Safe Replace DNSStore content and DNSZone content (#219)

Author: mosquito

aiomisc/service/dns/store.py

@@ -1,4 +1,4 @@
-from typing import Optional, Sequence, Tuple
+from typing import Iterable, Mapping, Optional, Sequence, Tuple
 
 from .records import DNSRecord, RecordType
 from .tree import RadixTree
@@ -49,3 +49,22 @@ def get_zone_for_name(self, name: str) -> Optional[Tuple[str, ...]]:
     @staticmethod
     def get_reverse_tuple(zone_name: str) -> Tuple[str, ...]:
         return tuple(zone_name.strip(".").split("."))[::-1]
+
+    def replace(
+        self, zones_data: Mapping[str, Iterable[DNSRecord]],
+    ) -> None:
+        """
+        Atomically replace all zones with new ones this method is safe
+        because it replaces all zones at once. zone_data is a mapping
+        zone name and a sequence of DNSRecord objects.
+
+        If any of the zones or records is invalid, nothing will be replaced.
+
+        This method is useful for reload configuration from disk
+        or database or etc.
+        """
+        new_zones: RadixTree[DNSZone] = RadixTree()
+        for zone_name, records in zones_data.items():
+            zone = DNSZone(zone_name, *records)
+            new_zones.insert(self.get_reverse_tuple(zone.name), zone)
+        self.zones = new_zones

aiomisc/service/dns/zone.py

@@ -1,28 +1,33 @@
 from collections import defaultdict
-from typing import DefaultDict, Sequence, Set, Tuple
+from typing import DefaultDict, Iterable, Sequence, Set, Tuple
 
 from .records import DNSRecord, RecordType
 
 
+RecordsType = DefaultDict[Tuple[str, RecordType], Set[DNSRecord]]
+
+
 class DNSZone:
-    records: DefaultDict[Tuple[str, RecordType], Set[DNSRecord]]
+    records: RecordsType
     name: str
 
     __slots__ = ("name", "records")
 
-    def __init__(self, name: str):
+    def __init__(self, name: str, *records: DNSRecord) -> None:
         if not name.endswith("."):
             name += "."
         self.name = name
         self.records = defaultdict(set)
 
+        for record in records:
+            self.add_record(record)
+
     def add_record(self, record: DNSRecord) -> None:
-        if not self._is_valid_record(record):
+        if not self.check_record(record):
             raise ValueError(
                 f"Record {record.name} does not belong to zone {self.name}",
             )
-        key = (record.name, record.type)
-        self.records[key].add(record)
+        self.records[(record.name, record.type)].add(record)
 
     def remove_record(self, record: DNSRecord) -> None:
         key = (record.name, record.type)
@@ -37,8 +42,26 @@ def get_records(
     ) -> Sequence[DNSRecord]:
         if not name.endswith("."):
             name += "."
-        key = (name, record_type)
-        return tuple(self.records.get(key, ()))
+        return tuple(self.records.get((name, record_type), ()))
 
-    def _is_valid_record(self, record: DNSRecord) -> bool:
+    def check_record(self, record: DNSRecord) -> bool:
         return record.name.endswith(self.name)
+
+    def replace(self, records: Iterable[DNSRecord]) -> None:
+        """
+        Atomically replace all records in specified zone with new ones.
+        This method is safe because it replaces all records at once.
+
+        If any of the records does not belong to the zone, ValueError
+        will be raised and no records will be replaced.
+        """
+        new_records: RecordsType = defaultdict(set)
+
+        for record in records:
+            if not self.check_record(record):
+                raise ValueError(
+                    f"Record {record.name} does not "
+                    f"belong to zone {self.name}",
+                )
+            new_records[(record.name, record.type)].add(record)
+        self.records = new_records

