feat: Drop winston and simpplify the logger

Drop winston in favour of creating a simple logger that allows extracting error object properties (including message) while keeping the log message.

BREAKING CHANGE: The logger do not allow using winston's API anymore as we dropped winston

Author: ikhemissi

.circleci/config.yml

@@ -31,6 +31,9 @@ jobs:
       - run:
           name: Lint
           command: npm run lint
+      - run:
+          name: Test
+          command: npm run test
       - persist_to_workspace:
           root: ~/repo
           paths:

.eslintrc.json

@@ -5,13 +5,17 @@
 		"promise",
 		"security"
 	],
+	"env": {
+		"mocha": true
+	},
 	"rules": {
 		"array-bracket-newline": [2, "consistent"],
 		"array-element-newline": [2, "consistent"],
 		"arrow-body-style": [2, "as-needed"],
 		"capitalized-comments": 2,
 		"comma-dangle": 2,
 		"dot-location": [2, "property"],
+		"no-console": 0,
 		"no-empty-function": 2,
 		"no-magic-numbers": 0,
 		"no-tabs": [2, {"allowIndentationTabs": true}],

README.md

@@ -7,30 +7,8 @@
 npm install --save @5app/logger
 ```
 
-Then, generate a logger in your app and use it to log messages.
-
-```javascript
-const {logger} = require('@5app/logger');
-
-logger.info('An email was sent', {
-  email: 'customer@5app.com',
-  template: 'template1',
-});
-
-logger.error(new Error('Unknown playlist 123'));
-```
-
-Alternatively, you can create a new instance of logger where you can specify the metadata, logging level, and whether you want simple logs or not:
-
 ```javascript
-const {getLogger} = require('@5app/logger');
-
-const logger = getLogger({
-  simple: process.env.NODE_ENV === 'development',
-  metadata: {
-    tag: process.env.TAG, // release tag, e.g. docker container tag
-  },
-});
+const logger = require('@5app/logger');
 
 logger.info('An email was sent', {
   email: 'customer@5app.com',
@@ -42,57 +20,21 @@ logger.error(new Error('Unknown playlist 123'));
 
 ## Options
 
-The logger generator accepts the following options:
+The logger can optionally be customised using the following environment variables:
 
-### simple
+- `LOGS_FORMAT`: if set to `json`, the logger will log messages in json format instead of pretty messages (default behaviour).
+- `LOGS_LEVEL`: minimum logging level, by default it will be `debug`. Accepted values are `'debug'`, `'info'`, `'warn'`, and `'error'`
+- `TAG`: release tag (e.g. docker image tag) to be added to the log messages
 
-This boolean value specifies whether we should log pretty dev-friendly messages instead of JSON or not.
-By default, simple will be false.
+## Logging levels
 
-Example:
-```javascript
-const {getLogger} = require('@5app/logger');
+Logging levels are (from lower to higher priority): `'debug'`, `'info'`, `'warn'`, and `'error'`.
+The logger provides the logging functions with the following signatures: `logger.<level>(message, objectOrError)`
 
-// This logger will log dev-friendly messages
-const logger = getLogger({
-  simple: true,
-});
+Here is an example of how the logger can be used:
 ```
-
-The default logger uses the environment variable `LOGS_FORMAT` to determine if the logs are going to be generated in json (`json`) or simple console logs (any other value other than `json`).
-
-### metadata
-
-Metadata is an object containing service metadata like the release tag or the A/B testing experiment we are running.
-This object will be added to each log entry when using the JSON mode.
-
-Example:
-```javascript
-const {getLogger} = require('@5app/logger');
-
-// This logger will add details about the current release and A/B experiment to every log line
-const logger = getLogger({
-  metadata: {
-    release: '1.2.3',
-    experiment: 12345,
-  },
-});
-```
-
-### level
-
-You can specify a minimum logging level using the `level` parameter or using the `LOGS_LEVEL` environment variable.
-By default, the logging level will be [debug (npm)](https://github.com/winstonjs/winston#logging-levels).
-
-Example:
-```javascript
-const {getLogger} = require('@5app/logger');
-
-// This logger will add details about the current release and A/B experiment to every log line
-const logger = getLogger({
-  level: 'warn',
-});
-
-logger.info('this message will not be logged');
-logger.warn('you will see this message');
+logger.error('An error happened', new ApiError('The api call failed', 404)); // will log the message, the error message, the stack trace, and the statusCode error property
+logger.warn('Be warned', {a: 1, b: Date.now(), c: 'some string'});
+logger.info('An event happened', {a: 1, b: Date.now(), c: 'some string'});
+logger.debug('A minor operation', {a: 1, b: Date.now(), c: 'some string'});
 ```

getLogger.js

@@ -1,20 +1,20 @@
-const getLogger = require('./getLogger');
+const simple = require('./outputs/simple');
+const json = require('./outputs/json');
+const levels = require('./levels');
+const priority = require('./priority');
 
-const {
-	LOGS_FORMAT,
-	LOGS_LEVEL,
-	TAG
-} = process.env;
+const {LOGS_FORMAT, LOGS_LEVEL} = process.env;
 
-const logger = getLogger({
-	simple: LOGS_FORMAT !== 'json',
-	level: LOGS_LEVEL || 'debug',
-	metadata: {
-		tag: TAG
-	}
+const logger = LOGS_FORMAT === 'json' ? json : simple;
+const minimumPriority = priority(LOGS_LEVEL || 'debug');
+
+// eslint-disable-next-line no-empty-function
+const noLog = () => {};
+
+const methods = {};
+
+Object.keys(levels).forEach(level => {
+	methods[level] = priority(level) >= minimumPriority ? (message, context) => logger(level, message, context) : noLog;
 });
 
-module.exports = {
-	logger,
-	getLogger
-};
+module.exports = methods;

index.js

@@ -0,0 +1,10 @@
+const chalk = require('chalk');
+
+const levels = {
+	error: {priority: 4, color: chalk.red},
+	warn: {priority: 3, color: chalk.yellow},
+	info: {priority: 2, color: chalk.green},
+	debug: {priority: 1, color: chalk.grey, colorAll: true}
+};
+
+module.exports = levels;

levels.js

@@ -0,0 +1,36 @@
+const priority = require('../priority');
+
+const {TAG: tag} = process.env;
+
+function formatError(data) {
+	if (data instanceof Error) {
+		return {
+			error: data.message,
+			stacktrace: data.stack ? data.stack.split('\n').slice(1, 3)
+				.map(line => line.trim()) : undefined,
+			statusCode: data.statusCode
+		};
+	}
+
+	return data;
+}
+
+function log(level, message, context = {}) {
+	let contextObject = context;
+
+	if (priority(level) >= priority('error')) {
+		contextObject = formatError(context);
+	}
+
+	const payload = JSON.stringify({
+		level,
+		message,
+		tag,
+		timestamp: new Date().toISOString(),
+		...contextObject
+	});
+
+	console.log(payload);
+}
+
+module.exports = log;

outputs/json.js

@@ -0,0 +1,23 @@
+const util = require('util');
+const levels = require('../levels');
+
+// Precalculate each level logging options
+const prefixes = Object.keys(levels).reduce((map, level) => {
+	map[level] = levels[level].color(`${level}:`);
+	return map;
+}, {});
+
+// Simple logging function
+function log(level, message, context = '') {
+	const prefix = prefixes[level] || '';
+	const {colorAll, color} = levels[level];
+
+	if (colorAll) {
+		console.log(color(util.format(`${level}: ${message}`, context)));
+	}
+	else {
+		console.log(`${prefix} ${message}`, context);
+	}
+}
+
+module.exports = log;