Module logging 

High-performance multi-layer logging for the Janus trading system.

Runtime Log Level Changes

After calling init_logging, use LoggingGuard::create_controller to obtain a Box<dyn LogLevelController> that can be installed into JanusState for the API module to expose as POST /api/log-level.

This module implements the Layered Registry Model described in the Janus Supervisor Architecture Refactor document. It splits logging into two independent pipelines:

• Layer 1 — Operational Telemetry: Human-readable logs to stdout, filtered by RUST_LOG / EnvFilter, with runtime-reloadable log levels via a [ReloadHandle].

• Layer 2 — HFT Data Stream: High-frequency market data events written to a non-blocking rolling file appender. Events are buffered in a ring buffer and flushed by a dedicated worker thread, fully decoupling the latency-sensitive trading path from disk I/O.

Architecture

┌───────────────────────────────────────────────────┐
│                 tracing Registry                   │
│                                                    │
│  ┌──────────────────────┐  ┌────────────────────┐ │
│  │  Layer 1: Ops/Stdout │  │ Layer 2: HFT File  │ │
│  │  EnvFilter (reload)  │  │ Targets("janus::   │ │
│  │  fmt::layer().pretty │  │   hft" = TRACE)    │ │
│  │                      │  │ non_blocking writer │ │
│  └──────────────────────┘  └────────────────────┘ │
└───────────────────────────────────────────────────┘

Critical: WorkerGuard Lifetime

The LoggingGuard returned by init_logging must be held alive in main() until the very end of the program. Dropping it prematurely causes the non-blocking HFT writer’s buffer to be discarded, losing market data audit trail entries during shutdown.

Usage

use janus_core::logging::{init_logging, LoggingConfig};

#[tokio::main]
async fn main() -> anyhow::Result<()> {
    let config = LoggingConfig::default();
    let guard = init_logging(config)?;

    // ... application code ...

    // `guard` drops here — HFT buffer is flushed
    Ok(())
}

Structs

LoggingConfig

Configuration for the multi-layer logging system.

LoggingGuard

Holds resources that must outlive the logging system.

Functions

init_logging

Initialize the multi-layer tracing subscriber.