evict entries continuously from seen_unfinished_blocks (#17207)

remove entries from the seen-unfinished-blocks cache continuously, rather than emptying it periodically

chia/full_node/full_node.py

@@ -1598,7 +1598,6 @@ class FullNode:
 
         if record.height % 1000 == 0:
             # Occasionally clear data in full node store to keep memory usage small
-            self.full_node_store.clear_seen_unfinished_blocks()
             self.full_node_store.clear_old_cache_entries()
 
         if self.sync_store.get_sync_mode() is False:

chia/full_node/full_node_store.py

@@ -45,8 +45,11 @@ class FullNodeStore:
     candidate_blocks: Dict[bytes32, Tuple[uint32, UnfinishedBlock]]
     candidate_backup_blocks: Dict[bytes32, Tuple[uint32, UnfinishedBlock]]
 
-    # Header hashes of unfinished blocks that we have seen recently
-    seen_unfinished_blocks: Set[bytes32]
+    # Block hashes of unfinished blocks that we have seen recently. This is
+    # effectively a Set[bytes32] but in order to evict the oldest items first,
+    # we use a Dict that preserves insertion order, and remove from the
+    # beginning
+    seen_unfinished_blocks: Dict[bytes32, None]
 
     # Unfinished blocks, keyed from reward hash
     unfinished_blocks: Dict[bytes32, Tuple[uint32, UnfinishedBlock, PreValidationResult]]
@@ -86,10 +89,12 @@ class FullNodeStore:
     serialized_wp_message: Optional[Message]
     serialized_wp_message_tip: Optional[bytes32]
 
+    max_seen_unfinished_blocks: int
+
     def __init__(self, constants: ConsensusConstants):
         self.candidate_blocks = {}
         self.candidate_backup_blocks = {}
-        self.seen_unfinished_blocks = set()
+        self.seen_unfinished_blocks = {}
         self.unfinished_blocks = {}
         self.finished_sub_slots = []
         self.future_eos_cache = {}
@@ -108,6 +113,7 @@ class FullNodeStore:
         self.tx_fetch_tasks = {}
         self.serialized_wp_message = None
         self.serialized_wp_message_tip = None
+        self.max_seen_unfinished_blocks = 1000
 
     def add_candidate_block(
         self, quality_string: bytes32, height: uint32, unfinished_block: UnfinishedBlock, backup: bool = False
@@ -148,12 +154,13 @@ class FullNodeStore:
     def seen_unfinished_block(self, object_hash: bytes32) -> bool:
         if object_hash in self.seen_unfinished_blocks:
             return True
-        self.seen_unfinished_blocks.add(object_hash)
+        self.seen_unfinished_blocks[object_hash] = None
+        if len(self.seen_unfinished_blocks) > self.max_seen_unfinished_blocks:
+            # remove the least recently added hash
+            to_remove = next(iter(self.seen_unfinished_blocks))
+            del self.seen_unfinished_blocks[to_remove]
         return False
 
-    def clear_seen_unfinished_blocks(self) -> None:
-        self.seen_unfinished_blocks.clear()
-
     def add_unfinished_block(
         self, height: uint32, unfinished_block: UnfinishedBlock, result: PreValidationResult
     ) -> None:

tests/core/full_node/stores/test_full_node_store.py

@@ -114,7 +114,9 @@ async def test_basic_store(
     h_hash_1 = bytes32.random(seeded_random)
     assert not store.seen_unfinished_block(h_hash_1)
     assert store.seen_unfinished_block(h_hash_1)
-    store.clear_seen_unfinished_blocks()
+    # this will crowd out h_hash_1
+    for _ in range(store.max_seen_unfinished_blocks):
+        store.seen_unfinished_block(bytes32.random(seeded_random))
     assert not store.seen_unfinished_block(h_hash_1)
 
     # Add/get unfinished block