Logger extension for Nodiator

Provides low configuration logging and visibility utility for tracking messages execution.

Table of contents

• Installation
• Quick Start
  • Example output
• Logging levels
• Custom logger
• Exceptions levels override
• License

Installation

npm i @nodiator/extension-logger
# or
yarn add @nodiator/extension-logger

Quick Start

import { LoggerExtension } from '@nodiator/extension-logger';

const mediator = MediatorFactory.create();
mediator.use(new LoggerExtension());

Example output

[Mediator] Requested GetHistoryUseCase (id=14e8899b-85e4-4936-9852-3933f71dd4dc)
[Mediator]  -- handling GetHistoryUseCase (id=14e8899b-85e4-4936-9852-3933f71dd4dc) with HistoryPipeline
[Mediator]  -- handling GetHistoryUseCase (id=14e8899b-85e4-4936-9852-3933f71dd4dc) with GetHistoryUseCaseHandler
[Mediator]  -- GetHistoryUseCaseHandler responded to GetHistoryUseCase (id=14e8899b-85e4-4936-9852-3933f71dd4dc)
[Mediator]  -- HistoryPipeline responded to GetHistoryUseCase (id=14e8899b-85e4-4936-9852-3933f71dd4dc)
[Mediator]  -- GetHistoryUseCase (id=14e8899b-85e4-4936-9852-3933f71dd4dc) took 0.009s
[Mediator] GetHistoryUseCase (id=14e8899b-85e4-4936-9852-3933f71dd4dc) handled

Based on express example.

Levels

Extension supports following levels of logging: DEBUG, INFO, WARN, ERROR and NONE. The default one is INFO and allows all logs to be visible besides those marked as DEBUG.

mediator.use(
  new LoggerExtension({
    dynamicOptions: () => ({ level: MediatorLoggingLevels.DEBUG }),
  })
);

Note that dynamicOptions property is function called each time configuration data is needed which allows to implement logic to change logging behaviour without app reload.

Custom logger

By default messages are logged via console methods. This behavior can be overwritten by

class CustomLogger implements MediatorLogger {
  debug(msg: string) {
    ...
  }
  info(msg: string) {
    ...
  }
  warn(msg: string) {
    ...
  }
  error(msg: string) {
    ...
  }
}

mediator.use(
  new LoggerExtension({
    logger: new CustomLogger(),
  })
);

Exceptions levels override

Some exceptions may not necessarily fit into error level. This behavior can be customized via

const mediator = MediatorFactory.create({
  exceptionsLoggingLevels: {
    [MediatorLoggingLevels.WARN]: [MessageTimeoutException],
  },
});

With above configuration all mediator timeout exceptions will be logged as warnings.

License

This project is licensed under the MIT License - see the LICENSE file for details.