background hangs when ran in within blocks

[mumoshu]

Hi,

Thanks a lot for the great software!
I'm getting more and more excited as I see how flexible SSHKit (and of course Capistrano 3) is :)

I have found that background hangs when used within within blocks.
I'm running Capistrano 3.0.1 with SSHKit on Ubuntu 12.04.

With the code below, run cap test will_hang1 to reproduce the hangs. You can also run cap test wont_hang to see how to fix those.

As far as I know, the problem here is that nohup seems to hang when executed after cd.
We can probably avoid the hangs by changing background to emit shell commands like cd the_dir; ( ( nohup the_command &>/dev/null ) & ).

I suspect that the issue is arrising from Net::SSH(ref). So I believe that we can do a work-around on SSHKit side or just document it in Usage Examples.

# config/deploy/test.rb

task :will_hang1 do
  on roles(:local) do
    within '/home/vagrant' do
      background 'nc -l 12345'
    end
  end
end

# FYI, Don't do the below, too!
task :will_hang2 do
  on roles(:local) do
    execute "( ( cd /home/vagrant; nohup nc -l 12345 &>/dev/null ) & )"
  end
end

task :wont_hang do
  on roles(:local) do
    execute "cd /home/vagrant; ( ( nohup nc -l 12345 &>/dev/null ) & )"
  end
end

Regards,
Yusuke

[leehambley]

Hi Yusuke, thanks for the feedback.

Do you think it'd be possible to change the composition of the stringer method to fix this with the first format? I admit to not having tried the background() method in the wild, I assumed that syntax would be correct!

I think for most cases, the 3rd example you posted is correct. In Capistrano the composition of things using the DSL is quite convenient for the most cases, but in advanced cases composing your own command as a string is often easier (although then one sacrifices access to the command map, which is a feature which mostly exists for Capistrano)

I would be fine with removing background() if it's clear that it doesn't work properly.

[stas]

Hi guys,
I'm also having troubles with background.

nohup: failed to run command `RBENV_ROOT=/home/deployer/.rbenv': No such file or directory

I guess the issue is caused by the wrong order of rbenv hooks or something.

[leehambley]

Opened a new issue, background will be removed.