Re: [LEAPSECS] Google, Amazon, now Microsoft

[Brooks Harris]

On 2015-06-03 10:55 AM, Poul-Henning Kamp wrote:



In message <556f0c92.4020...@edlmax.com>, Brooks Harris writes:


You're saying this to the bloke who implemented a prototype adaptive
optics solution for the ESO ELT on a plain, unmodified FreeBSD
kernel ?

I didn't know that, very impressive. Is there information anywhere how
it was done?

I did a presentation at a workshop at ESO in december 2012, the
slides seems to be here:

 https://www.eso.org/sci/meetings/2012/RTCWorkshop/proceedings.html

Oh great! On quick glance that's just the sort of RT discussion I was 
interested in. I'll study it more.

I'm not sure what the legal status is for deeper info.  You'd have
to ask them for access.  The person to talk to is Nick Kornweibel.

And dig deeper when I can.

I bring the RT aspect [...]

The first point here is that commodity *NIX, be it LINUX, FreeBSD
or something else is often used to pull time into systems, even
if they themselves don't do the RT part.
Yes, right, as I said, if not so clearly, "some sort of hardware 
assist". In my land we have things like SDI, perhaps on PCI, feeding 
video/audio in "real-time", or "device control" (remote control of 
video/audio devices) protocols that arrive at serial ports (COM or USB 
or something) in "real-time". Those sources often have high quality 
oscillators and timebases and the protocols support deterministic 
delivery to the port. You then have to carefully interface through 
worker threads and buffers to hang the timestamps on the video/audio 
samples, etc. That can be tricky, and often involving the manufacture's 
NT device drivers (some work better than others!), or you may need to 
build a driver yourself, notoriously tricky, but down there you can get 
really close to the metal (ring 0) if you're careful. But its never an RTOS.




The other thing to notice is that even if it is not RT in the strict
classical sense, commodity *NIX does things which matter on
microsecond resolution timescales.  (As for instance the ESO thing).

Right. Thanks,




The time on Microsoft Azure will be Different by a second, everywhere
http://www.theregister.co.uk/2015/05/29/windows_azure_second_out_of_sync/

As I said earlier - A) Where did they get this information? B) Is it
true? C) Is that how Windows is behaving?

A) Ask them.

Can try.

(M$ probably notified their customers ?)

They did -

How the Windows Time service treats a leap second
https://support.microsoft.com/en-us/kb/909614



B) I have no reason to doubt it.  The Reg is usually very good on truth.

I doubt it now -

"Contrary to one post I recently read, Microsoft doesn’t implement a 
leap second time zone by time zone – in other words, in a rolling 
fashion, like the way we watch new year celebrations count down around 
the world. Essentially, the leap second occurs at the same time 
everywhere."


Another look at the impact of the coming 2015 leap second (not much)
http://blogs.msdn.com/b/mthree/archive/2015/06/01/2015-leap-second-060115.aspx 



Also How the Windows Time Service Works
https://technet.microsoft.com/en-us/library/cc773013(v=ws.10).aspx



C) Probably only in Azure.

As above, I doubt it.

Other Windows will probably do the
usual Windows thing:  Step a second some time later.
Yes. It looks like it can be kept pretty close with a careful use of 
Windows Time Service, but thats not usually active on typical machines.


Leap Seconds are not the only thing might upset the apple cart -

Summary of Windows Azure Service Disruption on Feb 29th, 2012
http://azure.microsoft.com/blog/2012/03/09/summary-of-windows-azure-service-disruption-on-feb-29th-2012/

-Brooks




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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Rob Seaman]

Others may point out that median and average are different things.  (Or that 
the tails of a distribution may contribute more than measures of central 
tendency.)

But more fundamentally, programming is not a one-dimensional skill.  Raw coding 
speed is different from debugging or data engineering or algorithm design.  
Expertise at laying out DB schema is distinct from creating coherent new 
architectures.  Engineering complex systems is a different skillset from 
designing user-friendly user interfaces.  Etc and so forth.  And basic 
infrastructure like timekeeping has orthogonal dependencies on all these and 
vice versa.

Rob
—

> On Jun 3, 2015, at 8:39 AM, Sanjeev Gupta  wrote:
> 
> On Wed, Jun 3, 2015 at 4:25 AM, Poul-Henning Kamp  bsd.dk > wrote:
> Which is like saying that if only 50% of all programmers weren't
> below the skill-median, we wouldn't have the problem.
> 
> What?!?!?
> 
> 50% of programmers are below average?  Why is no one doing something about it?
> 
> We should not rest till at least half are above average!

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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Sanjeev Gupta]

On Tue, Jun 2, 2015 at 3:34 AM, Clive D.W. Feather  wrote:

>
> Ah, there's almost a four-way meet. Afghanistan (UTC+4.5), Tajikistan
> (UTC+6), and China (UTC+8) meet at a point and, less than 20 kilometres
> south of there, is the China/Pakistan (UTC+5) border. There don't seem to
> be roads, but an off-road vehicle ought to be able to do it in an hour.


I do not think lack of roads is your biggest problem in this case.  Driving
around with a back seat full of equipment with ariels and batteries, in an
area that has seen disputed borders since the mid-1800s, would add years to
your visble age.  A Leap Second may not be noticed.

Note that according to India, Pakistan has no border with China, it is
Indian teritorry.  YMMV.

-- 
Sanjeev Gupta
+65 98551208 http://www.linkedin.com/in/ghane
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Sanjeev Gupta]

On Wed, Jun 3, 2015 at 4:25 AM, Poul-Henning Kamp 
wrote:

> Which is like saying that if only 50% of all programmers weren't
> below the skill-median, we wouldn't have the problem.
>

What?!?!?

50% of programmers are below average?  Why is no one doing something about
it?

We should not rest till at least half are above average!

-- 
Sanjeev Gupta
+65 98551208 http://www.linkedin.com/in/ghane
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Poul-Henning Kamp]

In message <556f0c92.4020...@edlmax.com>, Brooks Harris writes:

>> You're saying this to the bloke who implemented a prototype adaptive
>> optics solution for the ESO ELT on a plain, unmodified FreeBSD
>> kernel ?
>I didn't know that, very impressive. Is there information anywhere how
>it was done?

I did a presentation at a workshop at ESO in december 2012, the
slides seems to be here:

https://www.eso.org/sci/meetings/2012/RTCWorkshop/proceedings.html

I'm not sure what the legal status is for deeper info.  You'd have
to ask them for access.  The person to talk to is Nick Kornweibel.

>I bring the RT aspect [...]

The first point here is that commodity *NIX, be it LINUX, FreeBSD 
or something else is often used to pull time into systems, even
if they themselves don't do the RT part.

The other thing to notice is that even if it is not RT in the strict
classical sense, commodity *NIX does things which matter on 
microsecond resolution timescales.  (As for instance the ESO thing).

>The time on Microsoft Azure will be Different by a second, everywhere
>http://www.theregister.co.uk/2015/05/29/windows_azure_second_out_of_sync/
>
>As I said earlier - A) Where did they get this information? B) Is it
>true? C) Is that how Windows is behaving?

A) Ask them.  (M$ probably notified their customers ?)

B) I have no reason to doubt it.  The Reg is usually very good on truth.

C) Probably only in Azure.  Other Windows will probably do the
   usual Windows thing:  Step a second some time later.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Brooks Harris]

On 2015-06-02 04:25 PM, Poul-Henning Kamp wrote:


In message <556d8c59.9040...@edlmax.com>, Brooks Harris writes:


A lot of Windows machines are doing things where you would expect
people to care about leap-seconds:  Nuclear power plants control
systems, Air Traffic Control computers, Surgery robots, Patient
Monitors, Power grid disturbance detectors etc.  etc. etc.

