Schedules
You can setup one or more schedules at which Moab will enqueue tasks into a queue for you. Schedules belong to a single queue only. You can continue enqueuing tasks into a queue with a schedule normally.
Schedule is set in form of a cron expression with a required timezone. Each schedule under the hood will basically
call Enqueue with parameters payload, dedupe_key, expires_in_seconds, keepalive_timeout_in_seconds, and
retry_strategy set from that schedule. payload is always the same. dedupe_key can be used to avoid a situation
when a previous task is still in the queue and has not been processed yet, but the next tick of the schedule has already
arrived (see more in Unique Tasks section). expires_in_seconds,
keepalive_timeout_in_seconds, and retry_strategy can be used to override the default values set on the queue itself.
Internally, the scheduler works periodically by looking a few minutes ahead of the schedule and enqueuing tasks with
specified scheduled_at timestamp. This way tasks appear in the queue exactly according to specified schedule,
regardless of precision and frequency at which the scheduler runs.
Cron Expressions
A complete cron expression consists of 7 segments: <second> <minute> <hour> <day> <month> <weekday> <year>. However,
just 5 will do and this is most commonly used. 5 segments are interpreted as: <minute> <hour> <day> <month> <weekday>.
In this case a default value of 0 is prepended for <second> position. In a 6 segments expression, if 6th segment
matches <year> (4 digits at least) it will be interpreted as: <minute> <hour> <day> <month> <weekday> <year>
and a default value of 0 is prepended for <second> position.
- For each segment you can have multiple choices separated by comma:
0 0,30 * * * *means either 0th or 30th minute. - To specify range of values you can use dash:
0 10-15 * * * *means 10th, 11th, 12th, 13th, 14th and 15th minute. - To specify range of step you can combine a dash and slash:
0 10-15/2 * * * *means every 2 minutes between 10 and 15, i.e 10th, 12th and 14th minute. - For the
<day>and<weekday>segment, there are additional modifiers (optional):- Day of Month (3rd of 5 segments or 4th of 6+ segments):
Lstands for last day of month (Lcould mean 29th for February in leap year)Wstands for closest week day (10Wis the closest week days (MON-FRI) to 10th date)
- Day of Week (5th of 5 segments or 6th of 6+ segments):
Lstands for last weekday of month (2Lis last tuesday)#stands for nth day of week in the month (1#2is second monday)
- Day of Month (3rd of 5 segments or 4th of 6+ segments):
- You can mix the multiple choices, ranges and steps in a single expression:
0 5,12-20/4,55 * * * *matches if any one of 5 or 12-20/4 or 55 matches the minute.