In this commit, we create a new chainfee package, that houses all fee
related functionality used within the codebase. The creation of this new
package furthers our long-term goal of extracting functionality from the
bloated `lnwallet` package into new distinct packages. Additionally,
this new packages resolves a class of import cycle that could arise if a
new package that was imported by something in `lnwallet` wanted to use
the existing fee related functions in the prior `lnwallet` package.
Because the BestBlock method of ChainIO is not exposed through any
RPC we want to get rid of it so we can use the sweeper outside of
lnd too. Since the chain notifier now also delivers the current best
block we don't need the BestBlock method any more.
In this commit, we introduce the ability to bump the fee of an input
within the UtxoSweeper. Once its fee rate is bumped, a replacement
transaction (RBF) will be broadcast with the newer fee rate (assuming
the newer fee rate is high enough to be valid), replacing any
conflicting lower fee rate transactions.
Note that this currently doesn't validate the fee preference of the
bump. This responsibility is delegated to the caller, so care must be
taken to ensure the new fee preference is sufficient.
In this commit, we address another issue that arose with the
introduction of the fee rate buckets. We'll use an example to explain
the problem space:
Let's say we have inputs A, B, and C within the same fee rate bucket. If
A's fee rate is bumped to a higher bucket, then it's currently possible
for the lower fee rate bucket to be swept first, which would produce an
invalid RBF transaction since we're removing an input from the original
without providing a higher fee. By the time we get to the higher fee
rate bucket, we broadcast a valid RBF transaction _only_ sweeping input
A, which would evict the transaction sweeping inputs B and C from the
mempool.
To prevent this eviction, we can simply broadcast the higher fee rate
sweep transactions first, to ensure we have valid RBF transactions.
In this commit, we introduce support for arbitrary client fee
preferences when accepting input sweep requests. This is possible with
the addition of fee rate buckets. Fee rate buckets are buckets that
contain inputs with similar fee rates within a specific range, e.g.,
1-10 sat/vbyte, 11-20 sat/vbyte, etc. Having these buckets allows us to
batch and sweep inputs from different clients with similar fee rates
within a single transaction, allowing us to save on chain fees.
With this addition, we can now get rid of the UtxoSweeper's default fee
preference. As of this commit, any clients using the it to sweep inputs
specify the same fee preference to not change their behavior. Each of
these can be fine-tuned later on given their use cases.
This commit is a step to split the lnwallet package. It puts the Input
interface and implementations in a separate package along with all their
dependencies from lnwallet.
In this commit, we extract the existing determineFeePerKw method on the
RPC server into a new file in the sweep package. Along the way, we
consolidate code by introducing a new FeePreference struct, which allows
the caller to express their fee preference either in blocks to
confirmation, or a direct fee rate. This move takes a small step to
father decoupling calls in the main RPC server.
In this commit, the sweep package is extended from just tx generation to
an active sweeper that collects sweep inputs and autonomously proceeds
to publish the sweep tx after the batch window time interval has passed
without new inputs being added.
In this commit, we modify the newly introduced UtxoSweeper.CreateSweepTx
to accept the confirmation target as a param of the method rather than a
struct level variable. We do this as this allows each caller to decide
at sweep time, what the fee rate should be, rather than using a global
value that is meant to work in all scenarios. For example, anytime
we're sweeping an output with a CLTV lock that's has a dependant
transaction we need to sweep/cancel, we may require a higher fee rate
than a regular force close with a CSV output.
This commit restores the sweep behavior of
filtering inputs with unknown witness types
from the final sweep transaction. Currently,
such inputs will be included without adding
anything to the weight estimate, possibly
creating a transaction with insufficient fees.
This commit introduces a common interface for sweep
inputs. It eliminates the type checking from UtxoSweeper.
Also the formerly present Amount() getter is removed. It was redundant
because this value is present in SignDesc().Output.Value as well.