In many of those uses the PC is not doing the mission critical timing.
No event-driven multitasking OS can do precise timing [...]

You're saying this to the bloke who implemented a prototype adaptive
optics solution for the ESO ELT on a plain, unmodified FreeBSD
kernel ?
I didn't know that, very impressive. Is there information anywhere how 
it was done?


I bring the RT aspect up because its not often mentioned in the 
discussion. It seems LEAPSECS is inhabited mostly by Linux folks, at 
least the conversaions seem to revolve around it more. The discussion 
often seems to treat PCs as if they are RTOS. I know Windows (and as I 
said elsewhere, I hate it, but here I am :-) ) and the possible 
differences in timekeeping in various OSs (and applications) are part of 
the complexity of the topic. The nature and performance of them and how 
timekeeping is implemented in each is of interest to me.




Anyway, the PC doesn't need to do the RT parts directly in order
to mess them up with wrong timestamps.
Right. This thread started on the topic of Azure's possibly treating the 
application of the Leap Second to local time differently than the POSIX 
spec, as stated by the "The Register" article -


The time on Microsoft Azure will be Different by a second, everywhere
http://www.theregister.co.uk/2015/05/29/windows_azure_second_out_of_sync/

As I said earlier - A) Where did they get this information? B) Is it 
true? C) Is that how Windows is behaving?


Investigating, including running some c++ tests of the Windows time APIs 
to observe the counting, I think that article is dead wrong, or, at 
least, misstates the situation. My tests suggest the counting is the 
same as POSIX (or maybe like NTP, that is freeze v.s. reset), and 
another link to a blog from a Microsoft guy who states -


"Contrary to one post I recently read, Microsoft doesn’t implement a 
leap second time zone by time zone – in other words, in a rolling 
fashion, like the way we watch new year celebrations count down around 
the world. Essentially, the leap second occurs at the same time everywhere."


Another look at the impact of the coming 2015 leap second (not much)
http://blogs.msdn.com/b/mthree/archive/2015/06/01/2015-leap-second-060115.aspx

-Brooks




But this is not something they are happy about doing, much less
proud of doing, but weighing the risks of "heterogeneous" leap-second
handling and the risk of being up to half a second wrong about time
for most of a day, they picked the second risk.


The failures folks are frightened of are bugs evoked by the Leap Second.
At least some of which are just "stupid" bugs, like threading races when
outputting the Leap Second event to the system log, not basic
timekeeping calculation errors. If all parts of the system did POSIX and
NTP correctly the timekeeping would not reflect UTC correctly because
neither POSIX or NTP do that anyway, but the systems wouldn't hang or
crash. As it is they have to "smear" to minimize the problems.

Which is like saying that if only 50% of all programmers weren't
below the skill-median, we wouldn't have the problem.



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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Poul-Henning Kamp]

In message <556d8c59.9040...@edlmax.com>, Brooks Harris writes:

>> A lot of Windows machines are doing things where you would expect
>> people to care about leap-seconds:  Nuclear power plants control
>> systems, Air Traffic Control computers, Surgery robots, Patient
>> Monitors, Power grid disturbance detectors etc.  etc. etc.

>In many of those uses the PC is not doing the mission critical timing. 
>No event-driven multitasking OS can do precise timing [...]

You're saying this to the bloke who implemented a prototype adaptive
optics solution for the ESO ELT on a plain, unmodified FreeBSD
kernel ?

Anyway, the PC doesn't need to do the RT parts directly in order
to mess them up with wrong timestamps.

>> But this is not something they are happy about doing, much less
>> proud of doing, but weighing the risks of "heterogeneous" leap-second
>> handling and the risk of being up to half a second wrong about time
>> for most of a day, they picked the second risk.
>>
>The failures folks are frightened of are bugs evoked by the Leap Second. 
>At least some of which are just "stupid" bugs, like threading races when 
>outputting the Leap Second event to the system log, not basic 
>timekeeping calculation errors. If all parts of the system did POSIX and 
>NTP correctly the timekeeping would not reflect UTC correctly because 
>neither POSIX or NTP do that anyway, but the systems wouldn't hang or 
>crash. As it is they have to "smear" to minimize the problems.

Which is like saying that if only 50% of all programmers weren't
below the skill-median, we wouldn't have the problem.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Brooks Harris]

On 2015-06-01 02:46 AM, Poul-Henning Kamp wrote:


In message<556bfd47.4050...@edlmax.com>, Brooks Harris writes:


Multiply this by 250 million [1] PC's still happily running XP
and you can better understand why Microsoft hasn't been that
interested in leap seconds, NTP, or participating in the hh:59:60
timestamp nightmare.

Yes, they've got a very large number of badly administrated systems in
the field. In more tightly administrated systems it can be done better.
But its all "good enough" for current purposes.

That's not as obvious as you seem to think.
I meant for typical deployments, that is, most Windows machines are 
sitting at home, on a desk at work, etc. The timekeeping need only be 
good enough to keep timestamps moving forward and it works well enough 
for Windows to have achieved a commanding market share in those areas. 
Windows machines in data centers or more tightly administrated systems 
may be doing better timing.

A lot of Windows machines are doing things where you would expect
people to care about leap-seconds:  Nuclear power plants control
systems, Air Traffic Control computers, Surgery robots, Patient
Monitors, Power grid disturbance detectors etc.  etc. etc.
In many of those uses the PC is not doing the mission critical timing. 
No event-driven multitasking OS can do precise timing - you need a 
real-time OS or hardware/firmware to do that. Windows on a PC can't do 
(highly) precise or accurate time by itself - it needs some sort of 
hardware assist. And even then its timestamps are subject to the 
behavior of the specific hardware and the OS's thread scheduler.

Fact is that most of the people involved in these systems have no idea
what a leap-second is, and more crucially:  Once they learn that, they
have no idea what the system they designed will do when one happens.


It would make sense, like Google and Amazon, that their in-house
data centers would want to more precisely and deterministically
handle leap seconds. But note all three companies have decided to
jump or smear time instead of creating a true leap second.

As I understand it its not that they are interested in "precise" or
"accurate" time - they are interested in smoothing over the Leap Second
to avoid problems potentially caused by the Leap Second jump in the many
OSs running in the data centers.

They are very much interested in both *precise* and *accurate* time,

Sure, but

that's why they have to do something in the first place.
I don't think that's true. The reason they "smear" is to hide the Leap 
Second from parts of the system that might have a bug evoked by the 
change. Its not for accurate time - in fact its explicitly compromising 
accurate time to protect the system from failures.


Time, technology and leaping seconds
http://googleblog.blogspot.com/2011/09/time-technology-and-leaping-seconds.html

If they were not interested in good timekeeping, they could just
let the computers free-run their clocks and pretend this is the 1980ies.

And yes, the smoothing and ramping and steps are all attempts to
win predictability at the expense of accuracy,

Right, as above, but

when faced with at
huge amount of software written by the kind of people mentioned above.




But this is not something they are happy about doing, much less
proud of doing, but weighing the risks of "heterogeneous" leap-second
handling and the risk of being up to half a second wrong about time
for most of a day, they picked the second risk.

The failures folks are frightened of are bugs evoked by the Leap Second. 
At least some of which are just "stupid" bugs, like threading races when 
outputting the Leap Second event to the system log, not basic 
timekeeping calculation errors. If all parts of the system did POSIX and 
NTP correctly the timekeeping would not reflect UTC correctly because 
neither POSIX or NTP do that anyway, but the systems wouldn't hang or 
crash. As it is they have to "smear" to minimize the problems.


