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https://github.com/aljazceru/python-teos.git
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aa12fa2cf8
The sleep flag was used to avoid doing useless work when no data was hold by the tower. However, from the implementation of the data persistence on, the Watcher and Responder should at least keep track of the last known block. The current apporach was making this harder.
490 lines
21 KiB
Python
490 lines
21 KiB
Python
import json
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from queue import Queue
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from threading import Thread
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from pisa import LOG_PREFIX
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from common.logger import Logger
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from pisa.cleaner import Cleaner
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from pisa.carrier import Carrier
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from pisa.block_processor import BlockProcessor
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CONFIRMATIONS_BEFORE_RETRY = 6
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MIN_CONFIRMATIONS = 6
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logger = Logger(actor="Responder", log_name_prefix=LOG_PREFIX)
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class TransactionTracker:
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"""
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A :class:`TransactionTracker` is used to monitor a ``penalty_tx``. Once the dispute is seen by the
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:obj:`Watcher <pisa.watcher.Watcher>` the penalty transaction is decrypted and the relevant appointment data is
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passed along to the :obj:`Responder`.
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Once the :obj:`Responder` has succeeded on broadcasting the penalty transaction it will create a
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:obj:`TransactionTracker` and monitor the blockchain until the end of the appointment.
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Args:
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locator (:obj:`str`): A 16-byte hex-encoded value used by the tower to detect channel breaches. It serves as a
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trigger for the tower to decrypt and broadcast the penalty transaction.
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dispute_txid (:obj:`str`): the id of the transaction that created the channel breach and triggered the penalty.
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penalty_txid (:obj:`str`): the id of the transaction that was encrypted under ``dispute_txid``.
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penalty_rawtx (:obj:`str`): the raw transaction that was broadcast as a consequence of the channel breach.
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appointment_end (:obj:`int`): the block at which the tower will stop monitoring the blockchain for this
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appointment.
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"""
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def __init__(self, locator, dispute_txid, penalty_txid, penalty_rawtx, appointment_end):
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self.locator = locator
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self.dispute_txid = dispute_txid
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self.penalty_txid = penalty_txid
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self.penalty_rawtx = penalty_rawtx
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self.appointment_end = appointment_end
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@classmethod
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def from_dict(cls, tx_tracker_data):
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"""
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Constructs a :obj:`TransactionTracker` instance from a dictionary. Requires that all the fields are populated
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(``not None``).
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Useful to load data from the database.
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Args:
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tx_tracker_data (:obj:`dict`): a dictionary with an entry per each field required to create the
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:obj:`TransactionTracker`.
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Returns:
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:obj:`TransactionTracker`: A ``TransactionTracker`` instantiated with the provided data.
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Raises:
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ValueError: if any of the required fields is missing.
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"""
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locator = tx_tracker_data.get("locator")
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dispute_txid = tx_tracker_data.get("dispute_txid")
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penalty_txid = tx_tracker_data.get("penalty_txid")
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penalty_rawtx = tx_tracker_data.get("penalty_rawtx")
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appointment_end = tx_tracker_data.get("appointment_end")
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if any(v is None for v in [locator, dispute_txid, penalty_txid, penalty_rawtx, appointment_end]):
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raise ValueError("Wrong transaction tracker data, some fields are missing")
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else:
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tx_tracker = cls(locator, dispute_txid, penalty_txid, penalty_rawtx, appointment_end)
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return tx_tracker
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def to_dict(self):
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"""
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Exports a :obj:`TransactionTracker` as a dictionary.
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Returns:
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:obj:`dict`: A dictionary containing the :obj:`TransactionTracker` data.
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"""
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tx_tracker = {
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"locator": self.locator,
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"dispute_txid": self.dispute_txid,
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"penalty_txid": self.penalty_txid,
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"penalty_rawtx": self.penalty_rawtx,
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"appointment_end": self.appointment_end,
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}
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return tx_tracker
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def to_json(self):
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"""
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Exports a :obj:`TransactionTracker` as a json-encoded dictionary.
