Pick random server port on init (#333)

This gives the initialised template a stable port to `skuba start` on.
With any luck the randomness will also reduce the chance of collisions
in the event that you need to run multiple projects locally at once.

Author: 72636c

.changeset/fifty-ladybugs-fly.md

@@ -0,0 +1,5 @@
+---
+'skuba': patch
+---
+
+**init:** Pick random server port

src/cli/init/getConfig.ts

@@ -7,6 +7,7 @@ import fs from 'fs-extra';
 import { copyFiles } from '../../utils/copy';
 import { isErrorWithCode } from '../../utils/error';
 import { log } from '../../utils/logging';
+import { getRandomPort } from '../../utils/port';
 import {
   TEMPLATE_CONFIG_FILENAME,
   TEMPLATE_DIR,
@@ -143,12 +144,15 @@ export const getTemplateConfig = (dir: string): TemplateConfig => {
   }
 };
 
-const baseToTemplateData = ({ ownerName, repoName }: BaseFields) => {
+const baseToTemplateData = async ({ ownerName, repoName }: BaseFields) => {
   const [orgName, teamName] = ownerName.split('/');
 
+  const port = String(await getRandomPort());
+
   return {
     orgName,
     ownerName,
+    port,
     repoName,
     // Use standalone username in `teamName` contexts
     teamName: teamName ?? orgName,
@@ -159,7 +163,7 @@ export const configureFromPrompt = async (): Promise<InitConfig> => {
   const { ownerName, repoName } = await runForm(BASE_PROMPT_PROPS);
   log.plain(chalk.cyan(repoName), 'by', chalk.cyan(ownerName));
 
-  const templateData = baseToTemplateData({ ownerName, repoName });
+  const templateData = await baseToTemplateData({ ownerName, repoName });
 
   const destinationDir = repoName;
 
@@ -258,7 +262,7 @@ const configureFromPipe = async (): Promise<InitConfig> => {
   const { destinationDir, templateComplete, templateName } = result.value;
 
   const templateData = {
-    ...baseToTemplateData(result.value.templateData),
+    ...(await baseToTemplateData(result.value.templateData)),
     ...result.value.templateData,
   };
 

src/cli/init/types.ts

@@ -33,6 +33,9 @@ const InitConfig = t.Record({
       // Derived from ownerName
       orgName: t.String,
       teamName: t.String,
+
+      // Generated by init command
+      port: t.String,
     })
     .And(t.Dictionary(t.String, 'string')),
 

src/utils/port.test.ts

@@ -0,0 +1,16 @@
+import { randomIntBetween } from './port';
+
+describe('randomIntBetween', () => {
+  it('generates integers between min and max inclusive', () => {
+    const min = 1000;
+    const max = 2000;
+
+    for (let i = 0; i < 1000; i++) {
+      const output = randomIntBetween(min, max);
+
+      expect(output).toBeGreaterThanOrEqual(min);
+      expect(output).toBeLessThanOrEqual(max);
+      expect(Number.isSafeInteger(output)).toBe(true);
+    }
+  });
+});

src/utils/port.ts

@@ -0,0 +1,20 @@
+import getPort from 'get-port';
+
+/* Smallest 5-digit port; these are less common than 4-digit ports. */
+const MIN_PORT = 10000;
+
+/** Largest port in the IANA user port range. */
+const MAX_PORT = 49151;
+
+export const randomIntBetween = (min: number, max: number) =>
+  min + Math.floor(Math.random() * (1 + max - min));
+
+export const getRandomPort = () => {
+  // Seed some random ports to use, if available.
+  // get-port falls back to the private port range.
+  const preferredPorts = new Array(10)
+    .fill(null)
+    .map(() => randomIntBetween(MIN_PORT, MAX_PORT));
+
+  return getPort({ port: preferredPorts });
+};

template/express-rest-api/package.json

@@ -22,7 +22,7 @@
     "format": "skuba format",
     "lint": "skuba lint",
     "start": "ENVIRONMENT=local skuba start",
-    "start:debug": "ENVIRONMENT=local skuba start --inspect-brk",
+    "start:debug": "yarn start --inspect-brk",
     "test": "skuba test --coverage",
     "test:watch": "skuba test --watch"
   }

template/express-rest-api/src/config.ts

@@ -29,7 +29,7 @@ const configs: Record<Environment, () => Omit<Config, 'environment'>> = {
     region: 'ap-southeast-2',
     version: 'local',
 
-    port: Env.nonNegativeInteger('PORT', { default: undefined }),
+    port: Env.nonNegativeInteger('PORT', { default: Number('<%- port %>') }),
   }),
 
   test: () => ({

template/greeter/package.json

@@ -16,7 +16,7 @@
     "format": "skuba format",
     "lint": "skuba lint",
     "start": "ENVIRONMENT=local skuba start",
-    "start:debug": "ENVIRONMENT=local skuba start --inspect-brk",
+    "start:debug": "yarn start --inspect-brk",
     "test": "skuba test --coverage",
     "test:watch": "skuba test --watch"
   }

template/koa-rest-api/package.json

@@ -36,7 +36,7 @@
     "format": "skuba format",
     "lint": "skuba lint",
     "start": "ENVIRONMENT=local skuba start",
-    "start:debug": "ENVIRONMENT=local skuba start --inspect-brk",
+    "start:debug": "yarn start --inspect-brk",
     "test": "skuba test --coverage",
     "test:watch": "skuba test --watch"
   }

template/koa-rest-api/src/config.ts

@@ -29,7 +29,7 @@ const configs: Record<Environment, () => Omit<Config, 'environment'>> = {
     region: 'ap-southeast-2',
     version: 'local',
 
-    port: Env.nonNegativeInteger('PORT', { default: undefined }),
+    port: Env.nonNegativeInteger('PORT', { default: Number('<%- port %>') }),
   }),
 
   test: () => ({

template/lambda-sqs-worker/package.json

@@ -29,8 +29,8 @@
     "format": "skuba format",
     "lint": "skuba lint",
     "smoke": "serverless invoke --data '{}' --function Worker",
-    "start": "ENVIRONMENT=local skuba start",
-    "start:debug": "ENVIRONMENT=local skuba start --inspect-brk",
+    "start": "ENVIRONMENT=local skuba start --port <%- port %>",
+    "start:debug": "yarn start --inspect-brk",
     "test": "skuba test --coverage",
     "test:watch": "skuba test --watch"
   }