Capistrano (> 3) 中的这个错误阻止我部署我的 Rails 应用程序。我的 Capistrano 配置在另一个环境中运行良好。
DEBUG [6c7d7bed] Command: if test ! -d /opt/my_app/releases/20140429175529; then echo "Directory does not exist '/opt/my_app/releases/20140429175529'" 1>&2; false; fi
cap aborted!
NoMethodError: undefined method `recv' for #<IO:fd 49>
/Users/such/.rvm/gems/ruby-2.1.1@my_app/gems/net-ssh-2.8.0/lib/net/ssh/buffered_io.rb:65:in `fill'
/Users/such/.rvm/gems/ruby-2.1.1@my_app/gems/net-ssh-2.8.0/lib/net/ssh/transport/packet_stream.rb:86:in `next_packet'
/Users/such/.rvm/gems/ruby-2.1.1@my_app/gems/net-ssh-2.8.0/lib/net/ssh/transport/session.rb:178:in `block in poll_message'
/Users/such/.rvm/gems/ruby-2.1.1@my_app/gems/net-ssh-2.8.0/lib/net/ssh/transport/session.rb:173:in `loop'
/Users/such/.rvm/gems/ruby-2.1.1@my_app/gems/net-ssh-2.8.0/lib/net/ssh/transport/session.rb:173:in `poll_message'
/Users/such/.rvm/gems/ruby-2.1.1@my_app/gems/net-ssh-2.8.0/lib/net/ssh/transport/session.rb:210:in `block in wait'
/Users/such/.rvm/gems/ruby-2.1.1@my_app/gems/net-ssh-2.8.0/lib/net/ssh/transport/session.rb:208:in `loop'
/Users/such/.rvm/gems/ruby-2.1.1@my_app/gems/net-ssh-2.8.0/lib/net/ssh/transport/session.rb:208:in `wait'
/Users/such/.rvm/gems/ruby-2.1.1@my_app/gems/net-ssh-2.8.0/lib/net/ssh/transport/session.rb:87:in `initialize'
/Users/such/.rvm/gems/ruby-2.1.1@my_app/gems/net-ssh-2.8.0/lib/net/ssh.rb:200:in `new'
/Users/such/.rvm/gems/ruby-2.1.1@my_app/gems/net-ssh-2.8.0/lib/net/ssh.rb:200:in `start'
/Users/such/.rvm/gems/ruby-2.1.1@my_app/gems/sshkit-1.4.0/lib/sshkit/backends/connection_pool.rb:24:in `create_or_reuse_connection'
/Users/such/.rvm/gems/ruby-2.1.1@my_app/gems/sshkit-1.4.0/lib/sshkit/backends/netssh.rb:173:in `ssh'
/Users/such/.rvm/gems/ruby-2.1.1@my_app/gems/sshkit-1.4.0/lib/sshkit/backends/netssh.rb:126:in `block in _execute'
/Users/such/.rvm/gems/ruby-2.1.1@my_app/gems/sshkit-1.4.0/lib/sshkit/backends/netssh.rb:123:in `tap'
/Users/such/.rvm/gems/ruby-2.1.1@my_app/gems/sshkit-1.4.0/lib/sshkit/backends/netssh.rb:123:in `_execute'
/Users/such/.rvm/gems/ruby-2.1.1@my_app/gems/sshkit-1.4.0/lib/sshkit/backends/netssh.rb:66:in `execute'
/Users/such/.rvm/gems/ruby-2.1.1@my_app/gems/sshkit-1.4.0/lib/sshkit/backends/abstract.rb:75:in `within'
/Users/such/.rvm/gems/ruby-2.1.1@my_app/gems/capistrano-3.2.1/lib/capistrano/tasks/deploy.rake:207:in `block (3 levels) in <top (required)>'
/Users/such/.rvm/gems/ruby-2.1.1@my_app/gems/sshkit-1.4.0/lib/sshkit/backends/netssh.rb:54:in `instance_exec'
/Users/such/.rvm/gems/ruby-2.1.1@my_app/gems/sshkit-1.4.0/lib/sshkit/backends/netssh.rb:54:in `run'
/Users/such/.rvm/gems/ruby-2.1.1@my_app/gems/sshkit-1.4.0/lib/sshkit/runners/parallel.rb:12:in `block (2 levels) in execute'
Tasks: TOP => deploy:set_current_revision
(See full trace by running task with --trace)
The deploy has failed with an error: #<NoMethodError: undefined method `recv' for #<IO:fd 49>>
我正在使用代理连接到我的远程服务器（在两个环境中）。SSH 连接工作正常。
set :ssh_options, proxy: Net::SSH::Proxy::Command.new('ssh user@gateway -W %h:%p')
有没有人遇到过这个问题？
解决方法
我对该错误的薄弱理解是，在 ssh 协商之后，有时返回到 net-ssh 的套接字是一个意外的文件描述符。我已经添加了：
gem 'sshkit', github: 'msimonin/sshkit', branch: 'gateway'
到我的 Gemfile 以便 ssh 连接只建立一次。
相关配置为：
SSHKit.config.backend.configure do |ssh|
ssh.gateway = 'user@gateway'
end
这种方式工作得很好。我等不及合并拉取请求了。