How to get Traefik to route to dynamic hostname and port mappings?

[lpeabody]

I don't understand well enough the mechanism used to calculate the services and routers that Traefik uses to direct requests to containers. Hopefully y'all can help me sort that out.

Hard requirements:

• Multiple instances of this project must be able to run at the same time on the same system.
• Primary domain must map to the react app (whatever service is running it).
• Documentation domain serves a static HTML website on domain docs-primary-domain.

We have a React app that we run and should be able to access through the DDEV site's default domain (generated based on the project directory name). The React app runs on port 3000, so, https://primary-domain.ddev.site should bring up the React app when its running.

We also have a static documentation site that should be accessible at https://docs-primary-domain.ddev.site.

Both off these sites are currently served through the web service.

Typically the way I would do this with Traefik would be something like:

services:
  web:
      labels:
          - traefik.http.routers.react-router.rule=Host($DDEV_HOSTNAME)
          - traefik.http.routers.react-router.service=react-service
          - traefik.http.services.react-service.loadbalancer.server.port=3000
          - traefik.http.routers.docs-router.rule=Host(docs-$DDEV_HOSTNAME)
          - traefik.http.routers.docs-router.service=docs-service
          - traefik.http.services.docs-service.loadbalancer.server.port=80

So, this would serve the documentation site through https://docs-DDEV_HOSTNAME, and the react application through https://DDEV_HOSTNAME.

In this way, I'd be able to access the docs site web server service and the react application service from every instance of my project running locally, with DDEV_HOSTNAME calculated dynamically based on the project directory.

However, given DDEV's implementation of the Traefik router, it's completely unclear to me how to accomplish something similar using a hardcoded file configuration. It might be and I just don't know what the algorithm is that produces that file (I checked to see if it's well documented but I so far haven't read anything that would indicate how to do this).

Does anyone have any pointers? Thanks in advance.

[stasadev]

Hi @lpeabody,

Let me share my thoughts:

In this way, I'd be able to access the docs site web server service and the react application service from every instance of my project running locally, with DDEV_HOSTNAME calculated dynamically based on the project directory.

Remove the name from .ddev/config.yaml, and the hostname will be based on the project directory.

We also have a static documentation site that should be accessible at https://docs-primary-domain.ddev.site.

There is an option additional_hostnames https://ddev.readthedocs.io/en/latest/users/extend/additional-hostnames/

But unfortunately, dynamic subdomains based on the main domain are not supported, see issue:

• Have a way to make an additional hostname a subdomain without re-typing the project name #5486

So something like this:

additional_hostnames:
    - docs.$DDEV_PROJECT

will not work. Or maybe I misunderstood, and you can do something similar in a single project instance:

additional_hostnames:
    - primary-domain
    - docs.primary-domain
    - secondary-domain
    - docs.secondary-domain
    - ...

The React app runs on port 3000, so, https://primary-domain.ddev.site should bring up the React app when its running.

Use web_extra_exposed_ports https://ddev.readthedocs.io/en/latest/users/extend/customization-extendibility/#exposing-extra-ports-via-ddev-router

In this way, I'd be able to access the docs site web server service and the react application service from every instance of my project running locally, with DDEV_HOSTNAME calculated dynamically based on the project directory.

Communicating between projects https://ddev.readthedocs.io/en/latest/users/usage/faq/#can-different-projects-communicate-with-each-other

[lpeabody]

Communicating between projects https://ddev.readthedocs.io/en/latest/users/usage/faq/#can-different-projects-communicate-with-each-other

So, communicating between projects is not the primary driver here. I'm effectively running two web services per-project that need to be run in isolation from other instances of the project running on the same system (for example, you are developing multiple branches of the same project simultaneously).

Remove the name from .ddev/config.yaml, and the hostname will be based on the project directory.

To be clear, we're already doing this. I'm saying that we must maintain this requirement as part of any solution to what I'm asking for in my original support request. I specifically specified it as a requirement because of what I thought a suggestion might be:

There is an option additional_hostnames https://ddev.readthedocs.io/en/latest/users/extend/additional-hostnames/

But unfortunately, dynamic subdomains based on the main domain are not supported, see issue:

#5486

So, glad we're on the same page there.

Use web_extra_exposed_ports https://ddev.readthedocs.io/en/latest/users/extend/customization-extendibility/#exposing-extra-ports-via-ddev-router

We're also doing this.

It looks like this might not be possible, but I feel like it should be because this is such a basic tenant of Docker.

[stasadev]

Write your thoughts on how this would be useful in #5486 to add value to it. This is important for our prioritizing the DDEV features that need to be developed. Because when I read this issue, I see that it has taken a different direction, so it's not clear how it can be used.

[lpeabody]

Good suggestion, I've added my feedback on that issue.