[ovirt-devel] [proposal] deprecate VDSM ping in favor of ping2 and confirmConnectivity

[Petr Horacek]

Method with saved caller's IP address is an option, but it would
require rewriting of network's connectivity check mechanism. We would
need to introduce some extra IPC between supervdsm and vdsm for this
IIUIC.

The reason for ping2 is backward compatibility. It is undocumented,
but Engine still depends on it and older versions will probably stay
like that. In case we remove the side-effect and old Engine calls new
ping1 it would never confirm network connectivity.

2017-08-08 15:19 GMT+02:00 Martin Sivak <msivak at redhat.com>:
>>> A ping that has no side effects and a "watchdog" mechanism to confirm
>>> connectivity.
>>
>> This sounds as exactly the right solution right now.
>
> Just to clarify: Removing the undocumented side effects from ping. Not
> introducing ping2.
>
> Martin
>
> On Tue, Aug 8, 2017 at 10:47 AM, Martin Sivak <msivak at redhat.com> wrote:
>>> The proposed solution is focused on making sure a command does one thing and
>>> not two:
>>> A ping that has no side effects and a "watchdog" mechanism to confirm
>>> connectivity.
>>
>> This sounds as exactly the right solution right now.
>>
>>>>> Still someone could call conirmConnectivity, no?
>>
>> We do not protect any other endpoints that can cause the host to go
>> wild (storage or even setupNetworks). I agree with Edward it is the
>> responsibility of the caller to do the right thing. You need to be
>> root or have the certificate to talk to VDSM anyway.
>>
>> Martin
>>
>> On Tue, Aug 8, 2017 at 8:24 AM, Edward Haas <ehaas at redhat.com> wrote:
>>>
>>>
>>> On Mon, Aug 7, 2017 at 11:06 PM, Nir Soffer <nsoffer at redhat.com> wrote:
>>>>
>>>> On Mon, Aug 7, 2017 at 5:28 PM Roy Golan <rgolan at redhat.com> wrote:
>>>>>
>>>>> Still someone could call conirmConnectivity, no? so the state isn't
>>>>> guarded from localhost tinkering anyhow. If you really need a solution you
>>>>> can acuire a token for this operation by setupNetworks, and confirm
>>>>> connectivity with this token passed back.
>>>>>
>>>>> I'm not sure about the severity of the problem here, I'll let other
>>>>> reply, but I'm against this kind of solution.
>>>>>
>>>>>
>>>>>
>>>>> On Mon, 7 Aug 2017 at 15:32 Petr Horacek <phoracek at redhat.com> wrote:
>>>>>>
>>>>>> Hello,
>>>>>>
>>>>>> current VDSM ping verb has a problem - it confirms network
>>>>>> connectivity as a side-effect. After Engine calls setupNetwork it
>>>>>> pings VDSM host to confirm that external network connectivity is not
>>>>>> broken. This prohibits other users to call ping from localhost since
>>>>>> it would confirm connectivity even though networking could be broken.
>>>>
>>>>
>>>> Vdsm can save the client ip setting up the network. Getting a ping from
>>>> this
>>>> client can confirm that the connectivity was restored. pings from other
>>>> hosts
>>>> can be ignored.
>>>>
>>>> The client address is available in a thread local variable
>>>> (context.client_host)
>>>> during all api calls. see vdsm.common.api.context_string() for example
>>>> usage.
>>>>
>>>> This infrastructure is available in 4.1.
>>>
>>>
>>> The proposed solution is focused on making sure a command does one thing and
>>> not two:
>>> A ping that has no side effects and a "watchdog" mechanism to confirm
>>> connectivity.
>>>
>>> Does it make sense to confirm connectivity from localhost? In many cases it
>>> probably does not,
>>> but there may be cases where it does make sense... it is not the
>>> functionality to determine what
>>> makes sense or not, it is the usage of it who has the responsibility to use
>>> it correctly.
>>>
>>>>
>>>> Nir
>>>>
>>>>>>
>>>>>>
>>>>>> In order to fix this problem ping should be split to ping2 (which just
>>>>>> returns Success with no side-effect) and confirmConnectivity. Change
>>>>>> on VDSM side was introduced in [1], we still need to expose new verbs
>>>>>> in Engine.
>>>>>>
>>>>>> Regards,
>>>>>> Petr
>>>>>>
>>>>>> [1] https://gerrit.ovirt.org/#/c/80119/
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