fix: assign a random port for devtools in case of conflict (#136)

Fixes #77

packages/server/lib/index.js

@@ -164,14 +164,28 @@ export default class DevTool {
 	 * @see {@link DevTool.stop}
 	 */
 	start() {
-		return new Promise((resolve) => {
+		return new Promise((resolve, reject) => {
 			const start = new Date().getTime();
-			this.server = this.app.listen(this.port, () => {
-				const ms = new Date().getTime() - start;
-				this.port = this.server.address().port;
-				this.#log.trace(`dev tool server started on port "${this.port}" (in ${ms} ms)`);
-				resolve();
-			});
+			this.server = this.app
+				.listen(this.port, () => {
+					const ms = new Date().getTime() - start;
+					this.port = this.server.address().port;
+					this.#log.trace(`dev tool server started on port "${this.port}" (in ${ms} ms)`);
+					resolve();
+				})
+				.on("error", (e) => {
+					if (e.code === "EADDRINUSE") {
+						this.#log.trace(`dev tool server port ${this.port} is already in use, trying a random port`);
+						this.server = this.app.listen(0, () => {
+							const ms = new Date().getTime() - start;
+							this.port = this.server.address().port;
+							this.#log.trace(`dev tool server started on port "${this.port}" (in ${ms} ms)`);
+							resolve();
+						});
+					} else {
+						reject(e);
+					}
+				});
 		});
 	}
 

packages/server/lib/index.test.js

@@ -71,16 +71,38 @@ test("starting on a random port", async (t) => {
 		error: t.mock.fn(),
 		fatal: t.mock.fn(),
 	};
-	devTool = new DevTool({ logger, port: 0 });
+	const a = new DevTool({ logger, port: 4321 });
+	const b = new DevTool({ logger, port: 4321 });
+	await a.start();
+	await b.start();
+	await a.stop();
+	await b.stop();
+
+	assert.match(logger.trace.mock.calls[0].arguments[0], /dev tool server started on port "4321"/);
+	assert.match(logger.trace.mock.calls[2].arguments[0], /dev tool server started on port "/);
+	assert.notEqual(logger.trace.mock.calls[2].arguments[0], "undefined");
+	assert.notEqual(logger.trace.mock.calls[2].arguments[0], "null");
+	assert.notEqual(logger.trace.mock.calls[2].arguments[0], "8172");
+	assert.equal(logger.trace.mock.calls.length, 5);
+});
+
+test("assigns a random port if the specified port isn't available", async (t) => {
+	const logger = {
+		trace: t.mock.fn(),
+		debug: t.mock.fn(),
+		info: t.mock.fn(),
+		warn: t.mock.fn(),
+		error: t.mock.fn(),
+		fatal: t.mock.fn(),
+	};
+	devTool = new DevTool({ logger });
 	devTool.register(podlet);
 
 	await devTool.start();
 	await devTool.stop();
 
-	assert.match(logger.trace.mock.calls[0].arguments[0], /dev tool server started on port "/);
-	assert.notEqual(logger.trace.mock.calls[0].arguments[0], "undefined");
-	assert.notEqual(logger.trace.mock.calls[0].arguments[0], "null");
-	assert.notEqual(logger.trace.mock.calls[0].arguments[0], "8172");
+	assert.match(logger.trace.mock.calls[0].arguments[0], /dev tool server started on port "8172" \(in/);
+	assert.match(logger.trace.mock.calls[1].arguments[0], /dev tool server shutdown in/);
 	assert.equal(logger.trace.mock.calls.length, 2);
 });