Chapter 10. Fabric Agents

Abstract

The Fabric agent, which is responsible for provisioning on each container instance, is a key component of the Fabric infrastructure. When it comes to troubleshooting the behavior of a Fabric container, it is valuable to have an understanding of what the Fabric agent does and how it works.

10.1. Introduction

Fabric agent

The Fabric agent is the part of Fabric that is responsible for applying profiles to containers. The agent can run in any container and its role is to retrieve profile information from the registry and apply them to the container.
To be specific, the Fabric agent performs the following actions:
  1. Retrieves the profiles and versions assigned to the container on which it is running.
  2. Reconfigures the container.
  3. Calculates what needs to be installed, removed or updated on the container.
  4. Performs the requisite install, remove, and update actions.

Agent modules

In reality, the Fabric agent is composed of the following two modules:
[fabric-configadmin]
The Fabric configuration admin bridge. Translates the registry information into configuration information.
[fabric-agent]
The deployment agent. Reads the translated configuration and provisions the container accordingly.
Often, the term, agent, refers just to the deployment agent ([fabric-agent] module), but here we discuss both of the agent modules and describe the role of each in some detail.