Remaining Tasks For JMT Commit App Hash Implementation

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Overview

This article details the remaining tasks and TODOs following the implementation of the JMT (Jellyfish Merkle Tree) commit app hash feature. The current implementation provides a functional foundation, but further development is required to achieve production-readiness. Our primary focus is on ensuring a robust and reliable system for state persistence and efficient app hash computation. This article serves as a comprehensive roadmap for the next phase of development, outlining key areas of improvement and testing requirements.

The completed work demonstrates significant progress, including the successful integration of JMT with BaseApp for state persistence, the replacement of placeholder app hashes with actual merkle root computations, and the creation of a module-agnostic architecture. We have also added a GlobalAppStore with namespace-based isolation and updated the ABCI server to return the correct app hash. However, several crucial tasks remain to be addressed before the system can be confidently deployed in a production environment.

The following sections break down the remaining tasks by component, outlining the specific areas that require attention. We have categorized these tasks by priority, helping to guide the development efforts towards the most critical improvements first. This structured approach will ensure that we address the most pressing issues and build a solid foundation for future enhancements.

Completed Work

The following items have been successfully completed:

  • βœ… Integrated JMT with BaseApp for state persistence
  • βœ… Replaced placeholder app hash with actual merkle root computation
  • βœ… Made architecture module-agnostic (no hardcoded core modules)
  • βœ… Added GlobalAppStore with namespace-based isolation
  • βœ… Updated ABCI server to return correct app hash

These accomplishments lay the groundwork for a robust and scalable system. The integration of JMT with BaseApp is a significant step forward, providing a reliable mechanism for state management. The module-agnostic architecture allows for greater flexibility and extensibility, enabling us to easily incorporate new modules and functionalities in the future. The GlobalAppStore provides a crucial layer of isolation between namespaces, enhancing security and preventing conflicts. Finally, the updated ABCI server ensures that the correct app hash is returned, which is essential for maintaining consensus and verifying the integrity of the blockchain.

Major TODOs by Component

1. BaseApp (crates/helium-baseapp/src/lib.rs)

High Priority

  • [ ] Integration with actual CometBFT (lines 75-78, 84-94)
    • Currently, the system returns hard-coded default responses. This is a placeholder implementation that needs to be replaced with proper CometBFT integration. CometBFT is the consensus engine that powers the blockchain, and its correct integration is crucial for the system to function properly.
    • The integration will involve implementing a proper CometBFT RPC client that can communicate with the CometBFT node. This client will be responsible for sending requests to CometBFT and receiving responses, allowing the BaseApp to participate in the consensus process.
  • [ ] WASI module execution forwarding (lines 133-139, 194-200, 209-215, 305-311)
    • This includes the execution of ante handlers, begin/end blockers, and transaction processing. WASI (WebAssembly System Interface) modules are a key part of the architecture, allowing for flexible and secure execution of smart contracts and other logic.
    • Currently, the system does not properly forward execution to WASI modules. This needs to be implemented to enable the execution of smart contracts and other application logic within the blockchain.

Medium Priority

  • [ ] State change collection during transactions (lines 257-259)
    • Currently, changes are committed directly to the state. This should be modified to collect and batch changes per transaction, improving performance and atomicity.
    • The current approach of directly committing changes to the state can lead to performance bottlenecks and inconsistencies. By collecting changes during a transaction and then committing them in a batch, we can improve efficiency and ensure that transactions are atomic, meaning that they either succeed completely or fail completely.
  • [ ] Proper error handling (lines 260-262)
    • This includes implementing rollback mechanisms on transaction failure to ensure state consistency guarantees. Robust error handling is essential for maintaining the integrity of the blockchain and preventing data corruption.
    • The current error handling is inadequate and needs to be improved. Specifically, we need to implement mechanisms to rollback state changes if a transaction fails. This will ensure that the state remains consistent even in the face of errors.

2. ABCI Server (crates/helium-server/src/abci_server.rs)

  • [ ] Snapshot management (lines 105, 210)
    • This includes the ability to list snapshots, offer snapshots, and apply snapshot chunks. Snapshots are crucial for efficient state synchronization and recovery.
    • Snapshot management is a critical feature for any blockchain system. It allows nodes to quickly synchronize with the network and recover from failures. The ABCI server needs to be able to list existing snapshots, offer snapshots to other nodes, and apply snapshot chunks to rebuild its state.
  • [ ] Consensus parameter updates (lines 107, 227)
    • This involves implementing height-based consensus parameter changes and validator set updates. The ability to dynamically adjust consensus parameters is essential for adapting to changing network conditions and maintaining security.
    • Consensus parameters, such as block size and gas limits, may need to be adjusted over time to optimize network performance and security. The ABCI server needs to be able to handle these updates based on the current block height.
    • Validator set updates are also crucial for maintaining the integrity of the blockchain. The ABCI server needs to be able to process changes to the validator set, such as adding or removing validators.
  • [ ] Evidence handling (line 227)
    • This involves processing misbehavior evidence from CometBFT. Handling evidence of misbehavior is crucial for maintaining the integrity of the network and punishing malicious actors.
    • CometBFT provides mechanisms for detecting and reporting misbehavior by validators. The ABCI server needs to be able to process this evidence and take appropriate action, such as slashing the stake of a misbehaving validator.

