Callback API

The Callback API allows you to hook into the logging lifecycle for monitoring, tracing, and custom extensions.

Quick Reference: Method Aliases

Full Method	Alias(es)	Description
setLogCallback()	-	Set log callback
setColorCallback()	-	Set color callback
setLoggedCallback()	-	Set logged callback
setFilteredCallback()	-	Set filtered callback
setSinkErrorCallback()	-	Set sink error callback
setInitializedCallback()	-	Set initialized callback
setDestroyedCallback()	-	Set destroyed callback
setCrashCallback()	onCrash()	Set crash callback
setThreadStartCallback()	onThreadStart()	Set thread pool start callback
setThreadStopCallback()	onThreadStop()	Set thread pool stop callback
setTaskSubmittedCallback()	onTaskSubmitted()	Set task submitted callback
setTaskDequeuedCallback()	onTaskDequeued()	Set task dequeued callback
setTaskExecutedCallback()	onTaskExecuted()	Set task executed callback
setWorkStolenCallback()	onWorkStolen()	Set work stolen callback
setQueueOverflowCallback()	onQueueOverflow()	Set queue overflow callback
setWriteCallback()	onWrite()	Set write callback (Sink)
setFlushCallback()	onFlush()	Set flush callback (Sink)
setErrorCallback()	onError()	Set error callback (Sink)
setRotationCallback()	onRotation()	Set rotation callback (Sink)
setStateChangeCallback()	onStateChange()	Set state change callback (Sink)
setCompressionStartCallback()	onCompressionStart()	Set compression start callback (Compression)
setCompressionCompleteCallback()	onCompressionComplete()	Set compression complete callback (Compression)
setCompressionErrorCallback()	onCompressionError()	Set compression error callback (Compression)
setDecompressionCompleteCallback()	onDecompressionComplete()	Set decompression complete callback (Compression)
setArchiveDeletedCallback()	onArchiveDeleted()	Set archive deleted callback (Compression)

Core Callbacks

Log Callback

Invoked when a log record is successfully processed.

pub const LogCallback = *const fn (record: *const Record) anyerror!void;

Usage:

fn myLogCallback(record: *const logly.Record) !void {
    if (record.level == .err) {
        // Handle error...
    }
}

logger.setLogCallback(&myLogCallback);

Color Callback

Invoked when determining the color for a specific log level.

pub const ColorCallback = *const fn (level: Level, default_color: []const u8) []const u8;

Usage:

fn myColorCallback(level: logly.Level, default: []const u8) []const u8 {
    if (level == .info) return "\x1b[35m"; // Magento for Info
    return default;
}

logger.setColorCallback(&myColorCallback);

Lifecycle Callbacks

These callbacks are configured via Config or specialized setter methods.

on_record_filtered

Invoked when a record is dropped due to level filtering or other rules.

callback: *const fn(context: ?*anyopaque, level: Level) void

on_sink_error

Invoked when a sink fails to write a message.

callback: *const fn(context: ?*anyopaque, err: anyerror) void

on_logger_initialized

Invoked after the logger is fully initialized.

callback: *const fn(context: ?*anyopaque) void

on_logger_destroyed

Invoked just before the logger is deinitialized.

callback: *const fn(context: ?*anyopaque) void

on_crash_callback

Invoked immediately when a panic, Windows VEH exception, or POSIX signal occurs.

callback: *const fn(message: []const u8) void

on_thread_pool_callback

Invoked by the thread pool for worker lifecycle and queue events:

• setThreadStartCallback(thread_id)
• setThreadStopCallback(thread_id, tasks_processed, uptime_ms)
• setTaskSubmittedCallback(priority, queue_depth)
• setTaskDequeuedCallback(priority, wait_time_us)
• setTaskExecutedCallback(execution_time_us, success)
• setWorkStolenCallback(victim_thread, thief_thread)
• setQueueOverflowCallback(queue_size, capacity)