Document on : Time Manager in OpenBMC --> Need your review.

[Rick Altherr]

On Thu, Aug 25, 2016 at 4:59 AM, vishwa <vishwa at linux.vnet.ibm.com> wrote:

> Rick,
>
> Thanks for the thoughts. I have put my response in-line. Please let me
> know if you have any feedback on this.
>
> On 08/23/2016 05:14 AM, Rick Altherr wrote:
>
> In the future, please just send the text inline instead of as an
> attachment.
>
> I don't understand the setting hierarchy.  To me,
> /org/openbmc/settings/Host/host0 implies I am modifying something related
> to the host CPU, not the BMC.  TimeMode only applies to the BMC so having
> it under host0 feels weird.
>
> Agree. Doing this in 'host0' is not appropriate. However, the current
> 'settingsd' framework does not allow multiple levels since the need until
> now was only for 'host'. Now that we have a requirement to get something
> new, I have suggested a change to have another entry called 'bmc' and that
> work will be taken in future sprints. So when that change is made, I will
> make a corresponding change to clock as well.
>
> 1. I like the clear separation of NTP vs manual.
>
> 2.1. "Both" seems like what we have today which doesn't really work at
> all.  I suggest omitting it.  "Split" feels like it should work for all
> cases.  If TimeMode is NTP, an offset is recorded.  If TimeMode is Manual,
> the BMC time is set.
>
> We had one of the customers ask for "Both" and that is why we are putting
> this in there.
>

What are they expecting in terms of behavior?  "Both" has the host and BMC
fighting for ownership of the BMC system time which has quirky behavior.


> For the *split* mode, whether it is NTP / Manual, it still demands an
> update to offset.
>

In "Split" with Manual, the BMC time is meant to be set from the host.  In
that case, the offset can be assumed to be zero and the BMC clock set to
the provided time.


>
> APIs:
> 1. What time zone does SetTime assume?  If UTC, make sure to add tests for
> a valid leap second and leap year.
>
>
> It does not handle Time Zones. Its a mere seconds since epoch. Okay.. I
> will add the tests.
>

Seconds since epoch != UTC.  Specifically for a leap second event, a single
POSIX time point is used for both 23:59:60 and the following 00:00:00.  If
the API is supposed to be UTC, specifically state that in the API.  If it's
supposed to be a POSIX time, have them provide a 64-bit integer.


>
> 2. I really dislike APIs that change behavior.  Provide separate
> GetBmcTime and GetHostTime APIs if you must.
>
> I like this idea. Implemented it.
>
> 3. SetNTP is a very limiting name.  if this really changes TimeMode, call
> it SetTimeMode.  That way we can support things like 1588, GPS, etc later.
>
>
> I have changed the way NTP setting gets set completely. There will not be
> an exposed API to change NTP setting. The changes that are done to
> 'time_mode' will be picked up automatically by the daemon and then
> appropriate services are started / stopped.
>
>
> Changes to NetworkManager:
> - I don't see the point of UseNTP for SetDHCP.  Configuring an NTP address
> is different from using NTP as a time source.  It's up to the DHCP server
> to provide NTP options.  Whether the BMC uses them is controlled by
> TimeMode.
>
> The only reason I wanted this in there is if someone wants to take a call
> to put NTP choice in there while changing the BMC networking to DHCP, they
> can do it right then and there than having to make another call.
>

I'm hearing that you are optimizing for a case that we don't know is
important to optimize for.  BMC networking settings are conceptually
unrelated to time settings.  Combining them in the API adds a lot more
complexity as all the places the NTP settings can be modified needs to be
considered.

>
> In addition to this, there are 2 parts to having NTP as TimeMode.
> (1) We can let timesyncd choose NTP settings that have been given by DHCP
> (2) Let timesyncd choose NTP settings that were manually entered using
> "SetNtpAddress"
>

Both of those cases can be handled with a single SetNtpAddress API.


>
> - Add a SetNtpServer API instead of adding to SetAddress4.  NTP is
> entirely separate from IPv4 address configuration.
>
> I do have SetNtpServer and the reason I also chose to make it a part of
> SetAddress4 was the exact same reason I mentioned for the UseNTP= for DHCP.
>
>
> On Thu, Aug 18, 2016 at 4:08 AM, vishwa <vishwa at linux.vnet.ibm.com> wrote:
>
>> Team,
>>
>> Please help look into this document that describes what I think the
>> TimeManager on openBMC systems should look like.
>>
>> Please weigh in your thoughts.
>>
>> Thanks.
>>
>> Vishwanath.
>>
>> _______________________________________________
>> openbmc mailing list
>> openbmc at lists.ozlabs.org
>> https://lists.ozlabs.org/listinfo/openbmc
>>
>>
>
>
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