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fix(x/staking): dust share #18841

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merged 7 commits into from
Feb 20, 2024
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@JoowonYun JoowonYun commented Dec 20, 2023

Description

Closes: #13086

Amount less than 1stake remains in the share, delegation is removed.

PS. If you agree with this policy, I will add test code and migration details.


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  • reviewed "Files changed" and left comments if necessary
  • included the necessary unit and integration tests
  • added a changelog entry to CHANGELOG.md
  • updated the relevant documentation or specification, including comments for documenting Go code
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  • reviewed state machine logic, API design and naming, documentation is accurate, tests and test coverage

Summary by CodeRabbit

  • New Features
    • Introduced a more efficient handling of small delegation shares during the undelegation process to avoid leaving dust shares.
  • Bug Fixes
    • Ensured complete unbonding of small amounts that are less than the minimum share tolerance.
  • Tests
    • Added tests to ensure the correct undelegation behavior with small delegation shares.
  • Documentation
    • Updated CHANGELOG.md with details on significant changes, including:
      • State machine and API breaking changes.
      • Updates to CLI commands and balance query endpoint compatibility.
      • Introduction of a flag to disable fast node migration.

@JoowonYun JoowonYun requested a review from a team as a code owner December 20, 2023 10:16
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coderabbitai bot commented Dec 20, 2023

Walkthrough

Walkthrough

The code changes aim to address the persistence of "dust shares" on validators after delegation removal. By implementing a tolerance-based condition to fully unbond small delegation shares, the update ensures that residual dust shares are effectively cleared, enhancing user experience and minimizing unnecessary gas fees.

Changes

File Path Change Summary
x/staking/keeper/delegation.go Replaced the logic for capping shares with a tolerance condition to fully unbond small delegation shares.
x/staking/keeper/delegation_test.go Added TestUndelegateWithDustShare to test the handling of small delegation shares during undelegation.
CHANGELOG.md Updated to reflect changes related to addressing delegations with dust shares.

Assessment against linked issues

Objective Addressed Explanation
Address the issue of "dust" shares remaining after delegation removal ( #13086 )
Ensure that undelegating, redelegating, or delegating a larger amount removes the "dust" shares ( #13086 )
Provide examples of affected accounts to illustrate the occurrence of the issue ( #13086 ) Providing specific examples is not a code change; it would typically be part of testing or documentation.
The issue should be addressed across multiple validators, not specific to one ( #13086 ) The fix is universally applied to handle dust shares on all validators, not limited to specific instances.

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@JoowonYun can you please provide a changelog entry, along with a unit test or update an existing unit test case?

@julienrbrt julienrbrt changed the title fix: dust share fix(x/staking): dust share Dec 20, 2023
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JoowonYun commented Dec 21, 2023

@JoowonYun can you please provide a changelog entry, along with a unit test or update an existing unit test case?

Of course. I'll add it.

@facundomedica facundomedica self-assigned this Dec 21, 2023
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utACK. I think the changelog entries could be a bit more explanatory.

@@ -1201,7 +1201,12 @@ func (k Keeper) ValidateUnbondAmount(
// due to rounding, however we don't want to truncate the shares or take the
// minimum because we want to allow for the full withdraw of shares from a
// delegation.
if shares.GT(delShares) {
tolerance, err := validator.SharesFromTokens(math.OneInt())
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update the comment above

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@JoowonYun JoowonYun Dec 28, 2023

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CHANGELOG.md Outdated
@@ -89,6 +89,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
* (simulation) [#17911](https://github.com/cosmos/cosmos-sdk/pull/17911) Fix all problems with executing command `make test-sim-custom-genesis-fast` for simulation test.
* (simulation) [#18196](https://github.com/cosmos/cosmos-sdk/pull/18196) Fix the problem of `validator set is empty after InitGenesis` in simulation test.
* (baseapp) [#18551](https://github.com/cosmos/cosmos-sdk/pull/18551) Fix SelectTxForProposal the calculation method of tx bytes size is inconsistent with CometBFT
* (x/staking) [#18841](https://github.com/cosmos/cosmos-sdk/pull/18841) Fix delegation when undelegate dust share
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this deserves a more thorough explanation. "implement a minimum shares per delegation" or something

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@JoowonYun JoowonYun Dec 28, 2023

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CHANGELOG.md Outdated
@@ -193,6 +194,7 @@ Ref: https://keepachangelog.com/en/1.0.0/

* (x/upgrade) [#16244](https://github.com/cosmos/cosmos-sdk/pull/16244) Upgrade module no longer stores the app version but gets and sets the app version stored in the `ParamStore` of baseapp.
* (x/staking) [#17655](https://github.com/cosmos/cosmos-sdk/pull/17655) `HistoricalInfo` was replaced with `HistoricalRecord`, it removes the validator set and comet header and only keep what is needed for IBC.
* (x/staking) [#18841](https://github.com/cosmos/cosmos-sdk/pull/18841) The existing dust share delegation must be removed.
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same as above

