Use cron

[Martin Weissenboeck]

I use web2py with nginx.Now I need cron . I have read, that habe to use "-Y" to activate it. But where is the place for this option, which configuration file?

Regards, Martin

[AGRogers]

Sorry, can't help there. I have just started to use the Scheduler which is part of web2py. It was easy to setup and seems to work well. Is there a reason you can't use it? 

On Thu, 23 Jul 2020, 1:53 pm Martin Weissenboeck, <mwei...@gmail.com> wrote:

I use web2py with nginx.Now I need cron . I have read, that habe to use "-Y" to activate it. But where is the place for this option, which configuration file?

Regards, Martin

--
Resources:
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- http://web2py.com/book (Documentation)
- http://github.com/web2py/web2py (Source code)
- https://code.google.com/p/web2py/issues/list (Report Issues)
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[Martin Weissenboeck]

Yes, I could use the scheduler. But it's a very small app (only 50 lines of code) and I wanted to learn how to use cron. 

Regards, Martin

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[Dave S]

On Thursday, July 23, 2020 at 2:15:43 AM UTC-7, mweissen wrote:

Yes, I could use the scheduler. But it's a very small app (only 50 lines of code) and I wanted to learn how to use cron. 

Regards, Martin

What OS are you running on?

/dps

 

AGRogers <roge...@gmail.com> schrieb am Do., 23. Juli 2020, 10:56:

Sorry, can't help there. I have just started to use the Scheduler which is part of web2py. It was easy to setup and seems to work well. Is there a reason you can't use it? 

On Thu, 23 Jul 2020, 1:53 pm Martin Weissenboeck, <mwei...@gmail.com> wrote:

I use web2py with nginx.Now I need cron . I have read, that habe to use "-Y" to activate it. But where is the place for this option, which configuration file?

Regards, Martin

--
Resources:
- http://web2py.com
- http://web2py.com/book (Documentation)
- http://github.com/web2py/web2py (Source code)
- https://code.google.com/p/web2py/issues/list (Report Issues)
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[Martin Weissenboeck]

Ubuntu 16

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[Jose C]

Just FYI, the web2py book states:

Try to avoid web2py cron, and use a background process instead. web2py cron can start too many Python instances and cause excessive memory usage.

Using scheduler means an additional long running process using up memory to monitor and manage the scheduler.

I'd recommend using your system crontab to run any background processes.  This can be invoked within the full web2py environment (if needed) from crontab as follows:

# Runs every 5 minutes.
*/5 * * * *  python3  /path/to/web2py.py --no_gui --no-banner -S <web2py_app_name> -M -R  /path/to/process/background_process.py

HTH,

[Martin Weissenboeck]

Thank you!

Martin

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[Dave S]

On Tuesday, July 28, 2020 at 1:53:18 AM UTC-7, Jose C wrote:

Just FYI, the web2py book states:

Try to avoid web2py cron, and use a background process instead. web2py cron can start too many Python instances and cause excessive memory usage.

Using scheduler means an additional long running process using up memory to monitor and manage the scheduler.

This is a problem for you?  I've had my scheduler running on AWS and Postgres for months without issue.  I actually have a second scheduler running in sqlite3 on the same machine.  No issue.

 

I'd recommend using your system crontab to run any background processes.  This can be invoked within the full web2py environment (if needed) from crontab as follows:

# Runs every 5 minutes.
*/5 * * * *  python3  /path/to/web2py.py --no_gui --no-banner -S <web2py_app_name> -M -R  /path/to/process/background_process.py

HTH,

Things that aren't python are better run via system cron, but the scheduler does a fine job for application-related pythonic work.

/dps

 

[Jose C]

Hi Dave,

This is a problem for you?  I've had my scheduler running on AWS and Postgres for months without issue.  I actually have a second scheduler running in sqlite3 on the same machine.  No issue.

Actually it becomes more of an issue if you are on a shared server with a limited shared resources plan.  Some limit number of long running processes as well as RAM.  Also there is the extra RAM used (my scheduler process started at 35Mb and slowly crept up over time). 

Things that aren't python are better run via system cron, but the scheduler does a fine job for application-related pythonic work.

 

My main problem was I had a few situations where my main scheduler process would just completely hang on a task (not the same one each time).  Never figured out the actual cause (no errors or tickets) but I had to write a script that would periodically (run from cron ;)  ) interrogate the scheduler worker tables for last run times and status and warn me if something was out of bounds.  Fiddling with worker statuses, etc. in the tables didn't resolve the issue - I had to kill -9 the process and restart it.  This is with 2.18.5 on CentOS.  When I refactored the code to move to python3 I moved to using crontab and, with my use case, not had a single problem since.  Each task runs independently and one 'glitch' does not stop all other tasks from running which caused me some grief.