使用em-ssh并行连接多个主机时的“协商超时”

Question

我使用em-ssh gem（它是EventMachine的net-ssh适配器）在多个远程主机上执行一些shell命令。命令在第一台主机上成功执行，但在其他主机上失败，它会抱怨“EventMachine :: Ssh :: ConnectionTerminated”  和“EventMachine :: Ssh :: NegotiationTimeout”。 似乎这些主机正在竞争可能是端口的东西？有人可以解释这个吗？

def em_ssh_connection(ssh_host,ssh_user,ssh_password,&cb)
  EM.run do
    EM::Ssh.start("#{ssh_host}","#{ssh_user}",:password => "#{ssh_password}") do|connection|
      connection.errback do |err|
        @logger.info "#{err} (#{err.class})"
        EM.stop
      end
      connection.callback do |ssh|
        @logger.info "succcessfully connected with #{ssh_host},#{ssh_user},#{ssh_password}"
        yield ssh
        ssh.close
        EM.stop
      end
    end
  end
end 

def search_servers(ssh_host,ssh_user,ssh_password)
  em_ssh_connection(ssh_host,ssh_user,ssh_password) {|ssh|
    command = 'sed -n \'/.*server s1 [0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}/=\' '+"#{@haproxy_conf}"
    myarray = em_ssh_exec(ssh,command)
    if myarray[2] == 0
      if myarray[0] != ""
        @logger.info "all tcp servers(lines): #{myarray[0]}"
        lines = myarray[0].split("\n")
        if lines.length >0
          start_line = lines[0].to_i
          stop_line = lines[lines.length-1].to_i
          @logger.info "start_line:#{start_line},stop_line:#{stop_line}"
          delete_tcp_upstream(ssh,start_line,stop_line)
        else
        end
      else
        @logger.info "the stream field in proxy file is empty"
      end
    else
      @logger.info "search all servers command failed:#{myarray[1]}"
    end
  }
end

def clear_haproxy(&cb)
   search_servers(@ssh_host1,@ssh_user1,@ssh_password1)
   search_servers(@ssh_host2,@ssh_user2,@ssh_password2)
   cb.call
end