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Returns:
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:obj:`str`: A json-encoded dictionary containing the :obj:`TransactionTracker` data.
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"""
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return json.dumps(self.to_dict())
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class Responder:
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"""
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The :class:`Responder` is the class in charge of ensuring that channel breaches are dealt with. It does so handling
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the decrypted ``penalty_txs`` handed by the :obj:`Watcher <pisa.watcher.Watcher>` and ensuring the they make it to
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the blockchain.
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Args:
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db_manager (:obj:`DBManager <pisa.db_manager.DBManager>`): a ``DBManager`` instance to interact with the
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database.
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Attributes:
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trackers (:obj:`dict`): A dictionary containing the minimum information about the :obj:`TransactionTracker`
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required by the :obj:`Responder` (``penalty_txid``, ``locator`` and ``end_time``).
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Each entry is identified by a ``uuid``.
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tx_tracker_map (:obj:`dict`): A ``penalty_txid:uuid`` map used to allow the :obj:`Responder` to deal with
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several trackers triggered by the same ``penalty_txid``.
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unconfirmed_txs (:obj:`list`): A list that keeps track of all unconfirmed ``penalty_txs``.
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missed_confirmations (:obj:`dict`): A dictionary that keeps count of how many confirmations each ``penalty_tx``
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has missed. Used to trigger rebroadcast if needed.
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block_queue (:obj:`Queue`): A queue used by the :obj:`Responder` to receive block hashes from ``bitcoind``. It
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is populated by the :obj:`ChainMonitor <pisa.chain_monitor.ChainMonitor>`.
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db_manager (:obj:`DBManager <pisa.db_manager.DBManager>`): A ``DBManager`` instance to interact with the
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database.
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"""
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def __init__(self, db_manager):
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self.trackers = dict()
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self.tx_tracker_map = dict()
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self.unconfirmed_txs = []
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self.missed_confirmations = dict()
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self.block_queue = Queue()
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self.db_manager = db_manager
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self.carrier = Carrier()
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self.last_known_block = db_manager.load_last_block_hash_responder()
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def awake(self):
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responder_thread = Thread(target=self.do_watch, daemon=True)
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responder_thread.start()
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return responder_thread
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@staticmethod
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def on_sync(block_hash):
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"""
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Whether the :obj:`Responder` is on sync with ``bitcoind`` or not. Used when recovering from a crash.
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The Watchtower can be instantiated with fresh or with backed up data. In the later, some triggers may have been
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missed. In order to go back on sync both the :obj:`Watcher <pisa.watcher.Watcher>` and the :obj:`Responder`
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need to perform the state transitions until they catch up.
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If a transaction is broadcast by the :obj:`Responder` and it is rejected (due to a double-spending for example)
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and the :obj:`Responder` is off-sync then the :obj:`TransactionTracker` is abandoned.
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This method helps making that decision.
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Args:
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block_hash (:obj:`str`): the block hash passed to the :obj:`Responder` in the ``handle_breach`` request.
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Returns:
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:obj:`bool`: Whether or not the :obj:`Responder` and ``bitcoind`` are on sync.
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"""
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block_processor = BlockProcessor()
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distance_from_tip = block_processor.get_distance_to_tip(block_hash)
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if distance_from_tip is not None and distance_from_tip > 1:
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synchronized = False
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else:
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synchronized = True
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return synchronized
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def handle_breach(self, uuid, locator, dispute_txid, penalty_txid, penalty_rawtx, appointment_end, block_hash):
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"""
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Requests the :obj:`Responder` to handle a channel breach. This is the entry point of the :obj:`Responder`.
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Args:
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uuid (:obj:`str`): a unique identifier for the appointment.
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locator (:obj:`str`): the appointment locator provided by the user (16-byte hex-encoded).
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dispute_txid (:obj:`str`): the id of the transaction that created the channel breach.
