From the documentation:
interval = [<number>|<cron schedule>]
* How often to run the specified command (in seconds), or a valid cron schedule.
* NOTE: when you specify a cron schedule, the input does not run the script on start-up.
* If you specify the interval as a number, it may have a fractional component; e.g., 3.14
* The cron implementation for data inputs does not currently support names of months or days.
* Defaults to 60.0 seconds.
* The special value 0 forces this scripted input to be run continuously; that is, as soon as the script exits, the input restarts it.
* The special value -1 causes the scripted input to run once on start-up.
There is no minimum it seems. Maybe your script is not quick enough? Or maybe look at setting it to 0; then it starts again after the command exits.
... View more