Struct ContextLogger 

pub struct ContextLogger { /* private fields */ }

A logger wrapper that enhances log records with contextual properties.

ContextLogger wraps an existing logging implementation and adds additional context properties to log records. These context properties are taken from the current context stack, which is managed by the LogContext type.

Example

use log::{info, LevelFilter};
use context_logger::{ContextLogger, LogContext};

// Create a logger.
let env_logger = env_logger::builder().build();
let max_level = env_logger.filter();
// Wrap it with ContextLogger to enable context propagation.
let context_logger = ContextLogger::new(env_logger);
// Initialize the resulting logger.
context_logger.init(max_level);

// Create a context with properties
let ctx = LogContext::new()
    .record("request_id", "req-123")
    .record("user_id", 42);

// Use the context while logging
let _guard = ctx.enter();
info!("Processing request"); // Will include request_id and user_id properties

See LogContext for more information on how to create and manage context properties.

Implementations

impl ContextLogger

pub fn new<L>(inner: L) -> Self

where L: Log + 'static,

Creates a new ContextLogger that wraps the given logging implementation.

The inner logger will receive log records enhanced with context properties from the current context stack.

pub fn init(self, max_level: LevelFilter)

Initializes the global logger with the context logger.

This should be called early in the execution of a Rust program. Any log events that occur before initialization will be ignored.

Panics

Panics if a logger has already been set.

pub fn try_init(self, max_level: LevelFilter) -> Result<(), SetLoggerError>

Initializes the global logger with the context logger.

This should be called early in the execution of a Rust program. Any log events that occur before initialization will be ignored.

Errors

Returns an error if a logger has already been set.

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

Adds a default record that will be included in all log entries.

Default records are automatically added to all log entries, regardless of the current context. They are defined when the logger is created and remain constant throughout the application’s lifetime.

Behavior with Duplicate Keys

When logging, default records are added first, followed by records from the current context. If multiple records with the same key exist, the behavior depends on the underlying logger implementation. In most implementations, later records with the same key will typically replace earlier ones.

Example

use log::{info, LevelFilter};
use context_logger::{ContextLogger, LogContext};

// Create a logger with default records
let logger = ContextLogger::new(env_logger::builder().build())
    .default_record("service", "api")
    .default_record("version", "1.0.0");
// Initialize it
logger.init(LevelFilter::Info);
// Context records are added after default records
let _guard = LogContext::new()
    .record("request_id", "123")
    .enter();

info!("Processing request"); // Will include service="api", version="1.0.0", request_id="123"

Trait Implementations

impl Debug for ContextLogger

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

Formats the value using the given formatter.

impl Log for ContextLogger

fn enabled(&self, metadata: &Metadata<'_>) -> bool

Determines if a log message with the specified metadata would be logged.

fn log(&self, record: &Record<'_>)

Logs the Record.

fn flush(&self)

Flushes any buffered records.