-Brooks


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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Clive D.W. Feather]

Tom Van Baak said:
> Can you send me a definitive URL with global TZ rules so I can grep|sort|uniq 
> to get a feel for when DST transitions occurs?

The following database:

https://www.iana.org/time-zones

is about as definitive as you will find.

> I guess I thought it always was 2 am local (which implies jumps from 02h->03h 
> and 02h->01h).

That is very definitely *NOT* the case.

> Also, possibly related, do you know of any place where DST is +/- 2 hours 
> instead of +/- 1 hour? I ask because the still-in-development PE (phase 
> encoded) WWVB format appears to allow for such a (non US legal) transition. I 
> can't quite tell if it's a bug or typo or spec.

Look in the same database.

The UK certainly used to have two changes each way in the year (that is, from
GMT to GMT+1 to GMT+2). Some places only change by 30 minutes. I can't say
I've heard of anywhere jumping 2 hours in one go on a regular basis, but I
won't claim it's never happened.

-- 
Clive D.W. Feather  | If you lie to the compiler,
Email: cl...@davros.org | it will get its revenge.
Web: http://www.davros.org  |   - Henry Spencer
Mobile: +44 7973 377646
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Clive D.W. Feather]

Tom Van Baak said:
>>> DST changes at 2am in the US and 1am in the EU.
>> That is 01:00 UTC which is 02:00 standard / 03:00 summer time for most of
>> the EU.
> Tony, that's my understanding too, that all DST changes always occur at 2am 
> local time, both times a year.

No.

In the EU the changes occur at 01:00 UTC. That is:
* in the UK, the change is 01:00->02:00 and 02:00->01:00 local;
* in Germany, the change is 02:00->03:00 and 03:00->02:00 local;
* in Greece, the change is 03:00->04:00 and 04:00->03:00 local.

-- 
Clive D.W. Feather  | If you lie to the compiler,
Email: cl...@davros.org | it will get its revenge.
Web: http://www.davros.org  |   - Henry Spencer
Mobile: +44 7973 377646
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Clive D.W. Feather]

Pierpaolo Bernardi said:
>> http://eur-lex.europa.eu/legal-content/IT/TXT/?uri=CELEX:32000L0084
> By the way, I noticed only now that the English text says 01:00 GMT, while
> the Italian text says 01:00 Tempo Universale.

It's worse than that. Of the 22 official texts:

BG, CS, EL, EN, ET, FI, HU, LT, LV, MT, SK, and SV use terms equivalent
to "Greenwich", "Greenwich Time", or "GMT".

DE, ES, FR, IT, NL, PT, and RO use terms equivalent to "Universal Time".

PL says "uniwersalnego (GMT)".

DA and SL use "UTC".

-- 
Clive D.W. Feather  | If you lie to the compiler,
Email: cl...@davros.org | it will get its revenge.
Web: http://www.davros.org  |   - Henry Spencer
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Tom Van Baak]

> You'll need a faster car. Or a plane. Maybe we could get the guys on the 
> space station to try it?

Hi Brooks,

On the equator, timezones fly by about 1000 mph (earth diameter is ~25000 
miles, day is ~24 hours). So that excludes cars and commercial planes.

Even up here at 45 degrees latitude, timezones fly by about 700 mph 
(approximately the speed of sound). Still too fast for cars and private jets.

Your best bet is to contact someone in the arctic or antarctic and have them 
experience all 24 Azure leap seconds during the day of June 30, 2015. You 
perhaps have seen cool timezone photos from Amundsen-Scott.

I say this only partly in jest. It would make a fine blog entry for someone to 
pull this off. Not only would it be another dramatic refutation of ancient flat 
earth theories but it would also nicely demonstrate the increasing disparity 
between the needs of medieval astronomy, interstate railroads, and modern 
computing and timekeeping.

The guys at Google, Amazon, and Microsoft are only trying to solve real 
problems and best serve their customers. They are not stupid. The official ITU 
or the glossy DHS guidelines for leap seconds don't help them. So when they 
decide to smear or jump time in 2015 instead of implementing a 1960's solution 
you need to sit up and listen.

/tvb

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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Clive D.W. Feather]

Tom Van Baak said:
> Oh, I wasn't thinking of cheating and adjusting timezones with a mouse click. 
> For maximum photo effect, I was planning to drive my mobile (car) time lab 
> across two time zones the night of June 30 and catch two Azure leap seconds. 
> Timezones are too wide to hit three in under 2 hours.

I'm sure there must be places where 3 or more zones meet. Let's see:
* Russia/Finland/Norway triple point.
* 6 places in Russia and 3 on the border where 3 zones meet.
* Turkey/Iraq/Armenia triple point.
* Lots of other places where three countries meet.

And in the summer Arizona is UTC-7, New Mexico is UTC-6, and the part of
Mexico immediately south of NM is UTC-5. That ought to be doable in an hour.

Ah, there's almost a four-way meet. Afghanistan (UTC+4.5), Tajikistan
(UTC+6), and China (UTC+8) meet at a point and, less than 20 kilometres
south of there, is the China/Pakistan (UTC+5) border. There don't seem to
be roads, but an off-road vehicle ought to be able to do it in an hour.

-- 
Clive D.W. Feather  | If you lie to the compiler,
Email: cl...@davros.org | it will get its revenge.
Web: http://www.davros.org  |   - Henry Spencer
Mobile: +44 7973 377646
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Pierpaolo Bernardi]

On Mon, Jun 1, 2015 at 9:19 PM, Pierpaolo Bernardi 
wrote

In the EU, the change happens simultaneously in all countries at 01:00 UTC.
>
>
> The following is an authoritative source:
> http://eur-lex.europa.eu/legal-content/IT/TXT/?uri=CELEX:32000L0084
>

By the way, I noticed only now that the English text says 01:00 GMT, while
the Italian text says 01:00 Tempo Universale.

Sigh
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Pierpaolo Bernardi]

On Mon, Jun 1, 2015 at 6:35 PM, Tom Van Baak  wrote:

> > On 31 May 2015, at 03:28, Rob Seaman  wrote:
> >>
> >> DST changes at 2am in the US and 1am in the EU.
> >
> > That is 01:00 UTC which is 02:00 standard / 03:00 summer time for most of
> > the EU.
> >
> > Tony.
>
> Tony, that's my understanding too, that all DST changes always occur at
> 2am local time, both times a year.
>

In the EU, the change happens simultaneously in all countries at 01:00 UTC.


The following is an authoritative source:
http://eur-lex.europa.eu/legal-content/IT/TXT/?uri=CELEX:32000L0084

P.
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Tom Van Baak]

Rob (or Steve),

Can you send me a definitive URL with global TZ rules so I can grep|sort|uniq 
to get a feel for when DST transitions occurs? I guess I thought it always was 
2 am local (which implies jumps from 02h->03h and 02h->01h).

Also, possibly related, do you know of any place where DST is +/- 2 hours 
instead of +/- 1 hour? I ask because the still-in-development PE (phase 
encoded) WWVB format appears to allow for such a (non US legal) transition. I 
can't quite tell if it's a bug or typo or spec.

/tvb


- Original Message - 
From: "Rob Seaman" 
To: "Tom Van Baak" 
Cc: "Leap Second Discussion List" 
Sent: Monday, June 01, 2015 11:27 AM
Subject: Re: [LEAPSECS] Google, Amazon, now Microsoft


Hi Tom,

> Tony, that's my understanding too, that all DST changes always occur at 2am 
> local time, both times a year.
> 
> Rob, where did you see the 1am documented?

Got me. Rummaging through zoneinfo, however, many different pivot hours have 
been used. The point was just that there is nothing special about midnight 
local time.

