger a failover using the cmm_member_setqualif() function, see Triggering a Failover by Using the cmm_member_setqualif()Function.

Previous Previous     Contents     Index     Next Next