Class ChannelMonitor


  • public class ChannelMonitor
    extends Object
    A ChannelMonitor handles chain events (blocks connected and disconnected) and generates on-chain transactions to ensure no loss of funds occurs. You MUST ensure that no ChannelMonitors for a given channel anywhere contain out-of-date information and are actively monitoring the chain. Pending Events or updated HTLCs which have not yet been read out by get_and_clear_pending_monitor_events or get_and_clear_pending_events are serialized to disk and reloaded at deserialize-time. Thus, you must ensure that, when handling events, all events gotten are fully handled before re-serializing the new state. Note that the deserializer is only implemented for (BlockHash, ChannelMonitor), which tells you the last block hash which was block_connect()ed. You MUST rescan any blocks along the \"reorg path\" (ie disconnecting blocks until you find a common ancestor from both the returned block hash and the the current chain and then reconnecting blocks to get to the best chain) upon deserializing the object!
    • Method Detail

      • write

        public byte[] write()
        Serialize the ChannelMonitor object into a byte array which can be read by ChannelMonitor_read
      • get_latest_update_id

        public long get_latest_update_id()
        Gets the update_id from the latest ChannelMonitorUpdate which was applied to this ChannelMonitor.
      • get_funding_txo

        public TwoTuple_OutPointScriptZ get_funding_txo()
        Gets the funding transaction outpoint of the channel this ChannelMonitor is monitoring for.
      • get_outputs_to_watch

        public TwoTuple_TxidCVec_C2Tuple_u32ScriptZZZ[] get_outputs_to_watch()
        Gets a list of txids, with their output scripts (in the order they appear in the transaction), which we must learn about spends of via block_connected().
      • load_outputs_to_watch

        public void load_outputs_to_watch​(Filter filter)
        Loads the funding txo and outputs to watch into the given `chain::Filter` by repeatedly calling `chain::Filter::register_output` and `chain::Filter::register_tx` until all outputs have been registered.
      • get_and_clear_pending_monitor_events

        public MonitorEvent[] get_and_clear_pending_monitor_events()
        Get the list of HTLCs who's status has been updated on chain. This should be called by ChannelManager via [`chain::Watch::release_pending_monitor_events`].
      • get_and_clear_pending_events

        public Event[] get_and_clear_pending_events()
        Gets the list of pending events which were generated by previous actions, clearing the list in the process. This is called by the [`EventsProvider::process_pending_events`] implementation for [`ChainMonitor`]. [`EventsProvider::process_pending_events`]: crate::events::EventsProvider::process_pending_events [`ChainMonitor`]: crate::chain::chainmonitor::ChainMonitor
      • get_counterparty_node_id

        @Nullable
        public byte[] get_counterparty_node_id()
        Gets the `node_id` of the counterparty for this channel. Will be `None` for channels constructed on LDK versions prior to 0.0.110 and always `Some` otherwise. Note that the return value (or a relevant inner pointer) may be NULL or all-0s to represent None
      • get_latest_holder_commitment_txn

        public byte[][] get_latest_holder_commitment_txn​(Logger logger)
        Used by ChannelManager deserialization to broadcast the latest holder state if its copy of the Channel was out-of-date. You may also use this to broadcast the latest local commitment transaction, either because a monitor update failed with [`ChannelMonitorUpdateStatus::PermanentFailure`] or because we've fallen behind (i.e. we've received proof that our counterparty side knows a revocation secret we gave them that they shouldn't know). Broadcasting these transactions in the second case is UNSAFE, as they allow counterparty side to punish you. Nevertheless you may want to broadcast them if counterparty doesn't close channel with their commitment transaction after a substantial amount of time. Best may be to contact the other node operator out-of-band to coordinate other options available to you. In any-case, the choice is up to you. [`ChannelMonitorUpdateStatus::PermanentFailure`]: super::ChannelMonitorUpdateStatus::PermanentFailure
      • block_connected

