This is a proposal of new Knot feature: a system of (named) pipes, as a substitute for direct calling of user scripts from knotd process.
The user might want to call a script when an event occurs. First motivation for this is publishing CDS/CDNSKEY records - the user shall react with updating DS record at the parent zone.
The configuration might look like follows:
event: - fifo: /my/scripts/knot_hok_ds.fifo action: publish_ds
and the user script like this:
cat /my/scripts/knot_hok_ds.fifo | while read x; do perform_action "$x" done
Some notes to this solution:
- this avoids
popen()calls by knotd which are known to be very evil
- this avoids active waiting at the script side (would be harmful if many zones)
O_NONBLOCKhas to be used at knotd side. If no script is listening on the configured fifo, knot just logs a warning
- just one script can listen at a fifo. However, it is possible to configure more fifos for any set of possible event actions
- the emitted action request consists of a single line (terminated with
\n), with fields separated by colon
:, fields are: zone, action type, data ... do we need a timestamp?? can colon conflict with zone name or data???