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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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- Create a workflow from the Configuration view and assign the same Agent Cluster to all jobs. Once the configuration is completed deploy the workflow.
- The Agent Cluster is configured for round-robin scheduling and executes each subsequent job with the next Subagent.
- To test cluster behavior navigate to the Workflows view and select a workflow from the tree.
- Expand the workflow and add an order.
- Once the workflow has completed successfully open the log from the history panel.
- 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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