channel_db: raise specific exception when channelDB not loaded, allowing lnworker to mark payment as failed. (#8431)

On mobile, it can take a while before channelDB is loaded. If payment is attempted before the DB
is fully loaded, this would result in a payment failure, but also leaves the payment attempt in IN_PROGRESS
state. This patch adds a more specific ChannelDBNotLoaded exception class, so we can handle this case more
gracefully, since we know the payment didn't succeed.

electrum/channel_db.py

@@ -38,7 +38,7 @@ from aiorpcx import NetAddress
 
 from .sql_db import SqlDB, sql
 from . import constants, util
-from .util import profiler, get_headers_dir, is_ip_address, json_normalize
+from .util import profiler, get_headers_dir, is_ip_address, json_normalize, UserFacingException
 from .logging import Logger
 from .lnutil import (LNPeerAddr, format_short_channel_id, ShortChannelID,
                      validate_features, IncompatibleOrInsaneFeatures, InvalidGossipMsg)
@@ -59,6 +59,9 @@ FLAG_DISABLE   = 1 << 1
 FLAG_DIRECTION = 1 << 0
 
 
+class ChannelDBNotLoaded(UserFacingException): pass
+
+
 class ChannelInfo(NamedTuple):
     short_channel_id: ShortChannelID
     node1_id: bytes
@@ -375,7 +378,7 @@ class ChannelDB(SqlDB):
 
     def get_recent_peers(self):
         if not self.data_loaded.is_set():
-            raise Exception("channelDB data not loaded yet!")
+            raise ChannelDBNotLoaded("channelDB data not loaded yet!")
         with self.lock:
             ret = [self.get_last_good_address(node_id)
                    for node_id in self._recent_peers]
@@ -842,7 +845,7 @@ class ChannelDB(SqlDB):
     ) -> Set[ShortChannelID]:
         """Returns the set of short channel IDs where node_id is one of the channel participants."""
         if not self.data_loaded.is_set():
-            raise Exception("channelDB data not loaded yet!")
+            raise ChannelDBNotLoaded("channelDB data not loaded yet!")
         relevant_channels = self._channels_for_node.get(node_id) or set()
         relevant_channels = set(relevant_channels)  # copy
         # add our own channels  # TODO maybe slow?

electrum/lnworker.py

@@ -79,7 +79,7 @@ from .lnwatcher import LNWalletWatcher
 from .crypto import pw_encode_with_version_and_mac, pw_decode_with_version_and_mac
 from .lnutil import ImportedChannelBackupStorage, OnchainChannelBackupStorage
 from .lnchannel import ChannelBackup
-from .channel_db import UpdateStatus
+from .channel_db import UpdateStatus, ChannelDBNotLoaded
 from .channel_db import get_mychannel_info, get_mychannel_policy
 from .submarine_swaps import SwapManager
 from .channel_db import ChannelInfo, Policy
@@ -1202,6 +1202,9 @@ class LNWallet(LNWorker):
         except PaymentFailure as e:
             self.logger.info(f'payment failure: {e!r}')
             reason = str(e)
+        except ChannelDBNotLoaded as e:
+            self.logger.info(f'payment failure: {e!r}')
+            reason = str(e)
         finally:
             self.logger.info(f"pay_invoice ending session for RHASH={payment_hash.hex()}. {success=}")
         if success: