enter-exit-logger v1.1.0

enter-exit-logger

typescript/javascript method enter/exit logger based on log4js-node

enter-exit-logger helps to generate enter/exit traces for typescript methods using the disposable pattern. The trace logs are created with log4js-node.

Installation

Install module:

`npm install enter-exit-logger --save`

Quick Start

With enter-exit-logger method entry/exit logging can easily be added to typescript code. See log4js-node for further information concerning logging configuration.

import { XLog, using } from 'enter-exit-logger';
import { Logger, getLogger, levels, configure } from 'log4js'; 


export class Tester {
    // initialize a logger instance
    private static logger = getLogger('Tester');

    constructor(name: string) {
        using(new XLog(Tester.logger, levels.INFO, 'ctor', 'name = %s', name), (log) => {
            // ...
        });
    }

    private throwException(message: string) {
        using(new XLog(Tester.logger, levels.DEBUG, 'throwException', 'message = %s', message), (log) => {
            throw new Error(message);
        });
    }

    private doTestInternal(val: number): number {
        return using(new XLog(Tester.logger, levels.DEBUG, 'doTestInternal', 'val = %d', val), (log) => {
            log.log('value = %d', val);                 // log with same level as in XLog constructor

            this.throwException("exception tester");    // simulate exception
            return 2 * val;
        });
    }

    public doTest(name: string): number {
        return using(new XLog(Tester.logger, levels.INFO, 'doTest', 'name = %s', name), (log) => {
            try {
                return this.doTestInternal(4711);
            } catch (exc) {
                log.error('Error: ', exc);
            }
        });
    }
}

What effectively is logged is controlled by the logging configuration.

Example (in config/log4js.json):

{
    "appenders": [
        {
            "type": "file",
            "filename": "log4js.log",
            "category": ["Tester", "console"],
            "levels": ["ERROR"],
            "layout": {
                "type": "pattern",
                "pattern": "%d{ISO8601} [%-5p] %-20c %m"
            }
        },
        {
            "type": "console",
            "layout": {
                "type": "pattern",
                "pattern": "%d{ISO8601} [%[%-5p%]] %[%-20c%] %m"
            }
        }
    ],
    "levels": {
        "[all]": "INFO",
        "Tester": "DEBUG"
    },
    "replaceConsole": true
}

The appenders are logging sinks which control where the logs are written. The global levels section controls which level applies to which logger. The logger "all" means "all loggers" and defines the default level for all other loggers.