Why are rebar3 '"git://' dependency fetching hanging?

Questions / Help
1

Hi.

I’m using rebar 3.24.0 on Erlang/OTP 27.2 / Erts 15.2.

I’m trying to compile the Erlang app (https://github.com/yurrriq/nkcluster) and have a questions about the get-deps phase of rebar3.

  1. Q1: Why fetching a dependency from {git,"git://github.com/... hangs but fetching a dependency from {git,"https://github.com/... works normally?

  2. Q2: Is there a flag for rebar3 to turn on verbose output?

Example:

deps part from the rebar.config:

{deps, [
  {nkdist,
   {git, "git://github.com/yurrriq/nkdist.git",
    {branch, "master"}}},
  {nkpacket,
   {git, "git://github.com/yurrriq/nkpacket.git",
    {branch, "master"}}},
  {nkdocker,
   {git, "git://github.com/yurrriq/nkdocker.git",
    {branch, "master"}}},
  {eper,
   {git, "git://github.com/yurrriq/eper.git",
    {branch, "master"}}},
  {lager,
   {git, "git://github.com/basho/lager.git",
    {tag, "3.1.0"}}}
]}.

$ rebar3 compile

===> Fetching rebar3_run v0.5.0
make: Entering directory '/home/user/dev/erl/tmp/nkcluster/_build/default/plugins/rebar3_run/c_src'
make: Leaving directory '/home/user/dev/erl/tmp/nkcluster/_build/default/plugins/rebar3_run/c_src'
===> Analyzing applications...
===> Compiling rebar3_run
===> Verifying dependencies...
===> Fetching eper (from {git,"git://github.com/yurrriq/eper.git",{branch,"master"}})


... here fetching process hangs on the first git dependency - until timeout.

But if I change for all rebar.config dependencies {git, "git://... to {git, "https://..., the fetching process starts to go normally - again, until it encounters a depencency with {git, "git://....

2

About Q1, you can try git clone git://github.com/yurrriq/nkdist.git. It will hang, too.

That’s not a problem of rebar3. GitHub deprecated the git:// protocol in 2022 due to security concerns. Read more at Improving Git protocol security on GitHub - The GitHub Blog

3

Q1: Why does fetching a dependency from {git, "git://github.com/... hang, but fetching from {git, "https://github.com/... works normally?

This issue is likely caused by the differences in how the git:// and https:// protocols interact with your system’s environment. Here are a few possible reasons:

  • Firewall or Network Restrictions: Many corporate or personal firewalls block the git:// protocol as it uses a custom port (9418) instead of the standard HTTP/HTTPS ports (80/443). This could result in the fetch operation hanging until it times out.
  • Deprecation of git:// Protocol: GitHub has deprecated the git:// protocol in favor of https:// for better security and reliability. Some newer systems may no longer fully support git:// for fetching repositories.
  • Proxy Settings: If you’re working behind a proxy, it might only support https:// requests. The git:// protocol does not work with typical proxy configurations.
  • SSH vs. HTTPS Settings: If your environment is configured for HTTPS instead of SSH or doesn’t have SSH keys set up for GitHub, the git:// protocol may fail silently or hang.

So, replace all git:// URLs with https:// in your rebar.config. If you expect to work with SSH-based URLs, ensure you are using the correct format: git@github.com:owner/repo.git.

Q2: Is there a flag for rebar3 to turn on verbose output?

Yes, you can enable verbose output in rebar3 by using the --verbose flag. For example:

rebar3 compile --verbose

This will give you more detailed logs about the fetch process, which can help debug network or configuration issues.

4

Thank you for explanation.

you can enable verbose output in rebar3 by using the --verbose flag. For example:

$ rebar3 compile --verbose
===> Invalid option --verbose on task compile
5

DEBUG=1 rebar3 compile

Should be get you what you want

6

Oh… The --verbose flag is related to common tests(Commands | Rebar3)… @LeonardB provide correct answer, you need set DEBUG=1 variable(Base Config | Rebar3).