Automatic Failover

[jpjust]

According to below, in a multi node site, the automatic failover happens, for instance from Server A  (Central node)to Server B (Fail over node)

Now I want to bring Server B as Central node? How can I do that? Is it required to do that? Or I can just leave it AS IS.

Automatic failover

In a multi-node site, each node regularly checks the central node for a heartbeat. If after 10 minutes (the default timeout period is 10 minutes) there is no response from the central node, the site will automatically fail over to the failover candidate node. If there is more than one failover candidate node, the first node to get a lock on the database field becomes the central node. If the node that was previously the central node comes back online, it becomes a failover candidate node.

You can view the status of the nodes that make up your multi-node site in the QMC. The default view does not include the node type, but you can customize the node information that is displayed. To see the node information, and to configure the information displayed about each node, see Nodes.

The default timeout period for the central node is 10 minutes, but you can change it in the QMC. To change the default timeout, see Cluster settings.

[Maria_Halley]

@jpjust 

Could you maybe explain the question a bit more? 

[Benoit_C · Accepted solution]

Hello @jpjust,

You cannot use the QMC to change which node in your site is the central node. You can, however, use the QRS REST API to do this. Before manually reassigning a failover candidate node to a central node role, you must ensure that it is running the necessary services for the central node.

Use the following REST API calls:

• Run a GET to /qrs/serverNodeConfiguration to return a list of server GUIDs.

Run an empty POST to /qrs/failover/tonode/{serverNodeConfigurationID} where {serverNodeConfigurationID} is the ID of the node you want to become the central node.

Regards,

Benoit

[Albert_Candelario]

Hello @jpjust ,

Thanks for posting.

But, what is the issue or question you are having?

Cheers,

Albert

[Levi_Turner · Accepted solution]

The marked correct answer is spot on for the method of manually triggering a failover, but missed a key point which you asked:

>  Is it required to do that? Or I can just leave it AS IS.

Let's take the simplest possible architecture where failover is deployed:

In this architecture, we have the underlying metadata store (PostgreSQL) segmented from the Qlik Sense Enterprise on Windows services. Same for the persistence files (apps, extensions, logs, etc).

Insofar as you have the two persistence layers (database + flat files) stored off of the active / passive central nodes, then you needn't fail back to the node which was the active central node. This is the architectural purpose of an active / passive configuration, namely that it ought not matter who does the active responsibilities just that some node does perform them.

Hopefully that makes sense.

[jpjust]

Hi Levi - You are spot ON. That explains my question. Crystal Clear.

Thanks Levi!!

[jpjust]

Hi Albert, My concern was more like what will happen or what impact would it make if I do not fail back to the original server. According to Levi's explanation, because we have persistent layers there is no reason to manually fail back to the node which was the active central node.

Thanks

[TusharDev_Qlik]

HI @Levi_Turner 

We have internal FQDN created for current active server referring to IP address of Central server to access hub and QMC with that FQDN instead of using server hostnames directly in the url. Now the failover is working as expected but how do we make sure the FQDN also points to the failover node IP address to have no impact to end users or administrators.