3. Client CLI (crates/helium-cli/)

Most commands are currently stubs and require full implementation.

  • [ ] Query commands (src/cmd/query/*.rs)
    • This includes implementing queries for bank balances, staking validator information, and governance proposals. The CLI needs to provide users with the ability to query the state of the blockchain.
    • Currently, the query commands are mostly stubs. We need to implement the actual logic for querying different aspects of the blockchain state, such as bank balances, staking information, and governance proposals.
  • [ ] Transaction commands (src/cmd/tx.rs)
    • This involves implementing actual transaction building and signing, as well as broadcasting transactions to the network. The CLI needs to provide users with the ability to create and submit transactions to the blockchain.
    • The transaction commands are also currently stubs. We need to implement the logic for building transactions, signing them using the user's private key, and broadcasting them to the network.
  • [ ] Key management (src/cmd/keys.rs)
    • This includes implementing secure key storage and hardware wallet support. Secure key management is essential for protecting user funds and ensuring the integrity of transactions.
    • Key management is a critical aspect of the CLI. We need to implement secure key storage mechanisms to protect user private keys. We also need to provide support for hardware wallets, which offer an extra layer of security.

4. Architecture TODOs

  • [ ] File descriptor ownership design (PLAN.md line 161)
    • This involves designing a pattern for FD management in the microkernel. This affects WASI module integration and requires careful consideration to ensure security and stability.
    • File descriptor ownership is a complex issue in microkernel architectures. We need to design a clear and robust pattern for managing file descriptors to prevent security vulnerabilities and ensure that WASI modules can interact with the system safely.
  • [ ] Module binary management (crates/helium-server/src/main.rs line 86)
    • Currently, the system assumes modules exist in a fixed directory. This needs to be improved to allow for proper module discovery and loading, enabling a more flexible and dynamic system.
    • The current module management system is too restrictive. We need to implement a more flexible system that allows for module discovery and loading from different locations. This will make it easier to deploy and manage modules in a production environment.

Testing Requirements

State Persistence Testing

  • [ ] Test that state persists across BaseApp restarts. This is crucial for ensuring that data is not lost when the application restarts.
  • [ ] Verify JMT root hash consistency after restart. The JMT root hash should remain the same after a restart if the state has not changed.
  • [ ] Test recovery from partial commits. The system should be able to recover from situations where a commit is interrupted or incomplete.
  • [ ] Test concurrent access to JMT store. The JMT store should be able to handle concurrent access from multiple threads or processes without data corruption.

App Hash Construction Testing

  • [ ] Verify app hash changes only when state changes. The app hash should only change when the state of the application changes.
  • [ ] Test app hash computation with multiple namespaces. The app hash computation should correctly handle multiple namespaces.
  • [ ] Verify deterministic app hash for the same state. The app hash computation should be deterministic, meaning that it always produces the same hash for the same state.
  • [ ] Test app hash in ABCI Info/FinalizeBlock responses. The app hash should be correctly included in the ABCI Info and FinalizeBlock responses.

Integration Testing

  • [ ] End-to-end test with mock CometBFT. This will test the integration between the BaseApp and CometBFT.
  • [ ] WASI module loading and execution. This will test the loading and execution of WASI modules.
  • [ ] Multi-version state queries. This will test the ability to query the state at different versions.
  • [ ] State rollback scenarios. This will test the ability to rollback the state to a previous version.

Mock Implementations to Replace

  1. Transaction Processing - Currently returns success without processing. This needs to be replaced with actual transaction processing logic.
  2. Query Handling - Returns empty/default responses. This needs to be replaced with actual query handling logic.
  3. Validator Updates - No actual validator set changes. This needs to be implemented to allow for validator set updates.
  4. Module Discovery - Hardcoded module paths. This needs to be replaced with a dynamic module discovery mechanism.

Priority Recommendations

  1. Immediate (for MVP):
    • State change collection during transactions. This is crucial for performance and atomicity.
    • Comprehensive persistence testing. This is essential for ensuring data integrity.
    • Basic WASI module execution. This is needed to enable smart contract functionality.
  2. Short-term:
    • CometBFT integration. This is essential for consensus and network participation.
    • Proper error handling and rollback. This is crucial for maintaining state consistency.
    • Query command implementation. This is needed for basic CLI functionality.
  3. Long-term:
    • Full CLI functionality. This will provide a complete user interface for interacting with the blockchain.
    • Snapshot support. This will improve state synchronization and recovery.
    • Production-ready module management. This will enable flexible module deployment and management.

Related Issues

  • #19 - Original JMT commit app hash implementation request
  • #6 - Basic metrics infrastructure (may need integration)

Notes

The current implementation provides a solid foundation, but these remaining pieces are needed to be production-ready. The module-agnostic architecture allows for flexible module composition while maintaining state integrity through JMT. The successful completion of these tasks will pave the way for a robust and scalable blockchain platform.