topic Re: Cluster failover question in QlikView

Cluster failover question

Mon, 26 Jan 2026 18:19:17 GMT

Dear Community

I am working at a customer where we have the problem that one very large application disturbs the performance for other smaller applications. For arguments sake lets call the large application App A and the small application App B.

App A: size 1 GB, used by 5 users

App B: Size 50 MB, used by 200 users

Our idea is to set up clustered QVS machines (QVS 1 and QVS 2) where App A is loaded on QVS 1 and App B is loaded on QVS 2, so far no problems.

Question 1: What happens if QVS 1 fails, will App A then load on QVS 2 although we have specified that App A is only loaded on QVS 1 or will App A upon not finding QVS 1 now load on QVS 2?

Question 2: Is there any documentation where these failover scenarios are described?

Best Regards

/Mats

Re: Cluster failover question

Wed, 02 Apr 2014 12:51:09 GMT

Hi Mats,

Have you taken a look at the reference manual of the server attached?

Re: Cluster failover question

Wed, 02 Apr 2014 12:53:43 GMT

Hi Mats,

In time, it would be interesting to put the two apps on the same server and let the server decide which cluster will provide the app.

Re: Cluster failover question

Wed, 02 Apr 2014 12:58:24 GMT

I have looked into all kind of reference documents, I can not find an answer to my question there 😞

The whole purpose with having a clustered environment in this case is to run the heavy application on one QVS so that the rest of the applications can run on the other QVS .. I don't want to put everything on the same QVS unless one of the QVS machines fail.

So the question is: considering my setup, what will happen if either QVS 1 or 2 fails?

Re: Cluster failover question

Wed, 02 Apr 2014 13:19:29 GMT

Hi Mats,

I think the way its architecture was mounted will not get the desired effect for you. I see no other way out, but put both apps on the same server and improve performance with optimization techniques such as installation only services required for each server.

Re: Cluster failover question

Wed, 02 Apr 2014 13:25:45 GMT

Huh? It is designed and recommended to sometimes run applications only on a specific QVS in clustered environment.

In my case my QlikView environment will consist of three machines, a backend server where QDS, DSC and QMC is running and two (clustered) machines running QVS and QVWS

Re: Re: Cluster failover question

Wed, 02 Apr 2014 14:29:20 GMT

Mats,

I created a slightly different architecture and worked perfectly see the attached file.

Re: Cluster failover question

Wed, 02 Apr 2014 19:11:44 GMT

Claudio

Can you explain exactly how that answers my specific question on failover?

The architecture is from the QlikView system admin certification but when else than for that test would you ever set up an environment like that with the QVS and the QDS on the same machine?

Re: Cluster failover question

Bill_Britt — Thu, 03 Apr 2014 10:50:23 GMT

Hi Mats,

Question 1: What happens if QVS 1 fails, will App A then load on QVS 2 although we have specified that App A is only loaded on QVS 1 or will App A upon not finding QVS 1 now load on QVS 2? Yes, the document will load on the second server if the other server is down.

Question 2: Is there any documentation where these failover scenarios are described? I don't know of any.

Bill

Re: Re: Cluster failover question

Thu, 03 Apr 2014 11:07:30 GMT

Thank you Bill! Have you tested this yourself?

Best Regards

/Mats

Re: Re: Cluster failover question

Bill_Britt — Thu, 03 Apr 2014 11:41:33 GMT

HI Mats,

Yes, The load balancer is designed to check to see if the document is already open to put the user on the server that the document is loaded on. If not then open the document based on resources.

There is an option to "Document Available" that has to be set. You can also set a document to "Never" on a member of the cluster and that will stop the document from loading on that node.

Bill

Re: Re: Cluster failover question

Thu, 03 Apr 2014 11:47:12 GMT

Hi Bill

What I would like to do is to have the big App A loading only on QVS 1 and App B loading only on QVS 2 (so App A will be set to never load on QVS 2) but will that also be the case if then QVS 1 is down?

Best Regards

/Mats

Re: Re: Cluster failover question

Bill_Britt — Thu, 03 Apr 2014 12:33:49 GMT

If you set it to never, then it will never load on that node.

From the Help File

Document AvailableTo configure when the current document is to be available, select one of the following drop-down list options:

•Never, meaning that the current document will never be loaded on the node.

•Always, meaning that the document will always be available to be loaded on the node.

Bill

Re: Cluster failover question

korsikov — Wed, 04 Jun 2014 09:01:41 GMT

Hey. Does not work.

cluster on two node's 11.20.12354.0

That App A is available on the server QVS1 and AppB is available on both. Shutdown QVS1 server for the test. App A is not available in Access Point error "No connection", does not run on QVS2. AppB work fine in both situation.

Re: Cluster failover question

shane_spencer — Fri, 06 Jun 2014 08:58:21 GMT

It sounds like you have sacrifice resiliency for the sake of better performance (by pinning certain documents to a specific server). Perhaps this is something that Qlik need to work on, that in a failure scenario the pinned document will load on the resilient server.

i.e. Have a setting that states Load On Server 1 only. If Server 1 unavailable load on Server 2.

Re: Cluster failover question

korsikov — Fri, 06 Jun 2014 10:26:40 GMT

yes, so goes Q cluster works. Really wanted to be that in case of failure of the first node of the cluster, the application will still run on the second node.

I did so.

preloading the application you chose for me the necessary node. And in web server chosen by balancing "Preloaded document". In the case when both nodes are available all works well. But in case of failure of such a situation comes.

example:

AppA reload in QVS1. All node run

If we connect to AccessPoint appA open in QVS1.

QVS1 falure

appA reconnect and open in QVS2.

QVS1 go

appA avalable preloaded in QVS1 and QVS2. load balance "Preloaded document"

in this case, on which server the document opens?

The experiments showed that opens on the server where this point was open session or most open sessions.

But then that did not work out as we need to. All documents are to work on the second server.

Re: Cluster failover question

Mon, 09 Jun 2014 06:35:57 GMT

Hi Alexander

so you tested this? It seems like you then actually need to redistribute the appA to QVS2 to make it work there?

Thanks a lot

/Mats

Re: Cluster failover question

korsikov — Mon, 09 Jun 2014 07:31:07 GMT

how to make a distribution to one of the servers in the cluster? cluster uses a single shared storage. I need that to Annex A is always performed on one server, but in case of failure was available on other servers in the cluster. in our cluster is a server 2

Re: Cluster failover question

Bill_Britt — Mon, 09 Jun 2014 14:52:16 GMT

Hi Mats,

I wanted to add this screen shot to show the correct setup for this.

For the document to be load on server2 if server1 goes down the setting is Always. If you set it to Never the second server will never load it. Also, I have it set to Preload on Server1.

Bill