fix(mempool): data race in mempool prepare proposal handler

[yihuang]

Solution:

• use callback style iteration API, and hold the lock during the whole iteration.

A different approach from #21379

---

Author Checklist

All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow up issues.

I have...

• included the correct type prefix in the PR title, you can find examples of the prefixes below:
• confirmed ! in the type prefix if API or client breaking change
• targeted the correct branch (see PR Targeting)
• provided a link to the relevant issue or specification
• 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
• confirmed all CI checks have passed

Reviewers Checklist

All items are required. Please add a note if the item is not applicable and please add
your handle next to the items reviewed if you only reviewed selected items.

Please see Pull Request Reviewer section in the contributing guide for more information on how to review a pull request.

I have...

• confirmed the correct type prefix in the PR title
• confirmed all author checklist items have been addressed
• reviewed state machine logic, API design and naming, documentation is accurate, tests and test coverage

Summary by CodeRabbit

• Bug Fixes

  • Documented a fix for a data race issue in the SDK mempool, enhancing clarity in the CHANGELOG.

• New Features

  • Introduced a new method for transaction selection, allowing for flexible iteration with a callback function.
  • Updated existing transaction selection methods to improve clarity and usability by explicitly defining parameters.

• Tests

  • Added a new test for evaluating concurrency behavior in the transaction insertion and selection process.

[coderabbitai]

Walkthrough

Walkthrough

The changes involve enhancements to the mempool functionality within the SDK, including the introduction of a new transaction selection method SelectBy across multiple mempool implementations. The Select methods have been updated for clarity, and error handling has been improved in the transaction proposal process. A new concurrency test has also been added to evaluate the mempool's behavior under concurrent transaction operations. Additionally, a data race fix has been documented in the CHANGELOG.

Changes

File	Change Summary
CHANGELOG.md	Added entry for bug fix regarding data race in SDK mempool, referenced by pull request #21413; noted deprecation of String() method on address types.
baseapp/abci_utils.go	Modified PrepareProposalHandler to enhance transaction selection and error handling.
types/mempool/mempool.go	Updated Select method with thread-safety note; added SelectBy method for callback-based selection.
types/mempool/noop.go	Added SelectBy method to NoOpMempool for flexible transaction selection.
types/mempool/priority_nonce.go	Updated Select method parameters; added SelectBy method for custom transaction processing.
types/mempool/priority_nonce_test.go	Introduced TestIteratorConcurrency to evaluate concurrency behavior in transaction processing.
types/mempool/sender_nonce.go	Updated Select method parameters; added SelectBy method for enhanced transaction selection.

Sequence Diagram(s)

sequenceDiagram
    participant Client
    participant Mempool
    participant Transaction

    Client->>Mempool: Insert Transaction
    Mempool->>Transaction: Validate Transaction
    Transaction-->>Mempool: Return Validity
    Mempool->>Client: Confirm Insertion

Loading

sequenceDiagram
    participant Client
    participant Mempool
    participant Transaction

    Client->>Mempool: Select Transactions
    Mempool->>Transaction: Use SelectBy with Callback
    Transaction-->>Mempool: Return Selected Transactions
    Mempool->>Client: Provide Selected Transactions

Loading

---

Thank you for using CodeRabbit. We offer it for free to the OSS community and would appreciate your support in helping us grow. If you find it useful, would you consider giving us a shout-out on your favorite social media?

Share

• X
• Mastodon
• Reddit
• LinkedIn

Tips

Chat

There are 3 ways to chat with CodeRabbit:

• Review comments: Directly reply to a review comment made by CodeRabbit. Example:
  • I pushed a fix in commit <commit_id>.
  • Generate unit testing code for this file.
  • Open a follow-up GitHub issue for this discussion.
• Files and specific lines of code (under the "Files changed" tab): Tag @coderabbitai in a new review comment at the desired location with your query. Examples:
  • @coderabbitai generate unit testing code for this file.
  • @coderabbitai modularize this function.
• PR comments: Tag @coderabbitai in a new PR comment to ask questions about the PR branch. For the best results, please provide a very specific query, as very limited context is provided in this mode. Examples:
  • @coderabbitai generate interesting stats about this repository and render them as a table.
  • @coderabbitai show all the console.log statements in this repository.
  • @coderabbitai read src/utils.ts and generate unit testing code.
  • @coderabbitai read the files in the src/scheduler package and generate a class diagram using mermaid and a README in the markdown format.
  • @coderabbitai help me debug CodeRabbit configuration file.

Note: Be mindful of the bot's finite context window. It's strongly recommended to break down tasks such as reading entire modules into smaller chunks. For a focused discussion, use review comments to chat about specific files and their changes, instead of using the PR comments.

