Cron jobs and timezone handling

[IgnisDa]

I have a docker container which inherits from scratch. I have an apalis cron job which is supposed to execute at 0000 hrs and 1200 hrs everyday. It does execute but at exactly 0530 hrs for me (I live in Asia/Kolkata timezone which has that offset). How can I configure apalis so that it executes at 0000 hrs of my timezone?

Setting the TZ env variable does not work, probably due to the scratch docker environment.

I'm not really sure if this problem even belongs to this repository, but would love any pointers you'd have on debugging this issue.

[geofmureithi]

Currently apalis uses UTC.
https://docs.rs/apalis-cron/latest/src/apalis_cron/lib.rs.html#108
Is it possible you play around with a custom CronStream implementation? And then you can comment here what you find out then we shall see what solution is possible.

[IgnisDa]

Any suggestions on how I can test it? My first attempt will be replace Utc::now() and load it from TZ env var using chrono_tz. But how can I actually see in what timezone offset the function is being executed?

[geofmureithi]

I think UTC is standard, and based on the machine's time settings. Are you sure that is ok?
Anyways, I will try something and get back.

[IgnisDa]

Yes that behaviour is expected. However I'm running my application in an environment which does not have the timezone database (docker scratch).

[geofmureithi]

Could you give this a try?

RUN apt-get update && apt-get install -y tzdata
ENV TZ=Your/Timezone
RUN ln -snf /usr/share/zoneinfo/$TZ /etc/localtime && echo $TZ > /etc/timezone

Not sure it will work but just throwing it out there

[geofmureithi]

I think there is a fix that can help though.
Since cron offers a chance to set the timezone,

   pub fn after_owned<Z: TimeZone>(&self, after: DateTime<Z>) -> OwnedScheduleIterator<Z> {
        OwnedScheduleIterator::new(self.clone(), after)
    }

I will offer the same functionality as here:

 pub fn to_stream_with_timezone<T: Timezone>(self) -> BoxStream { .. }

[IgnisDa]

Could you give this a try?

RUN apt-get update && apt-get install -y tzdata
ENV TZ=Your/Timezone
RUN ln -snf /usr/share/zoneinfo/$TZ /etc/localtime && echo $TZ > /etc/timezone

Not sure it will work but just throwing it out there

Can't do this since this has to be set at build time, and I want users to be able to configure it at start-time.

I think there is a fix that can help though. Since cron offers a chance to set the timezone,

   pub fn after_owned<Z: TimeZone>(&self, after: DateTime<Z>) -> OwnedScheduleIterator<Z> {
        OwnedScheduleIterator::new(self.clone(), after)
    }

I will offer the same functionality as here:

 pub fn to_stream_with_timezone<T: Timezone>(self) -> BoxStream { .. }

Yeah, looks good to me!

[geofmureithi]

Awesome, this should be fixed in the next release.
On another note, I want to make a list of projects using apalis, hope I can include ryot there :)

[IgnisDa]

Awesome, this should be fixed in the next release.

What changes would I have to make?

hope I can include ryot there :)

I would be honored!

[geofmureithi]

What changes would I have to make?

I will document a new api, it will be in the release changelog.
You will update to the new api and will possibly need to add an env variable for the timezone config

[IgnisDa]

Cool makes sense. Thanks for your prompt response.

[IgnisDa]

Hey @geofmureithi any updates on this?

[geofmureithi]

Hopefully by the end of this month. OSS doesn't pay, I still have to pay my bills you know.

[IgnisDa]

Sorry if I came off as entitled. I understand.

[geofmureithi]

Ha, not really entitled. I should have added a smile emoji at the end. (Its just that my focus has been on other projects)
You are also building OSS stuff, I know you know.
Anyways, I did not prioritise this issue because I didn't consider it blocking. But it is a straight forward one. So yeah, this will be resolved over the weekend.

[IgnisDa]

Hi @geofmureithi. Were you able to get to this?

[geofmureithi]

Here is a quick solution for your case.

trait ToStreamWithTimezone {
    fn to_stream_with_timezone(self, tz: Timezone) -> BoxStream;
}

Then implement it for CronStream.
This is a simple workaround and can unblock you until this issue is fixed.
Let me know if this helps.

[IgnisDa]

I am not able to figure out how to use it. Is there any example?

[geofmureithi]

This is how the implementation would look:

impl<J: From<DateTime<TZ>> + Job + Send + 'static, T: Timer + Sync + Send + 'static, TZ> ToStreamWithTimezone for
    CronStream<J, T>
{
   fn to_stream_with_timezone(self, tz: TZ) -> BoxStream<'static, Result<Option<JobRequest<J>>, JobError>> {
        let stream = async_stream::stream! {
            let mut schedule = self.0.upcoming_owned(tz);
            loop {
                let next = schedule.next();
                match next {
                    Some(next) => {
                        let to_sleep = next - DateTime::<TZ>::now();
                        let to_sleep = to_sleep.to_std().map_err(|e| JobError::Failed(e.into()))?;
                        self.2.sleep(to_sleep).await;
                        yield Ok(Some(JobRequest::new(J::from(DateTime::<TZ>::now()))));
                    },
                    None => {
                        yield Ok(None);
                    }
                }

            }
        };
        stream.boxed()
    }
}

Let me know if it works, I haven't tested it.

[IgnisDa]

I could not get it working: IgnisDa/ryot@ae2987f

[geofmureithi]

I could not get it working

What was the error? Let me try to run it locally.

[IgnisDa]

I could not get generics working

[geofmureithi]

@IgnisDa Please check if this solution works for you. #178

[IgnisDa]

@geofmureithi I was not able to figure out how to use it. I tried it with chrono_tz::Asia::Kolkata but it did not work.

Here are the changes I made IgnisDa/ryot@bbb8bdd.

[geofmureithi]

The compiler is telling you of a missing From<DateTime<Tz>> implementation here

impl From<DateTimeUtc> for ScheduledJob {
    fn from(value: DateTimeUtc) -> Self {
        Self(value)
    }
}

[IgnisDa]

@geofmureithi Does not work.

IgnisDa/ryot@4c09f55

[geofmureithi]

Give it a try now.

[IgnisDa]

@geofmureithi Yep this works as expected. I think it can be merged.

[IgnisDa]

@geofmureithi Could you also publish to crates.io?

[geofmureithi]

Yeah on it

[IgnisDa]

Thank you very much for fixing this issue.

[IgnisDa]

@geofmureithi Were you able to get around to publishing it?

[geofmureithi]

#181