xbbg-log

Zero-GIL logging infrastructure for the xbbg workspace.

Provides a tracing-based setup designed for Rust-Python hybrid libraries where worker threads must never acquire the GIL. Python controls the log level via a single atomic store — no locks, no GIL, no contention.

Why this crate exists

The standard pyo3-log bridge acquires the GIL on every log event to forward to Python's logging module. In xbbg, worker threads poll live service sessions at 10ms intervals — GIL contention from logging caused measurable latency. This crate eliminates that entirely.

Architecture

tracing::debug!("...")
  → AtomicLevelFilter (reads AtomicU8, ~1ns, zero GIL)
  → fmt::layer
  → stderr

• No GIL: The atomic level check is a single Relaxed load
• Simple output path: Output goes directly to stderr; worker threads never touch Python logging
• Python and Rust logging are separate: Rust uses tracing, Python uses logging — no bridge

Crate structure

xbbg-log/
├── Cargo.toml
└── src/
    └── lib.rs      AtomicLevelFilter, init(), set_level(), re-exported tracing macros

Usage

From Python

import xbbg
xbbg.set_log_level("debug")   # sets AtomicU8, returns immediately
xbbg.set_log_level("warn")    # back to quiet (default)

From Rust (other workspace crates)

use xbbg_log::{trace, debug, info, warn, error};

info!(worker_id = 0, "request completed");
debug!(ticker = "AAPL US Equity", "parsing response");

All workspace crates depend on xbbg-log instead of tracing directly, so the macro re-exports and subscriber setup are centralized.

Developer override

Set RUST_LOG to a simple level to choose the initial Rust log level:

RUST_LOG=debug python my_script.py

Python can still change the level later via xbbg.set_log_level().

Modes

API