Scenario: Loss of a Non-primary Node in the Primary Site¶

The administrator deployed the cluster into a Primary and DR site.
The cluster is deployed following the Installation Guide.
The example here is a typical cluster deployment of 6 nodes, where 4 nodes are database servers and 2 nodes are proxy servers.

However, this scenario also applies to a cluster deployment of 8 nodes: 6 database servers and 2 proxy servers. In the case where more than one non-primary node is lost on the Primary site, the relevant recovery steps are repeated.

The design is preferably split over 2 physical data centers.

Data Centre: jhb
             application : AS01[172.29.42.100]
                           AS02[172.29.42.101]

             webproxy :    PS01[172.29.42.102]
                           AS01[172.29.42.100]
                           AS02[172.29.42.101]

             database :    AS01[172.29.42.100]
                           AS02[172.29.42.101]

Data Centre: cpt
             application : AS03[172.29.21.100]
                           AS04[172.29.21.101]

             webproxy :   PS02[172.29.21.102]
                          AS03[172.29.21.100]
                          AS04[172.29.21.101]

             database :   AS03[172.29.21.100]
                          AS04[172.29.21.101]

Node Failure

Normal operations continue where the cluster is processing requests and transactions are committed successfully up to the point where a loss of a non-primary node is experienced. In this 6-node example, AS02[172.29.42.101] failed while transactions were running.
Examine the cluster status running cluster status to determine the failed state:

platform@AS01:~$ cluster status


        Data Centre: unknown
        application : unknown_172.29.42.101[172.29.42.101] (not responding)

        webproxy : unknown_172.29.42.101[172.29.42.101] (not responding)

        database : unknown_172.29.42.101[172.29.42.101] (not responding)


        Data Centre: jhb
        application : AS01[172.29.42.100]

        webproxy : PS01[172.29.42.102]
                   AS01[172.29.42.100]

        database : AS01[172.29.42.100]


        Data Centre: cpt
        application : AS03[172.29.21.100]
                      AS04[172.29.21.101]

        webproxy : PS02[172.29.21.102]
                   AS03[172.29.21.100]
                   AS04[172.29.21.101]

        database : AS03[172.29.21.100]
                   AS04[172.29.21.101]

At this point, all transactions that are currently in flight are lost and will not recover.
The lost transactions have to be replayed or rerun.

Bulk load transactions cannot be replayed and have to be rerun. Before resubmitting a failed Bulk load job, carry out the following command on the primary node CLI in order to manually clear each failure transaction that still has a Processing status after a service restart. Use the command:

voss finalize_transaction <Trans ID>

The failed transaction status then changes from Processing to Fail.
With the database server AS02[172.29.42.101] still down, replaying the failed transactions are successful.

Recovery Steps if the server that is lost, is unrecoverable:

A new unified node needs to be deployed. Ensure the server name, IP information and data centre name is the same as on the server that was lost.
Delete the failed node database weight (database weight del <ip>), for example database weight del 172.29.42.101
Run cluster del 172.29.42.101, because this server no longer exists. Power off the deleted node, or disable its Network Interface Card.
Create the new unified node - see: Create a New VM Using the Platform-Install OVA.
Switch on the newly installed server.
An extra functions file (extra_functions.py) that is installed on the existing cluster needs to be re-installed on each added unified node. Request the Macro_Update_<version>.template file from VOSS Level 2 support and run the command app template Macro_Update_<version>.template.
If the node will be a unified or web proxy node, run cluster prepnode on it.
From the primary unified node, run cluster add <ip>, with the IP address of the new unified server to add it to the existing cluster.
Add database weights so that the weights distributed throughout the cluster
- Delete all database weights in the cluster. On a selected unified node, for each unified node IP, run database weight del <IP>.
- Re-add all database weights in the cluster. On each unified node, for each unified node IP, run database weight add <IP> <weight>
- Check weights - either individually for each node, or for the cluster by using the command:
  
  cluster run application database weight list
  
  Make sure all application nodes show correct weights.
Run cluster provision primary <ip of current primary> to join the new unified node to the cluster communications. It is recommended that this step is run in a terminal opened with the screen command.

Note

Upon cluster provision failure at any of the proxy nodes during provisioning, the following steps illustrate the cluster provisioning:

Run database config and check if nodes are either in STARTUP2 or SECONDARY or PRIMARY states with correct arbiter placement.
Login to web proxy on both primary and secondary site and add a web weight using web weight add <ip>:443 1 for all those nodes that you want to provide a web weight of 1 on the respective proxies.
Run cluster provision to mitigate the failure. It is recommended that this step is run in a terminal opened with the screen command.
Run cluster run all app status to check if all the services are up and running after cluster provisioning completes.

Note

If the existing nodes in the cluster do not see the new incoming cluster after cluster add, try the following steps:

Run cluster del <ip> from the primary node, <ip> being the IP of the new incoming node.
Run database weight del <ip> from the primary node, <ip> being the IP of the new incoming node.
Log into any secondary node (non primary unified node) and run cluster add <ip> ,<ip> being the IP of the new incoming node.
Run database weight add <ip> <weight> from the same session, <ip> being the IP of the new incoming node.
Use cluster run database cluster list to check if all nodes see the new incoming nodes inside the cluster.

Scenario: Loss of a Non-primary Node in the Primary Site¶

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