[one-users] VM shutdown/cancel/delete action concurrency

[Rolandas Naujikas]

Hi,

When testing on 3.8.1 I found, that shutdown/cancel/delete of VM in a 
host is done in parallel without ability to configure concurrency (like 
MAX_HOST in sched.conf). That leads to several problems:
(1) potential overload of storage with persistent images (ssh/qcow2 TM 
drivers)
(2) race conditions in ebtables/iptables, as those tools doesn't support 
concurrent execution

I saw (2) in my crash tests (submitting many VMs to the host with 
network=ebtables and doing onevm shutdown on them), which could be 
solved with "flock /tmp/ebtables sudo ebtables" and "flock /tmp/iptables 
sudo iptables" in OpenNebulaNetwork.rb as a workaround.

When MAX_HOST=1 in sched.conf, then there are no problems with 
ebtables/iptables concurrency in deploy time, but when MAX_HOST>1, then 
the (2) problem could also be.

Regards, Rolandas Naujikas