synchronizer: rm redundant get_history call if new block mined unconf

SomberNight · SomberNight · commit 6d016d70eee6 · 2025-11-03T15:44:02.000Z
This is an optimisation and possible hardening against traffic analysis.

After a new block is mined, we sometimes receive "blockchain.scripthash.subscribe" notifications. If so, this is often due to the just mined block including mempool txs we already knew about.

Normally we would call the "blockchain.scripthash.get_history" RPC, to get full history of the affected scripthash.
Instead now we first optimistically guess that all mempool txs touching this scripthash just got mined and see if by assuming that we can reproduce the announced sh status.
- if yes, we saved a network RTT by not having to call "blockchain.scripthash.get_history"
- if no, we request the history from the server using the RPC
diff --git a/electrum/synchronizer.py b/electrum/synchronizer.py
@@ -160,7 +160,18 @@ def is_up_to_date(self):
                 and not self._stale_histories
                 and self.status_queue.empty())
 
-    async def _maybe_request_history_for_addr(self, addr: str) -> List[dict]:
+    async def _maybe_request_history_for_addr(self, addr: str, *, ann_status: Optional[str]) -> List[dict]:
+        # First opportunistically try to guess the addr history. Might save us network requests.
+        old_history = self.adb.db.get_addr_history(addr)
+        def guess_height(old_height: int) -> int:
+            if old_height in (0, -1,):
+                return self.interface.tip  # maybe mempool tx got mined just now
+            return old_height
+        guessed_history = [(txid, guess_height(old_height)) for (txid, old_height) in old_history]
+        if history_status(guessed_history) == ann_status:
+            self.logger.debug(f"managed to guess new history for {addr}. won't call 'blockchain.scripthash.get_history'.")
+            return [{"height": height, "tx_hash": txid} for (txid, height) in guessed_history]
+        # request addr history from server
         sh = address_to_scripthash(addr)
         self._requests_sent += 1
         async with self._network_request_semaphore:
@@ -183,7 +194,7 @@ async def _on_address_status(self, addr, status):
             self._stale_histories.pop(addr, asyncio.Future()).cancel()
         finally:
             self._handling_addr_statuses.discard(addr)
-        result = await self._maybe_request_history_for_addr(addr)
+        result = await self._maybe_request_history_for_addr(addr, ann_status=status)
         hist = list(map(lambda item: (item['tx_hash'], item['height']), result))
         # tx_fees
         tx_fees = [(item['tx_hash'], item.get('fee')) for item in result]
diff --git a/tests/test_interface.py b/tests/test_interface.py
@@ -1,5 +1,6 @@
 import asyncio
 import collections
+from typing import Optional, Sequence, Iterable
 
 import aiorpcx
 from aiorpcx import RPCError
@@ -12,8 +13,13 @@
 from electrum.simple_config import SimpleConfig
 from electrum.transaction import Transaction
 from electrum import constants
+from electrum.wallet import Abstract_Wallet
+from electrum.blockchain import Blockchain
+from electrum.bitcoin import script_to_scripthash
+from electrum.synchronizer import history_status
 
 from . import ElectrumTestCase
+from . import restore_wallet_from_text__for_unittest
 
 
 class TestServerAddr(ElectrumTestCase):
@@ -86,6 +92,10 @@ async def switch_unwanted_fork_interface(self):
         pass
     async def switch_lagging_interface(self):
         pass
+    def blockchain(self) -> Blockchain:
+        return self.interface.blockchain
+    def get_local_height(self) -> int:
+        return self.blockchain().height()
 
 
 # regtest chain:
@@ -106,11 +116,11 @@ async def switch_lagging_interface(self):
 }
 
 _active_server_sessions = set()
-def _get_active_server_session() -> 'ServerSession':
+def _get_active_server_session() -> 'ToyServerSession':
     assert 1 == len(_active_server_sessions), len(_active_server_sessions)
     return list(_active_server_sessions)[0]
 