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penalty_txid (:obj:`str`): the id of the decrypted transaction included in the appointment.
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penalty_rawtx (:obj:`str`): the raw transaction to be broadcast in response of the breach.
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appointment_end (:obj:`int`): the block height at which the :obj:`Responder` will stop monitoring for this
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penalty transaction.
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block_hash (:obj:`str`): the block hash at which the breach was seen (used to see if we are on sync).
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Returns:
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:obj:`Receipt <pisa.carrier.Receipt>`: A ``Receipt`` indicating whether or not the ``penalty_tx`` made it
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into the blockchain.
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"""
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receipt = self.carrier.send_transaction(penalty_rawtx, penalty_txid)
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if receipt.delivered:
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self.add_tracker(
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uuid, locator, dispute_txid, penalty_txid, penalty_rawtx, appointment_end, receipt.confirmations
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)
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else:
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# TODO: Add the missing reasons (e.g. RPC_VERIFY_REJECTED)
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# TODO: Use self.on_sync(block_hash) to check whether or not we failed because we are out of sync
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logger.warning(
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"Tracker cannot be created", reason=receipt.reason, uuid=uuid, on_sync=self.on_sync(block_hash)
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)
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return receipt
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def add_tracker(self, uuid, locator, dispute_txid, penalty_txid, penalty_rawtx, appointment_end, confirmations=0):
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"""
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Creates a :obj:`TransactionTracker` after successfully broadcasting a ``penalty_tx``.
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A reduction of :obj:`TransactionTracker` is stored in ``trackers`` and ``tx_tracker_map`` and the
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``penalty_txid`` added to ``unconfirmed_txs`` if ``confirmations=0``. Finally, all the data is stored in the
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database.
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Args:
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uuid (:obj:`str`): a unique identifier for the appointment.
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locator (:obj:`str`): the appointment locator provided by the user (16-byte hex-encoded).
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dispute_txid (:obj:`str`): the id of the transaction that created the channel breach.
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penalty_txid (:obj:`str`): the id of the decrypted transaction included in the appointment.
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penalty_rawtx (:obj:`str`): the raw transaction to be broadcast.
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appointment_end (:obj:`int`): the block height at which the :obj:`Responder` will stop monitoring for the
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tracker.
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confirmations (:obj:`int`): the confirmation count of the ``penalty_tx``. In normal conditions it will be
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zero, but if the transaction is already on the blockchain this won't be the case.
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"""
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tracker = TransactionTracker(locator, dispute_txid, penalty_txid, penalty_rawtx, appointment_end)
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# We only store the penalty_txid, locator and appointment_end in memory. The rest is dumped into the db.
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self.trackers[uuid] = {
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"penalty_txid": tracker.penalty_txid,
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"locator": locator,
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"appointment_end": appointment_end,
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}
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if penalty_txid in self.tx_tracker_map:
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self.tx_tracker_map[penalty_txid].append(uuid)
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else:
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self.tx_tracker_map[penalty_txid] = [uuid]
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# In the case we receive two trackers with the same penalty txid we only add it to the unconfirmed txs list once
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if penalty_txid not in self.unconfirmed_txs and confirmations == 0:
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self.unconfirmed_txs.append(penalty_txid)
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self.db_manager.store_responder_tracker(uuid, tracker.to_json())
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logger.info(
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"New tracker added", dispute_txid=dispute_txid, penalty_txid=penalty_txid, appointment_end=appointment_end
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)
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def do_watch(self):
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"""
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Monitors the blockchain whilst there are pending trackers.
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This is the main method of the :obj:`Responder` and triggers tracker cleaning, rebroadcasting, reorg managing,
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etc.
