Struct LogContext

pub struct LogContext(/* private fields */);

A contextual properties that can be attached to log records.

LogContext represents a set of key-value pairs that will be automatically added to log messages when the context is active.

Implementations

impl LogContext

pub const fn new() -> Self

Creates a new, empty context.

pub fn record( self, key: impl Into<Cow<'static, str>>, value: impl Into<ContextValue>, ) -> Self

Adds property to this context.

Examples

use context_logger::LogContext;

let context = LogContext::new()
    .record("user_id", "user-123")
    .record("request_id", 42)
    .record("is_admin", true);

pub fn add_record( key: impl Into<Cow<'static, str>>, value: impl Into<ContextValue>, )

Adds property to the current active context.

This is useful for adding context information dynamically without having direct access to the context.

Note

If there is no active context, this operation will have no effect.

Examples

use context_logger::{LogContext, ContextValue};
use log::info;

fn process_request() {
    // Add context information dynamically
    LogContext::add_record("processing_time_ms", 42);
    info!("Request processed");
}

let _guard = LogContext::new()
    .record("request_id", "req-123")
    .enter();

process_request(); // Will log with both request_id and processing_time_ms

pub fn enter<'a>(self) -> LogContextGuard<'a>

Activating this context, returning a guard that will exit the context when dropped.

In Asynchronous Code

Warning: in asynchronous code Self::enter should be used very carefully or avoided entirely. Holding the drop guard across .await points will result in incorrect logs:

use context_logger::LogContext;

async fn my_async_fn() {
    let ctx = LogContext::new()
        .record("request_id", "req-123")
        .record("user_id", 42);
    // WARNING: This context will remain active until this
    // guard is dropped...
    let _guard = ctx.enter();
    // But this code causing the runtime to switch to another task,
    // while remaining in this context.
    tokio::task::yield_now().await;
    }

Please use the crate::FutureExt::in_log_context instead.

Trait Implementations

impl Debug for LogContext

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for LogContext

fn default() -> Self

Returns the “default value” for a type.