iRule queries in iCall scripts?

For posterity sake. In TMOS 11.6.1 tmsh::get_field_value only shows specific resource record counts when the zone is populated, the total number of records is always shown via "db-rrs".

tmsh::get_field_value $obj "db-rrs"

Issuing show /ltm dns zone field-fmt shows the fields that are avaulable to get_field_value:

show /ltm dns zone  field-fmt
    ...
    db-rrs 18
    ...
    type-cnt.0.cnt 13
    type-cnt.0.type A
    type-cnt.1.cnt 7
    type-cnt.1.type NAPTR
    type-cnt.2.cnt 2
    type-cnt.2.type NS
    type-cnt.3.cnt 1
    type-cnt.3.type SOA
    type-cnt.4.cnt 1
    type-cnt.4.type SRV

The type-cnt fields vary per zone and thus in coding it's important to find the right field first. I initially rewrote my code to compare db-rrs to a threshold, on the principle that if a zone is populated it must have more than 2 records (the standard two name-servers). I know that there are other options but did not want to do sideband or add extra VIPs etc. This worked for me, ymmv.

I then added more in depth checking on record types, this is how I retrieve the counters:

 Clear index and counters
set idx 0; set num_a_rec 0; set num_naptr_rec 0; set num_ns_rec 0; set num_soa_rec 0; set num_srv_rec 0
 Find fields containing record counters
while {[catch {tmsh::get_field_value $obj "type-cnt.${idx}.type"} rtype] == 0} {
  if { $rtype == "A" } {
    set num_a_rec     [tmsh::get_field_value $obj "type-cnt.${idx}.cnt"]
  } elseif { $rtype == "NAPTR" } {
    set num_naptr_rec [tmsh::get_field_value $obj "type-cnt.${idx}.cnt"]
  } elseif { $rtype == "NS" } {
    set num_ns_rec    [tmsh::get_field_value $obj "type-cnt.${idx}.cnt"]
  } elseif { $rtype == "SOA" } {
    set num_soa_rec   [tmsh::get_field_value $obj "type-cnt.${idx}.cnt"]
  } elseif { $rtype == "SRV" } {
    set num_srv_rec   [tmsh::get_field_value $obj "type-cnt.${idx}.cnt"]
  }
  incr idx
}

Also I changed to iCall which is best suited to running a script at a regular interval. It's powerful but has it's own limitations. Not all things irule are supported (tables for one) and I encountered a bug (proc can't be used in an iCall script on 11.6.1 - fixed in 12.0 apparently).