FIFO Mempool Feature

[ancazamfir]

This issue outlines improvement recommendations for the mempool repository. Recommendations are prioritized to help efforts towards production readiness.

High

CI/CD Pipeline Implementation

There is no automated testing or deployment pipeline:

• Add github actions workflows for testing, linting, and builds
• Include security scanning and dependency auditing
• Implement release process with semantic versioning
• Add code coverage reporting

Fix Critical Code Issues

There is at least one panic in Arc unwrap operation:

// fifo-mempool/src/app.rs:23
Err(_) => panic!("Cannot unwrap Arc<MempoolEvent> with multiple references")

• Replace panics with proper error handling

Performance Bottleneck in Transaction Removal

O(n) complexity in remove() function:

// Current implementation rebuilds entire collections
let mut new_txs = VecDeque::with_capacity(state.txs.len() - ignore.len());
let mut new_hashes = HashMap::with_capacity(state.txs.len() - ignore.len());

• Consider using more efficient data structures (e.g., IndexMap, BTreeMap)
• Implement lazy deletion or mark-and-sweep approach

Documentation Fixes

Basic documentation errors and missing content

• Add comprehensive API documentation
• Create integrator guide

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Medium

Comprehensive Testing Strategy

There are limited integration tests, with timing dependencies (sleeps)

• Add unit tests for all components
• Replace sleep-based tests with deterministic event-driven tests

Security Hardening

Input validation and DoS protection is not great

• Add bounds checking for transaction sizes
• Implement rate limiting for transaction submission (??)

Memory Management Optimization

No TTL or memory bounds for transactions

• Implement transaction time-to-live (TTL)
• Add memory usage monitoring and alerts

---

Low

Observability and Monitoring

Production-ready monitoring

• Implement Prometheus metrics for mempool statistics
• Add structured logging with correlating IDs

Network Layer Improvements

• Implement transaction batching for gossip
• Add transaction (syntactic) deduplication at mempool actor (keep mempool hash together with app hash)

Configuration Management

Limited configuration flexibility

• Add environment variable support
• Implement configuration validation at startup
• Include configuration templates and examples

Development Tooling

No development workflow automation

• Add pre-commit hooks for formatting and linting
• Include rust-toolchain.toml for version consistency

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Future Enhancements

• Advanced Mempool Features
• Transaction prioritization based on fees or other criteria
• Support for transaction dependencies and ordering (not FIFO anymore)
• Scalability: multi instance, sharding, etc.
• Protocol versioning
• Integration
• gRPC/REST API for external system integration
• notifications for transaction lifecycle events