@e2/core/README.md

Enterprise Application Framework
=================================

### What is this?

- [x] Read configuration from `conf/settings.yaml`
- [x] Merge configuration from `conf/${NODE_ENV}.yaml`, `conf/${NODE_ENV}.local.yaml` and environment variables. (if have)
- [x] Merge configuration from `data/settings.json` (only when DATA_DIR was defined ) 
- [x] Print merged configuration on application start
- [x] Do not print sensitive configuration name with `_URL`, `_KEY`, `_PASSWORD`, `_SECRET` or `_TOKEN` postfix
- [x] Auto create missing dir if the configuration name ends with `_DIR`. (e.g. LOG_DIR folder)
- [x] Configuration with `_DIR` or `_FILE` will resolve to absolute path automatically
- [x] Provide a `app.settings` object for application to access the final configuration
- [x] Provide a `app.logger` object for application to use, available transporters: Console, File or Webhook
- [x] Provide nested error object `Exception` which will concat all the stacktrace for nested errors
- [x] When transporter itself got errors. It will automatically fallback to another available transporter
- [x] Trap linux signals `SIGHUP`, `SIGINT`, `SIGQUIT`, `SIGTERM`
- [x] Log nodejs process events `uncaughtException`
- [x] Provide universal application event `beforeExit`, `exiting`, `exit`
- [x] The original log called on failed transporter will logged using fallback logger

### Why doing this?

- Because the things above is required for most enterprise applications. It should be shared across projects.
- It's very important. But it's not as important as application logic. It can save your time to bootstrap a new project.
- The same structure will make DevOps happy when doing deployment/monitoring on many projects. It should be standardized.
- Together with Agent Framework; it can be automatically inject into other classes when required. It should be easy to use.

### Installation

```bash
npm install @e2/core --save
```

OR

```bash
yarn add @e2/core
```

### Show me the code

```typescript
// TypeScript 2.2+
import { Application } from '@e2/core';

// enable config, logger support
const app = new Application(); // default, same with `Application({ confDir: 'conf', root: process.cwd() })`
// or
const app = new Application({ confDir: 'settings' }); // if your configuration folder is not 'conf' 
// or
const app = new Application({ confDir: 'settings', root: '/usr/share/myapp' }); // if your root folder is not current working folder 

console.log(app.settings);
app.logger.info('Hi, I am agent stack'); // the log will be automatically save in `LOG_DIR` folder 
```

```js
// Node 6+
var Application = require('@e2/core').Application;

// enable config, logger support
var app = new Application(); // default, same with `Application({ confDir: 'conf', root: process.cwd() })`
// or
var app = new Application({ confDir: 'settings' }); // if your configuration folder is not 'conf' 
// or
var app = new Application({ confDir: 'settings', root: '/usr/share/myapp' }); // if your root folder is not current working folder 

console.log(app.settings);
app.logger.info('Hi, I am agent stack'); // the log will be automatically save in `LOG_DIR` folder 

```

### Others

#### How do I rotate log files?

Consider we output our logs to `/usr/share/myapp/logs/agent.log`

We would rotate our log files with logrotate, by adding the following to `/etc/logrotate.d/myapp`:

```
/usr/share/myapp/logs/agent.log {
       su root
       daily
       rotate 7
       delaycompress
       compress
       notifempty
       missingok
       copytruncate
}
```