Hosting Upsource with Docker – DNS Dilemmas

Currently at work we are using an open source source code management tool called Kallithea. Unfortunately it doesn’t seem to be under active development any longer and is in general a bit unstable and lacking the features we need in a growing development team. For me the biggest pain point was not having a nice web interface to browse and review code. We’re currently evaluating other options (BitBucket, GitHub, VSO/TFS etc.) and trying to decide whether to self-host or not. This process is taking a bit of time, so I went looking for something to tide us over until we came up with a more permanent solution. This lead me to Upsource, one of JetBrains’ latest incarnations.

Upsource is web-based tool for browsing and reviewing code. The handy thing with Upsource is that it tacks onto your source code hosting tool, rather than being an all-in-one like the systems we are looking at moving to. This allowed me to quietly install it without ruffling any feathers and let members of the team decide whether or not they wanted to use it. Luckily I had a spare Linux box running Ubuntu on which I was quickly able to get it installed and hooked up with LDAP.

The interesting part came a month or later when the next version of Upsource was released (February 2017). As well as a bunch of handy new features (full-text search FTW) they also announced that new versions were being published as Docker images. This sounded like a good idea and one which would make future updates easier, so I followed the instructions to migrate my Upsource instance to being hosted under Docker. Unfortunately I found that after starting up my new version of Upsource inside a Docker container, it could no longer resolve internal URLs; neither those pointing to the source code repositories or to the LDAP server.

A bit of Googling revealed that this was a known issue with Docker on recent versions of Ubuntu: https://github.com/docker/docker/issues/23910. It sounds like it’s resolved in the latest version of Docker, but I couldn’t work out whether that had been released yet.

Luckily someone had already written up a handy blogpost showing how to get around the issue: https://robinwinslow.uk/2016/06/23/fix-docker-networking-dns/#the-permanent-system-wide-fix.

I went with the ‘quick fix’ approach described there:

  1. I ran this command to find the IP address of the DNS server running inside my company’s network. This spat out two contiguous IPs for me, so I just choose the first one.
    $ nmcli dev show | grep 'IP4.DNS'
    IP4.DNS[1]:                             10.0.0.2
    IP4.DNS[1]:                             10.0.0.3
  2. Added a –dns 10.0.0.2 argument to the docker run command I used to start the Upsource container.

Problem solved!

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