Rob

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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Brooks Harris]

On 2015-06-01 12:37 PM, Tom Van Baak wrote:

Tom Van Baak said:

On a positive note, this means one could actually experience more than one
Windows non-leap-second on June 30. Maybe this year I should try to
celebrate the leap second twice, in Mountain and in Pacific time. Time to
pull out the road map.

Why stop with Mountain and Pacific?  There are many more time zones to try.

If you don't capture the event you want, just change the time zone and try
again.  You have an hour to tweak things and get setup to try again.

Hi Hal,

Oh, I wasn't thinking of cheating and adjusting timezones with a mouse click. 
For maximum photo effect, I was planning to drive my mobile (car) time lab 
across two time zones the night of June 30 and catch two Azure leap seconds. 
Timezones are too wide to hit three in under 2 hours.
You'll need a faster car. Or a plane. Maybe we could get the guys on the 
space station to try it?




/tvb
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Rob Seaman]

Hi Tom,

> Tony, that's my understanding too, that all DST changes always occur at 2am 
> local time, both times a year.
> 
> Rob, where did you see the 1am documented?

Got me. Rummaging through zoneinfo, however, many different pivot hours have 
been used. The point was just that there is nothing special about midnight 
local time.

Rob

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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Tom Van Baak]

> Tom Van Baak said:
>> On a positive note, this means one could actually experience more than one
>> Windows non-leap-second on June 30. Maybe this year I should try to
>> celebrate the leap second twice, in Mountain and in Pacific time. Time to
>> pull out the road map.
> 
> Why stop with Mountain and Pacific?  There are many more time zones to try.
> 
> If you don't capture the event you want, just change the time zone and try 
> again.  You have an hour to tweak things and get setup to try again.

Hi Hal,

Oh, I wasn't thinking of cheating and adjusting timezones with a mouse click. 
For maximum photo effect, I was planning to drive my mobile (car) time lab 
across two time zones the night of June 30 and catch two Azure leap seconds. 
Timezones are too wide to hit three in under 2 hours.

/tvb
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Tom Van Baak]

> On 31 May 2015, at 03:28, Rob Seaman  wrote:
>>
>> DST changes at 2am in the US and 1am in the EU.
> 
> That is 01:00 UTC which is 02:00 standard / 03:00 summer time for most of
> the EU.
> 
> Tony.

Tony, that's my understanding too, that all DST changes always occur at 2am 
local time, both times a year.

Rob, where did you see the 1am documented?

/tvb

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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Tony Finch]

On 30 May 2015, at 23:05, Tom Van Baak  wrote:
>
> I understand that's why JD rolls over at noon instead of midnight. But,
> for the other 7 billion people on the planet, it's nice that the
> calendar, and local legal time, and even MJD rolls over at midnight
> instead of noon.

And GMT switches at noon or midnight depending on which side of 1925 you are :-)

Tony.
-- 
f.anthony.n.finchhttp://dotat.at/
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10 later. Moderate becoming rough or very rough, occasionally high later.
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Tony Finch]

On 31 May 2015, at 03:28, Rob Seaman  wrote:
>
> DST changes at 2am in the US and 1am in the EU.

That is 01:00 UTC which is 02:00 standard / 03:00 summer time for most of
the EU.

Tony.
-- 
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Poul-Henning Kamp]

In message <556bfd47.4050...@edlmax.com>, Brooks Harris writes:

>>Multiply this by 250 million [1] PC's still happily running XP
>>and you can better understand why Microsoft hasn't been that
>>interested in leap seconds, NTP, or participating in the hh:59:60
>>timestamp nightmare.

>Yes, they've got a very large number of badly administrated systems in 
>the field. In more tightly administrated systems it can be done better. 
>But its all "good enough" for current purposes.

That's not as obvious as you seem to think.

A lot of Windows machines are doing things where you would expect
people to care about leap-seconds:  Nuclear power plants control
systems, Air Traffic Control computers, Surgery robots, Patient
Monitors, Power grid disturbance detectors etc.  etc. etc.

Fact is that most of the people involved in these systems have no idea
what a leap-second is, and more crucially:  Once they learn that, they
have no idea what the system they designed will do when one happens.

>> It would make sense, like Google and Amazon, that their in-house
>> data centers would want to more precisely and deterministically
>> handle leap seconds. But note all three companies have decided to
>> jump or smear time instead of creating a true leap second.

>As I understand it its not that they are interested in "precise" or 
>"accurate" time - they are interested in smoothing over the Leap Second 
>to avoid problems potentially caused by the Leap Second jump in the many 
>OSs running in the data centers.

They are very much interested in both *precise* and *accurate* time,
that's why they have to do something in the first place.

If they were not interested in good timekeeping, they could just
let the computers free-run their clocks and pretend this is the 1980ies.

And yes, the smoothing and ramping and steps are all attempts to
win predictability at the expense of accuracy, when faced with at
huge amount of software written by the kind of people mentioned above.

But this is not something they are happy about doing, much less
proud of doing, but weighing the risks of "heterogeneous" leap-second
handling and the risk of being up to half a second wrong about time
for most of a day, they picked the second risk.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Brooks Harris]

Hi Tom,

On 2015-05-31 07:23 PM, Tom Van Baak wrote:

Hi Brooks,

I don't know enough about Windows timekeeping in general or versions of Windows 
in particular to give you any authoritative answer. But here's one data point 
that might help clarify what you and PHK are talking about.

On Windows XP, click on the clock icon and look at the "Internet Time" tab. It says my 
laptop will sync against "time.nist.gov" (choice of nist or microsoft) automatically once 
a week (no choice). You can also manually initiate a sync.
Right. There are more choices on more recent Windows versions (Vista, 7, 
8..). And the Server versions have more choices with Windows Time 
Service turned on.


I looked at the LAN packets during the weekly sync and it consists of a single 
NTP packet going out and a single reply coming back. See attached snapshot.

So, yes, Windows uses an NTP packet. But, no, it doesn't "run NTP".
Well, it must have an NTP client application to initiate the connection 
and communicate to the NTP server, no?


This one looks to be NTPv3.

I've implemented an SNTP client on Windows and it behaves very much like 
the standard "Internet Time".




Multiply this by 250 million [1] PC's still happily running XP and you can 
better understand why Microsoft hasn't been that interested in leap seconds, 
NTP, or participating in the hh:59:60 timestamp nightmare.
Yes, they've got a very large number of badly administrated systems in 
the field. In more tightly administrated systems it can be done better. 
But its all "good enough" for current purposes.



It would make sense, like Google and Amazon, that their in-house data centers 
would want to more precisely and deterministically handle leap seconds. But 
note all three companies have decided to jump or smear time instead of creating 
a true leap second.
As I understand it its not that they are interested in "precise" or 
"accurate" time - they are interested in smoothing over the Leap Second 
to avoid problems potentially caused by the Leap Second jump in the many 
OSs running in the data centers. Its a work around for the timekeeping 
flaws and bugs in the system's computers and applications that may fail 
on Leap Seconds in one way or another.


-Brooks


/tvb

[1] https://redmondmag.com/articles/2015/04/08/windows-xp-usage.aspx


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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Hal Murray]

Tom Van Baak said:
> On a positive note, this means one could actually experience more than one
> Windows non-leap-second on June 30. Maybe this year I should try to
> celebrate the leap second twice, in Mountain and in Pacific time. Time to
> pull out the road map.

Why stop with Mountain and Pacific?  There are many more time zones to try.

If you don't capture the event you want, just change the time zone and try 
again.  You have an hour to tweak things and get setup to try again.

-- 
These are my opinions.  I hate spam.



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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Tom Van Baak]

Hi Brooks,

I don't know enough about Windows timekeeping in general or versions of Windows 
in particular to give you any authoritative answer. But here's one data point 
that might help clarify what you and PHK are talking about.

