Скачать или смотреть Understanding Docker Swarm Routing Mesh

Explore the intricacies of `Docker Swarm Routing Mesh`, how to access your containers, and the essential ports you need to configure for seamless communication.
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Understanding Docker Swarm Routing Mesh: A Complete Guide

Docker Swarm Routing Mesh can be a bit challenging to navigate, especially for those who are new to container orchestration. If you're running a multi-node Docker Swarm setup, you might face questions about accessibility and network configuration. In this guide, we’ll discuss common queries regarding routing in Docker Swarm, providing a clear understanding of how networking operates within this environment.

The Scenario

Imagine you have a Docker Swarm setup with two nodes:

Node 1: Manager

Node 2: Worker

You have two applications defined in a Docker Compose file:

[[See Video to Reveal this Text or Code Snippet]]

Now, let’s address some important questions regarding access to your applications and the necessary network configurations.

Questions and Detailed Answers

1. Can I access app1 through Node 1 and be routed to the app1 container in Node 2?

Yes, you can access app1 through Node 1, and the request can potentially be routed to the app1 container running on Node 2. Docker's Routing Mesh handles requests to the published port (8080 in this case) and load balances the incoming traffic across all the app1 containers running in the swarm.

2. Will I be able to access app2 through Node 2 on port 9080?

Yes, but only if Node 2 is capable of routing traffic to Node 1, where app2 is running. Since app2 is constrained to run on the manager node (Node 1), any attempt to reach it on Node 2 will result in a redirection to Node 1, allowing you to access it on port 9080.

3. Are there any ports other than the ones specified in the Docker documentation that need to be open?

In terms of inter-node communication, aside from the standard ports listed in Docker’s documentation (TCP port 2377, TCP and UDP port 7946, and UDP port 4789), you should also consider the following:

Published Ports: Since you have published app1 on port 8080 and app2 on port 9080, you need to ensure these ports are open in your firewalls for node-to-node communications. This is crucial for accessing the applications from outside the Docker network.

Overlay Network Traffic: Docker uses the overlay network to facilitate communication among the containers. Requests made to the container IPs on port 5000 (as per the internal configuration) use port 4789 for tunneling, and thus do not require specific firewall rules since they operate within the Docker networking stack.

Conclusion

Docker Swarm’s Routing Mesh is a powerful feature that simplifies the management of service requests across multiple nodes, handling load balancing and ensuring high availability. By understanding how services communicate and the importance of configuring necessary ports, you can effectively manage your Docker Swarm environment.

By following these guidelines, you can ensure that your applications remain accessible and can communicate across the nodes in your Docker Swarm.

Feel free to reach out if you have more questions about Docker Swarm or need further assistance with your deployments. Happy Dockering!