eb4a0a06ac
This makes the fees package an internal package such that it will no longer be an exported module. The only place its functionality is really needed is for the internal implementation of dcrd itself and thus having an unnecessary exported module significantly increases the maintenance burden. This is part of the overall effort to reduce the total number of modules and eventually get to the point that it will be possible to follow semver for the root module. It is worth noting that there are a few constants, which will be listed below, that were exported from this module that callers might have previously relied upon. However, due to previous discussions about the goal of removing the module, a code search has revealed that there are no known callers that rely on them. The aforementioned constants are: - DefaultMaxBucketFeeMultiplier - DefaultMaxConfirmations - DefaultFeeRateStep Overview of the major changes: - Move the following files from fees -> internal/fees: - README.md - cmd/dumpfeedb/dumpfeedb.go - doc.go - estimator.go - log.go - Remove fees/go.mod and fees/go.sum - Make the README.md and doc.go files match the new reality - Update all import paths in the repository accordingly - Remove the dependency from the root go.mod - Run go mod tidy on all modules
108 lines
4.4 KiB
Go
108 lines
4.4 KiB
Go
// Copyright (c) 2018-2020 The Decred developers
|
|
// Use of this source code is governed by an ISC
|
|
// license that can be found in the LICENSE file.
|
|
|
|
/*
|
|
Package fees provides decred-specific methods for tracking and estimating fee
|
|
rates for new transactions to be mined into the network. Fee rate estimation has
|
|
two main goals:
|
|
|
|
- Ensuring transactions are mined within a target _confirmation range_
|
|
(expressed in blocks);
|
|
- Attempting to minimize fees while maintaining be above restriction.
|
|
|
|
Preliminaries
|
|
|
|
There are two main regimes against which fee estimation needs to be evaluated
|
|
according to how full blocks being mined are (and consequently how important fee
|
|
rates are): _low contention_ and _high contention_:
|
|
|
|
In a low contention regime, the mempool sits mostly empty, transactions are
|
|
usually mined very soon after being published and transaction fees are mostly
|
|
sent using the minimum relay fee.
|
|
|
|
In a high contention regime, the mempool is usually filled with unmined
|
|
transactions, there is active dispute for space in a block (by transactions
|
|
using higher fees) and blocks are usually full.
|
|
|
|
The exact point of where these two regimes intersect is arbitrary, but it should
|
|
be clear in the examples and simulations which of these is being discussed.
|
|
|
|
Note: a very high contention scenario (> 90% of blocks being full and
|
|
transactions remaining in the mempool indefinitely) is one in which stakeholders
|
|
should be discussing alternative solutions (increase block size, provide other
|
|
second layer alternatives, etc). Also, the current fill rate of blocks in decred
|
|
is low, so while we try to account for this regime, I personally expect that the
|
|
implementation will need more tweaks as it approaches this.
|
|
|
|
The current approach to implement this estimation is based on bitcoin core's
|
|
algorithm. References [1] and [2] provide a high level description of how it
|
|
works there. Actual code is linked in references [3] and [4].
|
|
|
|
Outline of the Algorithm
|
|
|
|
The algorithm is currently based in fee estimation as used in v0.14 of bitcoin
|
|
core (which is also the basis for the v0.15+ method). A more comprehensive
|
|
overview is available in reference [1].
|
|
|
|
This particular version was chosen because it's simpler to implement and should
|
|
be sufficient for low contention regimes. It probably overestimates fees in
|
|
higher contention regimes and longer target confirmation windows, but as pointed
|
|
out earlier should be sufficient for current fill rate of decred's network.
|
|
|
|
The basic algorithm is as follows (as executed by a single full node):
|
|
|
|
Stats building stage:
|
|
|
|
- For each transaction observed entering mempool, record the block at which it
|
|
was first seen
|
|
- For each mined transaction which was previously observed to enter the mempool,
|
|
record how long (in blocks) it took to be mined and its fee rate
|
|
- Group mined transactions into fee rate _buckets_ and _confirmation ranges_,
|
|
creating a table of how many transactions were mined at each confirmation
|
|
range and fee rate bucket and their total committed fee
|
|
- Whenever a new block is mined, decay older transactions to account for a
|
|
dynamic fee environment
|
|
|
|
Estimation stage:
|
|
|
|
- Input a target confirmation range (how many blocks to wait for the tx to be
|
|
mined)
|
|
- Starting at the highest fee bucket, look for buckets where the chance of
|
|
confirmation within the desired confirmation window is > 95%
|
|
- Average all such buckets to get the estimated fee rate
|
|
|
|
Simulation
|
|
|
|
Development of the estimator was originally performed and simulated using the
|
|
code in [5]. Simulation of the current code can be performed by using the
|
|
dcrfeesim tool available in [6].
|
|
|
|
Acknowledgements
|
|
|
|
Thanks to @davecgh for providing the initial review of the results and the
|
|
original developers of the bitcoin core code (the brunt of which seems to have
|
|
been made by @morcos).
|
|
|
|
## References
|
|
|
|
[1] Introduction to Bitcoin Core Estimation:
|
|
https://bitcointechtalk.com/an-introduction-to-bitcoin-core-fee-estimation-27920880ad0
|
|
|
|
[2] Proposed Changes to Fee Estimation in version 0.15:
|
|
https://gist.github.com/morcos/d3637f015bc4e607e1fd10d8351e9f41
|
|
|
|
[3] Source for fee estimation in v0.14:
|
|
https://github.com/bitcoin/bitcoin/blob/v0.14.2/src/policy/fees.cpp
|
|
|
|
[4] Source for fee estimation in version 0.16.2:
|
|
https://github.com/bitcoin/bitcoin/blob/v0.16.2/src/policy/fees.cpp
|
|
|
|
[5] Source for the original dcrfeesim and estimator work:
|
|
https://github.com/matheusd/dcrfeesim_dev
|
|
|
|
[6] Source for the current dcrfeesim, using this module:
|
|
https://github.com/matheusd/dcrfeesim
|
|
*/
|
|
package fees
|