Merge pull request #10031 from SomberNight/202507_walletdb_add_configvar_partial_writes_4

wallet_db: add configvar for partial_writes, disable by default

electrum/daemon.py

@@ -507,7 +507,7 @@ class Daemon(Logger):
             config: SimpleConfig,
     ) -> Optional[Abstract_Wallet]:
         path = standardize_path(path)
-        storage = WalletStorage(path)
+        storage = WalletStorage(path, allow_partial_writes=config.WALLET_PARTIAL_WRITES)
         if not storage.file_exists():
             raise FileNotFoundError(errno.ENOENT, os.strerror(errno.ENOENT), path)
         if storage.is_encrypted():

electrum/json_db.py

@@ -421,11 +421,7 @@ class JsonDB(Logger):
 
     @locked
     def write(self):
-        if (
-            not self.storage.file_exists()
-            or self.storage.is_encrypted()
-            or self.storage.needs_consolidation()
-        ):
+        if self.storage.should_do_full_write_next():
             self.write_and_force_consolidation()
         else:
             self._append_pending_changes()

electrum/simple_config.py

@@ -687,6 +687,11 @@ class SimpleConfig(Logger):
 This can eliminate a serious privacy issue where a malicious user can track your spends by sending small payments
 to a previously-paid address of yours that would then be included with unrelated inputs in your future payments."""),
     )
+    WALLET_PARTIAL_WRITES = ConfigVar(
+        'wallet_partial_writes', default=False, type_=bool,
+        long_desc=lambda: _("""Allows partial updates to be written to disk for the wallet DB.
+If disabled, the full wallet file is written to disk for every change. Experimental."""),
+    )
 
     FX_USE_EXCHANGE_RATE = ConfigVar('use_exchange_rate', default=False, type_=bool)
     FX_CURRENCY = ConfigVar('currency', default='EUR', type_=str)

electrum/storage.py

@@ -64,11 +64,17 @@ class WalletStorage(Logger):
 
     # TODO maybe split this into separate create() and open() classmethods, to prevent some bugs.
     #      Until then, the onus is on the caller to check file_exists().
-    def __init__(self, path):
+    def __init__(
+        self,
+        path,
+        *,
+        allow_partial_writes: bool = False,
+    ):
         Logger.__init__(self)
         self.path = standardize_path(path)
         self._file_exists = bool(self.path and os.path.exists(self.path))
         self.logger.info(f"wallet path {self.path}")
+        self._allow_partial_writes = allow_partial_writes
         self.pubkey = None
         self.decrypted = ''
         try:
@@ -112,6 +118,7 @@ class WalletStorage(Logger):
 
     def append(self, data: str) -> None:
         """ append data to file. for the moment, only non-encrypted file"""
+        assert self._allow_partial_writes
         assert not self.is_encrypted()
         with open(self.path, "rb+") as f:
             pos = f.seek(0, os.SEEK_END)
@@ -122,9 +129,18 @@ class WalletStorage(Logger):
             f.flush()
             os.fsync(f.fileno())
 
-    def needs_consolidation(self):
+    def _needs_consolidation(self):
         return self.pos > 2 * self.init_pos
 
+    def should_do_full_write_next(self) -> bool:
+        """If false, next action can be a partial-write ('append')."""
+        return (
+            not self.file_exists()
+            or self.is_encrypted()
+            or self._needs_consolidation()
+            or not self._allow_partial_writes
+        )
+
     def file_exists(self) -> bool:
         return self._file_exists
 

electrum/wallet.py

@@ -4189,7 +4189,7 @@ def create_new_wallet(
     gap_limit: Optional[int] = None
 ) -> dict:
     """Create a new wallet"""
-    storage = WalletStorage(path)
+    storage = WalletStorage(path, allow_partial_writes=config.WALLET_PARTIAL_WRITES)
     if storage.file_exists():
         raise UserFacingException("Remove the existing wallet first!")
     db = WalletDB('', storage=storage, upgrade=True)
@@ -4226,7 +4226,7 @@ def restore_wallet_from_text(
     if path is None:  # create wallet in-memory
         storage = None
     else:
-        storage = WalletStorage(path)
+        storage = WalletStorage(path, allow_partial_writes=config.WALLET_PARTIAL_WRITES)
         if storage.file_exists():
             raise UserFacingException("Remove the existing wallet first!")
     if encrypt_file is None:

electrum/wallet_db.py

@@ -1289,7 +1289,13 @@ class WalletDB(JsonDB):
         storage: Optional['WalletStorage'] = None,
         upgrade: bool = False,
     ):
-        JsonDB.__init__(self, s, storage=storage, encoder=MyEncoder, upgrader=partial(upgrade_wallet_db, do_upgrade=upgrade))
+        JsonDB.__init__(
+            self,
+            s,
+            storage=storage,
+            encoder=MyEncoder,
+            upgrader=partial(upgrade_wallet_db, do_upgrade=upgrade),
+        )
         # create pointers
         self.load_transactions()
         # load plugins that are conditional on wallet type