wee_reports picks up extensions.py delay

[WindnFog]

Here's an oddity.  To delay weewx from starting for 45 seconds after a reboot, I used Tom's 2019 suggestion of putting a delay of 45 in /usr/share/weewx/user/extensions.py . . . and this works well, except it also kicks in when you run wee_reports:

sudo wee_reports
^CTraceback (most recent call last):
  File "/usr/share/weewx/wee_reports", line 16, in <module>
    import user.extensions
  File "/usr/share/weewx/user/extensions.py", line 20, in <module>
    time.sleep(45)
KeyboardInterrupt   <--- I ctrl-C'ed out of this after 25-30 seconds.

Is there any way to change the code so that wee_reports doesn't execute the time.sleep(45) command?

- Paul VE1DX

[Tom Keffer]

Unfortunately, wee_reports has to load extensions.py, because there might be some user extensions in there, which it might need for the reports (for example, an xtypes extension). So, whatever is in there, is going to get executed.

I no longer think an arbitrary 45 second sleep is such a good idea. The engine already has something that causes it to wait until the time is greater than the timestamp on weewx.conf, so that should give some measure of protection against clock slew. But, the best way to approach the problem is through systemd time synchronizations.

If you really want to sleep, then it's probably best done with a WeeWX extension that's bound to the STARTUP event.

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[Paul Dunphy]

     Thanks for the quick reply, Tom.  This makes sense.  I had the 45 seconds in there from some debugging 6-8 months ago and I really don't need it anymore.  Just removed it.

- Paul VE1DX

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[WindnFog]

How to do that?  I *honestly* searched the message board off and on for the last month, scoured the documentation, etc.  It's nitpicking, but if I reboot my Pi, the server uptime is always shorter than the weewx uptime.  I get things like:

Weewx uptime:10 days, 1 hour, 38 minutes
Server uptime: 10 days, 1 hour, 36 minutes

My workaround is, as soon as I can ssh in after boot, I run:

sudo /etc/init.d/weewx stop

Wait 4-5 minutes and run

sudo /etc/init.d/weewx start

There has to be a better way . . . can one set a cron on that runs on boot, sleeps 5 minutes, and then starts weewx?  Is it waiting for ntp to set the time?  I dunno . . .

- Paul VE1DX

[vince]

On Tuesday, June 29, 2021 at 12:48:09 PM UTC-7 WindnFog wrote:

It's nitpicking, but if I reboot my Pi, the server uptime is always shorter than the weewx uptime.  I get things like:

Weewx uptime:10 days, 1 hour, 38 minutes
Server uptime: 10 days, 1 hour, 36 minutes

It does seem like nitpicking perhaps.

Is it really 'that' important to spend all this time worrying it ?

I did a trial on my pi4 with the simulator and see the same thing.  The weewx uptime is a minute more than the server uptime.  I'm guessing it has something to do with the order the threads get their brains straight but I didn't do much digging around.   If you want to look at the code, check out bin/weewx/station.py

If it bothers you that much, you could add a cron job that resets weewx a few minutes after reboot.

ref: https://www.tomshardware.com/how-to/run-script-at-boot-raspberry-pi

Perhaps a simple bash script ala "sleep 300 && systemctl restart weewx" or the like (untested).

[HRM Resident]

Makes sense, Vince. Indeed it is a -1 on the 1-10 scale of importance.  I was thinking of something like the cron restart script, but I wanted to be sure I hadn’t missed something obvious.  weewx is a mature product, and it’s been my experience that there’s little that you guys have not encountered.  

Since it’s not unique to me, I will put together a sleepy bash script that gives it a kick 5-8 minutes after a reboot.  No doubt, I would be the only one who noticed it when looking at my website.  It’s a difference that makes no difference, but looking at a program that has been running a little longer than the server has was always a curiosity. 

That’ll give me something to do tomorrow. Thanks for confirming that you see it too on a Pi 4.  With 4 cores, the threads getting their timing wires crossed temporarily is probably as good an explanation as any.

- Paul VE1DX 

On Jun 29, 2021, at 6:35 PM, vince <vince...@gmail.com> wrote:

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[vince]

FWIW, weewx in simulator mode in a Vagrant/VirtualBox VM of Rocky Linux 8.4 shows the 'same' uptime for weewx and system, but the VM is running on my 2012 MacBook Air which is much faster than a pi4 in every way, so I'm not certain it's a fair comparison.

[Paul Dunphy]

That did the trick:

Right after reboot:

Weewx uptime: 0 days, 0 hours, 1 minute

Server uptime: 0 days, 0 hours, 0 minutes

After the script ran (I wrote it exactly as you suggested):

Weewx uptime: 0 days, 0 hours, 4 minutes

Server uptime: 0 days, 0 hours, 10 minutes

- Paul VE1DX

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[Doug Jenkins]

One thing you can do with the Raspberry Pi is to add a RealTimeClock (RTC) board. I use the RasClock 4.0 RTC for my Raspberry Pi to retain the system clock. This solves any time variances on my WeeWx data verses the system clock