Azure function time trigger crontab configuration - getting it right

 

Azure function app that uses time trigger needs to be configured correctly otherwise it will behave differently. 

The crontab with 0 */5 * * * * runs as expected. It runs every 5 minutes.

The crontab with 0 5 * * * * configuration. We notice it runs every hour instead of 5 minutes. 

You can investigate further by using NCrontab library with the following codes.

var cron = NCrontab.CrontabSchedule.Parse("5 * * * *");

var start  = DateTime.Now;

var end = DateTime.Now.AddHours(1);

var occurences =  cron.GetNextOccurrences(start, end);

foreach (var occurence in occurences)

{

    Console.WriteLine(occurence);

}

And you will notice only 1 occurrences. 

If you update it to as 0 */5 * * * *, you will typically get 11 occurrences.

var cron = NCrontab.CrontabSchedule.Parse("*/5 * * * *");

var start  = DateTime.Now;

var end = DateTime.Now.AddHours(1);

var occurences =  cron.GetNextOccurrences(start, end);

foreach (var occurence in occurences)

{

    Console.WriteLine(occurence);

}