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cron expresion to run a JIRA service every other Wednesday

Tomas Arguinzones Yahoo

Hi...I have a JIRA service that I need to run every other Wednesday at 11:59 PM...I have been searching and apparently is not as easy as it sounds, since I have to create some kind of expression within the cron expression. The following cron expression: 0 59 23 ? * 4 will run every Wednesday at 11:59 PM and I need it to run every other Wednesday at 11:59 PM. Somehow I have to "divide" the nth week of the year by 2 and if the remaining is 1 then that means the script should run that Wednesday. For instance, the script should run the first Wednesday of the year, then the third Wednesday, then the fifth Wednesday and so on. How do I write an expression like that in the cron expression field in the Service section in JIRA?

Thanks

Accepted answers

crf

The short answer is that you can't. The cron expression syntax just isn't powerful enough to support that.

All comments

crf

The short answer is that you can't. The cron expression syntax just isn't powerful enough to support that.

crf

Longer answer:

Both Quartz (the scheduler that JIRA used to use) and Caesium (what I wrote to replace it) evaluate the cron expression by parsing it to a set of matching conditions and then tweaking what the current time is to figure out when it will next match. Quartz does this using a TreeSet of accepted integer values (pretty silly for the year field!) and Caesium has a more flexible rule-based implementation, but the expression language is identical (except that Caesium's implementation has a lot fewer bugs in it).

But other than the fact that the day-of-week value depends on the year, month, and day values, these fields are all evaluated more or less independently. When what you want involves an interaction between multiple fields that involves an OR condition or on knowledge of some flip-flopping state, there just isn't any way to say it.

For example, there is no way to say "run this job every 90 minutes". I've seen people attempt to do this by writing something like "0 0/90 * * * ?" and Quartz actually accepts this as valid, but it does not do what you wanted. Due to how the "0/90" is actually interpreted, it ends up exactly the same as just saying "0", and the job runs every hour instead of every 90 minutes.

For that specialized case, you can awkwardly work around the problem by creating multiple rules that fill in the gaps. For example, by combining:

0 0 */3 * * ? – to get the ones that fall on the hour
0 30 1/3 * * ? – to get the ones that fall on half-hour marks

But since there can occasionally be an odd number of Wednesdays in a month, there isn't any way to use this same strategy. You could get, say, the first and third Wednesday, but it would take 3 weeks instead of 2 when one of the months has an odd number of them.

Tomas Arguinzones Yahoo

Hi Chris...thank you for your detailed answer...so the question is, how do I run my JIRA service every other Wednesday? This is an script done in ScriptRunner so should I put the condition in the script itself? and If so, should I set the cron expression in the Interval field in JIRA to

0 59 23 ? * 4 (like it will execute every Wednesday at 11:59 PM) and then the condition in the script would decide whether that Wednesday the script should run or not?

Thank you for your assistance

crf

That sounds like a sensible plan, yes. The only problem is figuring out whether this is a time to run or a time to ignore it. Here are a few ideas:

You could save whether or not it ran last time (say, in a property set or plugin settings) and do the opposite. The only problem with this is that it relies on the job definitely running every other week, which wouldn't necessarily be true if you had extended downtime or restored from a backup.
You could calculate for yourself when the next time to run is, store that somewhere, and refuse to run unless it's actually that time (or close enough that clock skew and daylight savings won't cause trouble).

If I had to solve this problem, I think I would take the second path, and the logic would look something like this:

long now = System.currentTimeMillis();
long stored = Optional.ofNullable(getStoredTime()).orElse(0L);
if (now &lt; stored) {
    // too soon; wait for the next one
    return;
}
 
long later = Instant.now().plus(13, ChronoUnit.DAYS).toEpochMilli();
setStoredTime(later);
// run the job

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