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.

Commencez dans multi.py à Group.init et inspectez gateway_base.py autour de la ligne 360, où le patch signalé provoque un deadlock. Reproduisez l’initialisation avec de nombreuses passerelles SSH et comparez le comportement avec le patch joint. Le travail est terminé lorsque l’initialisation de Group se connecte aux hôtes en parallèle sans provoquer de deadlock, tandis que Group.remote_exec() continue de fonctionner.