Components and terminology¶
This chapter introduces the reader to the components of argocd-agent and its terminology.
Control plane cluster¶
The control plane or control plane cluster is the heart of the architecture. It holds all configuration, is responsible for distributing the configuration among agents and it hosts all central components used for observability and management. At the minimum, this cluster will host the argocd-agent's principal component and the Argo CD API server, including the Argo CD web UI.
The control plane cluster itself will not perform reconciliation of Argo CD Applications to any cluster, including itself.
Typically, there exists only one control plane cluster in any given setup.
The control plane cluster is sometimes called the hub.
Workload cluster¶
A workload cluster is a cluster that is the target for applications. In the classical Argo CD architecture, a workload cluster is one that you connect your Argo CD installation to, i.e. using argocd cluster add or its declarative equivalent.
In the case of argocd-agent, the workload cluster will host at least the argocd-agent's agent component and Argo CD's application controller for local reconciliation. In a nutshell, each workload cluster needs to have a low footprint version of Argo CD installed to it.
The workload cluster is sometimes called a spoke.
Principal¶
The principal is a central component of argocd-agent. It runs on the control plane cluster, and its main tasks are to distribute configuration and receive status information from and to the agents, respectively.
Agents need to be registered with the principal, and the principal will authenticate agents once they connect.
The principal provides additional services to the Argo CD API server, so that users will be able to view live resources and container logs from workload clusters.
The principal typically requires a limited set of privileges on the control plane cluster.
Agent¶
The agent is a component that gets installed to each workload cluster. It will be configured to connect to a specific principal, from which it will receive all configuration and to which it will send status updates.
Depending on the features an agent should provide, it will require limited to extended set of privileges on the workload cluster.
Each agent can run in one of the following modes: managed or autonomous. For more information, refer to the chapter about agent modes.
Hub¶
Spoke¶
See workload cluster