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"""
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# Distinguish fresh bootstraps from bootstraps from db
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if self.last_known_block is None:
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self.last_known_block = BlockProcessor.get_best_block_hash()
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while True:
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block_hash = self.block_queue.get()
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block = BlockProcessor.get_block(block_hash)
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logger.info("New block received", block_hash=block_hash, prev_block_hash=block.get("previousblockhash"))
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if len(self.trackers) > 0 and block is not None:
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txids = block.get("tx")
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logger.info("List of transactions", txids=txids)
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if self.last_known_block == block.get("previousblockhash"):
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self.check_confirmations(txids)
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height = block.get("height")
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completed_trackers = self.get_completed_trackers(height)
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Cleaner.delete_completed_trackers(
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completed_trackers, height, self.trackers, self.tx_tracker_map, self.db_manager
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)
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txs_to_rebroadcast = self.get_txs_to_rebroadcast()
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self.rebroadcast(txs_to_rebroadcast)
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# NOTCOVERED
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else:
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logger.warning(
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"Reorg found",
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local_prev_block_hash=self.last_known_block,
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remote_prev_block_hash=block.get("previousblockhash"),
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)
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# ToDo: #24-properly-handle-reorgs
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self.handle_reorgs(block_hash)
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# Clear the receipts issued in this block
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self.carrier.issued_receipts = {}
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if len(self.trackers) is 0:
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logger.info("No more pending trackers")
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# Register the last processed block for the responder
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self.db_manager.store_last_block_hash_responder(block_hash)
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self.last_known_block = block.get("hash")
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self.block_queue.task_done()
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def check_confirmations(self, txs):
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"""
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Checks if any of the monitored ``penalty_txs`` has received it's first confirmation or keeps missing them.
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This method manages ``unconfirmed_txs`` and ``missed_confirmations``.
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Args:
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txs (:obj:`list`): A list of confirmed tx ids (the list of transactions included in the last received
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block).
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"""
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# If a new confirmed tx matches a tx we are watching, then we remove it from the unconfirmed txs map
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for tx in txs:
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if tx in self.tx_tracker_map and tx in self.unconfirmed_txs:
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self.unconfirmed_txs.remove(tx)
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logger.info("Confirmation received for transaction", tx=tx)
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# We also add a missing confirmation to all those txs waiting to be confirmed that have not been confirmed in
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# the current block
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for tx in self.unconfirmed_txs:
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if tx in self.missed_confirmations:
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self.missed_confirmations[tx] += 1
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else:
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self.missed_confirmations[tx] = 1
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logger.info("Transaction missed a confirmation", tx=tx, missed_confirmations=self.missed_confirmations[tx])
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def get_txs_to_rebroadcast(self):
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"""
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Gets the transactions to be rebroadcast based on their ``missed_confirmation`` count.
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Returns:
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:obj:`list`: A list with all the ids of the transaction that have to be rebroadcast.
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"""
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txs_to_rebroadcast = []
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for tx, missed_conf in self.missed_confirmations.items():
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if missed_conf >= CONFIRMATIONS_BEFORE_RETRY:
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# If a transactions has missed too many confirmations we add it to the rebroadcast list
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txs_to_rebroadcast.append(tx)
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return txs_to_rebroadcast
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def get_completed_trackers(self, height):
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"""
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Gets the trackers that has already been fulfilled based on a given height (``end_time`` was reached with a
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minimum confirmation count).
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Args:
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height (:obj:`int`): the height of the last received block.
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Returns:
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:obj:`dict`: a dict (``uuid:confirmations``) of the completed trackers.
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"""
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completed_trackers = {}
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checked_txs = {}
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for uuid, tracker_data in self.trackers.items():
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appointment_end = tracker_data.get("appointment_end")
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penalty_txid = tracker_data.get("penalty_txid")
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if appointment_end <= height and penalty_txid not in self.unconfirmed_txs:
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if penalty_txid not in checked_txs:
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tx = Carrier.get_transaction(penalty_txid)
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else:
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tx = checked_txs.get(penalty_txid)
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if tx is not None:
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confirmations = tx.get("confirmations")
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checked_txs[penalty_txid] = tx
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if confirmations is not None and confirmations >= MIN_CONFIRMATIONS:
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# The end of the appointment has been reached
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completed_trackers[uuid] = confirmations
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return completed_trackers
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def rebroadcast(self, txs_to_rebroadcast):
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"""
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Rebroadcasts a ``penalty_tx`` that has missed too many confirmations. In the current approach this would loop
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forever si the transaction keeps not getting it.
