When we cancel a confirmation request, we should remove the request from
the height map regardless of the current height. Otherwise we end up in
the situation when the height is reached, the notification is attempted
sent which results in a crash.
If a concurrent call to cancel is made while the notifier is shutting
down, this would cause a panic (close of closed channel) since the
events are not removed from the notification sets.
This addresses a panic when a notification is canceled after its been
detected as included in a block and before its confirmation notification
is dispatched.
This prevents a deadlock while tearing down the TxNotifier if it's
currently blocked delivering a notification. By closing the quit chan
first, we ensure blocked sends/reads can exit and allow the TxNotifier
to proceed tearing down.
A height hint not being set would cause lnd to scan for the
confirmation/spend of a txid/outpoint/address from genesis.
The number of confirmations not being set within a confirmation request
would cause the internal TxNotifier to deadlock when dispatching
updates.
In this commit, we extend the BitcoindNotifier to support registering
scripts for spends notifications. Once the script has been detected as
spent within the chain, a spend notification will be dispatched through
the Spend channel of the SpendEvent returned upon registration.
For scripts that have been spent in the past, the rescan logic has been
modified to match on the script rather than the outpoint. This is done
by re-deriving the script of the output a transaction input is spending
and checking whether it matches ours.
For scripts that are unspent, a request to the backend will be sent to
alert the BitcoindNotifier of when the script was spent by a
transaction. To make this request we encode the script as an address, as
this is what the backend uses to detect the spend. The transaction will
then be proxied through the txUpdates concurrent queue, which will hand
it off to the underlying txNotifier and dispatch spend notifications to
the relevant clients.
Along the way, we also address an issue where we'd miss detecting that
an outpoint/script has been spent in the future due to not receiving a
historical dispatch request from the underlying txNotifier. To fix this,
we ensure that we always request the backend to notify us of the spend
once it detects it at tip, regardless of whether a historical rescan was
detected or not.
In this commit, we extend the BtcdNotifier to support registering
scripts for confirmation notifications. Once the script has been
detected as confirmed within the chain, a confirmation notification will
be dispatched to through the Confirmed channel of the ConfirmationEvent
returned upon registration.
For scripts that have confirmed in the past, the `historicalConfDetails`
method has been modified to skip the txindex and go straight to scanning
the chain manually if confirmation request is for a script. When
scanning the chain, we'll determine whether the script has been
confirmed by locating the script in an output of a confirmed
transaction.
For scripts that have yet to confirm, they will be properly tracked
within the TxNotifier.
In this commit, we refactor the TxNotifier's ProcessRelevantSpendTx to
also detect script spends. This can easily be done as the transaction
filtering logic was refactored into its own method in a previous commit.
In this commit, we modify the TxNotifier's ConnectTip method to also
detect whether a registered script has been confirmed or spent on-chain
by a transaction in the connected block. Once detected, notifications
for them will be queued up for dispatch as with txids/outpoints.
We've also refactored the ConnectTip method into smaller and reusable
methods, which will serve useful later.
In this commit, we refactor the HeightHintCache and its underlying
interfaces to be able to manipulate hints for ConfRequests and
SpendRequests. By doing so, we'll be able to manipulate hints for
scripts if the request includes either a zero hash or a zero outpoint.
These structs allow us to request notifications for either
txids/outpoints or output scripts. We'll be using these in later commits
to index confirmation and spend requests within the TxNotifier.
In this commit, we modify the TxNotifier's ConnectTip method to no
longer dispatch notifications to any clients who had a request fulfilled
within the height connected. Instead, it will queue the notifications
for dispatch and we add a new method NotifyHeight, which will actually
dispatch them. We do this to allow the users of the TxNotifier to be
more flexible when dispatching notifications.
In this commit, we'll now commit the current height of the TxNotifier as
the height hint for an outpoint/transaction after a rescan has been
completed and has determined that the outpoint is unspent/transaction is
unconfirmed. We do this to prevent another potentially long rescan if
the daemon is restarted before a new block comes in (which is when the
hints will be updated again).
In this commit, we address an issue w.r.t. updating the confirm hints
for transactions and spend hints for outpoints on chain updates.
Previously, upon a block being disconnected, we'd attempt to commit a
new height hint for all outstanding confirmation notifications. This is
not correct because we'll end up modifying the height hint for things
that have confirmed at a previous height than the one being
disconnected. This would cause issues on restart when attempting a
historical dispatch, as we would start scanning at a height above which
the transaction actually confirmed in.
This has been addressed by only updating the hints for outstanding
notifications that are still unconfirmed/unspent and for notifications
that were confirmed/spent within the block being connected/disconnected.
In this commit, we introduce support to the TxNotifier to detect
spending transactions of registered outpoints being reorged out of the
chain. In the event that a reorg does occur, we'll consume the Spend
notification if it hasn't been consumed yet, and dispatch a Reorg
notification instead.
In this commit, we add support to allow the TxNotifier to properly
determine whether a new block extending the chain contains a transaction
that spends a registered outpoint. In the event that it does, spend
notifications will be dispatched to all active registered clients for
such outpoint.
In this commit, we introduce the registration logic for spend
notifications to the TxNotifier. Most of this logic was taken from the
different existing ChainNotifier implementations, however, it features
some useful additions in order to make the ChainNotifier a bit more robust.
Some of these additions include the following:
1. RegisterSpend will now return a HistoricalSpendDispatch struct,
which includes the details for successfully determining if an outpoint
was spent in the past. A HistoricalSpendDispatch will only be returned
upon the first registration of an outpoint. This is done as,
previously, if multiple clients registered for the same outpoint, then
multiple historical rescans would also be dispatched, incurring a toll
on the backend itself.
2. UpdateSpendDetails will now be used to determine when a historical
rescan has completed, no matter if a spending transaction was found or
not. This is needed in order to responsibly update the spend hints for
outpoints at tip, otherwise we'd attempt to update them even though we
haven't yet determined if they have been spent or not. This will
dispatch notifications to all currently registered clients for the
same outpoint. In the event that another client registers later on,
then the spending details are cached in memory in order to prevent
further historical rescans.
In this commit, we introduce the required fields for the TxNotifier to
properly carry its duties in notifying its registered clients about the
spend of an outpoint. These are not yet used, but will be throughout the
some of the following commits.
In this commit, we add a new channel within the SpendEvent struct that
will be sent upon whenever the spending transaction of the registered
outpoint gets reorged out of the chain. This will pave the road for
successfully handling a funding transaction getting reorged out of the
chain among other things.
