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Re: HOW2 capture time of power-failure?

From William Unruh <unruh@invalid.ca>
Newsgroups comp.os.linux.misc, comp.sys.raspberry-pi
Subject Re: HOW2 capture time of power-failure?
Date 2014-10-28 04:56 +0000
Organization A noiseless patient Spider
Message-ID <m2n7m1$ndo$1@dont-email.me> (permalink)
References <XnsA3D2BB8ABDCA70xDEADBEEF@213.239.209.88> <m2m1rf$6bh$1@dont-email.me>

Cross-posted to 2 groups.

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On 2014-10-27, not.socialnetwork@gmail.com <not.socialnetwork@gmail.com> wrote:
> In article <XnsA3D2BB8ABDCA70xDEADBEEF@213.239.209.88>, Ian Malcolm <See.My.Sig.for.email@totally.invalid> wrote: 
>
>> not.socialnetwork@gmail.com wrote in news:m2jbi3$geq$1@dont-email.me:
>> 
>> > I need to capture the time-after-a-sound-file-starts-playing
>> > until the power is cut, with a resolution of 30 secs., over a
>> > period of 30 minutes.
>> > 
>> > While `ogg123  SoundFie.ogg` is playing, could the play-time
>> > be updated every 30 secs?  How?
>> > 
>> > == TIA.
>> > 
>> > PS. power-cuts without `umount` are no problem for rPi's
>> > SD nor USBstik.
>> 
>> However a power failure in the middle of a write commonly corrupts SD 
>> cards and in some cases has been known to make them unusable.
>> 
> Apparently the rPi <lands safetly> as <the voltage is dropping>.
> It's never failed during 5 cuts/day for 200 days.
>
>> Most RTC chips have a small amount of battery backed scratchpad RAM.  
>> Store timestamps for the start time + the current time in the scratchpad 
>> and update at least every 30 seconds.   Due to the risk of a power 
>> failure while updating the current time, you should use a checksum and 
>> use two different locations, alternating between them.
>> 
>> The details of how to implement this in a Python script will depend on 
>> the chip on your RTC module . . . .
>> -- 
>> Ian Malcolm. 
> No Python. Just a bash script.
>=======================================
> From: William Unruh <unruh@invalid.ca>
>
> ]Power is cut? What does that mean? 
> In the next paragraph, you've decided you know what it means.
>
>> While `ogg123  SoundFie.ogg` is playing, could the play-time
>> be updated every 30 secs?  How?
> ]How are you playing it, what is the player software?
>
> `ogg123  SoundFie.ogg` means <SoundFie.ogg>,
> is being played by "ogg123".
>
> ]Usually you can get a pretty good idea of the time of a power cut by
> ]looking at /var/log/messages and seeing when the last message
> ] was written before the cut.
>
>  tail /var/log/messages  <--after start playing
>  Oct 27 19:14:28 dog kernel: EXT4-fs: mounted filesystem sdc2 with ordered data mode
> tail: cannot open `==' for reading: No such file or directory
>
>  date  <-- during  playing
> Mon Oct 27 19:15:35 SAST 2014
>
>  tail /var/log/messages  <-- during  playing
> Oct 27 19:14:28 dog kernel: EXT4-fs: mounted filesystem sdc2 with ordered data mode
> tail: cannot open `==' for reading: No such file or directory
>
> ]POwer cuts are no problem for reading any medium. It is writing
> ]that is the problem.
>
> Yes, but as the other respondent implies: the system could be writng
> as part of it's <house-keeping>.
>==========================================
> Andrew Gabriel wrote:
>
> ]Pi's don't require much power, so you could keep the Pi running
> ]for a short time using stored power, and feed the real power loss
> ]signal into one of it's GPIO inputs, to be actioned by relevant
> ]software (such as logging the event and/or telling another system
> ]across the network), and finally trigger a clean shutdown before
> ]the stored power source runs out.
>
> No, no extra hardware than the existing control, by switching-off
> is allowed. Software could do:
>
> N=ReadFileOfLatestTimePlayedSinceTrackStart
> IF FileMarked=CutDuringPlay  // instead of during safePausePeriod
>    THEN <Calculate restart Play N secs before Cut>
>          ogg123 <M(N) secs FromBeginning>
>    END      
>    
> ]The risk is the flash memory microcode being interrupted in the
> ]middle of a critical operation, leaving some structure like the
> ]logical to physical block map corrupt, i.e. shuffling some of
> ]the blocks in the flash memory, although it may decide it's not
> ]going to play at all when next powered up.
> ]Enterprise class SSDs will protect themselves from this type of
> ]event, but cheap SD cards and USB sticks don't.
>
> Sure. But it's survived 1'000 power cuts.
> It must be designed to manage.
>
> Joe Beanfish wrote:-
> ]You could start a background process at the same time as the player to
> ]save a timestamp every 5-10 seconds.
>
> Exactly. I'm hoping someone will give me the code.

