javascript appender

Create appender for log4js-node to enable RELP usage from node.js applications.

User Story:
As a developer I would like to use jsa_01 to push log messages over relp to a compatible relp-server with syslog envelope

== Specs

^^^^^
Requirements Backlog
[options="header,footer"]
|=======================
|# |Title |User Story |Importance |Status
|1 |Rebind |Rebind of the rlp_02 connection must be done after configureable amount of messages | OPTIONAL |Open
|2 |Syslog |Wrap messages in syslog envelope |Must Have |WIP
|3 |RELP |Use rlp_02 library |Must Have |Done
|4 |Lossless|Retry indefinitely and do not lose messages |Must Have |Open
|5 |Robust|Processing must not hang indefinitely due to techinical issues but rather retry new connection |Must Have |Open
|6 |Source Data |Must include origin data in syslog structure-data within source-metadata | Must Have |WIP
|7 |Originator |Must include hostname within new syslog structured-data (SD) so utilization systems can utilize it |Must Have |Done
|8 |app-name |Syslog app-name must be configureable |Must Have |Done
|9 |hostname|syslog hostname must be configureable |Must Have |Done
|10 |server port|Server ports need to be configureable |Must Have |Done
|11 |Server address |server address needs to be configureable | Must Have |Done
|12 |Expose error SyslogMessage |Erros(expecptions) must not be hidden |Must Have |Open
|13 |Extra libraries |Do not use extra libraries |Must Have |Open
|14 |Variable checking|Check variables provided via configuration to be valid and raise errors if not in initilization |Must Have |Done
|15 |Debug flags|Allow passing debulg flags via configuration |OPTIONAL |Open

|=======================

== High-level Architecture

image::https://github.com/teragrep/jsa_01/blob/base-feat/images/JSA_01.png[]

== Implementation

The jsAppender to push log messages over relp to a compatible relp-server with syslog envelope.
For the
RELP connection - rlp_02 +
Generate the Syslog message - rlo_08 +
RELP compatible server - Java-relp-server-demo (tested on)

* asynchronus behaviour completely controlled by the Jasmine async works.
+
[source,node]
-----------------
npm install
-----------------

* Module usage:
+ The appender uses the rlo_08 for handling formatting log messages and rlp_02 to send the log event message to the RELP Server.
[source,javascript]
-----------------
const { SyslogMessage, Facility, SDElement, SDParam, Severity } = require('@teragrep/rlo_08')
const { RelpConnection, RelpBatch } = require('@teragrep/rlp_02')
-----------------

* Build
+
[source,java]
-----------------
mvn clean package
-----------------

OPTIONAL TIPS*

async waterfall method also possible for run in the node engine (need to adjust the code).

== Configuration

_type_ - _jsAppender_*
_hostname_ - _string_* (defaults to os.hostname()) - origin of the log messages
_appname_ - _string_*
_serverAddress_ - _string_*
_serverPort_ - _integer_* (defaults to 1601) - Port of the relp server is listening in

== Example (default config)
[source,javascript]
-----------------

log4js.configure( {
appenders: {jsa: { type: jsAppender, appName: 'teragrep' },
console: { type: 'console' },
},
categories: {
jsa: { appenders: ['jsa'], level: 'error' },
default: { appenders: ['jsa'], level: 'trace' },
},
})
-----------------

This configuration will send the log event messages to the RELP Server.