-class ServerSession(aiorpcx.RPCSession, Logger):
+class ToyServerSession(aiorpcx.RPCSession, Logger):
 
     def __init__(self, *args, **kwargs):
         aiorpcx.RPCSession.__init__(self, *args, **kwargs)
@@ -120,6 +130,12 @@ def __init__(self, *args, **kwargs):
         self.txs = {
             "bdae818ad3c1f261317738ae9284159bf54874356f186dbc7afd631dc1527fcb": bfh("020000000001010000000000000000000000000000000000000000000000000000000000000000ffffffff025100ffffffff0200f2052a010000001600140297bde2689a3c79ffe050583b62f86f2d9dae540000000000000000266a24aa21a9ede2f61c3f71d1defd3fa999dfa36953755c690689799962b48bebd836974e8cf90120000000000000000000000000000000000000000000000000000000000000000000000000"),
         }  # type: dict[str, bytes]
+        self.txid_to_block_height = collections.defaultdict(int)  # type: dict[str, int]
+        self.subbed_headers = False
+        self.notified_height = None  # type: Optional[int]
+        self.subbed_scripthashes = set()  # type: set[str]
+        self.sh_to_funding_txids = collections.defaultdict(set)  # type: dict[str, set[str]]
+        self.sh_to_spending_txids = collections.defaultdict(set)  # type: dict[str, set[str]]
         self._method_counts = collections.defaultdict(int)  # type: dict[str, int]
         _active_server_sessions.add(self)
 
@@ -136,8 +152,11 @@ async def handle_request(self, request):
             'blockchain.headers.subscribe': self._handle_headers_subscribe,
             'blockchain.block.header': self._handle_block_header,
             'blockchain.block.headers': self._handle_block_headers,
+            'blockchain.scripthash.subscribe': self._handle_scripthash_subscribe,
+            'blockchain.scripthash.get_history': self._handle_scripthash_get_history,
             'blockchain.transaction.get': self._handle_transaction_get,
             'blockchain.transaction.broadcast': self._handle_transaction_broadcast,
+            'blockchain.transaction.get_merkle': self._handle_transaction_get_merkle,
             'server.ping': self._handle_ping,
         }
         handler = handlers.get(request.method)
@@ -162,9 +181,13 @@ async def _handle_server_features(self) -> dict:
     async def _handle_estimatefee(self, number, mode=None):
         return 1000
 
-    async def _handle_headers_subscribe(self):
+    def _get_headersub_result(self):
         return {'hex': BLOCK_HEADERS[self.cur_height].hex(), 'height': self.cur_height}
 
+    async def _handle_headers_subscribe(self):
+        self.subbed_headers = True
+        return self._get_headersub_result()
+
     async def _handle_block_header(self, height):
         return BLOCK_HEADERS[height].hex()
 
@@ -186,10 +209,97 @@ async def _handle_transaction_get(self, tx_hash: str, verbose=False):
             raise RPCError(DAEMON_ERROR, f'daemon error: unknown txid={tx_hash}')
         return rawtx.hex()
 
