Docker Swarm DNS naming (1 Viewer)

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In Docker Swarm mode, each service is given a DNS name that is automatically managed by Docker's built-in DNS resolution mechanism. This DNS naming enables services to communicate with each other using service names instead of having to rely on IP addresses.

The basic DNS naming convention for Docker Swarm services is as follows:

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<service-name>.<network-name>

Here, <service-name> is the name of the service you defined when creating it in Docker Swarm, and <network-name> is the name of the overlay network the service is connected to.

For example, if you have a service named web connected to an overlay network named frontend, you could access it from another service using the DNS name web.frontend.

Here's how you can create a service in Docker Swarm and utilize its DNS name:

1. Create an Overlay Network (if not already created):

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docker network create -d overlay frontend

1. Create a Service:

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docker service create --name web --network frontend nginx

1. Access the Service from Another Container:

Assuming you have another service connected to the same frontend network, you can access the web service using its DNS name:

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docker service create --name client --network frontend alpine sleep infinity
docker service exec -it client sh

# Now, inside the client container, you can ping the 'web' service
ping web

Keep in mind that Docker Swarm's DNS naming works within the context of the overlay network. If you need to communicate between services in different overlay networks, you would typically need to rely on DNS names in conjunction with external DNS resolution or some other routing mechanism.

Also, Docker Swarm services can have multiple replicas running on different nodes. The DNS name will resolve to one of the replicas' IP addresses. If you need load balancing or service discovery, Docker Swarm handles this internally.

Remember that these instructions are based on the Docker Swarm DNS naming as of my last knowledge update in September 2021. Please refer to the Docker documentation or any updates since then for the most accurate and up-to-date information.

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