Contributing to ApexStore

First off, thank you for considering contributing to ApexStore! 🎉

This document provides guidelines and instructions for contributing to the project. Following these guidelines helps maintain code quality and makes the review process smoother.

📜 Table of Contents

🤝 Code of Conduct

Our Pledge

We are committed to providing a welcoming and inspiring community for all. We pledge to:

  • Be respectful and inclusive
  • Accept constructive criticism gracefully
  • Focus on what is best for the community
  • Show empathy towards other community members

Expected Behavior

  • Use welcoming and inclusive language
  • Be respectful of differing viewpoints and experiences
  • Gracefully accept constructive criticism
  • Focus on what is best for the community

Unacceptable Behavior

  • Trolling, insulting/derogatory comments, and personal or political attacks
  • Public or private harassment
  • Publishing others' private information without explicit permission
  • Other conduct which could reasonably be considered inappropriate

🚀 Getting Started

Prerequisites

  1. Rust Toolchain (1.70 or later)

    curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

  2. Git

    # Ubuntu/Debian
sudo apt-get install git

# macOS
brew install git

  3. Code Editor (Recommended: VS Code with rust-analyzer)

Initial Setup

  1. Fork the Repository

  2. Clone Your Fork

    git clone https://github.com/YOUR_USERNAME/ApexStore.git
cd ApexStore

  3. Add Upstream Remote

    git remote add upstream https://github.com/ElioNeto/ApexStore.git

  4. Install Dependencies

    cargo build

  5. Run Tests

    cargo test

For detailed setup instructions, see SETUP.md.

🔄 Development Workflow

Automated Workflow Overview

ApexStore uses GitHub Actions to automate the development workflow:

  • Feature/Fix branches → Auto-create PR to develop + run tests
  • Develop → Auto-create release PR to main
  • Main → Create release tag + close related issues

See WORKFLOWS.md for complete documentation.

1. Create a Feature Branch

# Update your fork
git checkout main
git pull upstream main

# Create a new branch from main
git checkout -b feature/your-feature-name

Branch Naming Conventions:

  • feature/ - New features (e.g., feature/compaction-strategy)
  • fix/ - Bug fixes (e.g., fix/wal-corruption)
  • docs/ - Documentation changes (e.g., docs/api-guide)
  • refactor/ - Code refactoring (e.g., refactor/codec-interface)
  • test/ - Test additions/improvements (e.g., test/integration-suite)
  • perf/ - Performance improvements (e.g., perf/bloom-filter-optimization)

2. Make Your Changes

# Make changes to the code
vim src/core/engine.rs

# Test your changes
cargo test --all-features

# Format code
cargo fmt

# Check for issues
cargo clippy --all-features -- -D warnings

3. Commit Your Changes

git add .
git commit -m "feat: add compaction strategy interface (#55)"

Important: Reference issues in commit messages using #issue_number for automatic tracking.

See Commit Messages for formatting guidelines.

4. Push to Your Fork

git push origin feature/your-feature-name

What Happens Next:

  • ✅ GitHub Actions automatically runs tests
  • ✅ Auto-creates PR to develop branch
  • ✅ Adds comment to referenced issues (if any)
  • ✅ Runs Clippy and format checks

5. Pull Request Review

Once the automated PR is created:

  1. Review the PR description
  2. Wait for CI checks to pass
  3. Address any reviewer feedback
  4. PR will be merged to develop once approved

Note: You don't need to manually create PRs - the workflow handles this automatically!

📝 Coding Standards

Rust Style Guide

We follow the Rust API Guidelines and Rust Style Guide.

Key Principles:

  1. Use cargo fmt - All code must be formatted

    cargo fmt --all

  2. Pass cargo clippy - Zero warnings policy

    cargo clippy --all-features -- -D warnings

  3. Write Documentation - Public APIs must have doc comments

    #![allow(unused)]
fn main() {
/// Retrieves a value from the store by key.
///
/// # Arguments
///
/// * `key` - The key to look up
///
/// # Returns
///
/// * `Ok(Some(value))` - Key found
/// * `Ok(None)` - Key not found
/// * `Err(e)` - Error occurred
///
/// # Example
///
/// ```
/// let value = engine.get(b"user:123")?;
/// ```
pub fn get(&self, key: &[u8]) -> Result<Option<String>> {
    // Implementation
}
}

SOLID Principles

This project follows SOLID principles:

  • Single Responsibility: Each module/struct has one clear purpose
  • Open/Closed: Extend behavior through traits, not modification
  • Liskov Substitution: Implementations must be interchangeable
  • Interface Segregation: Small, focused traits
  • Dependency Inversion: Depend on abstractions, not concretions

