logging.md

Logging

Overview

Aurelia provides a flexible logging system that allows developers to implement structured and configurable logging across their applications. The logging mechanism is designed to be lightweight, extensible, and easy to use, supporting various log levels and custom output methods.

Getting Started

Importing Logging Utilities

To begin using logging in Aurelia, you'll need to import the necessary modules:

import {LogManager} from 'aurelia-framework';
import {ConsoleAppender} from 'aurelia-logging-console';

Basic Configuration

To set up logging, you'll typically configure it in your application's main configuration:

export function configure(aurelia) {
  // Add a console appender
  LogManager.addAppender(new ConsoleAppender());

  // Optionally set a default log level
  LogManager.setLevel(LogManager.logLevel.debug);

  aurelia.use
    .standardConfiguration()
    .globalResources();

  aurelia.start().then(() => aurelia.setRoot());
}

Creating a Logger

To create a logger in your application or component:

import {LogManager} from 'aurelia-framework';

export class MyComponent {
  constructor() {
    this.logger = LogManager.getLogger(this.constructor.name);
  }

  someMethod() {
    this.logger.debug('Debug message');
    this.logger.info('Information message');
    this.logger.warn('Warning message');
    this.logger.error('Error message');
  }
}

Log Levels

Aurelia supports multiple log levels to control the verbosity of logging:

Log Level	Description
none	No logging
error	Critical errors only
warn	Warnings and errors
info	Informational messages, warnings, and errors
debug	Detailed debugging information, including all previous levels

Setting Log Levels

You can set the global log level using:

// Set to debug level
LogManager.setLevel(LogManager.logLevel.debug);

Note: Log levels are hierarchical. Setting a level includes all levels above it.

Appenders

What are Appenders?

Appenders are responsible for outputting log messages. Aurelia provides a default ConsoleAppender, but you can create custom appenders.

Default ConsoleAppender

The ConsoleAppender writes log messages to the browser console:

import {ConsoleAppender} from 'aurelia-logging-console';

// Add console appender
LogManager.addAppender(new ConsoleAppender());

Creating Custom Appenders

You can create a custom appender by implementing the Appender interface:

class CustomAppender {
  debug(logger, message, ...rest) {
    // Custom debug logging logic
  }

  info(logger, message, ...rest) {
    // Custom info logging logic
  }

  warn(logger, message, ...rest) {
    // Custom warning logging logic
  }

  error(logger, message, ...rest) {
    // Custom error logging logic
  }
}

// Add the custom appender
LogManager.addAppender(new CustomAppender());

Advanced Usage

Multiple Appenders

You can add multiple appenders to route logs to different destinations:

LogManager.addAppender(new ConsoleAppender());
LogManager.addAppender(new CustomRemoteLoggerAppender());