[libvirt] [PATCH v2] network: make openvswitch call timeout compile time configurable

[Boris Fiuczynski]

On 01/25/2017 04:16 AM, Laine Stump wrote:
> On 01/24/2017 10:53 AM, Boris Fiuczynski wrote:
>> Since a successful completion of the calls to openvswitch is expected
>> a long timeout should be chosen to account for heavily loaded systems.
>> Therefore this patch increases the timeout value from 5 to 120 seconds
>> as default value and also allows to set the openvswitch timeout value
>> by specifying with-ovs-timeout when running configure.
>
> Why make it configurable during build? I don't think we do this with any
> other type of timeout value or limit. If you think it may need to change
> based on circumstances, why not just put it in libvirtd.conf and be done
> with it?
>
> In the meantime, I agree with Michal that any machine that takes 120
> seconds to get a response from any ovs command is beyond the limits of
> usable; we certainly shouldn't cater our defaults to that.
>
The first version of the patch was send in November last year hard 
coding the default value which resulted in this response.
https://www.redhat.com/archives/libvir-list/2016-November/msg01063.html
That is why I created the current proposal. Certainly allowing the ovs 
timeout to be specified in libvirtd.conf allows much more flexibility 
than the current patch provides.

The system we saw ovs timeout problems on had 128 cpus with a load avg 
of 74 and the system shows 41% idle. I would not call that an 
unreasonable load level on a system and I also would not expect getting 
errors like:
error: Disconnected from qemu:///system due to keepalive timeout
error: Failed to start domain zs93k1g80002
error: internal error: connection closed due to keepalive timeout
when trying to start a domain which are caused by ovs command timing 
out. Please notice that the virsh start command itself, for the domain, 
did exceed the keepalive time limit.
In addition a later retry with the same amount of load on the system 
succeeded with starting the domain instead of running into the previous 
error again caused by the ovs timeout when an ovs port is created.

-- 
Mit freundlichen Grüßen/Kind regards
    Boris Fiuczynski

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