Example:

#![allow(unused)]
fn main() {
// ✅ Good - depends on trait
pub struct LsmEngine<W: WriteAheadLog> {
    wal: W,
}

// ❌ Bad - depends on concrete type
pub struct LsmEngine {
    wal: FileBasedWal,
}
}

Error Handling

  1. Use Result<T, LsmError> for fallible operations

    #![allow(unused)]
fn main() {
pub fn put(&mut self, key: &[u8], value: &str) -> Result<()> {
    self.wal.append(key, value)?;
    self.memtable.insert(key, value);
    Ok(())
}
}

  2. Provide Context with error types

    #![allow(unused)]
fn main() {
use thiserror::Error;

#[derive(Error, Debug)]
pub enum LsmError {
    #[error("WAL corruption at offset {0}")]
    WalCorruption(u64),
    
    #[error("Key too large: {size} bytes (max: {max})")]
    KeyTooLarge { size: usize, max: usize },
}
}

  3. Don't Panic in library code (use Result instead)

Performance Considerations

  1. Minimize Allocations

    #![allow(unused)]
fn main() {
// ✅ Good - reuse buffer
let mut buffer = Vec::with_capacity(1024);
for item in items {
    buffer.clear();
    serialize_into(&mut buffer, item)?;
}

// ❌ Bad - allocate each iteration
for item in items {
    let buffer = serialize(item)?;
}
}

  2. Use Appropriate Data Structures

    • BTreeMap for sorted data
    • HashMap for fast lookups
    • Vec for sequential access

  3. Benchmark Changes

    cargo bench

🧪 Testing Guidelines

Test Types

  1. Unit Tests - Test individual functions/modules

    #![allow(unused)]
fn main() {
#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_memtable_insert() {
        let mut memtable = MemTable::new();
        memtable.insert(b"key", "value");
        assert_eq!(memtable.get(b"key"), Some("value".to_string()));
    }
}
}

  2. Integration Tests - Test component interactions

    #![allow(unused)]
fn main() {
// tests/integration_test.rs
#[test]
fn test_engine_recovery() {
    let config = LsmConfig::default();
    let mut engine = LsmEngine::new(config).unwrap();
    
    engine.put(b"key", "value").unwrap();
    drop(engine);
    
    let engine = LsmEngine::new(config).unwrap();
    assert_eq!(engine.get(b"key").unwrap(), Some("value".to_string()));
}
}

  3. Property Tests - Test invariants (optional, using proptest)

Test Requirements

  • All new code must have tests
  • Tests must pass on all platforms
  • Test coverage should increase, not decrease
  • Use descriptive test names 
    #![allow(unused)]
fn main() {
#[test]
fn test_get_returns_none_for_nonexistent_key() { /* ... */ }
}

Running Tests

# Run all tests
cargo test --all-features

# Run specific test
cargo test test_memtable_insert

# Run with output
cargo test -- --nocapture

# Run integration tests only
cargo test --test '*'

# Run with coverage (requires tarpaulin)
cargo tarpaulin --out Html

📝 Commit Messages

We follow the Conventional Commits specification.

Format

<type>(<scope>): <subject> (#issue)

<body>

<footer>

Types

  • feat - New feature
  • fix - Bug fix
  • docs - Documentation changes
  • style - Code style changes (formatting, etc.)
  • refactor - Code refactoring
  • perf - Performance improvements
  • test - Test additions/modifications
  • chore - Build process, dependencies, tooling
  • ci - CI/CD changes

Examples

Simple commit:

feat: add bloom filter to SSTable reader

With scope and issue:

fix(wal): prevent corruption on unclean shutdown (#42)

With body:

feat(compaction): implement leveled compaction strategy (#47)

Adds a new LeveledCompaction struct that implements the Compaction
trait. This strategy reduces read amplification by maintaining
sorted levels with exponentially increasing sizes.

Closes #47

Breaking change:

feat(api)!: change SSTable format to V2

BREAKING CHANGE: SSTable V2 is incompatible with V1.
Migration tool will be provided in v1.4.

