Using Discourse Dev with Traefik (without ‘Bad Gateway’ + ‘blocked host’)


  • Traefik grabs the first port it sees, which on the dev image is 1080- we want port 9292. Use --label=traefik.http.routers.discourse-dev.port=9292
  • You need to set a dev host using en env var in the container: -e DISCOURSE_DEV_HOSTS=your_dev_hostname \

With the dev version of Discourse working, I wanted to let its connectivity be managed by the traefik proxy. But whichever way I sliced it, I would get a Bad Gateway error. The usual suspect for this is not setting a port, or having the service on a different network from traefik itself. However, this issue persisted for me.

I had to add the following to (discourse_source_root)/bin/docker/boot_dev, in the docker run ... section:

    --network=traefik_default \
    --label=traefik.port=80 \ \
    --label=traefik.http.routers.discourse-dev.rule=Host\(\`$DEVHOST\`\) \ \

I set DEVHOST=<my dev host> earlier in the file, or you can use the host there directly. The last line points traefik at the correct port (9292) in the discourse-dev container.

Accessing by host then produces a page with a blocked host error:

Blocked host: discourse_dev_host
To allow requests to discourse_dev_host, add the following to your environment configuration:
config.hosts << “discourse_dev_host”

Setting DISCOURSE_DEV_HOSTS permits access on those hosts. We need to do this in the container, so add the following to the same section in the same file:


Which permits access via that (or those) hostname(s).

[solved] ‘Connection closed’ in Discourse Dev Install

tl;dr: this was a temporary issue solved by a later commit, if you checked out discourse after 28 Oct but before 4 Nov, git pull to update

Having installed a production Discourse forum, I wanted to get a local dev instance up and running for testing.

There are good instructions for doing just that using Docker. Don’t do what I did: follow the production install method and assume that will work by pointing the prod hostname at it in /etc/hosts.

Unfortunately, when I followed the instructions to set up the dev instance, I was greeted with an ‘Unable to connect’ screen. (ERR_FAILED). Even using telnet from the same host failed:

bertieb@ubunutu-vm:~/discourse$ telnet 9292
Connected to
Escape character is '^]'.
Connection closed by foreign host.

Dang. I tried this across fresh Arch and Ubuntu Server (19.10 + 18.04.3 LTS) installs and got the same thing.

Installing the non-Docker version worked but only for localhost; then a comment on that guide’s topic pointed me at a recent change to interface binding. Checking out the commit before that change let me connect from other hosts in both the Docker and non-Docker versions.

As of 2019-11-04 a later commit sorted this issues and added a specific flag (-b) for permitting connections from other hosts.