Merge branch 'main' into dependabot/npm_and_yarn/multi-cf87d80143

.github/workflows/node.js.yml

@@ -0,0 +1,31 @@
+# This workflow will do a clean installation of node dependencies, cache/restore them, build the source code and run tests across different versions of node
+# For more information see: https://docs.github.com/en/actions/automating-builds-and-tests/building-and-testing-nodejs
+
+name: Node.js Unit Tests
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        node-version: [18.x, 20.x, 22.x]
+        # See supported Node.js release schedule at https://nodejs.org/en/about/releases/
+
+    steps:
+    - uses: actions/checkout@v4
+    - name: Use Node.js ${{ matrix.node-version }}
+      uses: actions/setup-node@v4
+      with:
+        node-version: ${{ matrix.node-version }}
+        cache: 'npm'
+    - run: npm ci
+    - run: npm run build --if-present
+    - run: npm test

README.md

@@ -53,10 +53,14 @@ underPressure(app, {
   maxEventLoopDelay: 1000, // Maximum event loop delay in milliseconds
   maxHeapUsedBytes: 200 * 1024 * 1024, // Maximum heap used in bytes
   maxRssBytes: 300 * 1024 * 1024, // Maximum RSS memory used in bytes
+  maxEventLoopUtilization: 0.98 // Maximum event loop utilisation
   message: 'Server Under Pressure', // Custom response message
 });
 
 app.get('/', (req, res) => {
+  if (app.locals.isUnderPressure()) {
+    // Avoind heavy computations here
+  }
   res.send('Hello World!');
 });
 

src/index.ts

@@ -78,6 +78,25 @@ export function underPressure(
 
   const retryAfter = opts.retryAfter || 10;
 
+  function isUnderPressure() {
+    if (checkMaxEventLoopDelay && eventLoopDelay > maxEventLoopDelay) {
+      return true;
+    }
+
+    if (checkMaxHeapUsedBytes && heapUsed > maxHeapUsedBytes) {
+      return true;
+    }
+
+    if (checkMaxRssBytes && rssBytes > maxRssBytes) {
+      return true;
+    }
+
+    return (
+      checkMaxEventLoopUtilization &&
+      eventLoopUtilized > maxEventLoopUtilization
+    );
+  }
+
   function updateEventLoopDelay() {
     eventLoopDelay = Math.max(0, histogram.mean / 1e6 - resolution);
 
@@ -143,5 +162,6 @@ export function underPressure(
     next();
   }
 
+  app.locals.isUnderPressure = isUnderPressure;
   app.use(underPressureHandler);
 }

test/index.test.ts

@@ -150,3 +150,14 @@ test('working with event Loop delay', async (t) => {
   t.equal(response.text, 'Service Unavailable');
   t.equal(response.headers['retry-after'], '20');
 });
+
+test('isUnderPressure should be made available to app.locals', async (t) => {
+  const app = express();
+
+  underPressure(app, {
+    maxHeapUsedBytes: 100,
+    retryAfter: 20,
+  });
+
+  t.equal(typeof app.locals.isUnderPressure, 'function');
+});