Make a file with the following content

#!/bin/bash
for ((i=0;i<10;i++))
do
while ps auxww |grep ogg123 |grep -v grep >/dev/null
do
date >/tmp/timestamp
sleep 10
done
sleep 10
done

and run it in the background when you start the ogg program.

>
>== TIA.
>

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Thread

HOW2 capture time of power-failure? not.socialnetwork@gmail.com - 2014-10-26 17:38 +0000
  Re: HOW2 capture time of power-failure? Ian Malcolm <See.My.Sig.for.email@totally.invalid> - 2014-10-26 18:26 +0000
    Re: HOW2 capture time of power-failure? not.socialnetwork@gmail.com - 2014-10-27 18:10 +0000
      Re: HOW2 capture time of power-failure? Gordon Henderson <gordon+usenet@drogon.net> - 2014-10-27 18:29 +0000
        Re: HOW2 capture time of power-failure? not.socialnetwork@gmail.com - 2014-10-28 21:26 +0000
      Re: HOW2 capture time of power-failure? William Unruh <unruh@invalid.ca> - 2014-10-28 04:56 +0000
        Re: HOW2 capture time of power-failure? Dom <domafp@blueyonder.co.uk> - 2014-10-28 06:29 +0000
          Re: HOW2 capture time of power-failure? William Unruh <unruh@invalid.ca> - 2014-10-28 06:41 +0000
            Re: HOW2 capture time of power-failure? not.socialnetwork@gmail.com - 2014-10-29 00:12 +0000
  Re: HOW2 capture time of power-failure? William Unruh <unruh@invalid.ca> - 2014-10-26 19:23 +0000
    Re: HOW2 capture time of power-failure? spam-no-spam@Freeola.net.invalid (Windmill) - 2014-11-04 13:19 +0000
      Re: HOW2 capture time of power-failure? William Unruh <unruh@invalid.ca> - 2014-11-05 21:56 +0000
        Re: HOW2 capture time of power-failure? Joe Beanfish <joebeanfish@nospam.duh> - 2014-11-06 14:12 +0000
        Re: HOW2 capture time of power-failure? nba@users.sourceforge.net (Niels Baggesen) - 2014-11-06 16:15 +0100
          Re: HOW2 capture time of power-failure? William Unruh <unruh@invalid.ca> - 2014-11-06 16:00 +0000
        Re: HOW2 capture time of power-failure? spam-no-spam@Freeola.net.invalid (Windmill) - 2014-11-06 20:37 +0000
      Re: HOW2 capture time of power-failure? Joe Beanfish <joebeanfish@nospam.duh> - 2014-11-06 14:13 +0000
  Re: HOW2 capture time of power-failure? andrew@cucumber.demon.co.uk (Andrew Gabriel) - 2014-10-26 20:28 +0000
  Re: HOW2 capture time of power-failure? Joe Beanfish <joebeanfish@nospam.duh> - 2014-10-27 13:17 +0000
  Re: HOW2 capture time of power-failure? Jean-David Beyer <jeandavid8@verizon.net> - 2014-10-28 13:43 -0400
    Re: HOW2 capture time of power-failure? Ant <ant@zimage.comANT> - 2014-10-29 08:18 -0700
  Re: HOW2 capture time of power-failure? Joe Beanfish <joebeanfish@nospam.duh> - 2014-10-29 13:28 +0000
    Re: HOW2 capture time of power-failure? not.socialnetwork@gmail.com - 2014-10-30 08:32 +0000
      background processes (was HOW2 capture time of power-failure?) Joe Beanfish <joebeanfish@nospam.duh> - 2014-10-30 13:16 +0000
        Re: background processes (was HOW2 capture time of power-failure?) not.socialnetwork@gmail.com - 2014-11-03 03:25 +0000
          Re: background processes (was HOW2 capture time of power-failure?) "David W. Hodgins" <dwhodgins@nomail.afraid.org> - 2014-11-02 23:34 -0500
          Re: background processes (was HOW2 capture time of power-failure?) William Unruh <unruh@invalid.ca> - 2014-11-03 08:25 +0000
          Re: background processes (was HOW2 capture time of power-failure?) Martin Gregorie <martin@address-in-sig.invalid> - 2014-11-03 12:56 +0000
            Re: background processes (was HOW2 capture time of power-failure?) not.socialnetwork@gmail.com - 2014-11-06 19:19 +0000
              Re: background processes (was HOW2 capture time of power-failure?) Martin Gregorie <martin@address-in-sig.invalid> - 2014-11-07 02:36 +0000
              Re: background processes (was HOW2 capture time of power-failure?) Joe Beanfish <joebeanfish@nospam.duh> - 2014-11-07 14:28 +0000
                Re: background processes (was HOW2 capture time of power-failure?) not.socialnetwork@gmail.com - 2014-11-08 03:32 +0000

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