[Freeipa-devel] Structured DNS record API proposal

[Martin Kosek]

On Tue, 2011-09-20 at 11:22 -0500, Endi Sukma Dewata wrote:
> On 9/20/2011 6:15 AM, Martin Kosek wrote:
> >>> ACK.  Proposal looks like it will work fairly easily with the UI.
> >>> We'll have to make some chagnes due to the Add doing something
> >>> different based on the type, but that is the case anyway.
> >>
> >> Yes, I was thinking how can we integrate this new API to WebUI. AFAIK
> >> you use dnsrecord-add $ZONE $REC --a-rec=... --mx-rec=... for adding a
> >> new DNS record and dnsrecord-mod $ZONE $REC --mx-rec=... when for
> >> example the mx record is being modified. All MX values (even the
> >> unmodified ones) are passed to dnsrecord-mod.
> >>
> >> 1) I was wondering how the new dnsrecord-<rrtype>-add commands can be
> >> used. I suppose WebUI will know a list of DNS record types with these
> >> new structured commands and offer the user new window to add a record
> >> for these types instead of typing them directly to the text box as it is
> >> now.
> 
> When adding a DNS record the user will specify the name and the type, 
> then the UI will show a set of fields based on the selected record type.
> 
> So instead of a generic 'data' field like below (click Add):
> 
> http://edewata.fedorapeople.org/freeipa/install/ui/index.html#dns=dnszone&identity=dns&navigation=identity&dnszone-facet=default&dnszone-pkey=ayoung.boston.devel.redhat.com
> 
> it will be similar to Permissions (click Add):
> 
> http://edewata.fedorapeople.org/freeipa/install/ui/index.html#rolebased=permission&ipaserver=rolebased&navigation=ipaserver
> 
> The UI will use the type to pick the correct dnsrecord-<rrtype>-add 
> command and each parameter in that command will have a corresponding 
> field to enter the value.

Yes, I think this will work fine. Would it make sense to create
dnsrecord-<rr-type>-add commands also for non-structured DNS records? I
mean for example for A, AAAA, PTR, CNAME, ... record, which have just
one simple value or let plain old dnsrecord-add --a-rec=... handle it?

> 
> >> 2) But my main concern here is how the modification of current DNS
> >> records should work. Say, we have 2 MX records for example.com. How can
> >> we modify one of it in a new structured interface?
> >>
> >> We would have to implement dnsrecord-mx-show method so that you can fill
> >> all the text areas (preference, mailserver). Question is how to refer
> >> the value we want to show since DNS records are multivalued. We could
> >> pass --dnsrecord="..." with DNS record value, e.g. "0 mx.example.com."
> >> and then use the same value for dnsrecord-mx-mod. The whole command
> >> sequence would look this way:
> >>
> >> dnsrecord-find example.com      -- get all DNS records for example.com
> >> dnsrecord-show example.com @    -- show DNS records directly in the zone
> >> NS: "ns.example.com"
> >> MX: "0 mx1.example.com."
> >> MX: "1 mx2.example.com."<<  user wants to modify this one ->  new window
> 
> I think for each record value the primary keys are the zone name, record 
> name, and the value itself. To simplify operations, we should use the 
> value as a single string. For CLI, users can copy & paste the value more 
> easily.

Agreed. As Adam Tkac suggested, we can simplify this with interactive
prompt so that user doesn't have to copy&paste, but just choose a record
to -show/-mod.

> 
> For UI it depends whether (1) we're going to keep the current edit page 
> where all records with the same name are considered a single entry, or 
> whether (2) we're going to edit each record value in a separate page. 
> See ticket #1478.
> 
> If we stay with (1), the link to the edit page consists of zone name and 
> record name only. But if we pick (2) the link consists of zone name, 
> record name, value, and type (which can be obtained from -find output).

This is more of a UXD decision, server API will remain intact. I just
see 2 issues here:

1) If you let user edit multiple structured DNS records, you would have
to call dnsrecord-<rr-type>-show multiple times so that you can populate
all the fields. This can slow down things.

2) Some DNS records may be pretty large. MX record data is small, but
for example CERT records have an entire certificate stored in it.
Wouldn't there be a problem if we place the large DNS record in URL?

> 
> >> dnsrecord-mx-show example.com --dnsrecord="1 mx1.example.com."
> >> PREFERENCE: 1	<<  user modifies this to 0
> >> MAILSERVER: mx2.example.com.
> 
> For consistency, the record value should be specified as an argument 
> instead of an option (like in automount). So it will be like this:
> 
> dnsrecord-mx-show "example.com" "@" "1 mx1.example.com."
> PREFERENCE: 1
> MAILSERVER: mx2.example.com

This can be done.

> 
> If we stay with (1) the UI will have to call the dnsrecord-<rrtype>-show 
> for each value to get the value of each fields. The UI will need to 
> implement a new widget (or section) that can handle multiple fields 
> which will be duplicated for each value.

Ah, yes - as I wrote above. This would also take more time to process.

> 
> The edit page for (2) is much simpler since it only needs to handle a 
> single type at a time. The output of the -show command will be used to 
> populate each field.
> 
> >> dnsrecord-mx-mod example.com --dnsrecord="1 mx1.example.com." --preference=0
> 
> When updating the value, option (1) is a bit more complicated because 
> the UI will have to find the dirty record and then find the dirty field. 
> Option (2) is simpler because it will only need to find the dirty field, 
> but both will execute the following command:
> 
> dnsrecord-mx-mod "example.com" "@" "1 mx1.example.com." --preference=0
> 
> I think option (2) is more clear to users because we only have to 
> introduce 2 concepts: zone and record (which is the individual value). 
> With option (1) we will have to explain the underlying LDAP entry that 
> will be deleted automatically when the last record value is deleted.
> 

When I look at it, option (2) looks better for our case.

Martin