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

We find the following layers in the architecture:

Operational Layer: Subagents and Director Agent Instances
- Subagents and Director Agent instances are similarly installed.
- Director Agent instances orchestrate Subagents, they . They include a Subagent that can be used if users wish to execute jobs from a Director Agent.
Functional Layer: Subagent Cluster and Director Agent Cluster
- Jobs are assigned Subagent Clusters to specify that the jobs 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 scheduling, active-passive cluster) or for each next execution of a job (round-robin, active-active cluster).
- The Director Agent Cluster is independent from Subagent Clusters. The purpose of clustering is to provide high availability for the role of orchestrating Subagents.

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The article is focused on fail-over of a Director Agent. For fail-over scenarios with Subagent Clusters see JS7 - How to perform fail-over of Subagents in an Agent Cluster.

For command line references see the JS7 - Agent - Command Line Operation article.

Architecture

The JS7 - Agent Cluster documentation provides an in-depth explanation of the architecture. For guidance on planning Agent Clusters, refer to the JS7 - Strategies for Agent Clustering resources.

The Agent Cluster architecture comprises several facets related to clustering, which can be classified into two distinct layers:

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Director Agents orchestrate Subagents, therefore a Director Agent Cluster is independent from Subagent Clusters. Users can operate a single Director Agent instance and they can operate two Director Agent instances that act as a cluster.
The Controller connects to Director Agents to exchange order information. The Controller does not connect to Subagents.
Technically each Director Agent instance includes a Subagent that can be used in a Subagent Cluster. However, for high availability it is recommended to focus a Director Agent's role to orchestration of Subagents and not on execution of jobs in a Subagent Cluster.

Manage Director Agent Clusters

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The active and standby Director Agent instances will switch roles.
As a prerequisite for switch-over
- the Director Agent Cluster has to be coupled,
- the Subagent in a Director Agent instance must not have running jobs.
After switch-over the Standby Director Agent will become active and the now standby the previously active Director Agent instance will be restarted.

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