On Windows XP, click on the clock icon and look at the "Internet Time" tab. It 
says my laptop will sync against "time.nist.gov" (choice of nist or microsoft) 
automatically once a week (no choice). You can also manually initiate a sync.

I looked at the LAN packets during the weekly sync and it consists of a single 
NTP packet going out and a single reply coming back. See attached snapshot.

So, yes, Windows uses an NTP packet. But, no, it doesn't "run NTP".

Multiply this by 250 million [1] PC's still happily running XP and you can 
better understand why Microsoft hasn't been that interested in leap seconds, 
NTP, or participating in the hh:59:60 timestamp nightmare. It would make sense, 
like Google and Amazon, that their in-house data centers would want to more 
precisely and deterministically handle leap seconds. But note all three 
companies have decided to jump or smear time instead of creating a true leap 
second.

/tvb

[1] https://redmondmag.com/articles/2015/04/08/windows-xp-usage.aspx
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Poul-Henning Kamp]

In message <556b74ee.2040...@edlmax.com>, Brooks Harris writes:

>> Because that is the only sane thing for them to do, given the (broken)
>> timekeeping in the software they run.

>Well, broken in what way for what purpose? An awful lot of people use 
>it.. 

Yeah, and more insects eat shit every minute than there ever will
be humans on the planet.

Quality is not a mater of majority.

>> The fundamental question about leapseconds is not about where Rob can
>> find the sun at noon, but about teaching an awful lot of rather crap
>> programmers how to cope with a infrequent and intractable complexity
>> on short notice.

>I don't think its fair to insult all the programmers.

That's why I wrote "an awful lot" rather than "all".


>> It seems like Daniels scheduling on this one may show us which is more
>> important.
>
>Sorry, lost track of what that comment refers to..

As far as I can tell, Daniel Gambis would have had no trouble
justifying scheduling this leapsecond at either the preceeding or
succeesding new years eve, but he decided to stick not to blunt the
impact and scheduled it Tue/Wed July 1st.

I'm glad he did, it's the only way to end the prophetizing:  What
ever happens or don't happen on july 1st will be valuable *factual*
input to the ITU decicion making process.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Brooks Harris]

Hi Poul-Henning,

On 2015-05-31 03:33 PM, Poul-Henning Kamp wrote:


In message <556b5d76.6000...@edlmax.com>, Brooks Harris writes:


Most Windows boxes don't run NTP.

I don't think that's true. As far as I know, Windows, either personal or
Server versions, synchronize using NTP, and did so with SNTP until Win
2000, then NTPV3, then NTPV4. I glean this from accumulated knowledge -
its difficult to find authoritative information from Microsoft about it.

So that depends what you mean by "NTP".

If you mean that your packets look like NTP packets, then yes, it does
run NTP.

OK.

But I mean "use the NTP clock model".
Right. OK, well, its not made clear exactly what it does with its 
counting over the Leap Second (like NTP "freeze" or POSIX "reset") or 
how its applied to local timescales. .



On my personal laptop running Win 7, I don't have Active Directory, and
the W32Time service is *not* started. But it will synchronize via the
usual desktop "Internet Time" mechanisms. It uses either
"time.nist.gov", "time.windows.com", etc. These are NTP servers.

But what happens when the leap-second hits ?

Most likely, at some random time after the leapsecond, your clock
steps a second.

Right, for normal personal computers. Severs may be more tightly synched.



Windows of any version is fundamentally following NTP.

Not even close.
Well, what I mean its it relies on NTP for its time in some way or 
other. I didn't mean it *is* NTP, so I'll retract the comment in that form.


That's why Meinberg still maintains their NTPD client.
Right. The discussion didn't start out about accuracy, but about the 
counting rules.


You should find Martins presentation from FOSDEM about this.


But that doesn't answer the first question about how the Leap Second is
applied to local time by Azure and/or Windows.

Because that is the only sane thing for them to do, given the (broken)
timekeeping in the software they run.
Well, broken in what way for what purpose? An awful lot of people use 
it.. Its time is not "precise" and/or "accurate" without some help from 
somewhere, but its good enough to have become the largest platform. I 
could write a three volume tome on "Why I Hate Windows". But its the 
environment, like it or not.


The fundamental question about leapseconds is not about where Rob can
find the sun at noon, but about teaching an awful lot of rather crap
programmers how to cope with a infrequent and intractable complexity
on short notice.
I don't think its fair to insult all the programmers. Timekeeping is a 
specialty, and a controversial specialty. Most programmers are trying to 
use system timekeeping services on various platforms and applications 
that are not well documented, and often flawed. The fact there are bugs 
is no surprise and until a concerted effort is made to improve the 
underlying standards and implementations it will be a trash..


It seems like Daniels scheduling on this one may show us which is more
important.

Sorry, lost track of what that comment refers to..

-Brooks

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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Poul-Henning Kamp]

In message <556b6735.20784.5a32d...@dan.tobias.name>, "Daniel R. Tobias" writes
:
>On 31 May 2015 at 19:33, Poul-Henning Kamp wrote:
>
>> Most likely, at some random time after the leapsecond, your clock
>> steps a second.
>
>...which is basically how most computers deal with time 
>synchronization, excepting the minority that actually attempt 
>continuous high precision and accuracy; the computer's clock, not all 
>that accurate a timepiece, drifts off from external standards within 
>the period (hours, days, weeks) between synchronizations, and has to 
>step a few seconds one way or the other to catch up (possibly 
>smoothed out to prevent discontinuities that harm processes in 
>progress); the leap second, if any, is lost in the noise.

I have no idea what kind of computers you are talking about here,
but your description has very little to do with the computer where
leap-seconds matter.

You may be right for the typical kids game-computer and the computer
in your set-top-box, and for such purposes I doubt leap seconds are
going to wreck havoc[1].

I'm talking about "work computers" (and so is Microsoft Azure) and
here timekeeping matters, because otherwise emails are after the
replies to them, databases don't agree about stock, medicine does
not live up to FDA rules etc. etc. etc.

In this world, NTP rules, PTP is the up and coming kids where
it really matters, and leap-seconds are not at all lost in
the noise.

The big problem here, is that we have lost a generation of good
IT-people to the dot-com period[2], and they think, like you
seem to think, that "What Me Worry?".



[1] Although, if all Playstations and X-Boxes suddenly go into a
full CPU-spin at the same time, that might tilt certain weaker
electrical grids.

[2] The IT profession grew by a factor of about 1000 during the
dot-com years.  Everybody who could sit still in front of a keyboard
and read an O'Really? book was suddenly a web-programmer.  It is
probably historys greatest dumbing down of any trade - ever - and
we're still spending a lot of our energy educating these people.


-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Warner Losh]

> On May 31, 2015, at 1:55 PM, Daniel R. Tobias  wrote:
> 
> On 31 May 2015 at 19:33, Poul-Henning Kamp wrote:
> 
>> Most likely, at some random time after the leapsecond, your clock
>> steps a second.
> 
> ...which is basically how most computers deal with time
> synchronization, excepting the minority that actually attempt
> continuous high precision and accuracy; the computer's clock, not all
> that accurate a timepiece, drifts off from external standards within
> the period (hours, days, weeks) between synchronizations, and has to
> step a few seconds one way or the other to catch up (possibly
> smoothed out to prevent discontinuities that harm processes in
> progress); the leap second, if any, is lost in the noise.

This is precisely the attitude that prevents leap seconds from
being implemented properly. “It’s just a second” and “we’ve never
cared, so why should we start” are lame cop-outs.

