UCP architecture
Estimated reading time: 12 minutesUniversal Control Plane is a containerized application that runs on Docker Enterprise Edition, extending its functionality to simplify the deployment, configuration, and monitoring of your applications at scale.
UCP 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) instance 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.
A swarm is a collection of nodes that are in the same Docker cluster. Nodes in a Docker swarm operate in one of two modes: Manager or Worker. If nodes are not already running in a swarm when installing UCP, nodes will be configured to run in swarm mode.
When you deploy UCP, it starts running a globally scheduled service called
ucp-agent
. This service monitors the node where it’s running and starts
and stops UCP services, based on whether the 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. Theucp-agent
accomplishes this by deploying several containers on the node. 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. Theucp-agent
deploys a subset of containers on worker nodes.
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’s 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 it ensures they keep running. The UCP components that are deployed on a node depend on whether the node is a manager or a worker.
OS-specific component names
Some UCP component names depend on the node’s operating system. For example, on Windows, the
ucp-agent
component is nameducp-agent-win
. Learn about architecture-specific images.
Internally, UCP uses the following components:
- Calico 3.0.1
- Kubernetes 1.8.11
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 |
---|---|
k8s_calico-kube-controllers | A cluster-scoped Kubernetes controller used to coordinate Calico networking. Runs on one manager node only. |
k8s_calico-node | The Calico node agent, which coordinates networking fabric according to the cluster-wide Calico configuration. Part of the calico-node daemonset. Runs on all nodes. Configure the CNI plugin by using the --cni-installer-url flag. If this flag isn’t set, UCP uses Calico as the default CNI plugin. |
k8s_install-cni_calico-node | A container that’s responsible for installing the Calico CNI plugin binaries and configuration on each host. Part of the calico-node daemonset. Runs on all nodes. |
k8s_POD_calico-node | Pause container for the calico-node pod. |
k8s_POD_calico-kube-controllers | Pause container for the calico-kube-controllers pod. |
k8s_POD_compose | Pause container for the compose pod. |
k8s_POD_kube-dns | Pause container for the kube-dns pod. |
k8s_ucp-dnsmasq-nanny | A dnsmasq instance used in the Kubernetes DNS Service. Part of the kube-dns deployment. Runs on one manager node only. |
k8s_ucp-kube-compose | A custom Kubernetes resource component that’s responsible for translating Compose files into Kubernetes constructs. Part of the compose deployment. Runs on one manager node only. |
k8s_ucp-kube-dns | The main Kubernetes DNS Service, used by pods to resolve service names. Part of the kube-dns deployment. Runs on one manager node only. Provides service discovery for Kubernetes services and pods. A set of three containers deployed via Kubernetes as a single pod. |
k8s_ucp-kubedns-sidecar | Health checking and metrics daemon of the Kubernetes DNS Service. Part of the kube-dns deployment. Runs on one manager node only. |
ucp-agent | Monitors the node and ensures the right UCP services are running. |
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-dsinfo | Docker system information collection script to assist with troubleshooting. |
ucp-interlock | Monitors swarm workloads configured to use Layer 7 routing. Only runs when you enable Layer 7 routing. |
ucp-interlock-proxy | A service that provides load balancing and proxying for swarm workloads. Only runs when you enable Layer 7 routing. |
ucp-kube-apiserver | A master component that serves the Kubernetes API. It persists its state in etcd directly, and all other components communicate with API server directly. |
ucp-kube-controller-manager | A master component that manages the desired state of controllers and other Kubernetes objects. It monitors the API server and performs background tasks when needed. |
ucp-kubelet | The Kubernetes node agent running on every node, which is responsible for running Kubernetes pods, reporting the health of the node, and monitoring resource usage. |
ucp-kube-proxy | The networking proxy running on every node, which enables pods to contact Kubernetes services and other pods, via cluster IP addresses. |
ucp-kube-scheduler | A master component that handles scheduling of pods. It communicates with the API server only to obtain workloads that need to be scheduled. |
ucp-kv | Used to store the UCP configurations. Don’t use it in your applications, since it’s for internal use only. Also used by Kubernetes components. |
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-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-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 |
---|---|
k8s_calico-node | The Calico node agent, which coordinates networking fabric according to the cluster-wide Calico configuration. Part of the calico-node daemonset. Runs on all nodes. |
k8s_install-cni_calico-node | A container that’s responsible for installing the Calico CNI plugin binaries and configuration on each host. Part of the calico-node daemonset. Runs on all nodes. |
k8s_POD_calico-node | “Pause” container for the Calico-node pod. By default, this container is hidden, but you can see it by running docker ps -a . |
ucp-agent | Monitors the node and ensures the right UCP services are running |
ucp-interlock-extension | Helper service that reconfigures the ucp-interlock-proxy service based on the swarm workloads that are running. |
ucp-interlock-proxy | A service that provides load balancing and proxying for swarm workloads. Only runs when you enable Layer 7 routing. |
ucp-dsinfo | Docker system information collection script to assist with troubleshooting |
ucp-kubelet | The kubernetes node agent running on every node, which is responsible for running Kubernetes pods, reporting the health of the node, and monitoring resource usage |
ucp-kube-proxy | The networking proxy running on every node, which enables pods to contact Kubernetes services and other pods, via cluster IP addresses |
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 |
Pause containers
Every pod in Kubernetes has a pause container, which is an “empty” container that bootstraps the pod to establish all of the namespaces. Pause containers hold the cgroups, reservations, and namespaces of a pod before its individual containers are created. The pause container’s image is always present, so the allocation of the pod’s resources is instantaneous.
By default, pause containers are hidden, but you can see them by running
docker ps -a
.
docker ps -a | grep -I pause
8c9707885bf6 dockereng/ucp-pause:3.0.0-6d332d3 "/pause" 47 hours ago Up 47 hours k8s_POD_calico-kube-controllers-559f6948dc-5c84l_kube-system_d00e5130-1bf4-11e8-b426-0242ac110011_0
258da23abbf5 dockereng/ucp-pause:3.0.0-6d332d3 "/pause" 47 hours ago Up 47 hours k8s_POD_kube-dns-6d46d84946-tqpzr_kube-system_d63acec6-1bf4-11e8-b426-0242ac110011_0
2e27b5d31a06 dockereng/ucp-pause:3.0.0-6d332d3 "/pause" 47 hours ago Up 47 hours k8s_POD_compose-698cf787f9-dxs29_kube-system_d5866b3c-1bf4-11e8-b426-0242ac110011_0
5d96dff73458 dockereng/ucp-pause:3.0.0-6d332d3 "/pause" 47 hours ago Up 47 hours k8s_POD_calico-node-4fjgv_kube-system_d043a0ea-1bf4-11e8-b426-0242ac110011_0
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
.
Configurations use by UCP
Configuration name | Description |
---|---|
com.docker.interlock.extension | Configuration for the Interlock extension service that monitors and configures the proxy service |
com.docker.interlock.proxy | Configuration for the service responsible for handling user requests and routing them |
com.docker.license | The Docker EE license |
com.docker.ucp.config | The UCP controller configuration. Most of the settings available on the UCP UI are stored here |
com.docker.ucp.interlock.conf | Configuration for the core Interlock service |
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 swarm, 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.