Execution Elasticity

MediationZone can scale out both vertically and horizontally. Vertically by adding CPU and/or memory to the host, and horizontally by adding Execution Contexts (ECs) and/or Workflow instances to the execution cluster. A typical scale out scenario, is an online use case where the load is expected to grow over time. The solution is adding several workflow instances executing in parallel on additional ECs.

This can be achieved automatically by linking Workflow Templates to EC Templates/Groups. Then, each EC member started, will automatically start up a Workflow Instance. In the example below, the ECs are all named "A-*", and they will start the next Workflow Instance of the Template 'Base'.  

It is good practice to set up surveillance of the throughput and performance of the deployment, then trigger startup of a new EC when a threshold has been reached. The reverse works as well; that is, you can scale down by removing EC:s using the same mechanism.

A summary of the different MediationZone Desktop dialogues used for enabling automatic scaling:

• Pico Manager; defines the EC Group/Template:
  
  
• Workflow Template; defines which EC Group/Template the workflows shall execute on.
  
  
• Autostart Workflow; enables automatic startup of workflows.
  
  
• Execution Manager → Autostart tab; this is where the status can be viewed. In the example below, the EC Group/Template is "ecbackend", and the WF Template is "realtime_realtime_loadbalance". 

Note that you can link several Workflow Templates to the same EC Group/Template. This way, you can start several workflows on one EC automatically.