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@JoowonYun JoowonYun Dec 28, 2023

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Comment on lines 1200 to 1210
// Depending on the share, amount can be smaller than unit amount(1stake).
// All shares smaller than the minimum share are unboned.
tolerance, err := validator.SharesFromTokens(math.OneInt())
if err != nil {
return shares, err
}

if delShares.Sub(shares).LT(tolerance) {
shares = delShares
}
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The logic introduced to handle dust shares during unbonding appears to be correct. It checks if the remaining shares after unbonding are less than the tolerance (which is the smallest unit of shares that can be unbonded) and if so, it sets the shares to be unbonded to the total delegation shares. This ensures that no dust shares remain.

However, the comment on line 1201 could be improved for clarity. It currently reads "All shares smaller than the minimum share are unboned." which might be a typo and could be confusing. It should clearly state that any remaining shares smaller than the minimum share unit will be completely unbonded to avoid dust shares.

- // All shares smaller than the minimum share are unboned.
+ // If the remaining shares after unbonding are smaller than the minimum share unit, 
+ // they are considered dust and will be completely unbonded to avoid leaving dust shares.

Committable suggestion

IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation.

Suggested change
// Depending on the share, amount can be smaller than unit amount(1stake).
// All shares smaller than the minimum share are unboned.
tolerance, err := validator.SharesFromTokens(math.OneInt())
if err != nil {
return shares, err
}
if delShares.Sub(shares).LT(tolerance) {
shares = delShares
}
// Depending on the share, amount can be smaller than unit amount(1stake).
// If the remaining shares after unbonding are smaller than the minimum share unit,
// they are considered dust and will be completely unbonded to avoid leaving dust shares.
tolerance, err := validator.SharesFromTokens(math.OneInt())
if err != nil {
return shares, err
}
if delShares.Sub(shares).LT(tolerance) {
shares = delShares
}

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lgtm

CHANGELOG.md Outdated Show resolved Hide resolved
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LGTM. @facundomedica mind taking a quick look please?

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I have a one question.
To remove dust delegation in the existing chain, it should be migration like below.
https://github.com/xpladev/xpla/pull/109/files#diff-85cee45041d35d29fecd2c334c7e4635cc2536f09f9bb1ecc1788243ab70d933R19-R37

For this purpose, I am curious about the policy on whether it is correct to up the ConsensusVersion of the staking module and create a migration function, or whether it through the upgrade handler like above.

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alexanderbez commented Jan 3, 2024

If you want a migration to happen in a module, like the one you linked, you need to bump the consensus version yes. Otherwise, the migration won't be triggered.

Alternatively, you can manually call this migration in your app's upgrade handler.

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github-actions bot commented Feb 3, 2024

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

@github-actions github-actions bot added the Stale label Feb 3, 2024
@julienrbrt julienrbrt removed the Stale label Feb 6, 2024
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Review Status

Actionable comments generated: 3

Configuration used: .coderabbit.yml

Commits Files that changed from the base of the PR and between ff6e240 and 5b229d5.
Files selected for processing (1)
  • CHANGELOG.md (3 hunks)
Additional comments: 2
CHANGELOG.md (2)
  • 100-100: The API Breaking Changes section mentions a significant change in the x/consensus module creation process. This entry is clear and specifies the PR for reference. It's important to ensure that all downstream dependencies and documentation are updated to reflect this change.
Verification successful

The search results indicate that the x/consensus module and its changes are mentioned in several places within the project, including the CHANGELOG.md, README.md, UPGRADING.md, and a specific README.md within the x/consensus directory itself. These references include details about the changes made to the x/consensus module, such as the introduction of a new module to handle Tendermint consensus parameters, changes in method signatures (e.g., NewKeeper now takes a KVStoreService), and guidance for migrating existing parameters from the deprecated x/params to the new x/consensus module.

Given this context, it appears that the documentation and upgrade guides have been updated to reflect the significant changes in the x/consensus module creation process. The presence of detailed entries in UPGRADING.md and README.md files, specifically addressing the x/consensus module, suggests that efforts have been made to ensure downstream dependencies and documentation are aligned with these changes.

Based on the information gathered, it seems reasonable to conclude that the necessary documentation and examples have been updated to account for the changes in the x/consensus module creation process.