And most systems I’ve used certainly are synchronized via NTP.
All macs, all my servers, etc all maintain a reasonably coherent
time scale. Failure to do this, btw, will lead many of the synchronization
algorithms and such to have false timeouts, or worse. Some
are resilient in the face of these weird steps. Others less so.

Then again, my data is skewed, since I never use Windows.

Warner



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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Daniel R. Tobias]

On 31 May 2015 at 19:33, Poul-Henning Kamp wrote:

> Most likely, at some random time after the leapsecond, your clock
> steps a second.

...which is basically how most computers deal with time 
synchronization, excepting the minority that actually attempt 
continuous high precision and accuracy; the computer's clock, not all 
that accurate a timepiece, drifts off from external standards within 
the period (hours, days, weeks) between synchronizations, and has to 
step a few seconds one way or the other to catch up (possibly 
smoothed out to prevent discontinuities that harm processes in 
progress); the leap second, if any, is lost in the noise.

-- 
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Dan's Domain Site: http://domains.dan.info/


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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Poul-Henning Kamp]

In message <556b5d76.6000...@edlmax.com>, Brooks Harris writes:

>> Most Windows boxes don't run NTP.
>I don't think that's true. As far as I know, Windows, either personal or 
>Server versions, synchronize using NTP, and did so with SNTP until Win 
>2000, then NTPV3, then NTPV4. I glean this from accumulated knowledge - 
>its difficult to find authoritative information from Microsoft about it.

So that depends what you mean by "NTP".

If you mean that your packets look like NTP packets, then yes, it does
run NTP.

But I mean "use the NTP clock model".

>On my personal laptop running Win 7, I don't have Active Directory, and 
>the W32Time service is *not* started. But it will synchronize via the 
>usual desktop "Internet Time" mechanisms. It uses either 
>"time.nist.gov", "time.windows.com", etc. These are NTP servers.

But what happens when the leap-second hits ?

Most likely, at some random time after the leapsecond, your clock
steps a second.

>Windows of any version is fundamentally following NTP.

Not even close.

That's why Meinberg still maintains their NTPD client.

You should find Martins presentation from FOSDEM about this.

>But that doesn't answer the first question about how the Leap Second is 
>applied to local time by Azure and/or Windows.

Because that is the only sane thing for them to do, given the (broken)
timekeeping in the software they run.

The fundamental question about leapseconds is not about where Rob can
find the sun at noon, but about teaching an awful lot of rather crap
programmers how to cope with a infrequent and intractable complexity
on short notice.

It seems like Daniels scheduling on this one may show us which is more
important.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Brooks Harris]

On 2015-05-31 04:40 AM, Poul-Henning Kamp wrote:


In message<556abecf.2050...@edlmax.com>, Brooks Harris writes:


My question is, if Azure is doing this, what is Windows itself doing?

No.


for that no new information is available and the most recent
guidance was that "somewhere between a second and an hour later
the clock will step a second".

"most recent guidance" from whom?

As I understand it, the clock would step a second when it syncs with
NTP, but note there are apparently different capability NTP clients in
various Windows versions. But what happens in different timezones?

Most Windows boxes don't run NTP.
I don't think that's true. As far as I know, Windows, either personal or 
Server versions, synchronize using NTP, and did so with SNTP until Win 
2000, then NTPV3, then NTPV4. I glean this from accumulated knowledge - 
its difficult to find authoritative information from Microsoft about it.


Where Servers and Windows Time Service are concerned, this is the best 
explanation I've found -


Disrupting time management in a Microsoft Windows 2008 Active Directory 
environment using NTP

https://www.os3.nl/_media/2012-2013/courses/ssn/disrupting_time_management_in_a_microsoft_windows_2008_active_directory_environment_using_ntp.pdf

There are good reference in that article.

There are more recent articles pertaining to Server versions, where 
Active Directory and the Windows Time Service (the W32Time (Windows 
Time) service) are in use.


How the Windows Time Service Works
https://technet.microsoft.com/en-us/library/cc773013(v=ws.10).aspx

On my personal laptop running Win 7, I don't have Active Directory, and 
the W32Time service is *not* started. But it will synchronize via the 
usual desktop "Internet Time" mechanisms. It uses either 
"time.nist.gov", "time.windows.com", etc. These are NTP servers.



Some of them run some oddball M$ time-sync protocol where they ask
their domain-controllers -- if they have one.
As above - the domain controller is configured or discovers an NTP 
server. The NT5DS protocol routes the NTP through the domain controller.


Where domain-controllers get their time is anyones guess.

As above - an NTP server as configured or discovered.

Windows of any version is fundamentally following NTP.

But that doesn't answer the first question about how the Leap Second is 
applied to local time by Azure and/or Windows.


Also -

NIST Internet Time Service (ITS)
http://www.nist.gov/pml/div688/grp40/its.cfm

The story around Leap Seconds and Windows: It’s likely not Y2K
http://blogs.msdn.com/b/mthree/archive/2015/01/08/leap-seconds-010815.aspx

Part two of the story around Leap Seconds and Windows: #NotY2K
http://blogs.msdn.com/b/mthree/archive/2015/01/14/leap-seconds-011415.aspx

-Brooks






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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Poul-Henning Kamp]

In message <20150531145859.ga10...@ucolick.org>, Steve Allen writes:

>UCO/Lick knows that, even with the best available version of NTP, the
>sloppy (or even lack of) hardware clock on some motherboards [...]

This is *UTTER* bull-shit.

There is usable clock-hardware on all PC boards all the way back to the
original IBM PC, and Microsoft has never claimed that lack of hw was
the reason for this.

The main reason why good timekeeping support has never been a priority
for Microsoft is that it would allow people to measure how ridiculous
shitty their so-called Operating Systems are at all sorts of low-level
activities.

Recent versions of Windows have grown various hack-ish API's, mostly
because there was no to play video without it.  Most of these API's
are not good for anything else.

-- 
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Steve Allen]

On Sun 2015-05-31T14:28:59 +, Poul-Henning Kamp hath writ:
> >But they have servers in multiple locations, so if they are running on the
> >local time zone they will not leap at the same time...
>
> Welcome to the (probably painful) world of "heuristic handling of
> leap seconds".

And it's not just Microsoft, and not just this next leap.

The APNIC APRICOT 2015 lightning talks were mentioned on LEAPSECS back
in March.  There was a talk about the handling of the 2012 leap second
and the desynch that happened among machines running NTP from
different servers.  Even with NTP the clock behavior in one stratum of
client was different from clocks in another stratum because
knowing "what time is it" is a measurement process.

The slides are at
http://www.slideshare.net/apnic/the-leap-second-is-coming-by-tomonori-takada-apricot-2015
The video of the talk is available on the APNIC channel on Youtube:
https://www.youtube.com/watch?v=E_AMR3ECIxQ&feature=youtu.be&t=51m
Starting at Minute 51.

In the case of Microsoft the disclaimer at the bottom of
https://technet.microsoft.com/en-us/library/cc773013(v=ws.10).aspx
still says W32Time cannot guarantee better than 1 to 2 seconds.

UCO/Lick knows that, even with the best available version of NTP, the
sloppy (or even lack of) hardware clock on some motherboards means
that some Windows systems cannot do better than 1 to 2 seconds.

Applications running on networks with these sorts of machines are
probably already robust against 1 to 2 second offsets because those
happen all the time, but that still means we cannot use the timestamps
from Windows for science.  According to the best rumors, the failure
of Qantas/Amadeus in 2012 was because of the 1 second offset between
machines.  And in 2012 the financial markets were not running, so
as PHK writes, this next leap should be very interesting.

