log-args-runtime

Runtime support crate for the log_args procedural macros, providing context storage and enriched logging macros.

Note: This is part of the log-args workspace. For complete setup and usage examples, see the main documentation.

Features

Context Storage: Lightweight store that merges sync/async context across boundaries
Enriched Logging: Drop-in macros (info!, warn!, error!, debug!, trace!) with automatic context
Cross-Boundary Propagation: Context inheritance across closures, async spawns, and WebSocket upgrades
Structured Output: Optional with_context feature for JSON logging with flattened events

Installation

[dependencies]
log-args-runtime = { version = "0.1.4", features = ["with_context"] }
tracing = "0.1"
tracing-subscriber = { version = "0.3", features = ["json"] }

Note: The with_context feature includes a structured context field in log events. Disable it if you only want direct field logging.

Setup

For structured JSON logging with context fields at the top level:

fn init_logging() {
    tracing_subscriber::fmt()
        .json()
        .flatten_event(true)
        .init();
}

Usage

use tracing::info;

fn main() {
    init_logging();

    // Push request-scoped context
    log_args_runtime::push_context(|ctx| {
        ctx.insert("tenant_id".into(), "acme".into());
        ctx.insert("session_id".into(), "web".into());
    });

    // Logs include merged context when `with_context` is enabled
    log_args_runtime::info!("Processing request");
}

Integration: When using log_args procedural macros, they automatically redefine logging macros within annotated functions to include function parameters and span context.

Architecture

This crate works in tandem with the log_args procedural macro:

log_args: Compile-time macro that rewrites functions to capture parameters and set up context propagation
log-args-runtime: Runtime support providing context storage and enriched logging macros

Examples

See the workspace examples for complete demonstrations:

cargo run --example basic_usage
cargo run --example span_propagation
cargo run --example selective_fields

License

MIT - See LICENSE for details.

log-args-runtime 0.1.4