From fc39697bddd6149ca50a0f7f11b3e47ca5e235d3 Mon Sep 17 00:00:00 2001
From: Viranch Mehta <email@viranch.me>
Date: Mon, 16 Aug 2021 20:33:22 -0700
Subject: [PATCH] consider only first PTR value for getting changes

---
 octodns/manager.py       | 26 ++------------------------
 octodns/provider/base.py | 32 +++++++++++++++++++++++++++++++-
 2 files changed, 33 insertions(+), 25 deletions(-)

diff --git a/octodns/manager.py b/octodns/manager.py
index a991b4b..104e445 100644
--- a/octodns/manager.py
+++ b/octodns/manager.py
@@ -294,30 +294,8 @@ class Manager(object):
             for processor in processors:
                 plan = processor.process_plan(plan, sources=sources,
                                               target=target)
-            if not plan:
-                continue
-
-            # Multi value PTR check
-            for change in plan.changes:
-                record = change.new
-                if not record:
-                    # Delete - doesn't need to be checked
-                    continue
-
-                if record._type == 'PTR' and len(record.values) > 1 and not \
-                   target.SUPPORTS_MUTLIVALUE_PTR:
-                    self.log.warn('target=%s does not support multi-value PTR '
-                                  'record %s; using %s as its only answer',
-                                  target, record.fqdn, record.value)
-                    # Make a new copy of the record so as to not change a
-                    # potentially shared object
-                    change.new = Record.new(record.zone, record.name, {
-                        'type': record._type,
-                        'ttl': record.ttl,
-                        'value': record.value,
-                    }, source=record.source, lenient=lenient)
-
-            plans.append((target, plan))
+            if plan:
+                plans.append((target, plan))
 
         # Return the zone as it's the desired state
         return plans, zone
diff --git a/octodns/provider/base.py b/octodns/provider/base.py
index 729c9ee..fcb557a 100644
--- a/octodns/provider/base.py
+++ b/octodns/provider/base.py
@@ -7,6 +7,7 @@ from __future__ import absolute_import, division, print_function, \
 
 from six import text_type
 
+from ..record import Record
 from ..source.base import BaseSource
 from ..zone import Zone
 from .plan import Plan
@@ -44,6 +45,35 @@ class BaseProvider(BaseSource):
         '''
         return []
 
+    def _process_change(self, change):
+        '''
+        Process/manipulate each change for feature-specific corner cases
+        '''
+        if not self._include_change(change):
+            return False
+
+        # Multi value PTR records
+        record = change.new
+        if record and record._type == 'PTR' and len(record.values) > 1 and \
+           not self.SUPPORTS_MUTLIVALUE_PTR:
+            # replace with a single-value copy
+            change.new = Record.new(record.zone, record.name, {
+                'type': 'PTR',
+                'ttl': record.ttl,
+                'values': [record.value],
+            }, source=record.source)
+
+            existing = change.existing
+            if existing and not existing.changes(change.new, self):
+                # if new single-value replacement turns out to be the same,
+                # skip the change
+                return False
+
+            self.log.warn('does not support multi-value PTR records; will '
+                          'use only %s for %s', record.value, record.fqdn)
+
+        return True
+
     def plan(self, desired, processors=[]):
         self.log.info('plan: desired=%s', desired.name)
 
@@ -63,7 +93,7 @@ class BaseProvider(BaseSource):
 
         # allow the provider to filter out false positives
         before = len(changes)
-        changes = [c for c in changes if self._include_change(c)]
+        changes = [c for c in changes if self._process_change(c)]
         after = len(changes)
         if before != after:
             self.log.info('plan:   filtered out %s changes', before - after)