CodeRabbit Commands (Invoked using PR comments)

• @coderabbitai pause to pause the reviews on a PR.
• @coderabbitai resume to resume the paused reviews.
• @coderabbitai review to trigger an incremental review. This is useful when automatic reviews are disabled for the repository.
• @coderabbitai full review to do a full review from scratch and review all the files again.
• @coderabbitai summary to regenerate the summary of the PR.
• @coderabbitai resolve resolve all the CodeRabbit review comments.
• @coderabbitai configuration to show the current CodeRabbit configuration for the repository.
• @coderabbitai help to get help.

Other keywords and placeholders

• Add @coderabbitai ignore anywhere in the PR description to prevent this PR from being reviewed.
• Add @coderabbitai summary to generate the high-level summary at a specific location in the PR description.
• Add @coderabbitai anywhere in the PR title to generate the title automatically.

Documentation and Community

• Visit our Documentation for detailed information on how to use CodeRabbit.
• Join our Discord Community to get help, request features, and share feedback.
• Follow us on X/Twitter for updates and announcements.

[julienrbrt]

Assigning the same reviewers as #21379 (cc @kocubinski & @sontrinh16)

[kocubinski]

LGTM, makes sense to me to provide both non thread-safe and thread-safe iteration (through the use of a callback and iteration scoped locking)

[coderabbitai]

Actionable comments posted: 0

Review details

Configuration used: .coderabbit.yml
Review profile: CHILL

Commits

Files that changed from the base of the PR and between 58af7ee and cb9a589.

Files selected for processing (7)

• CHANGELOG.md (1 hunks)
• baseapp/abci_utils.go (3 hunks)
• types/mempool/mempool.go (1 hunks)
• types/mempool/noop.go (1 hunks)
• types/mempool/priority_nonce.go (2 hunks)
• types/mempool/priority_nonce_test.go (2 hunks)
• types/mempool/sender_nonce.go (2 hunks)

Files skipped from review due to trivial changes (1)

• CHANGELOG.md

Additional context used

Path-based instructions (6)

types/mempool/noop.go (1)

Pattern **/*.go: Review the Golang code for conformity with the Uber Golang style guide, highlighting any deviations.

types/mempool/mempool.go (1)

Pattern **/*.go: Review the Golang code for conformity with the Uber Golang style guide, highlighting any deviations.

types/mempool/sender_nonce.go (1)

Pattern **/*.go: Review the Golang code for conformity with the Uber Golang style guide, highlighting any deviations.

types/mempool/priority_nonce.go (1)

Pattern **/*.go: Review the Golang code for conformity with the Uber Golang style guide, highlighting any deviations.

baseapp/abci_utils.go (1)

Pattern **/*.go: Review the Golang code for conformity with the Uber Golang style guide, highlighting any deviations.

types/mempool/priority_nonce_test.go (2)

Pattern **/*.go: Review the Golang code for conformity with the Uber Golang style guide, highlighting any deviations.

---

Pattern **/*_test.go: "Assess the unit test code assessing sufficient code coverage for the changes associated in the pull request"

Additional comments not posted (13)

types/mempool/noop.go (1)

21-21: Method SelectBy correctly implemented as no-op.

The method SelectBy in NoOpMempool is correctly implemented according to its intended no-op nature, aligning with the PR's objectives to handle data races by ensuring that the lock is held during iteration, even though it does not perform any operations.

types/mempool/mempool.go (2)

16-16: Thread-safety note added to Select method.

The addition of a thread-safety note to the Select method is a crucial update for clarifying its usage constraints in concurrent environments. This is a good practice for preventing potential issues in multi-threaded scenarios.

---

20-20: New method SelectBy added for thread-safe iteration.

The addition of the SelectBy method to the Mempool interface is a significant enhancement, providing a thread-safe mechanism for iterating over the mempool using a callback function. This method is crucial for ensuring safe concurrent operations and aligns with the PR's objectives to address data races.

types/mempool/sender_nonce.go (3)

162-162: Updated Select method enhances clarity and usability.

The update to the Select method in the SenderNonceMempool class, which now explicitly defines the context and transaction byte arrays, enhances its clarity and usability. This change is important for developers to understand the expected inputs and their roles in the transaction selection process.

---

168-168: New method doSelect improves code organization.

The addition of the doSelect method to the SenderNonceMempool class is a positive change, improving code organization and separation of concerns by encapsulating the selection logic. This refactoring is a good practice for maintaining clean and maintainable code.

---

196-196: New method SelectBy added for flexible and thread-safe transaction processing.

The addition of the SelectBy method to the SenderNonceMempool class is a significant enhancement, providing a flexible and thread-safe mechanism for iterating over selected transactions based on custom logic defined in the callback. This method is crucial for ensuring safe concurrent operations and aligns with the PR's objectives to address data races.

types/mempool/priority_nonce.go (5)

354-358: Ensure proper locking during transaction selection.

The changes to the Select method ensure that the mutex is locked during the transaction selection process, which is crucial for preventing data races. This aligns with the PR's objective to fix data race issues.

