timeToNextExecution returns Duration evaluates to 0 about cron-utils HOT 3 CLOSED

@greenlaw110 thank you for reporting this!
Could you please provide the cron expression you are using to execute the code, and perhaps a test that reproduces the issue? Thank you in advance!

from cron-utils.

Actually any cron expression lead to the same result. That's because the pattern I've used to applying cron-util. As you see schedule method is executed right at the time cron task should invoke (actually just invoked), thus you want to get the timeToNextExecution exactly when it's due to execution, the library returns 0, which is the timeToCurrentExecution. I end up with something like following to workaround the issue:

void schedule(AppJobManager manager, _Job job) {
    DateTime now = DateTime.now();
    ExecutionTime executionTime = ExecutionTime.forCron(cron);
    Duration nextExecution = executionTime.timeToNextExecution(now.withDurationAdded(1, 1));
    long seconds = nextExecution.getStandardSeconds();
    int times = 1;
    while (seconds == 0) {
        nextExecution = executionTime.timeToNextExecution(now.withDurationAdded(1, times++));
        seconds = nextExecution.getStandardSeconds();
    }
    manager.executor().schedule(job, seconds, TimeUnit.SECONDS);
}

from cron-utils.

@greenlaw110 I tried to reproduce the issue, but I do not get the issue.
If you have too short intervals, then you will get zero seconds; depending on the cron expression you consider. But if you invoke nextExecution.getMillis(), you may notice that time to next execution decreases accurately.

Also looking at different cron setups, returns accurate results, where Duration interval to next execution is not zero seconds. Example: using the following code, you get a non-zero value most of time.

ExecutionTime executionTime = ExecutionTime.forCron(quartzCronParser.parse("5 * * * * *"));
DateTime now = DateTime.now();
Duration nextExecution = executionTime.timeToNextExecution(now);
long seconds = nextExecution.getStandardSeconds();

Please validate and let us know the result. Will be happy to help on it.

from cron-utils.