CODEWITHSUNDEEP
docker-composeport
vuenoob
vuenoob

Reputation: 117

Docker: run multiple container on same tcp ports with different hostname

Is there a way to run multiple docker containers on the same ports? For example, I have used the ports 80/443 (HTTP), 3306 (TCP/MySQL) and 22 (TCP/SSH) in my docker-compose file. Now I want to run this docker-compose for different hostnames on the same ip address on my machine. - traffic from example1.com (default public ip) => container1 - traffic from example2.com (default public ip) => container2 I have already found a solution only for the HTTP traffic by using an additional nginx/haproxy as a proxy on my machine. But unfortunately, this can't handle other TCP ports.

Upvotes: 3

Views: 971

Answers (1)

David Maze
David Maze

Reputation: 158908

This isn't possible in the general (non-HTTP) case.

At a lower level, if I connect to 10.20.30.40:3306, the Linux kernel selects a single process that's listening on that port and sends the request there. You're not allowed to bind(2) a second process to the same port. (This is also why you get an error if you try to docker run -p picking a host port that's already in use.)

In the case of HTTP, there's the further detail that the host-name part of the URL is also sent in an HTTP Host: header: the Web browser both does a DNS lookup for e.g. stackoverflow.com and connects to its IP address, and also sends a Host: stackoverflow.com HTTP header. That's the specific mechanism that lets you run a proxy on port 80, and then forward to some other backend service via a virtual-host setup.

That mechanism is very specific to HTTP, though, and doesn't work for other protocols that don't have support for it. I don't think either MySQL or ssh have similar mechanisms in their wire protocol.

(In the particular situation you describe this is probably relatively easy to handle. You wouldn't want to make either your internal database or an sshd visible publicly, so delete their ports: from your docker-compose.yml file, and then just worry about proxying the HTTP service. It's pretty unusual and a complex setup to run sshd in Docker so you also might remove that and simplify your stack a little.)

Upvotes: 1

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