Automatic generation of SOA Serial numbers based on the modification dates of zone and records

[peteeckel]

fixes #73

This PR implements the strategy outlined in discussion #64.

Every time a zone or a record is changed in NetBox DNS, the "last_updated" field is set to the time of the change. The code submitted updates the SOA SERIAL field for a zone on every change of a record in the zone or the zone itself to an integer number representing the maximum Epoch time stamp of the zone object's and all related records' "last_updated" fields.

Special care needs to be taken in case of the deletion of records, as the operation does not change anything in the zone object, so the serial number would not change. To avoid that issue, the zone's "last_updated" field is set to the current time
every time a record belonging to the zone is deleted.

Changes to SOA records are exempt from calculating the zone's serial number to avoid the risk of endless loops (which is rather low, but still present and since the SOA record will only change when the SOA related fields in the zone change the SOA record is not interesting for the serial calculation.

There is a new setting in the PLUGINS_CONFIG field for netbox_dns: zone_soa_serial_auto can be set to a boolean value determining whether new records should have automatic SOA generation enabled or not. The default for new zones is "True".

On migration, all existing zones will have the "zone_soa_auto" flag set to "False" to provide backward compatibility and avoid data loss.

[peteeckel]

Rebased to today's main branch and ready for merging.

[hatsat32]

Hi, peter. Thanks for this great PR. May I ask you a question, please?

In the zone_edit.html file I see you changed the form field order, leave a lot of comments, and removed the tags field. I think we should keep tags field :)

If you only want to change field order we can use fieldsets in Meta class with object_edit.html template:

class XForm:
    ...
    class Meta:
    ...
        fieldsets = (
            ('Zone', ('name', 'status', 'nameservers', 'default_ttl', 'tags')),
            ('SOA', ('soa_ttl', 'soa_mname', 'soa_serial_auto', .....)),
        )

The above example is a little bit dirty but it should give you an idea.

If I am missing something just let me know.

[peteeckel]

Hi Süleyman! Thanks, you're absolutely right - the tags field got lost on the way, that certainly wasn't intended (in fact I have a PR in preparation that adds tags to one of the search fields where it was missing, so I certainly don't want to lose the tags feature anywhere).

You'll have noticed that the zone_edit.html template has been completely re-written, because the standard template didn't provide any way of optically structuring the input fields, and to provide an option of dynamically hiding and showing fields depending on, e.g. the "Generate SOA Serial" checkbox - unfortunately that's not ready yet, and currently I'm trying to get the current state usable for the first pre-production application and don't have too much time. So it's not just about ordering the fields.

And yes, the comments were left in by accident - they contain my first non-successful attempt at hiding fields dynamically. Gone now (for the time being).

I've added the missing "tags" field now.