        public TwoTuple_TxidCVec_C2Tuple_u32TxOutZZZ[] block_connected​(byte[] header,
                                                                       TwoTuple_usizeTransactionZ[] txdata,
                                                                       int height,
                                                                       BroadcasterInterface broadcaster,
                                                                       FeeEstimator fee_estimator,
                                                                       Logger logger)
        Processes transactions in a newly connected block, which may result in any of the following: - update the monitor's state against resolved HTLCs - punish the counterparty in the case of seeing a revoked commitment transaction - force close the channel and claim/timeout incoming/outgoing HTLCs if near expiration - detect settled outputs for later spending - schedule and bump any in-flight claims Returns any new outputs to watch from `txdata`; after called, these are also included in [`get_outputs_to_watch`]. [`get_outputs_to_watch`]: #method.get_outputs_to_watch
      • block_disconnected

        public void block_disconnected​(byte[] header,
                                       int height,
                                       BroadcasterInterface broadcaster,
                                       FeeEstimator fee_estimator,
                                       Logger logger)
        Determines if the disconnected block contained any transactions of interest and updates appropriately.
      • transactions_confirmed

        public TwoTuple_TxidCVec_C2Tuple_u32TxOutZZZ[] transactions_confirmed​(byte[] header,
                                                                              TwoTuple_usizeTransactionZ[] txdata,
                                                                              int height,
                                                                              BroadcasterInterface broadcaster,
                                                                              FeeEstimator fee_estimator,
                                                                              Logger logger)
        Processes transactions confirmed in a block with the given header and height, returning new outputs to watch. See [`block_connected`] for details. Used instead of [`block_connected`] by clients that are notified of transactions rather than blocks. See [`chain::Confirm`] for calling expectations. [`block_connected`]: Self::block_connected
      • transaction_unconfirmed

        public void transaction_unconfirmed​(byte[] txid,
                                            BroadcasterInterface broadcaster,
                                            FeeEstimator fee_estimator,
                                            Logger logger)
        Processes a transaction that was reorganized out of the chain. Used instead of [`block_disconnected`] by clients that are notified of transactions rather than blocks. See [`chain::Confirm`] for calling expectations. [`block_disconnected`]: Self::block_disconnected
      • best_block_updated

        public TwoTuple_TxidCVec_C2Tuple_u32TxOutZZZ[] best_block_updated​(byte[] header,
                                                                          int height,
                                                                          BroadcasterInterface broadcaster,
                                                                          FeeEstimator fee_estimator,
                                                                          Logger logger)
        Updates the monitor with the current best chain tip, returning new outputs to watch. See [`block_connected`] for details. Used instead of [`block_connected`] by clients that are notified of transactions rather than blocks. See [`chain::Confirm`] for calling expectations. [`block_connected`]: Self::block_connected
      • get_relevant_txids

        public TwoTuple_TxidBlockHashZ[] get_relevant_txids()
        Returns the set of txids that should be monitored for re-organization out of the chain.
      • current_best_block

        public BestBlock current_best_block()
        Gets the latest best block which was connected either via the [`chain::Listen`] or [`chain::Confirm`] interfaces.
      • rebroadcast_pending_claims

        public void rebroadcast_pending_claims​(BroadcasterInterface broadcaster,
                                               FeeEstimator fee_estimator,
                                               Logger logger)
        Triggers rebroadcasts/fee-bumps of pending claims from a force-closed channel. This is crucial in preventing certain classes of pinning attacks, detecting substantial mempool feerate changes between blocks, and ensuring reliability if broadcasting fails. We recommend invoking this every 30 seconds, or lower if running in an environment with spotty connections, like on mobile.
      • get_claimable_balances

        public Balance[] get_claimable_balances()
        Gets the balances in this channel which are either claimable by us if we were to force-close the channel now or which are claimable on-chain (possibly awaiting confirmation). Any balances in the channel which are available on-chain (excluding on-chain fees) are included here until an [`Event::SpendableOutputs`] event has been generated for the balance, or until our counterparty has claimed the balance and accrued several confirmations on the claim transaction. Note that for `ChannelMonitors` which track a channel which went on-chain with versions of LDK prior to 0.0.111, balances may not be fully captured if our counterparty broadcasted a revoked state. See [`Balance`] for additional details on the types of claimable balances which may be returned here and their meanings.