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Engine Nodes

The Engine Node data element keeps the state of a separate node. A node is defined as an instance that is deployed on its own environment (read JVM). Engine nodes are generated automatically.

  • name: An auto-generated name based on the getName() method of the java.lang.management.RuntimeMXBean class
  • status: Either 'active' or 'not responding'
  • host name: The name of the host on which the node is deployed
  • master: This is true if and only if the current node is the master node. Only one master node can exist at a time.
  • last active: Actively updated by the node itself. Used to see if the node is still active.
  • active since: When the node was started

Engine Node Services​

Each Engine node will regularly check for Engine Services for which it has no Engine Service Node. If one is found and the Engine Service has not reached its maximum number of nodes, the node will start a timer to start processing this Engine Service.

  • name: An auto-generated name based of the corresponding Engine Service
  • status: See below
  • engine node: Link to its parent engine node
  • engine service: Link to the corresponding engine service
  • last run at: Updated each time the workflow is processed
  • Next run: An estimate for the next timer tick

This is what the different status values mean:

  • 'Not running': If the linked EngineService has status 'stop'
  • 'Not responding': If the linked EngineNode has not been active recently
  • 'Waiting': If the engine is waiting for the next timer tick
  • 'Working': If the engine is currently processing the workflow
  • 'Shutting down'/'Ready for shutdown': Used when a shutdown signal has occurred. Used to close all running tasks before shutting down.
Exceeding the maximum

If at some time the maximum number of nodes has been exceeded (e.g. when the admin has reduced the number of nodes), the Engine Node will try to stop and remove Engine Node Services in order to match the new maximum.