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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Poul-Henning Kamp]

In message <087cc3e4-b63e-44ba-9ad6-22dce13a3...@dotat.at>, Tony Finch writes:

>> The opererative detail is this:
>> 
>>"Microsoft has determined that clocks on tens of thousands
>>of servers globally running Azure should switch to the leap
>>second at midnight in the time zone where they are based."
>> 
>> As far as I know, it is not like Microsoft has any choice, "local
>> midnight" is the only time their software makes it possible for
>> them to make sure that all servers jump at the same time.
>
>But they have servers in multiple locations, so if they are running on the
>local time zone they will not leap at the same time...

Welcome to the (probably painful) world of "heuristic handling of
leap seconds".

-- 
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Tony Finch]

> On 30 May 2015, at 06:52, Poul-Henning Kamp  wrote:
> 
> The opererative detail is this:
> 
>"Microsoft has determined that clocks on tens of thousands
>of servers globally running Azure should switch to the leap
>second at midnight in the time zone where they are based."
> 
> As far as I know, it is not like Microsoft has any choice, "local
> midnight" is the only time their software makes it possible for
> them to make sure that all servers jump at the same time.

But they have servers in multiple locations, so if they are running on the 
local time zone they will not leap at the same time...

Tony.
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Poul-Henning Kamp]

In message <556abecf.2050...@edlmax.com>, Brooks Harris writes:

>My question is, if Azure is doing this, what is Windows itself doing?

No.

>> for that no new information is available and the most recent
>> guidance was that "somewhere between a second and an hour later
>> the clock will step a second".
>"most recent guidance" from whom?
>
>As I understand it, the clock would step a second when it syncs with 
>NTP, but note there are apparently different capability NTP clients in 
>various Windows versions. But what happens in different timezones?

Most Windows boxes don't run NTP.

Some of them run some oddball M$ time-sync protocol where they ask
their domain-controllers -- if they have one.

Where domain-controllers get their time is anyones guess.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Brooks Harris]

On 2015-05-31 03:57 AM, Brooks Harris wrote:

On 2015-05-31 02:41 AM, Poul-Henning Kamp wrote:


In message <556a6bd2.50...@edlmax.com>, Brooks Harris writes:


I can't find any authoritative announcement or statement to this effect

>from Microsoft, [...]

Please note that this is *only* about Microsofts Azure cloud service,

Yes, that's what that articles says, but what does Microsoft say?

(which according to rumours are mostly used to run Exchange servers).

Indeed, rumors. What does Microsoft say?


This is *NOT* how your private/work Windows machine will behave,
Well, that's my question. Sure, a single machine catches up when it 
synchronizes to NTP. But what is Windows doing with the Leap Second 
count in each timezone?


The article I referenced earlier said "Applies To:" various Windows 
Server versions - it doesn't mention Vista, Win 7, Win 8, etc.


How the Windows Time Service Works
https://technet.microsoft.com/en-us/library/cc773013(v=ws.10).aspx

So, the timing mechanisms are complex, depending on Windows version, 
hardware, and administration choices.


My question is, if Azure is doing this, what is Windows itself doing?


for that no new information is available and the most recent
guidance was that "somewhere between a second and an hour later
the clock will step a second".

"most recent guidance" from whom?

As I understand it, the clock would step a second when it syncs with 
NTP, but note there are apparently different capability NTP clients in 
various Windows versions. But what happens in different timezones?


-Brooks


This says it applies to Server versions and Win 7, 8, etc.

How the Windows Time service treats a leap second Print Print Email Email
https://support.microsoft.com/en-us/kb/909614

It doesn't mention how it may apply to local time.

-Brooks










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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Brooks Harris]

On 2015-05-31 02:41 AM, Poul-Henning Kamp wrote:


In message <556a6bd2.50...@edlmax.com>, Brooks Harris writes:


I can't find any authoritative announcement or statement to this effect

>from Microsoft, [...]

Please note that this is *only* about Microsofts Azure cloud service,

Yes, that's what that articles says, but what does Microsoft say?

(which according to rumours are mostly used to run Exchange servers).

Indeed, rumors. What does Microsoft say?


This is *NOT* how your private/work Windows machine will behave,
Well, that's my question. Sure, a single machine catches up when it 
synchronizes to NTP. But what is Windows doing with the Leap Second 
count in each timezone?


The article I referenced earlier said "Applies To:" various Windows 
Server versions - it doesn't mention Vista, Win 7, Win 8, etc.


How the Windows Time Service Works
https://technet.microsoft.com/en-us/library/cc773013(v=ws.10).aspx

So, the timing mechanisms are complex, depending on Windows version, 
hardware, and administration choices.


My question is, if Azure is doing this, what is Windows itself doing?


for that no new information is available and the most recent
guidance was that "somewhere between a second and an hour later
the clock will step a second".

"most recent guidance" from whom?

As I understand it, the clock would step a second when it syncs with 
NTP, but note there are apparently different capability NTP clients in 
various Windows versions. But what happens in different timezones?


-Brooks






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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Poul-Henning Kamp]

In message <556a6bd2.50...@edlmax.com>, Brooks Harris writes:

>I can't find any authoritative announcement or statement to this effect 
>from Microsoft, [...]

Please note that this is *only* about Microsofts Azure cloud service,
(which according to rumours are mostly used to run Exchange servers).

This is *NOT* how your private/work Windows machine will behave,
for that no new information is available and the most recent
guidance was that "somewhere between a second and an hour later
the clock will step a second".


-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Rob Seaman]

On May 30, 2015, at 3:05 PM, Tom Van Baak  wrote:

> Oh, you're such an old earth+photon guy. Ask any space probe, neutrino, or 
> gravitational astronomer if they share your sleep problem. ;-)

As with timekeeping in general it is a question of complex systems-of-systems, 
e.g.:

http://hotwireduniverse.org or
http://arxiv.org/abs/1407.7552

Non-EM “multi-messenger” phenomena also exhibit diurnal signals and, of course, 
many space telescopes orbit the Earth and care about Earth orientation.  
Coordinated observing modes may depend on multiple telescopes of all 
wavelengths in several timezones and both ground and space-based.

> I understand that's why JD rolls over at noon instead of midnight. But, for 
> the other 7 billion people on the planet, it's nice that the calendar, and 
> local legal time, and even MJD rolls over at midnight instead of noon.

Decision-making related to timekeeping has often been very shallow.  DST 
changes at 2am in the US and 1am in the EU.  The operational pivot between one 
observing night and the next at our observatory is 9am.  Why assume midnight 
local time in the first place?

On May 30, 2015, at 4:52 AM, Poul-Henning Kamp  wrote:

> 2. Do any astronomers even use Microsofts Azure cloud thingie ?

There’s http://www.worldwidetelescope.org

Rob
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Brooks Harris]

Hi Tom and Rob,

On 2015-05-30 06:05 PM, Tom Van Baak wrote:

Perhaps one should point out that local midnight is pretty much the worst
possible time for astronomers to accommodate such a change?

Hi Rob,

Oh, you're such an old earth+photon guy. Ask any space probe, neutrino, or 
gravitational astronomer if they share your sleep problem. ;-)

I understand that's why JD rolls over at noon instead of midnight. But, for the 
other 7 billion people on the planet, it's nice that the calendar, and local 
legal time, and even MJD rolls over at midnight instead of noon.

I can totally sympathize with Microsoft's "fix" for leap seconds.
I can't find any authoritative announcement or statement to this effect 
from Microsoft, and most references seem to go back round to this "The 
Register" article. Where does this information come from?

Laugh if you want. But out of history, ignorance, compatibility, or dogma their 
first fix was never to accept or display a 61st second in the first place. 
Windows is more POSIX than POSIX, when you think about it.
Well, the lack of the 61st second (and 58 rollover) in most computer 
timescale implementations is at the root of the Leap Seconds problems. 
Windows shares that flaw - the Leap Second count itself goes missing.

