Components

Deis consists of a number of components that combine to create a distributed PaaS. Each Deis component is deployed as a container or set of containers.

Controller

The controller component is an HTTP API server. Among other functions, the controller contains the scheduler, which decides where to run app containers. The deis command-line client interacts with this component.

Database

The database component is a PostgreSQL server used to store durable platform state. Backups and WAL logs are pushed to Store.

Cache

The cache component is an optional instance of Redis. If the cache is running, it will be used by the Registry.

Caching can cause problems for deis pull, but may speed up access to small files when using a remote storage backend such as S3. The deisctl provisioning tool does not install or start the cache by default.

Builder

The builder component uses a Git server to process Application builds. The builder:

  1. Receives incoming git push requests over SSH
  2. Authenticates the user via SSH key fingerprint
  3. Authorizes the user’s access to write to the Git repository
  4. Builds a new Docker image from the updated git repository
  5. Adds the latest Config to the resulting Docker image
  6. Pushes the new Docker image to the platform’s Registry
  7. Triggers a new Release through the Controller

Note

The builder component does not incorporate Config directly into the images it produces. A Release is a pairing of an application image with application configuration maintained separately in the Deis Database.

Once a new Release is generated, a new set of containers is deployed across the platform automatically.

Registry

The registry component hosts Docker images on behalf of the platform. Image data is stored by Store.

Logspout

The logspout component is a customized version of progrium’s logspout that runs on all CoreOS hosts in the cluster and collects logs from running containers. It sends the logs to the Logger component.

Logger

The logger component is a syslog server that collects logs from Logspout components spread across the platform. This data can then be queried by the Controller.

Publisher

The publisher component is a microservice written in Go that publishes containers to etcd so they can be exposed by the platform Router.

Router

The router component uses Nginx to route traffic to application containers.

Store

The store component uses Ceph to store data for Deis components which need to store state, including Registry, Database and Logger.

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