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# Search for documentation or examples that might need updating due to the consensus module creation change.
rg --type md 'x/consensus' --exec cat {}

Length of output: 451



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# Corrected search for documentation or examples mentioning 'x/consensus' in markdown files.
rg --type md 'x/consensus'

Length of output: 1985

* 2797-2797: The link to the previous versions' CHANGELOG is a helpful resource for users looking to understand the historical context of changes. Ensure this link is kept up to date with the correct branch or tag to maintain accessibility.
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The verification process has successfully confirmed that the linked CHANGELOG.md for previous versions in the cosmos-sdk repository is accessible and returns a HTTP/2 200 status code, indicating that the link points to a valid resource. Therefore, the link is correctly maintained and accessible, aligning with the review comment's suggestion to ensure the link is kept up to date for user accessibility.

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curl -sI https://github.com/cosmos/cosmos-sdk/blob/c17c3caab86a1426a1eef4541e8203f5f54a1a54/CHANGELOG.md | grep HTTP/2 200

Length of output: 161



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#!/bin/bash
# Verify that the linked CHANGELOG.md for previous versions is accessible and points to the correct branch or tag.
curl -sI https://github.com/cosmos/cosmos-sdk/blob/c17c3caab86a1426a1eef4541e8203f5f54a1a54/CHANGELOG.md | grep "HTTP/2 200"

Length of output: 138

CHANGELOG.md Outdated
@@ -94,6 +94,10 @@ Every module contains its own CHANGELOG.md. Please refer to the module you are i
* (crypto) [#19371](https://github.com/cosmos/cosmos-sdk/pull/19371) Avoid cli redundant log in stdout, log to stderr instead.
* (client) [#19393](https://github.com/cosmos/cosmos-sdk/pull/19393/) Add `ReadDefaultValuesFromDefaultClientConfig` to populate the default values from the default client config in client.Context without creating a app folder.

### State Machine Breaking

* (x/staking) [#18841](https://github.com/cosmos/cosmos-sdk/pull/18841) In a undelegation or redelegation if the shares being un/re-delegated left correspond to less than 1 token (in base denom) the entire delegation gets removed.
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The description of the change under the State Machine Breaking section for the x/staking module is clear and directly references the PR addressing the issue. However, it would be beneficial to briefly explain the impact on existing delegations and the rationale behind removing entire delegations for clarity to the reader.

Consider adding a brief explanation of the impact on users and the rationale behind this change for better clarity.

@@ -1234,7 +1238,7 @@
* (x/group) [#13214](https://github.com/cosmos/cosmos-sdk/pull/13214) Add `withdraw-proposal` command to group module's CLI transaction commands.
* (x/auth) [#13048](https://github.com/cosmos/cosmos-sdk/pull/13048) Add handling of AccountNumberStoreKeyPrefix to the simulation decoder.
* (simapp) [#13107](https://github.com/cosmos/cosmos-sdk/pull/13107) Call `SetIAVLCacheSize` with the configured value in simapp.
* [#13301](https://github.com/cosmos/cosmos-sdk/pull/13301) Keep the balance query endpoint compatible with legacy blocks
* [#13301](https://github.com/cosmos/cosmos-sdk/pull/13301) Keep the balance query endpoint compatible with legacy blocks
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The addition regarding the balance query endpoint compatibility with legacy blocks is a valuable update for users relying on historical data. Ensure that this change is well-documented in the relevant API documentation to avoid confusion.

Recommend updating the API documentation to clearly reflect this compatibility change.

CHANGELOG.md Outdated
Comment on lines 94 to 103
* (crypto) [#19371](https://github.com/cosmos/cosmos-sdk/pull/19371) Avoid cli redundant log in stdout, log to stderr instead.
* (client) [#19393](https://github.com/cosmos/cosmos-sdk/pull/19393/) Add `ReadDefaultValuesFromDefaultClientConfig` to populate the default values from the default client config in client.Context without creating a app folder.

### State Machine Breaking

* (x/staking) [#18841](https://github.com/cosmos/cosmos-sdk/pull/18841) In a undelegation or redelegation if the shares being un/re-delegated left correspond to less than 1 token (in base denom) the entire delegation gets removed.

### API Breaking Changes

* (x/consensus) [#19488](https://github.com/cosmos/cosmos-sdk/pull/19488) Consensus module creation takes `appmodule.Environment` instead of individual services.
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📝 NOTE
This review was outside the diff hunks, and no overlapping diff hunk was found. Original lines [13321-13321]

The introduction of a flag to disable fast node migration and usage is an important feature that could affect deployment and operational strategies. It would be helpful to provide more context or a link to documentation on when and why to use this flag.

Consider adding more context or a link to documentation for the flag to disable fast node migration and usage, helping users understand its purpose and application scenarios.

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Files selected for processing (1)
  • CHANGELOG.md (2 hunks)
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Shares dust in the delegations
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