Introduction

The Agent Cluster is designed to provide horizontal scalability and fail-over capabilities for Agents in HA environments, see JS7 - Agent Cluster. It works without a single point of failure.

Use of a JS7 - Agent Cluster provides high availability and is a feature that is subject to the JS7 - License.

We find two separate tiers for clustering of Agents, see JS7 - Agent Cluster:

• Functional Layer: Subagent Cluster
  • Jobs are assigned Subagent Clusters to specify that they can be executed by any Subagent that is a member of the Subagent Cluster. The Subagent Cluster rules if a different Subagent will be chosen in case of fail-over only (fixed-priority) or for each next execution of a job (round-robin).
• Operational Layer: Director Agent Cluster
  • Director Agents orchestrate Subagents, therefore a Director Agent Cluster is independent from Subagent Clusters.
  • For testing of Director Agent Clusters see JS7 - How to test fail-over of Subagents in an Agent Cluster

Consider the wording in this article:

• Fail-over is an automated operation that occurs when a Subagent is aborted or killed. Fail-over is applied in case of abnormal termination.
• Switch-over is a manual operation performed by users disabling/enabling Subagents.

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Fail-over occurs when an Active Subagent is terminated abnormally. Fail-over means includes that the task currently being executed by the Subagent is considered to have failed and that the related order is set to a failed state. An Inactive Subagent is no longer considered for execution of jobs by a Director Agent:

• Subagent Clusters configured for round-robin scheduling will execute jobs with the remaining Subagents. 
• Subagent Clusters configured for fixed-priority scheduling will switch execution of jobs to the next Subagent.

Fail-over can be invoked caused by the following actions:

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1. Create a workflow from the Configuration view and assign the same Agent Cluster to all jobs. Once the configuration is completed deploy the workflow.
   
   
   
   
2. The Agent Cluster is configured for round-robin scheduling and executes each subsequent job with the next Subagent.
3. To test cluster behavior navigate to the Workflows view and select a workflow from the tree.
   
   
   
   
4. Expand the workflow and add an order.
   
   
   
   
5. Once the workflow has completed successfully open the log from the history panel.
   
   
   
   
6. In the log, you can identify that all jobs use different Subagents as the Agent Cluster is set up for round-robin scheduling. Each next job is executed with the next Subagent.

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