Group.__init() should be parallelised

• Bitbucket: https://bitbucket.org/hpk42/execnet/issue/28
• Originally reported by: @crusaderky
• Originally created at: 2014-01-22T16:51:21.959

Consider the following snippet:

hosts = [...list of hosts...]
group = execnet.Group(("ssh %s" % host for host in hosts))
group.remote_exec(something)

Imagine having a grid of 200 hosts.
While Group.remote_exec() will run on all the hosts in parallel, Group.__init__() will connect via ssh to each one of them, serially. On a typical LAN, this easily accounts to minutes.

I attach a patch for multi.py (on top of the latest hg commit) that is intended to fix the problem. However, with that patch the program deadlocks in gateway_base.py, line 360, and I can't figure out the reason.

Inizia in multi.py da Group.init e ispeziona gateway_base.py intorno alla riga 360, dove la patch segnalata causa un deadlock. Riproduci l'inizializzazione con molti gateway SSH e confronta il comportamento con la patch allegata. Il lavoro è completato quando l'inizializzazione di Group si connette agli host in parallelo senza causare deadlock e Group.remote_exec() continua a funzionare.