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DCP: 0007
Title: Revert Treasury Expenditure Policy
Author: Matheus Degiovani <contact@matheusd.com>
Status: Active
Created: 2021-06-23
License: CC0-1.0
License-Code: ISC
Requires: DCP0006

Table of Contents

Abstract

This proposes reverting the currently active maximum expenditure policy of the treasury account to the one specified in the original Politeia proposal for the decentralized treasury.

Motivation

The current algorithm that calculates the maximum expenditure allowed by a set of treasury spend transactions within a given window of blocks takes into account the average spent in a preceding window.

This is different than the policy that was originally proposed and approved by stakeholders in the original Politeia proposal for development of the decentralized treasury[1] and has caused an issue that has prevented payments from the treasury account from being performed.

This proposal modifies the consensus rules to ensure the maximum expenditure policy is in line with what was explicitly approved via Politeia voting, by using the total income into the treasury as the reference value to determine the spending limit.

The maximum expenditure amount is currently calculated by the dcrd reference node implementation by the maxTreasuryExpenditure()[2] function. This function defines the following policy:

The sum of treasury spend amounts inside the most recent expenditure window cannot exceed the average of the spent amount in the preceding N windows in addition to a 50% increase. If no amount is spent in the preceding windows, the maximum allowed amount equals a bootstrap amount in addition to a 50% increase.

For mainnet, the expenditure policy window has a size of 6912 blocks and 6 preceding windows are checked, for a total of 41472 blocks. A bootstrap amount of 16K DCR is used.

A deeper overview of the issue can be read on the Treasury Expenditure Policy Bug blog post[3].

Specification

Change the maximum expenditure policy to the following:

Given:

  • is the size of the policy window (number of blocks that are used to determine the maximum expenditure policy).
  • is the sum of the treasury transactions of type mined in block .
The maximum expenditure policy M for a given block at height h is defined as:

Informally:

  • is the sum of treasury spend transactions inside the most recent policy expenditure window.
  • is the sum of treasury add and treasurybase transactions inside the same window.
  • is the allowance for 150% of the treasury income for the window.

Rationale

Changing the expenditure policy to the one originally specified and approved by stakeholders in Politeia should not be controversial from a community discussion standpoint and solves the immediate issues facing the blocking of spending funds by the decentralized treasury.

The two policies are largely compatible at this point in time since the following relevant factors are valid under both policies:

  • The current average expenditure amount being withdrawn from the treasury.
  • The existing mainnet test treasury spend transaction.
Therefore, if no treasury spend transactions are mined such that they are incompatible to the new rule until the new rule is activated and sufficiently confirmed, it will be possible to remove legacy code dealing with the old policy.

Deployment

Voting Agenda Parameters

This proposal will be deployed to mainnet using the standard Decred on-chain voting infrastructure as follows:

Name Setting
Deployment Version 9
Agenda ID reverttreasurypolicy
Agenda Description Change the treasury maximum expenditure policy as defined in DCP0007
Start Time 1631750400 (Sep 16th, 2021 00:00:00 +0000 UTC)
Expire Time 1694822400 (Sep 16th, 2023 00:00:00 +0000 UTC)
Mask 0x06 (Bits 1 and 2)
Choices
Choice English Description Bits
abstain abstain voting for change 0x00
no keep the existing consensus rules 0x02 (Bit 1)
yes change to the new consensus rules 0x04 (Bit 2)

Voting Results

This proposal was approved by the stakeholder voting process and is now active.

Implementations MAY optimize their enforcement activation logic to apply the new rules specified by this proposal to the Active block and all of its descendants as opposed to tallying historical votes.

Status Block Hash Block Height
Voting Started 0000000000000000199b4ae1b9fe1649ce0a357e728ca12ad46d453c6e8f4ee5 641152
Locked In 0000000000000000320d41ff60cf34d15ae836a7298c94c0e690f18ff1cfbdfa 649216
Active 00000000000000002f4c6aaf0e9cb4d5a74c238d9bf8b8909e2372776c7c214c 657280

Compatibility

This is a hard-forking change to the Decred consensus. This means that once the agenda is voted in and becomes locked in, anybody running code that fully validates blocks must upgrade before the activation time or they will risk rejecting a chain containing a transaction that is invalid under the old rules.

Other software that performs full validation will need to modify their consensus enforcement rules accordingly.

The changes introduced by this proposal modify block acceptance criteria, but no transaction semantics are affected, therefore software other than full nodes or ones dealing directly with accounting of treasury transactions will not be affected by these changes.

Reference Implementation

policyWindow := b.chainParams.TreasuryVoteInterval *
    b.chainParams.TreasuryVoteIntervalMultiplier *
    b.chainParams.TreasuryExpenditureWindow

// First: sum up treasury spends, treasury adds and treasurybases inside the 
// most recent policyWindow.
spentRecent, addedRecent, _, err := b.sumPastTreasuryExpenditure(preTVINode, policyWindow)
if err != nil {
    return 0, err
}

// Treasury can spend up to 150% the amount received in the window.
addedPlusAllowance := addedRecent + addedRecent/2

// The maximum expenditure allowed for the next block is the difference
// between the maximum possible and what has already been spent in the most
// recent policy window. This is capped at zero on the lower end to account
// for cases where the policy _already_ spent more than the allowed.
var allowedToSpend int64
if addedPlusAllowance > spentRecent {
    allowedToSpend = addedPlusAllowance - spentRecent
}

return allowedToSpend, nil

Pull Requests

Revert Treasury Expenditure Policy

A reference implementation of the Revert Treasury Expenditure Policy in accordance with the results of the agenda vote is implemented by dcrd pull request 2680.

Deployment

A reference implementation of the required agenda definition is implemented by dcrd commit 0b99183.

Acknowledgements

Collaborators

Thanks to the following individuals who provided valuable feedback during the review process of this proposal (alphabetical order):

References

Inline References

  1. ^ https://proposals-archive.decred.org/proposals/c96290a
  2. ^ https://github.com/decred/dcrd/blob/afff2fdbcd4c57ade4f0d13e78ad2d3efaebcdec/blockchain/treasury.go#L650
  3. ^ //blog.decred.org/2021/06/25/Treasury-Expenditure-Policy-Bug/

Additional References

Copyright

This document is licensed under the CC0-1.0: Creative Commons CC0 1.0 Universal license.

The code is licensed under the ISC License.