Automatic Pruning

The following functions are available to set, modify, and read the pruning schedule:

// Set a pruning schedule with a duration and a retention period.
pruning.set_schedule("0 0 8 ? * SAT", 8.hours, 90.days)

// Retrieve the current pruning schedule returning `None` if no schedule is set.
val pruningSchedule = pruning.get_schedule()

// Set individual fields to modify the existing pruning schedule.
pruning.set_cron("0 /5 * * * ?")
pruning.set_retention(30.days)
pruning.set_max_duration(2.hours)

// Clear the pruning schedule disabling automatic pruning on a specific node.
pruning.clear_schedule()

Refer to the cron specification to customize the pruning schedule. Here are a few examples:

// Prune every evening at 8pm GMT for two hours
set_schedule("0 0 20 * * ?", 2.hours, retention)

// Prune every 5 minutes for one minute
set_schedule("0 /5 * * * ?", 1.minute, retention)

// Prune for one specific day
set_schedule("0 0 0 31 12 ? 2025", 1.day, retention)

For the maximum duration to specify a reliable pruning window end time, the leading fields of the cron expression must not be wildcards (*), as illustrated in the preceding examples. If the hour field is fixed, the fields for the minute and the second must be fixed too.

Schedule format

Cron expressions are formatted as seven whitespace-separated fields:

Field	Type and valid values*
seconds	number from 0 to 59
minutes	number from 0 to 59
hours	number from 0 to 23
day of the month	number from 1 to 31
month	number from 0 to 11 (0 = January) or the first three letters of the month name (JAN, FEB, MAR, etc)
day of the week	number from 1 to 7 (1 = Sunday) or the first three letters of the day name (SUN, MON, TUE, etc)
year (optional)	number from 1900 to 2099

*Ranges specified with “from .. to ..” are inclusive of both endpoints.

Note that, although a day-of-the-month value might be valid according to the preceding definition, it might not correspond to an actual date in certain months (such as the thirty-first of November). If you schedule pruning for the thirty-first of the month, every month with fewer than 31 days is skipped.

Advanced schedule formatting

• You can construct lists and ranges of values. For example, the day of the week could be a range like MON-FRI to refer to the days Monday through Friday, or TUE,FRI to refer to Tuesday and Friday exclusively. Or you could use a mix of both, for example, MON,WED-FRI, meaning “Monday, and also Wednesday through Friday.”

• Use the asterisk (*) as a wildcard that means “all possible values.”

• Use the question mark (?) as a wildcard that means “any value” in the day-of-the-month and day-of-the-week fields. For example, to specify “every Monday at noon,” use the ? character to indicate that any day of the month is valid: 0 0 12 ? * MON

• To apply increments to numeric values, use the slash character (/). For example, a value of 1/2 in the hours field means “every two hours starting from 1 AM” (1 AM, 3 AM, 5 AM, etc).

Here are some examples of valid schedules:

• 0 30 * * * * Every hour at half past

• 0 5/15 12,18-20 * * * Every fifteen minutes, starting from five past, at noon and from 6 to 8 PM

• 0 5/15 12,18-20 ? * MON,THU Same as above, but only on Mondays and Thursdays

• 0 0 22 1 * ? Every first day of the month at 10 PM

For more information about cron expressions, see the Apache Log4j API documentation.