DTR architecture

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These are the docs for DTR version 2.1

To select a different version, use the selector below.

Docker Trusted Registry is a containerized application that runs on-premises or on the cloud and allows you to store and manage your Docker images. It needs to be deployed on a worker node managed by UCP.

Since DTR exposes the standard Docker API you can continue using the Docker CLI client to push and pull images to DTR. Universal Control Plane integrates out of the box with DTR so that you can deploy services and applications to your UCP cluster, using the Docker images you store in DTR.

Under the hood

DTR needs to be deployed in a worker node managed by UCP.

For high-availability you can join multiple replicas to a DTR cluster. Learn more about high availability.

DTR internal components

When you install DTR on a node, the following containers are started:

NameDescription
dtr-api-<replica_id>Executes the DTR business logic. It serves the DTR web application, and API
dtr-etcd-<replica_id>A key-value store for persisting DTR configuration settings
dtr-jobrunner-<replica_id>Runs cleanup jobs in the background
dtr-nginx-<replica_id>Receives http and https requests and proxies them to other DTR components. By default it listens to ports 80 and 443 of the host
dtr-notary-server-<replica_id>Receives, validates, and serves content trust metadata, and is consulted when pushing or pulling to DTR with content trust enabled
dtr-notary-signer-<replica_id>Performs server-side timestamp and snapshot signing for content trust metadata
dtr-registry-<replica_id>Implements the functionality for pulling and pushing Docker images. It also handles how images are stored
dtr-rethinkdb-<replica_id>A database for persisting repository metadata

All these components are for internal use of DTR. Don’t use them in your applications.

Volumes used by DTR

DTR uses these named volumes for persisting data:

Volume nameDescription
dtr-ca-<replica_id>Root key material for the DTR root CA that issues certificates
dtr-etcd-<replica_id>DTR configuration data
dtr-notary-<replica_id>Certificate and keys for the Notary components
dtr-registry-<replica_id>Docker images data, if DTR is configured to store images on the local filesystem
dtr-rethink-<replica_id>Repository metadata
dtr-nfs-registry-<replica_id>Docker images data, if DTR is configured to store images on NFS

You can customize the volume driver used for these volumes, by creating the volumes before installing DTR. During the installation, DTR 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.

Networks used by DTR

To allow containers to communicate, when installing DTR the following networks are created:

NameTypeDescription
dtr-brbridgeAllows DTR components on the same node to communicate with each other in a secure way
dtr-oloverlayAllows DTR components running on different nodes to communicate, to replicate DTR data

Where DTR stores images

By default, Docker Trusted Registry stores images on the filesystem of the node where it is running, but you can configure it to use an external storage system.

You can also configure DTR to use these storage backends:

  • NFS
  • Amazon S3
  • Cleversafe
  • OpenStack Swift
  • Microsoft Azure

For highly available installations, you should use a cloud storage system instead of an NFS mount, since they usually have better performance.

How you interact with DTR

Since DTR exposes the standard Docker API you can continue using the Docker CLI client to push and pull images to DTR.

Universal Control Plane integrates out of the box with DTR so that you can deploy services and applications to your UCP cluster, using the Docker images you store in DTR.

Where to go next

docker, registry, dtr, architecture