errs = []
def test_server(errs, server)
lambda do |options|
begin
server =~ /(.+)@(.+)/
server_name, user = $2, $1
puts server_name
s = Net::SSH.start(server_name, user)
s.close
s = server
rescue Errno::EHOSTUNREACH, SocketError
puts "echec connexion #{server} : #{$!}"
errs << server
s = nil
end

    return s
end

end

Net::SSH::Multi.start(:on_error => :warn) do |session|

define the servers we want to use

session.use &test_server(errs, 'root@srv-04')
session.use &test_server(errs, 'root@srv-07')
session.use &test_server(errs, 'root@srv-08')
session.use &test_server(errs, 'root@fail-08.local')

execute commands on all servers

session.exec( "hostname" )

run the aggregated event loop

session.loop
end

unless errs.empty?
puts "The command failed on #{errs.size} hosts"
end