Cron-like way of scheduling tasks in TGScheduler

[bochecha]

Attached is a patch to add a new way of creating a task in the TGScheduler : a cron-like task.

This new Task class takes one parameter different from other Task classes: a string written in cron-like syntax.

This allows to schedule jobs with complex scheduling. For example, one might want to run a job every 15 minutes on business days during the working hours:

def hello():
    print "Hello World!"

cron_str = "*/15 8-12,14-18 * * MON-FRI"

task = add_cron_like_task(hello, cron_str, taskname="hello")

If this patch is accepted, I'll also update the documentation at  http://docs.turbogears.org/TGScheduler

Note: this patch introduces a new dependency on python-dateutil for TGScheduler.

[bochecha]

I just updated the patch to take into account your latest commits.

[bochecha]

Any news? Could someone review this patch?

FYI, we just deployed it in production and are pretty happy with it for now. Using a non-patched version of TGScheduler would be a big win of course, and I'll keep updating this patch with fixes we make for issues we would encounter on our setup. :)

[Chris Arndt]

I forwarded this to the current maintainer and asked him to comment on the patch.

[bochecha]

Looks like this wasn't the best day to comment on this patch again. :)

I just found an issue in python-dateutil.

Basically, if one of the parameters of the cron string is 0, then scheduler will go in an infinite loop and launch the task again and again and again and...

For example, if one schedules a task at 8:00 every day with the string 0 8 * * *, the issue is triggered.

I guess accepting this patch in TGScheduler will have to wait for the upstream issue to be resolved. :(

[vinces1979]

OK sorry for the delay in responding, I like the cron style scheduling and I can implement when this bug is fixed or a work around is found.

Please keep us updated, and thanks!

[bochecha]

Replying to vinces1979:

OK sorry for the delay in responding, I like the cron style scheduling and I can implement when this bug is fixed or a work around is found.

I just mailed the  python-dateutil maintainer (I couldn't find any bug tracker) with 2 patches for the issue.

This will need a trivial change to the TGScheduler patch afterwards.

I'll be running with patched dateutil and TGScheduler for now, which will hopefully provide some more testing.

However I'd rather not update the patch here for now, as I'm not sure it is a good idea to have TGScheduler depend on a privately patched version of dateutil.

Please keep us updated, and thanks!

I will.

[vinces1979]

Replying to bochecha:

Replying to vinces1979:

OK sorry for the delay in responding, I like the cron style scheduling and I can implement when this bug is fixed or a work around is found.

I just mailed the  python-dateutil maintainer (I couldn't find any bug tracker) with 2 patches for the issue.

This will need a trivial change to the TGScheduler patch afterwards.

I'll be running with patched dateutil and TGScheduler for now, which will hopefully provide some more testing.

However I'd rather not update the patch here for now, as I'm not sure it is a good idea to have TGScheduler depend on a privately patched version of dateutil.

Please keep us updated, and thanks!

I will.

Sounds good thanks!

[bochecha]

My patch was accepted in python-dateutil and Gustavo made a new release.

Attached is an updated version of the cron-like patch, adapted to this new dateutil release and fixing the aforementioned bug.

[vinces1979]

Replying to bochecha:

My patch was accepted in python-dateutil and Gustavo made a new release.

Attached is an updated version of the cron-like patch, adapted to this new dateutil release and fixing the aforementioned bug.

Thanks bochecha,

I will run over patch and test myself, and if all goes well I will push out a new release shortly

Vince

[bochecha]

In case you want to try it out, here's the what I'm planning on adding to  the documentation page:

``add_cron_like_task``
    Pass in ``cron_str`` with a string representing the scheduling in a
	cron-like syntax.

	For example, a task that needs to be executed every 15 minutes on working
	days / hours will be expressed as ``*/15 8-12,14-18 * * 1-5``

	Note:

		* just like with ``Cron``, week starts by a ``0`` on Sunday
		* months and days of week can alternatively be specified by the first 3
		letters of their name, case-insensitively. For example:
			* ``3`` is the same as ``WED``
			* ``1-5`` is the same as ``mon-fri``
		* months and days of week can be specified either by their number or the
		first 3 letters of their name, not both:
		    * ``JAN-12`` will raise an exception

[vinces1979]

pushed crontab2.patch into trunk, I will setup some extra tests and if everything goes good I will release 1.6 tomorrow

[vinces1979]

Replying to vinces1979:

pushed crontab2.patch into trunk, I will setup some extra tests and if everything goes good I will release 1.6 tomorrow

patched in r7059

[vinces1979]

All tests ran fine, I pushed out 1.6 to pypi this morning

[bochecha]

I just realized I could have done a much better job at documenting the usage of the CronLikeTask? class.

Here is a patch providing a nice rst documentation.

It's based on the Linux crontab(5) man page, as they already did a wonderful job at documenting Cron. :)

[bochecha]

Vince, any news?

Maybe I should have opened a new ticket?

[bochecha]

Is anybody here?

I submit an updated patch that applies on the current trunk.

[bochecha]

imprved docstring

[vinces1979]

Thanks for the patch I will review and merge into trunk

[chrisz]

Merged in to tgscheduler and tg1.1 in r7124 and r7126.