Concepts

Docker

Docker is an open source project to pack, ship, and run any application as a lightweight, portable, self-sufficient container. When you deploy an app with git push or tsuru app-deploy, tsuru builds a Docker image and then distributes it as units (Docker containers) across your cluster.

Clusters

A cluster is a named group of nodes. tsuru API has a scheduler algorithm that distributes applications intelligently across a cluster of nodes.

Nodes

A node is a physical or virtual machine with Docker installed.

Managed node

A managed node is a node created and managed by tsuru, using IaaS integration. tsuru manages this node, i.e. tsuru can heal and scale it.

Unmanaged node

An unmanaged node is a node created manually, and just registered with tsuru. tsuru is not able to manage these nodes, and it should be handled by whoever created it manually.

Applications

An application consists of:

• the program’s source code - e.g.: Python, Ruby, Go, PHP, JavaScript, Java, etc.
• an operating system dependencies list – in a file called requirements.apt
• a language-level dependencies list – e.g.: requirements.txt, Gemfile, etc.
• instructions on how to run the program – in a file called Procfile

An application has a name, a unique address, a platform, associated development teams, a repository, and a set of units.

Units

A unit is a container. A unit has everything an application needs to run; the fetched operational system and language level dependencies, the application’s source code, the language runtime, and the application’s processes defined in the Procfile.

Platforms

A platform is a well-defined pack with installed dependencies for a language or framework that a group of applications will need. A platform might be a container template (Docker image).

For instance, tsuru has a container image for Python applications, with virtualenv installed and other required things needed for tsuru to deploy applications on top of that platform. Platforms are easily extendable and managed by tsuru. Every application runs on top of a platform.

Services

A service is a well-defined API that tsuru communicates with to provide extra functionality for applications. Examples of services are MySQL, Redis, MongoDB, etc. tsuru has built-in services, but it is easy to create and add new services to tsuru. Services aren’t managed by tsuru, but by their creators.