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### 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. Failover Due to Master Disqualification. #### 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 the`cmm_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.
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