logstash Appender (HTTP) for log4js-node

The logstash appenders for log4js send NDJSON formatted log events to logstash receivers. This appender uses HTTP to send the events (there is another logstash appender that uses UDP).

``bash
npm install log4js @log4js-node/logstash-http
`

Configuration

* type - @log4js-node/logstash-http
* url - string - logFaces receiver servlet URL
* application - string (optional) - used to identify your application's logs
* logChannel - string (optional) - also used to identify your application's logs [but in a more specific way]
* logType - string (optional) - used for the type field in the logstash data
* timeout - integer (optional, defaults to 5000ms) - the timeout for the HTTP request.

This appender will also pick up Logger context values from the events, and add them as p_ values in the logFaces event. See the example below for more details.

Example (default config)

`javascript
log4js.configure({
appenders: {
logstash: { type: '@log4js-node/logstash-http', url: 'http://localhost:9200/_bulk', application: 'logstash-log4js', logType: 'application', logChannel: 'node' }
},
categories: {
default: { appenders: [ 'logstash' ], level: 'info' }
}
});

const logger = log4js.getLogger();
logger.addContext('requestId', '123');
logger.info('some interesting log message');
logger.error('something has gone wrong');
`
This example will result in two log events being sent to your localhost:9200. Both events will have a context.requestId property with a value of 123`.