Authoritative slave w/ bindbackend reports confusing error for new zones (yet works fine)

[gertvdijk]

• Program: Authoritative
• Issue type: Bug report

Short description

The Bind zone file backend on a slave reports "error" for new domains, while everything is actually OK.

Environment

• Operating system: Debian Stretch
• Software version: 4.1.8-1pdns.stretch
• Software source: PowerDNS repository

Steps to reproduce

1. Set up a master authoritative server, allow AXFR etc.
2. Connect a slave with the BIND backend. e.g. with a bindbackend.conf such as:

   zone "mydomain.tld" {
       type slave;
       file "mydomain.tld.db";
       masters { 10.1.2.3; };
   };

3. The slave will now start the initial AXFR for the new zone.

4. The logs indicate OK in the end, but note the error on line 3.

   [bindbackend] Parsing 1 domain(s), will report when done
   Master/slave communicator launching
   [bindbackend] error at 2019-03-28 16:23:18 +0000 no file found for new slave domain 'mydomain.tld'. Has not been AXFR'd yet
   [bindbackend] Done parsing domains, 1 rejected, 1 new, 0 removed
   About to create 3 backend threads for UDP
   1 slave domain needs checking, 0 queued for AXFR
   Received serial number updates for 1 zone, had 0 timeouts
   Domain 'mydomain.tld' is stale, master serial 1, our serial 0
   Initiating transfer of 'mydomain.tld' from remote '10.1.2.3'
   Starting AXFR of 'mydomain.tld' from remote 10.1.2.3:53
   AXFR started for 'mydomain.tld'
   AXFR of 'mydomain.tld' from remote 10.1.2.3:53 done
   Backend transaction started for 'mydomain.tld' storage
   Zone 'mydomain.tld' (bind-zones/mydomain.tld.db) reloaded
   AXFR done for 'mydomain.tld', zone committed with serial number 1
   Done launching threads, ready to distribute questions

Expected behaviour

Not report an error for a precondition that's not met by expectation as indicated in the same line (Has not been AXFR'd yet).

Actual behaviour

Unnecessary "error" message that indicates this it is fine:

[bindbackend] error at \<time> no file found for new slave domain 'mydomain.tld'. Has not been AXFR'd yet

Other information

n/a, explained in previous sections.

[gertvdijk]

Oh, I just found #3051 (#2405), which should have fixed it. Is it a regression?