Referencing Issues:

  • #123 - Reference issue
  • fixes #123, closes #123 - Will auto-close issue when PR merges
  • resolves #123 - Alternative close syntax

🔍 Pull Request Process

Before Pushing

  • Code compiles without errors
  • All tests pass (cargo test --all-features)
  • No clippy warnings (cargo clippy --all-features -- -D warnings)
  • Code is formatted (cargo fmt)
  • Documentation is updated (if applicable)
  • Tests are added for new functionality

Automated PR Creation

When you push to a feature/* or fix/* branch:

  1. ✅ Tests run automatically (CI/CD)
  2. ✅ PR is auto-created to develop branch
  3. ✅ Issues are commented (if referenced in commits)
  4. ✅ Checks must pass before merge

Manual Steps (If Needed)

If you need to create a PR manually:

  1. Go to your fork on GitHub
  2. Click "New Pull Request"
  3. Select develop as the base branch
  4. Fill out the PR template
  5. Submit the PR

PR Template

When creating a PR manually, use this template:

## Description

Brief description of changes.

## Type of Change

- [ ] Bug fix
- [ ] New feature
- [ ] Breaking change
- [ ] Documentation update

## Related Issues

Closes #123
Related to #456

## Testing

Describe how you tested your changes:
- [ ] Unit tests added
- [ ] Integration tests added
- [ ] Manual testing performed

## Checklist

- [ ] Code compiles
- [ ] Tests pass
- [ ] Clippy checks pass
- [ ] Code is formatted
- [ ] Documentation updated

## Screenshots (if applicable)

## Additional Notes

Review Process

  1. Automated Checks - CI runs tests and linters
  2. Code Review - Maintainer reviews code
  3. Feedback - Address review comments
  4. Approval - Maintainer approves PR
  5. Merge - Squash and merge to develop

Review Timeline

  • Simple PRs: 1-3 days
  • Complex PRs: 3-7 days
  • Breaking Changes: 7-14 days

📁 Project Structure

ApexStore/
├── src/
│   ├── core/              # Core domain logic
│   │   ├── engine.rs      # LSM engine orchestration
│   │   ├── memtable.rs    # In-memory storage
│   │   └── log_record.rs  # Data model
│   ├── storage/           # Persistence layer
│   │   ├── wal.rs         # Write-ahead log
│   │   ├── sstable.rs     # SSTable reader
│   │   └── builder.rs     # SSTable writer
│   ├── infra/             # Infrastructure
│   │   ├── codec.rs       # Serialization
│   │   ├── error.rs       # Error types
│   │   └── config.rs      # Configuration
│   ├── api/               # HTTP API (feature-gated)
│   ├── cli/               # CLI interface
│   └── features/          # Feature flags
├── tests/                 # Integration tests
├── benches/               # Benchmarks
└── docs/                  # Documentation

Module Guidelines

  • core/ - Domain logic, no external dependencies
  • storage/ - File I/O, persistence
  • infra/ - Cross-cutting concerns
  • api/ - External interfaces (feature-gated)

🎯 Areas for Contribution

High Priority

  1. CI/CD Testing Pipeline (#55)

    • Difficulty: Easy
    • Impact: High
    • Skills: GitHub Actions, YAML

  2. Compaction Implementation (#47)

    • Difficulty: Hard
    • Impact: High
    • Skills: Rust, algorithms, file I/O

  3. Efficient Iterators (#21, #22, #23)

    • Difficulty: Medium
    • Impact: High
    • Skills: Rust, data structures

Medium Priority

  1. Benchmarking Suite (#48)

    • Difficulty: Easy
    • Impact: Medium
    • Skills: Rust, criterion

  2. CLI Command Equalization (#65)

    • Difficulty: Medium
    • Impact: Medium
    • Skills: Rust, CLI design

  3. Checksums & Integrity (#25)

    • Difficulty: Easy
    • Impact: High
    • Skills: Rust, CRC32

Good First Issues

  1. Add More Tests

    • Difficulty: Easy
    • Impact: Medium
    • Skills: Rust, testing

  2. Binary Search Optimization (#37)

    • Difficulty: Easy
    • Impact: Medium
    • Skills: Rust, algorithms

  3. Documentation Improvements

    • Difficulty: Easy
    • Impact: Medium
    • Skills: Technical writing

Advanced Topics

  1. Replication Support

    • Difficulty: Very Hard
    • Impact: Very High
    • Skills: Distributed systems, Raft

  2. Snapshot Isolation

    • Difficulty: Hard
    • Impact: High
    • Skills: Concurrency, MVCC

❓ Questions?

🚀 Ready to Contribute?

  1. Find an issue or create one
  2. Comment that you're working on it
  3. Fork the repo and create a branch from main
  4. Make your changes with tests
  5. Push to your fork (automated PR will be created)
  6. Wait for review and address feedback

Thank you for contributing! 🎉

Last updated: March 2026