---

360-360: Good encapsulation of selection logic in doSelect.

The introduction of doSelect improves code modularity by separating the selection logic from the Select method. This is a good practice as it simplifies the main method and makes the code easier to maintain.

---

375-384: Enhanced flexibility and safety in SelectBy.

The SelectBy method introduces a flexible way to handle transaction selection with a callback function, enhancing the functionality of the mempool. The locking mechanism ensures thread safety, which is crucial given the context of the PR.

---

385-385: Proper handling of priority ties in reorderPriorityTies.

The reorderPriorityTies function ensures that transactions with the same priority are correctly ordered based on additional criteria. This is important for maintaining the integrity and predictability of the mempool.

---

385-385: Effective resolution of priority collisions in senderWeight.

The senderWeight function plays a crucial role in resolving priority collisions by calculating the weight for transactions from the same sender. This ensures fair and predictable transaction ordering in the mempool.

types/mempool/priority_nonce_test.go (1)

400-481: Suggest improvements for deterministic testing and verify concurrency handling.

The test function TestIteratorConcurrency is well-structured and uses appropriate synchronization mechanisms to handle concurrency. However, the use of rand.Intn(100) for generating transaction priorities might lead to non-deterministic test outcomes, which can make failures hard to reproduce.

Consider using a fixed seed with rand.New(rand.NewSource(seed)) for generating predictable random numbers, which can help in reproducing test failures more reliably.

The concurrency handling using context.WithCancel and sync.WaitGroup is correctly implemented.

Ensure that the mempool behaves correctly under concurrent conditions by adding more assertions if necessary, especially after the goroutine has inserted additional transactions.

baseapp/abci_utils.go (1)

Line range hint 289-368: Review of PrepareProposalHandler function changes

The changes in the PrepareProposalHandler function introduce a callback-style iteration for transaction selection, which is a significant shift from the previous iterator-based approach. This change aims to maintain the lock throughout the transaction selection process, addressing the data race issue identified in the PR.

1. Callback Implementation (Lines 294-358): The use of SelectBy with a callback function is a robust approach to ensure that the lock is maintained during the entire transaction selection process. This method allows for more controlled and safe handling of transactions, especially in a concurrent environment.

2. Error Handling (Lines 360-368): The error handling has been adjusted to handle errors after the transaction selection loop. This approach prevents the interruption of the transaction flow and allows for more efficient error management.

3. Transaction Validation and Removal (Lines 332, 364-368): The logic to append invalid transactions and subsequently remove them from the mempool is crucial for maintaining the integrity of the transaction pool. This ensures that only valid transactions are considered for proposals, enhancing the robustness of the system.

Overall, the changes are well-aligned with the objectives of the PR to address the data race issue and improve the efficiency and reliability of the transaction proposal process. The use of a callback-style iteration API is a significant improvement over the previous implementation.

The changes to the PrepareProposalHandler function are approved as they effectively address the identified issues and improve the transaction handling mechanism.

[coderabbitai]

Actionable comments posted: 0

Review details

Configuration used: .coderabbit.yml
Review profile: CHILL

Commits

Files that changed from the base of the PR and between cb9a589 and 13a1d77.

Files selected for processing (1)

• baseapp/abci_utils.go (4 hunks)

Files skipped from review as they are similar to previous changes (1)

• baseapp/abci_utils.go

[coderabbitai]

Actionable comments posted: 0

Review details

Configuration used: .coderabbit.yml
Review profile: CHILL

Commits

Files that changed from the base of the PR and between 13a1d77 and 63e9a80.

Files selected for processing (1)

• CHANGELOG.md (1 hunks)

Files skipped from review as they are similar to previous changes (1)

• CHANGELOG.md

[coderabbitai]

Actionable comments posted: 0

Review details

Configuration used: .coderabbit.yml
Review profile: CHILL

Commits

Files that changed from the base of the PR and between 63e9a80 and 86a613d.

Files selected for processing (1)

• baseapp/abci_utils.go (4 hunks)

Files skipped from review as they are similar to previous changes (1)

• baseapp/abci_utils.go

[julienrbrt]

For the backport in v0.50, we'll need to remove the added SelectBy method from the interface; otherwise it is a breaking change.

Could you add a changelog about the addition btw in this PR?

[yihuang]

For the backport in v0.50, we'll need to remove the added SelectBy method from the interface; otherwise it is a breaking change.

what if we add a new interface which has this method, and use it in abci_utils, that should be not API breaking I guess?

Could you add a changelog about the addition btw in this PR?

done

[coderabbitai]

Actionable comments posted: 0

Review details

Configuration used: .coderabbit.yml
Review profile: CHILL

Commits

Files that changed from the base of the PR and between 86a613d and 60040bc.

Files selected for processing (1)

• CHANGELOG.md (1 hunks)

Files skipped from review as they are similar to previous changes (1)

• CHANGELOG.md