UCP architecture

Estimated reading time: 6 minutes

Universal Control Plane is a containerized application that runs on the Commercially Supported (CS) Docker Engine, and extends its functionality to make it easier to deploy, configure, and monitor your applications at scale.

It also secures Docker with role-based access control so that only authorized users can make changes and deploy applications to your Docker cluster.

Once Universal Control Plane (UCP) is deployed, developers and IT operations no longer interact with Docker Engine directly, but interact with UCP instead. Since UCP exposes the standard Docker API this is all done transparently, so that you can use the tools you already know and love like the Docker CLI client and Docker Compose.

Under the hood

Docker UCP leverages the clustering and orchestration functionality provided by Docker.

When you deploy UCP, it starts running a globally scheduled service called ucp-agent. This service monitors the node where it is running and starts and stops UCP services, based on whether that node is a manager or a worker node.

If the node is a:

  • Manager: the ucp-agent service automatically starts serving all UCP components including the UCP web UI and data stores used by UCP. By promoting a node to manager, UCP automatically becomes highly available and fault tolerant.
  • Worker: on worker nodes the ucp-agent service starts serving a proxy service that ensures only authorized users and other UCP services can run Docker commands in that node.

UCP internal components

The core component of UCP is a globally-scheduled service called ucp-agent. When you install UCP on a node, or join a node to a swarm that is being managed by UCP, the ucp-agent service starts running on that node.

Once this service is running, it deploys containers with other UCP components, and ensures they keep running. The UCP components that are deployed on a node depend on whether that node is a manager or a worker.

UCP components in manager nodes

Manager nodes run all UCP services, including the web UI and data stores that persist the state of UCP. These are the UCP services running on manager nodes:

UCP component Description
ucp-agent Monitors the node and ensures the right UCP services are running
ucp-reconcile When ucp-agent detects that the node is not running the right UCP components, it starts the ucp-reconcile container to converge the node to its desired state. It is expected for the ucp-reconcile container to remain in an exited state when the node is healthy.
ucp-auth-api The centralized service for identity and authentication used by UCP and DTR
ucp-auth-store Stores authentication configurations, and data for users, organizations and teams
ucp-auth-worker Performs scheduled LDAP synchronizations and cleans authentication and authorization data
ucp-client-root-ca A certificate authority to sign client bundles
ucp-cluster-root-ca A certificate authority used for TLS communication between UCP components
ucp-controller The UCP web server
ucp-kv Used to store the UCP configurations. Don’t use it in your applications, since it’s for internal use only
ucp-metrics Used to collect and process metrics for a node, like the disk space available
ucp-proxy A TLS proxy. It allows secure access to the local Docker Engine to UCP components
ucp-swarm-manager Used to provide backwards-compatibility with Docker Swarm

UCP components in worker nodes

Worker nodes are the ones where you run your applications. These are the UCP services running on worker nodes:

UCP component Description
ucp-agent Monitors the node and ensures the right UCP services are running
ucp-reconcile When ucp-agent detects that the node is not running the right UCP components, it starts the ucp-reconcile container to converge the node to its desired state. It is expected for the ucp-reconcile container to remain in an exited state when the node is healthy.
ucp-proxy A TLS proxy. It allows secure access to the local Docker Engine to UCP components

Volumes used by UCP

Docker UCP uses these named volumes to persist data in all nodes where it runs:

Volume name Description
ucp-auth-api-certs Certificate and keys for the authentication and authorization service
ucp-auth-store-certs Certificate and keys for the authentication and authorization store
ucp-auth-store-data Data of the authentication and authorization store, replicated across managers
ucp-auth-worker-certs Certificate and keys for authentication worker
ucp-auth-worker-data Data of the authentication worker
ucp-client-root-ca Root key material for the UCP root CA that issues client certificates
ucp-cluster-root-ca Root key material for the UCP root CA that issues certificates for swarm members
ucp-controller-client-certs Certificate and keys used by the UCP web server to communicate with other UCP components
ucp-controller-server-certs Certificate and keys for the UCP web server running in the node
ucp-kv UCP configuration data, replicated across managers.
ucp-kv-certs Certificates and keys for the key-value store
ucp-metrics-data Monitoring data gathered by UCP
ucp-metrics-inventory Configuration file used by the ucp-metrics service
ucp-node-certs Certificate and keys for node communication

You can customize the volume driver used for these volumes, by creating the volumes before installing UCP. During the installation, UCP checks which volumes don’t exist in the node, and creates them using the default volume driver.

By default, the data for these volumes can be found at /var/lib/docker/volumes/<volume-name>/_data.

How you interact with UCP

There are two ways to interact with UCP: the web UI or the CLI.

You can use the UCP web UI to manage your cluster, grant and revoke user permissions, deploy, configure, manage, and monitor your applications.

UCP also exposes the standard Docker API, so you can continue using existing tools like the Docker CLI client. Since UCP secures your cluster with role-based access control, you need to configure your Docker CLI client and other client tools to authenticate your requests using client certificates that you can download from your UCP profile page.

Where to go next

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