EM-SSH

Em-ssh is a net-ssh adapter for EventMachine. For the most part you can take any net-ssh code you have and run it in the EventMachine reactor.

Em-ssh is not associated with the Jamis Buck's net-ssh library. Please report any bugs with em-ssh to https://github.com/simulacre/em-ssh/issues

Installation

gem install em-ssh

Synopsis

require "em-ssh"
EM.run do
  EM::Ssh.start(host, user, :password => password) do |connection|
    connection.errback do |err|
      $stderr.puts "#{err} (#{err.class})"
      EM.stop
    end
    connection.callback do |ssh|
      # capture all stderr and stdout output from a remote process
      ssh.exec!('uname -a').tap {|r| puts "\nuname: #{r}"}

      # capture only stdout matching a particular pattern
      stdout = ""
      ssh.exec!("ls -l /home") do |channel, stream, data|
        stdout << data if stream == :stdout
      end
      puts "\n#{stdout}"

      # run multiple processes in parallel to completion
      ssh.exec('ping -c 1 www.google.com')
      ssh.exec('ping -c 1 www.yahoo.com')
      ssh.exec('ping -c 1 www.rakuten.co.jp')

      #open a new channel and configure a minimal set of callbacks, then wait for the channel to finishes (closees).
      channel = ssh.open_channel do |ch|
        ch.exec "/usr/local/bin/ruby /path/to/file.rb" do |ch, success|
          raise "could not execute command" unless success

          # "on_data" is called when the process writes something to stdout
          ch.on_data do |c, data|
            $stdout.print data
          end

          # "on_extended_data" is called when the process writes something to stderr
          ch.on_extended_data do |c, type, data|
            $stderr.print data
          end

          ch.on_close { puts "done!" }
        end
      end

      channel.wait

      ssh.close
      EM.stop
    end
  end
end

See http://net-ssh.github.com/ssh/v2/api/index.html

Shell

Em-ssh provides an expect-like shell abstraction layer on top of net-ssh in EM::Ssh::Shell

Example

require 'em-ssh/shell'
EM.run do
  EM::Ssh::Shell.new(host, ENV['USER'], "") do |shell|
    shell.callback do
      shell.expect(Regexp.escape('~]$ '))
      $stderr.puts shell.expect(Regexp.escape('~]$ '),'uname -a')
      $stderr.puts shell.expect(Regexp.escape('~]$ '), '/sbin/ifconfig -a')
      EM.stop
    end
    shell.errback do |err|
      $stderr.puts "error: #{err} (#{err.class})"
      EM.stop
    end
  end
end

Run Multiple Commands in Parallel

require 'em-ssh/shell'

waitstr = Regexp.escape('~]$ ')
commands = ["uname -a", "uptime", "ifconfig"]
EM.run do
  EM::Ssh::Shell.new(host, user, "") do |shell|
    shell.errback do |err|
      $stderr.puts "error: #{err} (#{err.class})"
      EM.stop
    end

    shell.callback do
      commands.clone.each do |command|
        mys = shell.split # provides a second session over the same connection

        mys.on(:closed) do
          commands.delete(command)
          EM.stop if commands.empty?
        end

        mys.callback do
          $stderr.puts("waiting for: #{waitstr.inspect}")
          # When given a block, Shell#expect does not 'block'
          mys.expect(waitstr) do
            $stderr.puts "sending #{command.inspect} and waiting for #{waitstr.inspect}"
            mys.expect(waitstr, command) do |result|
              $stderr.puts "#{mys} result: '#{result}'"
              mys.close
            end
          end
        end

        mys.errback do |err|
          $stderr.puts "subshell error: #{err} (#{err.class})"
          mys.close
        end

      end
    end
  end
end

waitstr  = Regexp.escape('~]$ ')
commands = ["uname -a", "uptime", "ifconfig"]

require 'em-ssh/shell'
EM.run do
  EM::Ssh::Shell.new(host, user, "") do |shell|
    shell.errback do |err|
      $stderr.puts "error: #{err} (#{err.class})"
      $stderr.puts err.backtrace
      EM.stop
    end

    shell.callback do
      commands.clone.each do |command|
        Fiber.new {
          # When given a block Shell#split will close the Shell after
          # the block returns. If a block is given it must be called
          # within a Fiber.
          sresult = shell.split do |mys|
            mys.on(:closed) do
              commands.delete(command)
              EM.stop if commands.empty?
            end
            mys.errback do |err|
              $stderr.puts "subshell error: #{err} (#{err.class})"
              mys.close
            end

              mys.expect(waitstr)
              result = mys.expect(waitstr, command)
              $stderr.puts "#{mys} result: '#{result.inspect}'"
              result
          end
          $stderr.puts "split result: #{sresult.inspect} +++"
        }.resume

      end
    end
  end
end

Other Examples

See bin/em-ssh for an example of a basic replacement for system ssh.

See bin/em-ssh-shell for a more complex example usage of Shell.

Known Issues

Em-ssh relies on Fibers. MRI 1.9.2-p290 on OSX Lion has been known to segfault when using Fibers.

Testing

The specs for em-ssh require two accessible ssh servers. The quickest and most consistent way to get the servers up is to use Docker.

Containers run from krlmlr/debian-ssh:wheezy will be accessible with users 'docker' and 'root'.

If you have docker-compose installed:

SSH_KEY="$(cat ~/.ssh/id_rsa.pub)" docker-compose up

If you do not have docker-compose installed:

docker run -d -p 2222:22 -e SSH_KEY="$(cat ~/.ssh/id_rsa.pub)" krlmlr/debian-ssh:wheezy
docker run -d -p 2223:22 -e SSH_KEY="$(cat ~/.ssh/id_rsa.pub)" krlmlr/debian-ssh:wheezy

Once the two containers are running just run the specs.

rspec spec

If you want to use different ssh servers for testing you'll need to update the variables in spec/constants.rb

If you need to debug failing tests you can change the verbosity of EM::Ssh:

VERBOSITY=DEBUG rspec spec

Manual Testing

You can also run manual tests using the executable in bin.

bin/em-ssh-shell docker@localhost:2223 '$ ' 'ls -al' 'hostname' 'uname -a'

be bin/em-ssh docker@localhost:2223

Known Issues

If the server's signature changes from the one recorded in your known_hosts file EM::Ssh.start will hang
bin/em-ssh and bin/em-ssh-shell will ask for passwords even when one isn't required

Copyright

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.