Add rollback logic when db update fails after DNS changes

src/ddns_service/server.py

@@ -452,14 +452,29 @@ class DDNSRequestHandler(BaseHTTPRequestHandler):
 
         return hostname
 
+    def _rollback_dns(self, hostname, old_ip, record_type):
+        """Roll back a DNS record to its previous value."""
+        try:
+            if old_ip:
+                self.app.dns_service.update_record(
+                    hostname.hostname, hostname.zone,
+                    old_ip, hostname.dns_ttl)
+            else:
+                self.app.dns_service.delete_record(
+                    hostname.hostname, hostname.zone, record_type)
+        except Exception as e:
+            logging.error(f"DNS rollback failed ({record_type}): {e}")
+
     def _process_ip_update(self, client_ip, user, hostname, ipv4, ipv6, notify_change):
         """Process IP update for hostname."""
         now = now_utc()
 
+        old_ipv4 = hostname.last_ipv4
+        old_ipv6 = hostname.last_ipv6
         ipv4_changed = False
         ipv6_changed = False
+
         if ipv4:
-            hostname.last_ipv4_update = now
             if ipv4 != hostname.last_ipv4:
                 # Update DNS IPv4 record
                 try:
@@ -469,10 +484,8 @@ class DDNSRequestHandler(BaseHTTPRequestHandler):
                         ipv4,
                         hostname.dns_ttl
                     )
-                    hostname.last_ipv4 = ipv4
                     ipv4_changed = True
                 except Exception as e:
-                    hostname.save()
                     logging.error(f"DNS error: {e}")
                     raise DDNSError(
                         "Update failed",
@@ -484,7 +497,6 @@ class DDNSRequestHandler(BaseHTTPRequestHandler):
                     )
 
         if ipv6:
-            hostname.last_ipv6_update = now
             if ipv6 != hostname.last_ipv6:
                 # Update DNS IPv6 record
                 try:
@@ -494,11 +506,12 @@ class DDNSRequestHandler(BaseHTTPRequestHandler):
                         ipv6,
                         hostname.dns_ttl
                     )
-                    hostname.last_ipv6 = ipv6
                     ipv6_changed = True
                 except Exception as e:
-                    hostname.save()
                     logging.error(f"DNS error: {e}")
+                    # Roll back IPv4 DNS if it was changed
+                    if ipv4_changed:
+                        self._rollback_dns(hostname, old_ipv4, "A")
                     raise DDNSError(
                         "Update failed",
                         STATUS_DNSERR,
@@ -508,8 +521,32 @@ class DDNSRequestHandler(BaseHTTPRequestHandler):
                         ipv6=ipv6
                     )
 
+        if ipv4_changed:
+            hostname.last_ipv4 = ipv4
+            hostname.last_ipv4_update = now
+        if ipv6_changed:
+            hostname.last_ipv6 = ipv6
+            hostname.last_ipv6_update = now
+
         # Update database
-        hostname.save()
+        try:
+            hostname.save()
+        except DatabaseError as e:
+            logging.error(
+                f"DB save failed after retries: hostname={hostname.hostname} "
+                f"zone={hostname.zone}: {e}"
+            )
+            if ipv4_changed:
+                self._rollback_dns(hostname, old_ipv4, "A")
+            if ipv6_changed:
+                self._rollback_dns(hostname, old_ipv6, "AAAA")
+            raise DDNSError(
+                "Update failed",
+                STATUS_DNSERR,
+                client=client_ip,
+                hostname=hostname.hostname,
+                zone=hostname.zone
+            )
 
         changed_addrs = ""
         if ipv4_changed: