Key Info

Dobby is a management layer above the open-source crun OCI containerization tool, used for managing and running containers.

• Repository: https://github.com/rdkcentral/Dobby
• Language: C++
• License: Apache 2.0

Overview

Dobby is a container management tool, originally developed by Sky and open-sourced to the RDK community. Dobby is a daemon-based program that makes use of the crun runtime and provides a more user-friendly experience for starting/stopping containers, handles container lifecycle management and enhancing the base functionality provided by crun.

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Usage

The core component of Dobby is the DobbyDaemon. This should be started at STB boot and then listens over dbus for commands. The full dbus API of Dobby can be found here: https://github.com/rdkcentral/Dobby/blob/master/protocol/include/DobbyProtocol.h, although it is not recommended to communicate with Dobby manually over dbus. Instead, Dobby provides abstractions over dbus which are discussed later in this document.

Dobby ships with a systemd unit file called dobby.service, which allows Dobby to be started/stopped by systemd.

Command-Line

For debug builds of Dobby, the DobbyTool binary is installed on the STB. This is a simple command line app that communicates with Dobby directly over dbus to issue common commands. This is very useful for troubleshooting and testing Dobby.

Example:

# Extract OCI bundle to STB
$ tar -xzvf my_app_bundle.tar.gz

# Start container
$ DobbyTool start my_app ./my_app_bundle/

Integration with Thunder

OCIContainers Plugin

To control Dobby using a JSON-RPC API, then use the OCIContainer Thunder NanoService. This exposes the same functionality as DobbyTool, but in a manner more suited for integration into other code in RDK-V.

On platforms where Thunder is not available, the raw dbus interface can be used instead - OCIContainers only serves as an abstraction over dbus so other components that already communicate with JSON-RPC can easily control Dobby.

Example of OCIContainer to start a container from an OCI bundle:

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The OCIContainer code  contains a README.md file with detailed documentation on its usage -  see here: https://github.com/rdkcentral/rdkservices/blob/sprint/2009/OCIContainer/README.md

ProcessContainers

Thunder includes the ability to run plugins in containers as well as the traditional in/out of process modes. Thunder offers different back-ends for running Thunder plugins in containers, one of which is Dobby. This mode will communicate with Dobby to start/stop Thunder plugins inside Dobby containers. This provides the advantage of meaning Dobby is responsible for running all types of container on the STB, from native apps to Thunder plugins.

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Then for the plugin(s) you wish to run in a container, set the execution mode to "container" in the plugin configuration file.

Creating OCI bundles for Dobby

To run an application as a Dobby container, the application must be packed as an OCI bundle. This bundle can come from many different sources - it could be manually created or generated from an OCI image.

An OCI bundle consists of two key components:

• Root file system - a directory containing the root filesystem of the container
• Config.json - the container configuration

Source Code/Development

Dobby source code lives on the RDKCentral GitHub The exact structure of this bundle is defined in the OCI runtime specification here: https://github.com/opencontainers/runtime-spec/blob/master/spec.md. Dobby is fully compliant with version 1.0.2 of the specification.

For more information on how to create OCI bundles from scratch, see the following pages:

rdkcentral/Dobby and is Apache 2.0 licenced.

To develop Dobby, it is recommended to use Ubuntu 16.04. Dobby ships with a Vagrant file to create a development environment. More information is available here: https://github.com/

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rdkcentral/

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Dobby/

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tree/master/

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develop

If you would like to contribute code to this project you can do so through GitHub by forking the repository and sending a pull request. Before RDK accepts your code into the project you must sign the RDK Contributor License Agreement (CLA).

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