how-to-add-log-providers.md

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How To Add Log Providers

Log providers add the ability to send logging information to your own display/storage mechanism.

You can implement a logger by following the module pattern, see How To Add A Module.

Configuration

As mentioned above log providers follow the module pattern, the default configured console logger uses the following configuration:

"loggerProvider": {
    "modules": [
        {
            "enabled": true,
            "id": "console",
            "url": "http://localhost:8080/js/modules/log/console.bundle.js"
        }
    ]
}

Implementation

If you implement a logger module you need only override one method, log. From within this method you can send the logging data anywhere you want.

This method is deliberately not async, otherwise the whole of the logging pattern would require methods wanting to log to be async as well. Instead if you want to perform async operations like storing in a DB, or sending to a REST service, you should batch the information and send it with a background process.

class MyLogger implements LogProvider {
  /**
   * Log data as information.
   * @param identity The identity sending the message.
   * @param group The group sending the log message.
   * @param level The level of the message to log.
   * @param message The message to log.
   * @param optionalParams Optional parameters for details.
   */
  public log(
    identity: string,
    group: string,
    level: LogLevel,
    message: unknown,
    ...optionalParams: unknown[]
  ): void {}
}

You also need the entry point exported from the module.

export const entryPoints: { [type in ModuleTypes]?: ModuleImplementation } = {
  log: new MyLogger()
};

Using Logging

To use a logger in your code you need to import the createLogger method from log-provider.ts, this allows you to create an object from which you can call all the logging methods. The logging methods are the same as you would normally expect from the console object info, warn, error, trace, debug.

import { createLogger } from './logger-provider';

const logger = createLogger('Bootstrapper');

logger.info('The platform has started');

Additional Settings

As with any entity following the module pattern it can have custom settings, the default ConsoleLogger has some additional settings to specify which log levels it displays. By default it shows everything, but you could reduce the noise to just error and debug messages with the following configuration.

"loggerProvider": {
    "modules": [
        {
            "enabled": true,
            "id": "console",
            "url": "http://localhost:8080/js/modules/log/console.bundle.js",
            "data": {
                "includeLevels": ["error", "debug"]
            }
        }
    ]
}

Each log provider can have its own custom settings, so you could have a console logger showing all messages, and a remote logger which just gets sent error messages.

Also since the logging level is driven from the manifest settings you could make this entitlements based, providing different levels of logging per user. If a specific user is having problems, you could increase the verbosity of the logging messages for just that user.

Using Logging In Modules

We don't want to include the logging code directly in external modules as it bloats their size, instead when the a module has it's initialize method called it is passed the createLogger method, so it can use this create a logger and perform logging from within the module.

Generate From Template

You can generate the scaffold for a new module by using the following command line, where "My Logger" is the name you want to give your module:

npm run generate-module log "My Logger"

This will generate the code in the modules/log folder, add an entry into webpack to build it, and add it to the manifest so that the module is loaded.

Source Reference

• logger-provider.ts
• logger-shapes.ts
• console log.ts

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