remote build hanging on curl while trying to install Volta

I’m using a near-stock Dockerfile to deploy a Rails app. Running a fly deploy at the moment gets to the step where it installs Volta (RUN curl | bash), and hangs trying to connect to

Sending build context to Docker daemon  161.4kB
[+] Building 28.8s (9/23)
 => [internal] load remote build context
 => copy /context /
 => resolve image config for
 => CACHED docker-image://
 => [internal] load metadata for
 => CACHED [base 1/6] FROM
 => [base 2/6] RUN mkdir /app
 => [base 3/6] WORKDIR /app
 => [base 4/6] RUN mkdir -p tmp/pids
 => [base 5/6] RUN curl | bash
 => => #   % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
 => => #                                  Dload  Upload   Total   Spent    Left  Speed
 => => #   0     0    0     0    0     0      0      0 --:--:--  0:00:25 --:--:--     0

Sticking a -v in there only prints on line of debug information…


…which appears to resolve to an AWS instance, and is different from where my local machine resolves to (, which appears to be some kind of Google IP). Not sure if that’s interesting or if it’s just a proxy thing.

I did some sanity-checking, and is indeed working fine at the moment, even if I try to talk to it through a shell in the same Docker base image (running locally). This build has worked fine for the last ~month since I started this project, though I don’t know how much of that was due to hitting cache for this build step and never having to actually run curl.

Looks like there’s some network strangeness happening on the build machines, but I’m unsure how to debug further.

I’ve seen this issue once before but haven’t been able to reproduce since. Can you try wget instead of curl?

That works! It’s not ideal, since I have to apt-get update/install wget itself before installing Volta, but it does unblock the deploy.

As part of testing this I had to nuke my builder since I hit this issue, and now curl seems to work on the new one. Go figure.