This recent "fix"
I got to thinking - what does Windows itself do, what has it always 
done, in this respect? Its sort of an obvious question that never 
occurred to me. I think maybe it's always done what this article says 
Azure its now going to do (or has been doing all along?).


I was experimenting a bit with the Windows time API itself to see if I 
could determine this. My investigation is a bit inconclusive at the 
moment, but I can't see where there is any difference in the way it 
counts on local timescales, in other words all local timescales are 
identical including, it seems, that a Leap Second occurs just before 
midnight. I'm not sure yet.


Finding authoritative information about Windows time mechanisms is 
difficult. I've never found a detailed enough explanation to answer my 
questions satisfactorily. Parts are obvious enough - it follows NTP, and 
it has dynamic (with a Windows update) timezone information in its 
registry (which conveniently does not match tz database). I don't 
believe it retains the Leap Second history anywhere.


There is this recent article that shows just how complicated the 
questions actually are.. Oh, and note, Window has had a "smear" 
mechanism in it since at least 2000 Server. Its not clear from this if 
that smear would, or is intended to, "paper over" a Leap Second from NTP.


How the Windows Time Service Works
https://technet.microsoft.com/en-us/library/cc773013(v=ws.10).aspx

Also note -
GetSystemTimeAdjustment function
https://msdn.microsoft.com/en-us/library/windows/desktop/ms724394

SetSystemTimeAdjustment function
https://msdn.microsoft.com/en-us/library/windows/desktop/ms724943


avoids another side effect of leap seconds -- where it affects the Far East 
much more than Europe or even the US. Now every timezone gets the same 
treatment as London.

Its much more symmetrical and easier to implement that way.

Yes, I know it's "against UTC rules".
Can anyone point me to a standard or specification that *explicitly and 
clearly* states that a Leap Second is to be accounted for, or 
instantiated, in the local-time count at any other time-point than the 
last second of the day? I've seen it stated, but not as an official, 
international, agreement or specification. It seems to be only "common 
use", and if Windows isn't doing it then its not very common.


In glibc we see that __tzfile_compute() (amongst the many functions 
related to gmtime() ) executes rather complex code that appears to apply 
the Leap Second differently on different timezones.


I'm quite familiar with the details and source of the implementation of 
the POSIX time mechanisms as supplied by the Microsoft MSVC c/c++ 
environment. It doesn't have mechanisms to treat the Leap Second 
differently on different timezone like glibc seems to.


I've studied the POSIX spec in regard to time carefully. I don't see 
where it calls for treating different timezone Leap Second updates 
differently. Maybe I'm missing it? How is it that glibc seems to have 
taken up that convention? Why does Microsoft's implementation lack it? 
Can anyone explain this?




I'm also looking forward to reading the unpublished research papers that 
discuss the negative side of having 24+ different leap second events around the 
globe. What a mess.
Yes, it really doesn't make sense to have a discontinuity in the count 
in the middle of the day. Of course the whole of timekeeping barely 
makes sense. :-)


-Brooks

On a positive note, this means one could actually experience more than one 
Windows non-leap-second on June 30. Maybe this year I should try to celebrate 
the leap second twice, in Mountain and in Pacific time. Time to pull out the 
road map.

/tvb

_

Re: [LEAPSECS] Google, Amazon, now Microsoft

[Tom Van Baak]

> Perhaps one should point out that local midnight is pretty much the worst
> possible time for astronomers to accommodate such a change?

Hi Rob,

Oh, you're such an old earth+photon guy. Ask any space probe, neutrino, or 
gravitational astronomer if they share your sleep problem. ;-)

I understand that's why JD rolls over at noon instead of midnight. But, for the 
other 7 billion people on the planet, it's nice that the calendar, and local 
legal time, and even MJD rolls over at midnight instead of noon.

I can totally sympathize with Microsoft's "fix" for leap seconds. Laugh if you 
want. But out of history, ignorance, compatibility, or dogma their first fix 
was never to accept or display a 61st second in the first place. Windows is 
more POSIX than POSIX, when you think about it. This recent "fix" avoids 
another side effect of leap seconds -- where it affects the Far East much more 
than Europe or even the US. Now every timezone gets the same treatment as 
London. Yes, I know it's "against UTC rules".

I'm also looking forward to reading the unpublished research papers that 
discuss the negative side of having 24+ different leap second events around the 
globe. What a mess. On a positive note, this means one could actually 
experience more than one Windows non-leap-second on June 30. Maybe this year I 
should try to celebrate the leap second twice, in Mountain and in Pacific time. 
Time to pull out the road map.

/tvb

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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Poul-Henning Kamp]

In message , Rob Seaman writes:

>> The opererative detail is this:
>> 
>>  "Microsoft has determined that clocks on tens of thousands
>>  of servers globally running Azure should switch to the leap
>>  second at midnight in the time zone where they are based."
>> 
>> As far as I know, it is not like Microsoft has any choice, "local
>> midnight" is the only time their software makes it possible for
>> them to make sure that all servers jump at the same time.
>
>Perhaps one should point out that local midnight is pretty much the
>worst possible time for astronomers to accommodate such a change?

Rob,

1. Unfathomable!  Call them! I say, Call them Right Now, and make
   them see the errors of their ways!  How dare they Ignore the
   Needs of the True Masters Of The Universe ?!

2. Do any astronomers even use Microsofts Azure cloud thingie ?

-- 
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Rob Seaman]

On May 29, 2015, at 10:52 PM, Poul-Henning Kamp  wrote:

> In message <11BA4A073E104FD29BD9DB1892B7C60F@pc52>, "Tom Van Baak" writes:
> 
>> And now for something completely different...
>> 
>> http://www.theregister.co.uk/2015/05/29/windows_azure_second_out_of_sync/
> 
> The opererative detail is this:
> 
>   "Microsoft has determined that clocks on tens of thousands
>   of servers globally running Azure should switch to the leap
>   second at midnight in the time zone where they are based."
> 
> As far as I know, it is not like Microsoft has any choice, "local
> midnight" is the only time their software makes it possible for
> them to make sure that all servers jump at the same time.

Perhaps one should point out that local midnight is pretty much the worst 
possible time for astronomers to accommodate such a change?

“Only XYZ their software makes it possible” is not an engineering requirement.

Rob

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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Poul-Henning Kamp]

In message <11BA4A073E104FD29BD9DB1892B7C60F@pc52>, "Tom Van Baak" writes:

>And now for something completely different...
>
>http://www.theregister.co.uk/2015/05/29/windows_azure_second_out_of_sync/

The opererative detail is this:

"Microsoft has determined that clocks on tens of thousands
of servers globally running Azure should switch to the leap
second at midnight in the time zone where they are based."

As far as I know, it is not like Microsoft has any choice, "local
midnight" is the only time their software makes it possible for
them to make sure that all servers jump at the same time.

-- 
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Re: [LEAPSECS] Google, Amazon, now Microsoft

[Steve Allen]

On Fri 2015-05-29T17:19:19 -0700, Tom Van Baak hath writ:
> And now for something completely different...
>
> http://www.theregister.co.uk/2015/05/29/windows_azure_second_out_of_sync/

All of which are not congruent with the "Best Practices" document
that comes from DHS/NCCIC/USNO/NIST/USCG/etc.

The sysadmins of the world have made it very clear that they are
rejecting the sovereignty of frequency and the directives of ITU-R
TF.460 in favor of smears applied as is convenient.  This is telling
the ITU-R that the status quo is not acceptable and that their
recommendations are on the verge of being irrelevant.

This a huge gulf between the sysadmins, their regulators who have
required the use of UTC rather than TAI or GPS, and the precice time
and frequency communities.

--
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