-    async def _handle_transaction_broadcast(self, raw_tx: str):
+    async def _handle_transaction_get_merkle(self, tx_hash: str, height: int) -> dict:
+        # Fake stuff. Client will ignore it due to config.NETWORK_SKIPMERKLECHECK
+        return {
+            "merkle":
+            [
+                "713d6c7e6ce7bbea708d61162231eaa8ecb31c4c5dd84f81c20409a90069cb24",
+                "03dbaec78d4a52fbaf3c7aa5d3fccd9d8654f323940716ddf5ee2e4bda458fde",
+                "e670224b23f156c27993ac3071940c0ff865b812e21e0a162fe7a005d6e57851",
+                "369a1619a67c3108a8850118602e3669455c70cdcdb89248b64cc6325575b885",
+                "4756688678644dcb27d62931f04013254a62aeee5dec139d1aac9f7b1f318112",
+                "7b97e73abc043836fd890555bfce54757d387943a6860e5450525e8e9ab46be5",
+                "61505055e8b639b7c64fd58bce6fc5c2378b92e025a02583303f69930091b1c3",
+                "27a654ff1895385ac14a574a0415d3bbba9ec23a8774f22ec20d53dd0b5386ff",
+                "5312ed87933075e60a9511857d23d460a085f3b6e9e5e565ad2443d223cfccdc",
+                "94f60b14a9f106440a197054936e6fb92abbd69d6059b38fdf79b33fc864fca0",
+                "2d64851151550e8c4d337f335ee28874401d55b358a66f1bafab2c3e9f48773d"
+            ],
+            "block_height": height,
+            "pos": 710,
+        }
+
+    async def _handle_transaction_broadcast(self, raw_tx: str) -> str:
         tx = Transaction(raw_tx)
-        self.txs[tx.txid()] = bfh(raw_tx)
-        return tx.txid()
+        txid = tx.txid()
+        self.txs[txid] = bfh(raw_tx)
+        touched_sh = await self._process_added_tx(txid=txid)
+        if touched_sh:
+            await self._send_notifications(touched_sh=touched_sh)
+        return txid
+
+    async def _process_added_tx(self, *, txid: str) -> set[str]:
+        """Returns touched scripthashes."""
+        tx = Transaction(self.txs[txid])
+        touched_sh = set()
+        # update sh_to_funding_txids
+        for txout in tx.outputs():
+            sh = script_to_scripthash(txout.scriptpubkey)
+            self.sh_to_funding_txids[sh].add(txid)
+            touched_sh.add(sh)
+        # update sh_to_spending_txids
+        for txin in tx.inputs():
+            if parent_tx_raw := self.txs.get(txin.prevout.txid.hex()):
+                parent_tx = Transaction(parent_tx_raw)
+                ptxout = parent_tx.outputs()[txin.prevout.out_idx]
+                sh = script_to_scripthash(ptxout.scriptpubkey)
+                self.sh_to_spending_txids[sh].add(txid)
+                touched_sh.add(sh)
+        return touched_sh
+
+    async def _handle_scripthash_subscribe(self, sh: str) -> Optional[str]:
+        self.subbed_scripthashes.add(sh)
+        hist = self._calc_sh_history(sh)
+        return history_status(hist)
+
+    async def _handle_scripthash_get_history(self, sh: str) -> Sequence[dict]:
+        hist_tuples = self._calc_sh_history(sh)
+        hist_dicts = [{"height": height, "tx_hash": txid} for (txid, height) in hist_tuples]
+        for hist_dict in hist_dicts:  # add "fee" key for mempool txs
+            if hist_dict["height"] in (0, -1,):
+                hist_dict["fee"] = 0
+        return hist_dicts
+
+    def _calc_sh_history(self, sh: str) -> Sequence[tuple[str, int]]:
+        txids = self.sh_to_funding_txids[sh] | self.sh_to_spending_txids[sh]
+        hist = []
+        for txid in txids:
+            bh = self.txid_to_block_height[txid]
+            hist.append((txid, bh))
+        hist.sort(key=lambda x: x[1])  # FIXME put mempool txs last
+        return hist
+
+    async def _send_notifications(self, *, touched_sh: Iterable[str], height_changed: bool = False) -> None:
+        if height_changed and self.subbed_headers and self.notified_height != self.cur_height:
+            self.notified_height = self.cur_height
+            args = (self._get_headersub_result(),)
+            await self.send_notification('blockchain.headers.subscribe', args)
+        touched_sh = set(sh for sh in touched_sh if sh in self.subbed_scripthashes)
+        for sh in touched_sh:
+            hist = self._calc_sh_history(sh)
+            args = (sh, history_status(hist))
+            await self.send_notification("blockchain.scripthash.subscribe", args)
+
+    async def mine_block(self, *, txids_mined: Iterable[str] = None):
+        if txids_mined is None:
+            txids_mined = []
+        self.cur_height += 1
+        touched_sh = set()
+        for txid in txids_mined:
+            self.txid_to_block_height[txid] = self.cur_height
+            touched_sh |= await self._process_added_tx(txid=txid)
+        await self._send_notifications(touched_sh=touched_sh, height_changed=True)
 
 
 class TestInterface(ElectrumTestCase):
@@ -198,6 +308,7 @@ class TestInterface(ElectrumTestCase):
     def setUp(self):
         super().setUp()
         self.config = SimpleConfig({'electrum_path': self.electrum_path})
+        self.config.NETWORK_SKIPMERKLECHECK = True
         self._orig_WAIT_FOR_BUFFER_GROWTH_SECONDS = PaddedRSTransport.WAIT_FOR_BUFFER_GROWTH_SECONDS
         PaddedRSTransport.WAIT_FOR_BUFFER_GROWTH_SECONDS = 0
 
