6 Replies Latest reply: Sep 30, 2016 11:22 AM by dion verbeke RSS

    How does QS services in a multi-node environment work?

    Bilge Aydin

      1) I would like to understand how Qlik Sense Scheduler service on a Reload/scheduler node in a multi node environment work:


      Where does data reloading into QVF takes place? Is it on Reload/scheduler node? If so, does that mean that there will be a copy of the QVF file under C:\ProgramData\Qlik\Sense\Apps folder of Reload/scheduler node? And the QVF will be synchronized to central and engine nodes after reload?


      2) If central node is down, would engine nodes continue to serve the user, i.e, would users be able to access the apps on HUB? Would Reload/scheduler node be able to reload data into apps?


      Thanks,





        • Re: How does QS services in a multi-node environment work?
          Mattias Wijkström

          Hi Bilge,

           

          1) Reloading of apps take place on nodes that have the Scheduler setup as slave. You can find out which Schedulers that are slaves by looking at their settings in the QMC. A slave Scheduler uses the Engine on the same node to perform the reload. Anything stored under C:\ProgramData\Qlik\Sense\Apps is handled by the Engine but does not necessarily have anything to do with a reload. Files could be placed there due to an incoming sync.

           

          The meta data of a reloaded app will be sync'ed to the central node, and then further to other rim nodes. As soon as a node receives the meta data about the reloaded app and if it should have that app according to sync rules, it will download it (the binary data, the QVF) in chunks from any other node that have chunkes of the same "version" of it.

           

          An app stored by the Engine under C:\ProgramData\Qlik\Sense\Apps does not have to be the same size on different nodes even though it is the same "version". This is because the QVF file is a virtual file system which can expand but will not shrink under normal production circumstances.

           

          2) Every node will continue to work independently and will continue to serve users if configured to, when the central node is offline. However, no sync will occur as that always goes through the central node. An app can still be reloaded (if the script itself does not depend on the offline machine) on a node but will not be sync'ed to other nodes.

           

          /Mattias

          • Re: How does QS services in a multi-node environment work?
            Prem Prakash

            Hi Everyone,

             

            Do we have any concrete answer for the above post. I would like to know more on high availability implementation in QlikSense.

             

             

            As part of Qlik Architecture, we have main components, which will be hosted as servers.

            1.       Proxy

            2.       Engine

            3.       Scheduler

            4.       Central node.

            In the scenario of high availability how many servers we have to have and how it works.

             

            Assume a multimode with 4 servers (each one server for the above components), with high availability do we require 8 nodes? This looks not correct to me. Can you help on this?

             

             

            My question is How High Availability is enabled on a multi node environment?