Clustering

In order to ensure that CUE Print, DC-X and other external systems integrated with the Content Store via NewsML remain synchronized with the Content Store at all times, CUE Zipline needs to be permanently available. You can improve the availability of CUE Zipline by running several instances of it on different hosts in a cluster: if one of the instances becomes unavailable (because its host goes offline, for example), then one of the other instances can take over, and synchronization is not interrrupted.

When several instances of CUE Zipline are run as a cluster, one instance is the active instance. It monitors the Content Store for changes and exports changed content to CUE Print, DC-X and/or NewsML files, in accordance with its configuration. The other instances are inactive. If the active instance becomes unavailable for some reason, then one of the inactive instances will be redesignated as the active instance and continue processing from where the previous active instance stopped. On startup, the instances in a cluster negotiate between themselves to determine which one will be the active instance.

If all the instances in the cluster become unavailable for some reason, then processing will continue from where it was interrupted when the cluster is restarted.

Clustering only affects CUE Zipline's SSE-driven functionality, that is:

  • Synchronization of storyline content from CUE Content Store to CUE Print

  • Synchronization of binary assets from CUE Content Store to DC-X

  • Automated export of storyline content to NewsML

What this means is that inactive instances are not necessarily completely inactive - they will respond as normal to incoming requests from the CUE editor or from CUE Print to perform other functions such as:

  • On-demand synchronization of storyline content from CUE Print back to CUE Content Store

  • Converting Content Store print storylines into CUE Print texts for the purpose of generating print previews.

  • Converting rich text-based "classic" content items into storyline content items.

Inactive instances can also be used for automated import of NewsML files.

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