Very slow Docker image download

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A user, sudoman, experienced slow Docker image downloads while running ./launcher rebuild app, despite having sufficient bandwidth. marianord suggested that the issue lies between the VM provider and Docker Hub. Falco confirmed that Discourse uses Docker Hub and provided a workaround by pre-downloading the base image using docker pull. A potential long-term solution is to host images on GitHub Docker Registry once it becomes available.

1

When recently running ./launcher rebuild app, two Docker images were scheduled to download. One of them took a while, but another is taking a very long time (> 20 minutes).

Our vm has plenty of bandwidth. When checking nethogs, there was usually no download bandwidth at all for the Docker image that successfully downloaded (but occassionally that one was > 1 MB/s), and none for one I’m still waiting on.

I suppose that this is likely an issue with whatever Docker repository you’re using, but I thought I would bring it up. It might make more sense for us to compile our own Docker images, which is what we were doing earlier. Thanks.

2

My understanding is that Discourse uses Docker HUB, therefore, any issue in bandwidth and/or download speed is between your service provider (VM) and the Docker server itself.

3

Yes, we use Docker Hub and I know that sometimes it can be a bit slow.

A workaround you can use is to pre-download the base image before issuing the rebuild, with something like:

docker pull $(grep -o "discourse/base:[0-9.-]*" launcher)

Maybe when GitHub Docker Registry becomes usable we can also host the image in there.