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Potentially the fees could be bumped here if the transaction has some tower dedicated outputs (or allows it
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trough ``ANYONECANPAY`` or something similar).
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Args:
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txs_to_rebroadcast (:obj:`list`): a list of transactions to be rebroadcast.
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Returns:
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:obj:`list`: A list of :obj:`Receipts <pisa.carrier.Receipt>` with information about whether or not every
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transaction made it trough the network.
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"""
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# DISCUSS: #22-discuss-confirmations-before-retry
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# ToDo: #23-define-behaviour-approaching-end
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receipts = []
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for txid in txs_to_rebroadcast:
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self.missed_confirmations[txid] = 0
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# FIXME: This would potentially grab multiple instances of the same transaction and try to send them.
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# should we do it only once?
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for uuid in self.tx_tracker_map[txid]:
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tracker = TransactionTracker.from_dict(self.db_manager.load_responder_tracker(uuid))
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logger.warning(
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"Transaction has missed many confirmations. Rebroadcasting", penalty_txid=tracker.penalty_txid
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)
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receipt = self.carrier.send_transaction(tracker.penalty_rawtx, tracker.penalty_txid)
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receipts.append((txid, receipt))
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if not receipt.delivered:
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# FIXME: Can this actually happen?
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logger.warning("Transaction failed", penalty_txid=tracker.penalty_txid)
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return receipts
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# NOTCOVERED
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def handle_reorgs(self, block_hash):
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"""
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Basic reorg handle. It deals with situations where a reorg has been found but the ``dispute_tx`` is still
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on the chain. If the ``dispute_tx`` is reverted, it need to call the :obj:`ReorgManager` (Soon TM).
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Args:
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block_hash (:obj:`str`): the hash of the last block received (which triggered the reorg).
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"""
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for uuid in self.trackers.keys():
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tracker = TransactionTracker.from_dict(self.db_manager.load_responder_tracker(uuid))
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# First we check if the dispute transaction is known (exists either in mempool or blockchain)
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dispute_tx = self.carrier.get_transaction(tracker.dispute_txid)
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if dispute_tx is not None:
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# If the dispute is there, we check the penalty
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penalty_tx = self.carrier.get_transaction(tracker.penalty_txid)
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if penalty_tx is not None:
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# If the penalty exists we need to check is it's on the blockchain or not so we can update the
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# unconfirmed transactions list accordingly.
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if penalty_tx.get("confirmations") is None:
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self.unconfirmed_txs.append(tracker.penalty_txid)
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logger.info(
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"Penalty transaction back in mempool. Updating unconfirmed transactions",
|
|
penalty_txid=tracker.penalty_txid,
|
|
)
|
|
|
|
else:
|
|
# If the penalty transaction is missing, we need to reset the tracker.
|
|
self.handle_breach(
|
|
tracker.locator,
|
|
uuid,
|
|
tracker.dispute_txid,
|
|
tracker.penalty_txid,
|
|
tracker.penalty_rawtx,
|
|
tracker.appointment_end,
|
|
block_hash,
|
|
)
|
|
|
|
logger.warning(
|
|
"Penalty transaction banished. Resetting the tracker", penalty_tx=tracker.penalty_txid
|
|
)
|
|
|
|
else:
|
|
# ToDo: #24-properly-handle-reorgs
|
|
# FIXME: if the dispute is not on chain (either in mempool or not there at all), we need to call the
|
|
# reorg manager
|
|
logger.warning("Dispute and penalty transaction missing. Calling the reorg manager")
|
|
logger.error("Reorg manager not yet implemented")
|