Agent Overview

Introduction

The ZEDEDA Agent is software running on the edge nodes that manages the edge apps in the following ways: 

• Closed Loop App Management: ZEDEDA implements a closed-loop management system for applications. The Agent process running on the edge node continuously monitors the status of the running app instances. This status information is fed into an “application state machine” which tracks the current state and compares it to the desired state of the app. By comparing the actual state with the desired "runstate config" (read from the Patch Envelope), the system can determine whether corrective actions need to be taken on the container runtime. For example, it could take corrective actions such as starting, stopping, or restarting the container(s) to achieve a more consistent state.
  
  
• The ZEDEDA Agent translates the edge app instance management operations into compose app instance actions: start, stop, restart, purge and update command, delete.
  • Activate: compose app instance activate is handled in two ways:
    • New App Instance: the agent handles this as ‘compose up’
    • Existing App Instance which is currently Halted: the agent issues a ‘compose start’
  • Deactivate: compose app instance deactivate is translated to a ‘compose stop’
  • Reactivate: compose app instance reactivate is handled through a ‘compose restart’.
  • Purge and Update: compose app instance purge is handled as a two-step process:
    • First, the agent will issue a ‘compose down’ on the compose application instance. Unused container images are deleted and named compose volumes will be preserved.
    • Next, the agent will issue a ‘compose up’ on the compose application instance, thereby enforcing a re-pull of all container images.
      
      
• The ZEDEDA Agent facilitates shipping the Docker Compose logs and metrics coming out of EVE-OS for processing in the controller.

Next steps

This is a series of articles. You will likely follow them in this order.

1. Docker Compose Overview 
2. Create the Compose Runtime Application
3. Agent Overview - You are here!
4. Add a Docker Compose as an Edge App Type
5. Troubleshooting Docker Compose

After you’ve completed the series, you might be interested in the following articles. 

1. Manage your edge nodes and edge apps.