I've set up a `proxy` network with Traefik acting as the edge router, and I've also got containers providing various services attached to this network. Some of my Docker Compose files define a 'main' service that sits on both the `proxy` network and a specific service network (like `service-network`), while other services are isolated to just their own `service-network`. For example, I have a service called `db`. When my 'main' service tries to access `db`, it might connect to the `db` on the `service-network`, but there's also a possibility of hitting a different `db` on the `proxy` network if one exists. I'm wondering how Docker resolves these name conflicts—how does it determine which `db` service takes priority?
3 Answers
You might want to think about renaming your containers for clarity. I usually name them with a structure, like `app.dependency`, so for example, it could be `nextcloud.db`. That way, you always know which one you're trying to access!
If the same `db` service is attached to both networks, it might not necessarily matter which one it resolves to. Docker’s built-in DNS usually registers all services, and if you query `db`, it could potentially return both IP addresses in a round-robin fashion, splitting the traffic. But if you have truly different databases for unrelated purposes, it’s essential to verify which one should really be resolved. It might be worth diving deeper to figure it out if you're encountering specific issues.
In Docker Swarm, you can refer to services by their names within the same stack. For services in different stacks, you would use the stack name as a prefix (like `stackname_db`). This allows you to differentiate services even if they share the same name across different stacks. Is that the confusion you're facing?
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