Rust Review

Rust review guidelines

This project uses Rust for Coglet (crates/), the prediction server that runs inside Cog containers. It handles HTTP requests, worker process management, and prediction execution.

What linters already catch (skip these)

clippy runs in CI. cargo-deny audits dependencies for license/advisory issues. Don't flag issues these would catch.

What to look for

Error handling

• Use thiserror for typed errors in library code, anyhow for application errors
• Don't use .unwrap() or .expect() in non-test code unless the invariant is documented
• Error context: use .context() or .with_context() from anyhow, not bare ?

Ownership and lifetimes

• Unnecessary cloning where a borrow would work
• Lifetime issues that suggest a design problem (not just annotation noise)
• Arc/Mutex when simpler patterns exist

Async (tokio)

• Blocking operations inside async contexts (use spawn_blocking)
• Missing .await on futures (compiler catches some, but not all logical issues)
• Proper cancellation handling and cleanup
• Task/JoinHandle leaks

Safety

• Any unsafe block needs justification and a safety comment
• FFI boundaries with Python (PyO3) -- check for panics across FFI, GIL handling
• Memory safety in IPC between parent and worker processes

Architecture

• crates/coglet/ is the core: HTTP server, worker orchestration, IPC
• crates/coglet-python/ is PyO3 bindings for Python predictor integration
• Two-process architecture: parent (HTTP + orchestrator) and worker (Python execution)
• Don't mix IPC concerns with HTTP handling
• Snapshot tests use insta -- check if snapshots need updating

Dependencies

• New dependencies should be justified -- crates/deny.toml audits them
• Prefer std or existing deps over adding new ones for small tasks