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Re: Dynamic upgrading/Hot-swapping a service

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On 4/23/2017 10:01 AM, Phil Martel wrote:
> On 4/22/2017 11:55, Don Y wrote:
>> On 4/22/2017 4:09 AM, upsidedown@downunder.com wrote:
>>> I still do not see what your actual problem is.
>>
>> Find a piece of software that is currently executing:  your
>> microwave oven controller, your PC (consider it a *collection*
>> of software), your calculator, your ....
>>
>> Now, WHILE it is "solving some particular problem for which it
>> was designed", pause the clock and replace all the INSTRUCTIONS
>> in the program(s) with a new, revised program (it does <whatever>
>> only "better" (the 8 digit calculator now handles 12 digits; the
>> microwave oven now has 6 other types of cycles; the PC is now
>> running Windows 11 instead of DOS 3.3; etc.)
>>
>> Let the clock resume.  None of the actions that were running
>> at the time the clock was PAUSED should have been affected by
>> the upgrade.  I.e., if the calculator was in the middle of
>> computing "14!", it should continue to completion -- from
>> wherever it happened to have been, at the time -- yielding
>> the correct result.
>>
>> Note, however, that the result should now be displayed as
>> 8.71782912*10^10 or 87178291200 and NOT as 8.7178291*10^10
>> to reflect the extra precision that it has internally
>> as well as the extended "display"/reporting capability
>> (assuming, of course, that the original executable was
>> interrupted before any loss of precision).
> Since this group is for embedded processing, it is fair to ask why the original
> calculator would have a display with  more that 8 significant figures.

Why does the calculator *function* have to be implemented in
a calculator *package*?  Do you not use <math.h> in your
embedded applications?

With the tiniest bit of imagination, one should be able to consider
a new math library that had greater precision *or* different
algorithms that converged faster than the previous implementation.

Given that you (I) can not shut the application down "for
maintenance", how would you replace the library (used by multiple
modules) in the application while the system was powered up and
operating?   (see my previous examples for steps)

Replace "library" with "service" and you have my original question
(i.e., most libraries can be implemented *as* services with the
re-formalization of the interface communication overhead)

>> Put something in your microwave oven.  Set the timer to X.
>> After an arbitrary amount of time, pause the process (processor)
>> and replace the ROMs.  Resume the process.  EXPECT the entire
>> process -- start to finish -- to proceed exactly as it would
>> have had you not replaced the ROMs!
> This assumes that you can replace the ROMs by some hot-swap process that does
> not kill power to the RAM/registers that hold the state and quickly enough that
> the food will not cool substantially.

Again, imagination suggests you could implement the ROMs (i.e., the
program TEXT) in other media that *can* be (effectively) replaced "between
one clock cycle and the next".  This is all old technology.  The problem
lies in doing so while some consumer (client) might be ACTIVELY executing
within that block of program TEXT.

> Also, the old program state must be
> coded so that the new ROMs read and operate on it properly.

No, that isn't necessary.  In fact, different algorithms may use
inconsistent state vectors so that mapping from one algorithm to
another is not possible.  That doesn't preclude "interrupting"
existing processing, replacing the TEXT and finishing the
processing with the "new" algorithm.

> It sounds like a lot of work.

That's why things like Windows want you to reboot so often!  :>

OTOH, web sites and enterprise systems regularly roll out
updates WHILE still providing services -- because the cost
of shutting the systems/services down for that update can
be substantial ("We're sorry, but the on-line banking transaction
that you are engaged in AT THIS MOMENT will be aborted.  Please
try again later.")

(Would you want to have to *stop* your car to have the code in the
ABS system updated -- given that stopping the car might not be
possible, reliably, given the current state of the ABS code?  :> )

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Thread

Dynamic upgrading/Hot-swapping a service Don Y <blockedofcourse@foo.invalid> - 2017-04-20 16:05 -0700
  Re: Dynamic upgrading/Hot-swapping a service Don Y <blockedofcourse@foo.invalid> - 2017-04-20 16:11 -0700
  Re: Dynamic upgrading/Hot-swapping a service upsidedown@downunder.com - 2017-04-21 10:45 +0300
    Re: Dynamic upgrading/Hot-swapping a service Don Y <blockedofcourse@foo.invalid> - 2017-04-21 10:43 -0700
      Re: Dynamic upgrading/Hot-swapping a service upsidedown@downunder.com - 2017-04-21 23:06 +0300
        Re: Dynamic upgrading/Hot-swapping a service Don Y <blockedofcourse@foo.invalid> - 2017-04-21 17:51 -0700
          Re: Dynamic upgrading/Hot-swapping a service upsidedown@downunder.com - 2017-04-22 14:09 +0300
            Re: Dynamic upgrading/Hot-swapping a service Don Y <blockedofcourse@foo.invalid> - 2017-04-22 08:55 -0700
              Re: Dynamic upgrading/Hot-swapping a service Phil Martel <pomartel@comcast.net> - 2017-04-23 13:01 -0400
                Re: Dynamic upgrading/Hot-swapping a service Don Y <blockedofcourse@foo.invalid> - 2017-04-23 10:52 -0700
                Re: Dynamic upgrading/Hot-swapping a service Phil Martel <pomartel@comcast.net> - 2017-04-24 10:48 -0400
                Re: Dynamic upgrading/Hot-swapping a service Don Y <blockedofcourse@foo.invalid> - 2017-04-24 12:33 -0700
                Re: Dynamic upgrading/Hot-swapping a service Phil Martel <pomartel@comcast.net> - 2017-04-24 22:02 -0400
                Re: Dynamic upgrading/Hot-swapping a service Don Y <blockedofcourse@foo.invalid> - 2017-04-24 21:37 -0700
                Re: Dynamic upgrading/Hot-swapping a service Phil Martel <pomartel@comcast.net> - 2017-04-25 12:19 -0400
                Re: Dynamic upgrading/Hot-swapping a service Don Y <blockedofcourse@foo.invalid> - 2017-04-25 13:54 -0700

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