Re: cron-type scheduling in database or sequencer?

[Maren Purves <m.purves@jach.hawaii.edu>]

Kay-Uwe Kasemir wrote:
> Hi:
>
> Both the database and the sequencer have good support for
> periodic scheduling (scan field resp. delay() routine).
> But I now have a need for scheduling things at certain times,
> for example "at 00:15 and then every 6 hours",
> meaning: run at 00:15, 06:15, 12:15 and 18:15 each day.

spawn a task?

We have the following running every UT midnight
(originally written by Nick Rees):

taskSpawn ("dhsDailyUpdate", 100, 8, 20000, dhsDailyUpdate)
(this is from the IOS's startup script)


and it does:
/* dhsDailyUpdate - task that executes once a day at 00:00 UT to update 
the file number */

void dhsDailyUpdate()
{
    time_t    timeNextUpdate = 0;
    time_t    timeNow, timeToday, timeTomorrow;
    struct tm tmNow,   tmToday,   tmTomorrow;
    int secondsDelay;

    do
    {
        /* Find the current time in time_t and struct tm formats */
        timeNow = time(NULL);
        gmtime_r( &timeNow, &tmNow );

        /* Create a tm structure and time_t which is the beginning of 
today UTC */
        tmToday = tmNow;
        tmToday.tm_hour = 0;
        tmToday.tm_min  = 0;
        tmToday.tm_sec  = 0;
        timeToday = mktime( &tmToday );

        /* Now create a tm structure and time_t which is the beginning 
of tomorrow UTC
           Note we rely on the ability of mktime to notice month and year
           changes to sort these out just from the addition of the day 
number */
        tmTomorrow = tmToday;
        tmTomorrow.tm_mday++;
        timeTomorrow = mktime( &tmTomorrow );

        /* Now update the observation number if the next update is 
before today
           (the normal occurance) or after tomorrow (indicating that a 
time error
           has occurred in the last iteration */
        if (timeNextUpdate <= timeToday || timeNextUpdate > timeTomorrow )
        {
            DHS_ID pDrv = &dhsDrv;

            dhsObsnum ( pDrv );   <--------------- or whatever you want 
it to run
            timeNextUpdate = timeTomorrow;
        }

        /* Calculate the number of seconds left in today */
        secondsDelay = 86400 - (tmNow.tm_hour*3600 + tmNow.tm_min*60 + 
tmNow.tm_sec);
        taskDelay( secondsDelay * sysClkRateGet() );
    } while (TRUE);
}


Obviously you can make it run at other times and other frequencies.

Aloha,
Maren