From 84f48e36f4e419e3cd8aec04d69008616e9fbe87 Mon Sep 17 00:00:00 2001
From: Hornwitser <github@hornwitser.no>
Date: Sun, 1 Sep 2019 16:07:31 +0200
Subject: [PATCH] Improve error reporting at startup

Add StartupError that differentiates unhandled errors from errors with
known causes and use it to only print the "please report" banner when an
unhandled error occurs.

Also makes the error reporting more visible in the console.
---
 master.js | 51 +++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 43 insertions(+), 8 deletions(-)

diff --git a/master.js b/master.js
index 4af91d1e..bc63a58c 100644
--- a/master.js
+++ b/master.js
@@ -857,6 +857,29 @@ async function getPlugins(){
 	return plugins;
 }
 
+// Errror class for known errors occuring during startup
+class StartupError extends Error { }
+
+/**
+ * Calls listen on server capturing any errors that occurs
+ * binding to the port.
+ */
+function listen(server, ...args) {
+	return new Promise((resolve, reject) => {
+		function wrapError(err) {
+			reject(new StartupError(
+				`Server listening failed: ${err.message}`
+			));
+		}
+
+		server.once('error', wrapError);
+		server.listen(...args, () => {
+			server.off('error', wrapError);
+			resolve();
+		});
+	});
+}
+
 async function startServer() {
 	// Set the process title, shows up as the title of the CMD window on windows
 	// and as the process name in ps/top on linux.
@@ -921,7 +944,7 @@ async function startServer() {
 	// Only start listening for connections after all plugins have loaded
 	if (httpPort) {
 		let httpServer = require("http").Server(app);
-		httpServer.listen(httpPort);
+		await listen(httpServer, httpPort);
 		console.log("Listening for HTTP on port %s...", httpServer.address().port);
 	}
 
@@ -932,15 +955,16 @@ async function startServer() {
 			privateKey = await fs.readFile(config.sslPrivKey);
 
 		} catch (err) {
-			console.error(`Error loading ssl certificate: ${err.message}`);
-			await shutdown()
+			throw new StartupError(
+				`Error loading ssl certificate: ${err.message}`
+			);
 		}
 
 		let httpsServer = require("https").createServer({
 			key: privateKey,
 			cert: certificate
 		}, app)
-		httpsServer.listen(httpsPort);
+		await listen(httpsServer, httpsPort);
 		console.log("Listening for HTTPS on port %s...", httpsServer.address().port);
 	}
 }
@@ -949,10 +973,21 @@ module.exports = app;
 
 if (module === require.main) {
 	startServer().catch(err => {
-		console.error(
-			"Unexpected error occured while starting master, please report\n"+
-			"it to https://github.com/clusterio/factorioClusterio/issues"
-		);
+		if (!(err instanceof StartupError)) {
+			console.error(`
++---------------------------------------------------------------+
+| Unexpected error occured while starting master, please report |
+| it to https://github.com/clusterio/factorioClusterio/issues   |
++---------------------------------------------------------------+`
+			);
+		} else {
+			console.error(`
++----------------------------------+
+| Unable to to start master server |
++----------------------------------+`
+			);
+		}
+
 		console.error(err);
 		return shutdown();
 	});