CONTRIBUTING.md

# Contributing to Apache Iggy

## Issue First

Every new PR that introduces new functionality must link to an approved issue.
PRs without one may be closed at maintainer's discretion.

1. Create an issue or comment under existing
2. Wait for maintainer approval (`good-first-issue` label or comment)
    - Maintainer may request for more details or a different approach
3. Then code

## Size Limits

For new contributors we require to keep PRs under 500 lines of code, unless explicitly approved by a maintainer under linked issue.

## High-Risk Areas

These require design discussion in the issue before coding:

- Persistence (segments, indexes, state, crash recovery)
- Protocol (binary format, wire encoding)
- Concurrency (shards, inter-shard)
- Public API (HTTP, SDKs, CLI)
- Connectors

## PR Requirements

### Run It Locally

**If you can't run it, you can't submit it.**

Authors of PRs must run the code locally. "Relying on CI" is not acceptable.

### Single Purpose

One PR = one thing. Bug fix, refactor, feature - separate PRs. Mixed PRs will be closed.

### Quality Checks

For Rust code:

```bash
cargo fmt --all
cargo clippy --all-targets --all-features -- -D warnings
cargo build
cargo test
cargo machete
cargo sort --workspace
```

For other languages, check the README in `foreign/{language}/` (e.g., `foreign/go/`, `foreign/java/`).

### Pre-commit Hooks

We use [prek](https://github.com/j178/prek):

```bash
cargo install prek
prek install
```

## Code Style

### Comments: WHY, Not WHAT

```rust
// Bad: Increment counter
counter += 1;

// Good: Offset by 1 because segment IDs are 1-indexed in the wire protocol
counter += 1;
```

Don't comment obvious code. Do explain non-obvious decisions, invariants, and constraints.

### Commit Messages

Format: `type(scope): subject`

**Good examples from this repo:**

```none
fix(server): prevent panic when segment rotates during async persistence
fix(server): chunk vectored writes to avoid exceeding IOV_MAX limit
feat(server): add SegmentedSlab collection
refactor(server): consolidate permissions into metadata crate
chore(integration): remove streaming tests superseded by API-level coverage
```

Keep subject under 72 chars. Use body for details if needed.

## Close Policy

PRs may be closed if:

- Maintainer feels like proxy between maintainer and LLM
- No approved issue or no approval from a maintainer
- Code not ran and tested locally
- Mixed purposes or purposes not clear
- Can't answer questions about the change
- Inactivity for longer than 7 days

## Questions?

[Discussions](https://github.com/apache/iggy/discussions) or [Discord](https://discord.gg/apache-iggy)