@@ -207,7 +318,7 @@ def tearDown(self):
 
     async def asyncSetUp(self):
         await super().asyncSetUp()
-        self._server: asyncio.base_events.Server = await aiorpcx.serve_rs(ServerSession, "127.0.0.1")
+        self._server: asyncio.base_events.Server = await aiorpcx.serve_rs(ToyServerSession, "127.0.0.1")
         server_socket_addr = self._server.sockets[0].getsockname()
         self._server_port = server_socket_addr[1]
         self.network = MockNetwork(config=self.config)
@@ -255,3 +366,35 @@ async def test_transaction_broadcast(self):
         rawtx2 = await interface.get_transaction(tx.txid())
         self.assertEqual(rawtx1, rawtx2)
         self.assertEqual(_get_active_server_session()._method_counts["blockchain.transaction.get"], 0)
+
+    async def test_dont_request_gethistory_if_status_change_results_from_mempool_txs_simply_getting_mined(self):
+        """After a new block is mined, we recv "blockchain.scripthash.subscribe" notifs.
+        We opportunistically guess the scripthash status changed purely because touching mempool txs just got mined.
+        If the guess is correct, we won't call the "blockchain.scripthash.get_history" RPC.
+        """
+        interface = await self._start_iface_and_wait_for_sync()
+        w1 = restore_wallet_from_text__for_unittest("9dk", path=None, config=self.config)['wallet']  # type: Abstract_Wallet
+        w1.start_network(self.network)
+        await w1.up_to_date_changed_event.wait()
+        self.assertEqual(_get_active_server_session()._method_counts["blockchain.scripthash.get_history"], 0)
+        # fund w1 (in mempool)
+        funding_tx = "01000000000101e855888b77b1688d08985b863bfe85b354049b4eba923db9b5cf37089975d5d10000000000fdffffff0280969800000000001600140297bde2689a3c79ffe050583b62f86f2d9dae5460abe9000000000016001472df47551b6e7e0c8428814d2e572bc5ac773dda024730440220383efa2f0f5b87f8ce5d6b6eaf48cba03bf522b23fbb23b2ac54ff9d9a8f6a8802206f67d1f909f3c7a22ac0308ac4c19853ffca3a9317e1d7e0c88cc3a86853aaac0121035061949222555a0df490978fe6e7ebbaa96332ecb5c266918fd800c0eef736e7358d1400"
+        funding_txid = await _get_active_server_session()._handle_transaction_broadcast(funding_tx)
+        await w1.up_to_date_changed_event.wait()
+        while not w1.is_up_to_date():
+            await w1.up_to_date_changed_event.wait()
+        self.assertEqual(_get_active_server_session()._method_counts["blockchain.scripthash.get_history"], 1)
+        self.assertEqual(
+            w1.adb.get_address_history("bcrt1qq2tmmcngng78nllq2pvrkchcdukemtj5jnxz44"),
+            {funding_txid: 0})
+        # mine funding tx
+        await _get_active_server_session().mine_block(txids_mined=[funding_txid])
+        await w1.up_to_date_changed_event.wait()
+        while not w1.is_up_to_date():
+            await w1.up_to_date_changed_event.wait()
+        # see if we managed to guess new history, and hence did not need to call get_history RPC
+        self.assertEqual(_get_active_server_session()._method_counts["blockchain.scripthash.get_history"], 1)
+        self.assertEqual(
+            w1.adb.get_address_history("bcrt1qq2tmmcngng78nllq2pvrkchcdukemtj5jnxz44"),
+            {funding_txid: 7})
+
