Mitigate "MaxListenersExceededWarning" by reusing Logger instance

The full warning output was:
(node:43572) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 drain listeners added. Use emitter.setMaxListeners() to increase limit
(node:43572) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 error listeners added. Use emitter.setMaxListeners() to increase limit
(node:43572) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 close listeners added. Use emitter.setMaxListeners() to increase limit

Change-type: patch
Signed-off-by: Paulo Castro <paulo@balena.io>

lib/actions/build.coffee

@@ -108,7 +108,7 @@ module.exports =
 		helpers = require('../utils/helpers')
 		Logger = require('../utils/logger')
 
-		logger = new Logger()
+		logger = Logger.getLogger()
 		logger.logDebug('Parsing input...')
 
 		# `build` accepts `[source]` as a parameter, but compose expects it

lib/actions/deploy.coffee

@@ -185,7 +185,7 @@ module.exports =
 		helpers = require('../utils/helpers')
 		Logger = require('../utils/logger')
 
-		logger = new Logger()
+		logger = Logger.getLogger()
 		logger.logDebug('Parsing input...')
 
 		# when Capitano converts a positional parameter (but not an option)

lib/actions/join.ts

@@ -66,7 +66,7 @@ export const join: CommandDefinition<Args, Options> = {
 		const Logger = await import('../utils/logger');
 		const promote = await import('../utils/promote');
 		const sdk = balena.fromSharedOptions();
-		const logger = new Logger();
+		const logger = Logger.getLogger();
 		return Bluebird.try(() => {
 			return promote.join(logger, sdk, params.deviceIp, options.application);
 		}).nodeify(done);

lib/actions/leave.ts

@@ -51,7 +51,7 @@ export const leave: CommandDefinition<Args, {}> = {
 		const Logger = await import('../utils/logger');
 		const promote = await import('../utils/promote');
 		const sdk = balena.fromSharedOptions();
-		const logger = new Logger();
+		const logger = Logger.getLogger();
 		return Bluebird.try(() => {
 			return promote.leave(logger, sdk, params.deviceIp);
 		}).nodeify(done);

lib/actions/logs.ts

@@ -108,7 +108,7 @@ export const logs: CommandDefinition<
 		);
 		const Logger = await import('../utils/logger');
 
-		const logger = new Logger();
+		const logger = Logger.getLogger();
 
 		const servicesToDisplay =
 			options.service != null

lib/actions/tunnel.ts

@@ -94,7 +94,7 @@ export const tunnel: CommandDefinition<Args, Options> = {
 		const deviceOrApplication =
 			params.deviceOrApplication_raw || params.deviceOrApplication;
 		const Logger = await import('../utils/logger');
-		const logger = new Logger();
+		const logger = Logger.getLogger();
 		const balena = await import('balena-sdk');
 		const sdk = balena.fromSharedOptions();
 

lib/utils/device/deploy.ts

@@ -38,7 +38,7 @@ import { displayBuildLog } from './logs';
 
 // Define the logger here so the debug output
 // can be used everywhere
-const globalLogger = new Logger();
+const globalLogger = Logger.getLogger();
 
 export interface DeviceDeployOptions {
 	source: string;

lib/utils/logger.ts

@@ -19,6 +19,13 @@ import _ = require('lodash');
 import { EOL as eol } from 'os';
 import { StreamLogger } from 'resin-stream-logger';
 
+/**
+ * General purpose logger class with support for log streams and colours.
+ * Call `Logger.getLogger()` to retrieve a global shared instance of this
+ * class. The `new Logger()` pattern is not recommended because it may lead
+ * to Node printing "MaxListenersExceededWarning" warning messages to the
+ * console.
+ */
 class Logger {
 	public streams: {
 		build: NodeJS.ReadWriteStream;
@@ -33,7 +40,7 @@ class Logger {
 
 	public formatMessage: (name: string, message: string) => string;
 
-	constructor() {
+	protected constructor() {
 		const logger = new StreamLogger();
 		logger.addPrefix('build', chalk.blue('[Build]'));
 		logger.addPrefix('info', chalk.cyan('[Info]'));
@@ -64,6 +71,16 @@ class Logger {
 		this.formatMessage = logger.formatWithPrefix.bind(logger);
 	}
 
+	protected static logger: Logger;
+
+	/** Retrieve a global shared instance of this class */
+	public static getLogger() {
+		if (!this.logger) {
+			this.logger = new Logger();
+		}
+		return this.logger;
+	}
+
 	public logInfo(msg: string) {
 		return this.streams.info.write(msg + eol);
 	}

lib/utils/patterns.ts

@@ -333,7 +333,7 @@ export async function getOnlineTargetUuid(
 	applicationOrDevice: string,
 ) {
 	const Logger = await import('../utils/logger');
-	const logger = new Logger();
+	const logger = Logger.getLogger();
 	const appTest = validation.validateApplicationName(applicationOrDevice);
 	const uuidTest = validation.validateUuid(applicationOrDevice);