kunalghoshone/nomad-overlay-network repository overview

⁠Nomad Overlay Network Manager

⁠Overview

Nomad Overlay Network Manager is a lightweight service designed to enable seamless cross-host communication for Docker containers running on Nomad. It resolves a key limitation in Nomad, where containers across different hosts cannot communicate directly. By leveraging Docker Swarm's attachable overlay network and Consul's DNS-based service discovery, this tool ensures automatic container registration and deregistration.

⁠Features

• Automatic Network Attachment: Monitors new Docker containers and attaches them to the my-attachable-overlay network if they have NOMAD_KG_OVERLAY_NETWORK=true set as an environment variable.
• Consul DNS Registration: Retrieves container configuration and registers the container in Consul for easy DNS-based service discovery.
• Automatic Cleanup: Detects when a container is deleted and removes its corresponding DNS record from Consul.
• Fixes Nomad's Cross-Host Communication Issue: Enables direct communication between Nomad-deployed containers across different hosts.

⁠Prerequisites

Before using this tool, ensure you have the following:

• Docker Swarm initialized with an attachable overlay network named my-attachable-overlay
• A running Consul instance for service registration
• Nomad as the container orchestrator

⁠Deployment

⁠Using Docker Compose

Create a docker-compose.yml file (example provided below):

version: '3'
services:
  manager:
    image: kunalghoshone/nomad-overlay-network:latest
    volumes:
      - ./containers:/containers
      - /var/run/docker.sock:/var/run/docker.sock
    environment:
      - CONSUL_HTTP_ADDR=192.168.62.101:8500
      - CONSUL_URL=http://192.168.62.101:8500/
      - ENV_KEY_TO_CHECK=NOMAD_KG_OVERLAY_NETWORK
      - IS_CONTROLLER=false
      - OVERLAY_DOCKER_SWARM_NETWORK_NAME=my-attachable-overlay

⁠Running as a Standalone Container

You can also run the manager directly using Docker:

docker run -d \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -e CONSUL_HTTP_ADDR=192.168.62.101:8500 \
  -e CONSUL_URL=http://192.168.62.101:8500/ \
  -e ENV_KEY_TO_CHECK=NOMAD_KG_OVERLAY_NETWORK \
  -e IS_CONTROLLER=false \
  -e OVERLAY_DOCKER_SWARM_NETWORK_NAME=my-attachable-overlay \
  kunalghoshone/nomad-overlay-network:latest

⁠How It Works

1. The manager listens for Docker container events via docker.sock.
2. When a new container is created:
   • It checks if the container has NOMAD_KG_OVERLAY_NETWORK=true set.
   • If true, it retrieves the container's configuration.
   • The container is attached to the my-attachable-overlay network.
   • The container's details are registered in Consul's DNS system.
3. When a container is removed:
   • The manager detects its deletion.
   • It removes the corresponding DNS record from Consul.

⁠Troubleshooting

⁠Consul Registration Not Working

• Ensure Consul is running and accessible at CONSUL_HTTP_ADDR.
• Check if the container metadata is being retrieved correctly.

⁠Containers Not Communicating Across Hosts

• Verify that my-attachable-overlay exists and is attachable (docker network ls).
• Ensure Docker Swarm is properly configured.
• Confirm that Nomad is correctly launching containers with the required environment variable.

⁠License

This project is open-source and available under the MIT License.

⁠Contributions

Contributions are welcome! Feel free to submit issues or pull requests.

⁠Contact

For any questions or support, reach out via GitHub issues or the development community.

@github link https://github.com/kunalGhoshOne/Nomad-Overlay-Network⁠