An Extensible Config & Logging Application Bootstrap Function

release notes

Introduction

An opinionated application config and logging bootstrap that streamlines the use of the

• @alt-javascript/config,
• @alt-javascript/logger, and
• @alt-javascript/cdi

The Application class implements a familiar application context and dependency injection (cdi) implementation, supporting simple singleton and prototype component factory definitions, with a choice of manual or auto wiring (injection) of property references and config placeholders.

The Application class extends the standalone boot function, which binds a global root context with configured LoggerFactory to negate the need for requiring and injecting the application config in every module, and optionally the node-fetch implementation for config pulled from a service url.

The config, loggerFactory, LoggerCategoryCache are registered as injectable singleton components, and the logger is an injectable prototype. See the @alt-javascript/cdi package for more detail on how the dependency injection works.

Usage

The following example bootstraps an Application with an EmphemeraConfig (but could easily be a regular config or alt-javascript/config instance), with a basic config context component definition.

    const ephemeralConfig = new EphemeralConfig(
    {
        context: {
            SimpleClass: {
                Reference: SimpleClass,
            },
        },
    },
);

const applicationContext = Application.run({ config: ephemeralConfig });

const simpleClass = applicationContext.get('simpleClass');
assert.exists(simpleClass, 'simpleClass exists');

To use the module boot function standalone, substitute the named {config} module export, in place of the popular config default, and boot it – note, we use a named export for config, because the module exports other useful classes as well.

import {config} from '@alt-javascript/config';
import {LoggerFactory} from '@alt-javascript/logger';
import {boot} from '@alt-javascript/boot';

boot({config});

config.get('key');
config.get('nested.key');
config.get('unknown','use this instead'); // this does not throw an error

const logger = LoggerFactory.getLogger('@myorg/mypackage/MyModule');
logger.info('Hello World!')

To boot and use winston as the logging transport, boot a WinstonLoggerFactory instead.

MyApp.js

import {config} from '@alt-javascript/config';
import winston from 'winston';
import {LoggerFactory, WinstonLoggerFactory} from '@alt-javascript/logger';
import {boot} from '@alt-javascript/boot';
const winstonLoggerFactory = new WinstonLoggerFactory(config,winston,{/*my winston options*/})
boot({config:config, loggerFactory:winstonLoggerFactory});

Then in your application modules, you only need.

MyModule.js

import {LoggerFactory} from '@alt-javascript/logger';

// LoggerFactory.getLogger will now bind to the global root context loggerFactory, 
// configured with booted winstonLoggerFactory from MyApp.js.

const logger = LoggerFactory.getLogger('@myorg/mypackage/MyModule');
logger.info('Hello from MyModule!')

MyOtherModule.js

import {LoggerFactory} from '@alt-javascript/logger';

// Shared logging config, different file.

const logger = LoggerFactory.getLogger('@myorg/mypackage/MyOtherModule');
logger.info('Hello from MyOtherModule!')

Browser

The module is also able to be used directly in the browser, in combination with the config module. You can either import the LoggerFactory globally as an IIFE (Immediately Invoked Function Expression), as follows:

   <script src="https://cdn.jsdelivr.net/npm/@alt-javascript/boot/dist/alt-javascript-boot-iife.js"></script>
   <script>
       var config = ConfigFactory.getConfig({
           logging : {
               format : 'json',
               level : {
                   '/' : 'info',
                   '/MyPage': 'info'
               }
           }
           "http://127+0+0+1:8080" : {
               logging : {
                   format : 'json',
                   level : {
                       '/' : 'info',
                       '/MyPage' : 'debug'
                   }
               }             
           }

       })
       var logger = LoggerFactory.getLogger('/MyPage',config);
       logger.debug('Hello World');
   </script>

Or import the ES6 module bundle from a module, as follows:

import { boot } from 'https://cdn.jsdelivr.net/npm/@alt-javascript/logger/dist/alt-javascript-config-esm.js'

//...as above

License

May be freely distributed under the MIT license.

Copyright (c) 2021 Craig Parravicini