@opuscapita/logger

@opuscapita/logger

This module provides simple common logging. For further details of how to use this module, please have a look at the wiki.

Currently this module is released manually

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Known issues

Versions 1.3.x had an issue where logging logic was reversed (more severe logs not logged while less severe logged).

Versions

See https://github.com/OpusCapita/logger/releases

Minimum setup

Install logger to your project:

npm install @opuscapita/logger

After that you can directly use the logger component.

const Logger = require('@opuscapita/logger');

const logger = new Logger({context:{name:"My preferably unique logger name"});
logger.info('Hello world!');

logger.trace('Very detailed logs', {details: 'Variable data'});
logger.debug('Detailed logs, normally off', {details: 'Variable data'});
logger.info('Information', {details: 'This is normally logged on production - try to use it only when needed'});
logger.warn('Something wrong but handled', {error: errorThrown, details: 'It is something that is worth looking into but not an issue that require immediate work'});
logger.error('Something bad happened - someone MUST look at it', {details: 'There is a transaction broken or something similar - customer is impacted and someone needs to solve the issue'});
logger.fatal('System is down', {details: 'Use it is major outage happened (and likely system is not reliable)'});

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Default configuration

The default configuration object provides hints about what the module's standard behavior is like and which configuration options are available. For further details about the API, please have a look at the wiki.

{
    defaultLogLevel : Logger.LogLevel.Info,
    minLogLevel : Logger.LogLevel.Info,
    outputStreams : {
        [Logger.LogLevel.Trace] : process.stdout,
        [Logger.LogLevel.Debug] : process.stdout,
        [Logger.LogLevel.Info] : process.stdout,
        [Logger.LogLevel.Warning] : process.stdout,
        [Logger.LogLevel.Error] : process.stderr,
        [Logger.LogLevel.Fatal] : process.stderr
    },
    context : {
        name: null,
        serviceName : Logger.serviceName,
        serviceInstanceId : 0,
        correlationId : null,
        userId : null,
        requestUri : null
    }
}

Note that some settings would become obsolete in the future - logging configuration should be set by the environment, not by code. And the environment is preferably created by a code ;)

• defaultLogLevel and minLogLevel should dynamically change (user will be able to change configuration during runtime in the future)
• outputStreams could become more abstract - one can print to something else than a terminal/file but the concept generally is not planned to change
• context is going to move into local storage instead - logger shouldn't be contextified, session (call chain) should be

Configuration

• You should create a file logger.json in your project directory.
• You can have file etc/logger.json that takes precedence before logger.json if found.
• You can set environment variable LOGGER_CONFIG_FILE to a path that takes precedence before the two above.

The first file found - it would be the only used and monitored for changes.

See https://github.com/OpusCapita/logger/wiki/Configuration

An example self-explaining logger.json with explanation

{
  "serviceName": {
    "my service name": "Debug"
  },
  "name": {
    "my preferably unique logger name": "Trace",
    "some logger that I am not interested in": "Warning"
  },
  "requestUri": {
    "/api/health/check": "Fatal",
    "/api/buggy/endpoint": "Trace"
  },
  "userId": {
    "superduperadmin": "Trace"
  },
  
  "default": {
    "minLogLevel": "Info",
    "defaultLogLevel": "Info",
  }
  "--alternative default configuration entries you might consider--": {
    "formatter": "terminal",
    "formatter": "ci",
    "formatter": "ci-wide",
    "formatter": "color"
  }
}