tests/test_dns.py

@@ -516,3 +516,111 @@ def test_sshfp_create():
     assert record.data.fp_type == 1
     assert record.data.fingerprint == b"abcdefg"
     assert record.ttl == 300
+
+
+def test_zone_replace(dns_store):
+    zone = DNSZone("example.com.")
+    record1 = A.create(name="www.example.com.", ip="192.0.2.1")
+    record2 = A.create(name="api.example.com.", ip="192.0.2.2")
+    zone.add_record(record1)
+    dns_store.add_zone(zone)
+
+    zone.replace([record2])
+
+    records = dns_store.query("www.example.com.", RecordType.A)
+    assert len(records) == 0
+    records = dns_store.query("api.example.com.", RecordType.A)
+    assert len(records) == 1
+    assert record2 in records
+
+
+def test_zone_replace_multiple_records():
+    zone = DNSZone("example.com.")
+    record1 = A.create(name="www.example.com.", ip="192.0.2.1")
+    record2 = A.create(name="www.example.com.", ip="192.0.2.2")
+
+    zone.replace([record1, record2])
+    records = zone.get_records("www.example.com.", RecordType.A)
+    assert len(records) == 2
+    assert record1 in records
+    assert record2 in records
+
+
+def test_zone_replace_empty():
+    zone = DNSZone("example.com.")
+    record = A.create(name="www.example.com.", ip="192.0.2.1")
+    zone.add_record(record)
+
+    zone.replace([])
+    records = zone.get_records("www.example.com.", RecordType.A)
+    assert len(records) == 0
+
+
+def test_zone_replace_invalid_record():
+    zone = DNSZone("example.com.")
+    record = A.create(name="www.other.com.", ip="192.0.2.1")
+
+    with pytest.raises(ValueError, match="does not belong to zone"):
+        zone.replace([record])
+
+
+def test_store_replace_basic(dns_store):
+    zone1 = DNSZone("example.com.")
+    record1 = A.create(name="www.example.com.", ip="192.0.2.1")
+    zone1.add_record(record1)
+    dns_store.add_zone(zone1)
+
+    zone2 = DNSZone("test.com.")
+    record2 = A.create(name="www.test.com.", ip="192.0.2.2")
+    zone2.add_record(record2)
+    dns_store.add_zone(zone2)
+
+    # Replace with new data
+    new_record1 = A.create(name="api.example.com.", ip="192.0.2.3")
+    new_record2 = A.create(name="api.test.com.", ip="192.0.2.4")
+
+    dns_store.replace({
+        "example.com.": [new_record1],
+        "test.com.": [new_record2],
+    })
+
+    # Check old records are gone
+    records = dns_store.query("www.example.com.", RecordType.A)
+    assert len(records) == 0
+    records = dns_store.query("www.test.com.", RecordType.A)
+    assert len(records) == 0
+
+    # Check new records are present
+    records = dns_store.query("api.example.com.", RecordType.A)
+    assert len(records) == 1
+    assert new_record1 in records
+    records = dns_store.query("api.test.com.", RecordType.A)
+    assert len(records) == 1
+    assert new_record2 in records
+
+
+def test_store_replace_empty(dns_store):
+    zone = DNSZone("example.com.")
+    record = A.create(name="www.example.com.", ip="192.0.2.1")
+    zone.add_record(record)
+    dns_store.add_zone(zone)
+
+    dns_store.replace({})
+
+    assert dns_store.get_zone("example.com.") is None
+    records = dns_store.query("www.example.com.", RecordType.A)
+    assert len(records) == 0
+
+
+def test_store_replace_multiple_records_per_zone(dns_store):
+    new_record1 = A.create(name="www.example.com.", ip="192.0.2.1")
+    new_record2 = A.create(name="www.example.com.", ip="192.0.2.2")
+
+    dns_store.replace({
+        "example.com.": [new_record1, new_record2],
+    })
+
+    records = dns_store.query("www.example.com.", RecordType.A)
+    assert len(records) == 2
+    assert new_record1 in records
+    assert new_record2 in records