include garbage collection change

Author: kevinxh

packages/pwa-kit-runtime/CHANGELOG.md

@@ -1,5 +1,6 @@
 ## v2.9.1 (Mar 18, 2025)
 - Disable CloudWatch metrics sender retries [#2321](https://github.com/SalesforceCommerceCloud/pwa-kit/pull/2321)
+- Remove forced garbage collection on each invocation. Set `FORCE_GC=true` for the old behavior. [#2321](https://github.com/SalesforceCommerceCloud/pwa-kit/pull/2321)
 
 ## v2.9.0 (Jan 21, 2025)
 - Support Node 20 and NPM 10 in PWA Kit v2 [#2189](https://github.com/SalesforceCommerceCloud/pwa-kit/pull/2189)

packages/pwa-kit-runtime/src/ssr/server/build-remote-server.js

@@ -304,6 +304,8 @@ export const RemoteServerFactory = {
         const mixin = {
             options,
 
+            // Forcing a GC is no longer necessary, and will be
+            // skipped by default (unless FORCE_GC env-var is set).
             _collectGarbage() {
                 // Do global.gc in a separate 'then' handler so
                 // that all major variables are out of scope and
@@ -823,12 +825,15 @@ export const RemoteServerFactory = {
             context.callbackWaitsForEmptyEventLoop = false
 
             if (lambdaContainerReused) {
-                // DESKTOP-434 If this Lambda container is being reused,
-                // clean up memory now, so that we start with low usage.
-                // These regular GC calls take about 80-100 mS each, as opposed
-                // to forced GC calls, which occur randomly and can take several
-                // hundred mS.
-                app._collectGarbage()
+                const forceGarbageCollection = process.env.FORCE_GC
+                if (forceGarbageCollection && forceGarbageCollection.toLowerCase() === 'true') {
+                    // DESKTOP-434 If this Lambda container is being reused,
+                    // clean up memory now, so that we start with low usage.
+                    // These regular GC calls take about 80-100 mS each, as opposed
+                    // to forced GC calls, which occur randomly and can take several
+                    // hundred mS.
+                    app._collectGarbage()
+                }
                 app.sendMetric('LambdaReused')
             } else {
                 // This is the first use of this container, so set the

packages/pwa-kit-runtime/src/ssr/server/express.lambda.test.js

@@ -52,6 +52,48 @@ export const httpsAgent = new https.Agent({
     rejectUnauthorized: false
 })
 
+function createServerWithGCSpy() {
+    const route = jest.fn((req, res) => {
+        res.send('<html/>')
+    })
+
+    const options = {
+        buildDir: testFixtures,
+        mobify: testPackageMobify,
+        sslFilePath: path.join(testFixtures, 'localhost.pem'),
+        quiet: true,
+        port: TEST_PORT,
+        fetchAgents: {
+            https: httpsAgent
+        }
+    }
+
+    const {handler, server, app} = RemoteServerFactory.createHandler(options, (app) => {
+        app.get('/*', route)
+    })
+
+    const collectGarbage = jest.spyOn(app, '_collectGarbage')
+    const sendMetric = jest.spyOn(app, 'sendMetric')
+    return {route, handler, collectGarbage, sendMetric, server}
+}
+
+function createApiGatewayEvent() {
+    // Set up a fake event and a fake context for the Lambda call
+    const event = createEvent('aws:apiGateway', {
+        path: '/',
+        body: undefined
+    })
+
+    if (event.queryStringParameters) {
+        delete event.queryStringParameters
+    }
+
+    const context = AWSMockContext({
+        functionName: 'SSRTest'
+    })
+    return {event, context}
+}
+
 describe('SSRServer Lambda integration', () => {
     let savedEnvironment
     let server
@@ -371,47 +413,40 @@ describe('SSRServer Lambda integration', () => {
         })
     })
 
-    test('Lambda reuse behaviour', () => {
-        const route = jest.fn((req, res) => {
-            res.send('<html/>')
-        })
-
-        const options = {
-            buildDir: testFixtures,
-            mobify: testPackageMobify,
-            sslFilePath: path.join(testFixtures, 'localhost.pem'),
-            quiet: true,
-            port: TEST_PORT,
-            fetchAgents: {
-                https: httpsAgent
-            }
-        }
-
-        const {
-            app,
-            handler,
-            server: srv
-        } = RemoteServerFactory.createHandler(options, (app) => {
-            app.get('/*', route)
-        })
+    test('Lambda reuse -- Default Behavior', () => {
+        const {route, handler, collectGarbage, sendMetric, new_server} = createServerWithGCSpy()
+        const {event, context} = createApiGatewayEvent()
+        server = new_server
 
-        const collectGarbage = jest.spyOn(app, '_collectGarbage')
-        const sendMetric = jest.spyOn(app, 'sendMetric')
-        server = srv
-
-        // Set up a fake event and a fake context for the Lambda call
-        const event = createEvent('aws:apiGateway', {
-            path: '/',
-            body: undefined
-        })
+        const call = (event) =>
+            new Promise((resolve) => handler(event, context, (err, response) => resolve(response)))
 
-        if (event.queryStringParameters) {
-            delete event.queryStringParameters
-        }
+        return Promise.resolve()
+            .then(() => call(event))
+            .then((response) => {
+                // First request - Lambda container created
+                expect(response.statusCode).toBe(200)
+                expect(collectGarbage.mock.calls).toHaveLength(0)
+                expect(route.mock.calls).toHaveLength(1)
+                expect(sendMetric).toHaveBeenCalledWith('LambdaCreated')
+                expect(sendMetric).not.toHaveBeenCalledWith('LambdaReused')
+            })
+            .then(() => call(event))
+            .then((response) => {
+                // Second call - Lambda container reused
+                expect(response.statusCode).toBe(200)
+                expect(collectGarbage.mock.calls).toHaveLength(0)
+                expect(route.mock.calls).toHaveLength(2)
+                expect(sendMetric).toHaveBeenCalledWith('LambdaCreated')
+                expect(sendMetric).toHaveBeenCalledWith('LambdaReused')
+            })
+    })
 
-        const context = AWSMockContext({
-            functionName: 'SSRTest'
-        })
+    test('Lambda reuse -- with Forced Garbage Collection Enabled', () => {
+        process.env.FORCE_GC = 'true'
+        const {event, context} = createApiGatewayEvent()
+        const {route, handler, collectGarbage, sendMetric, new_server} = createServerWithGCSpy()
+        server = new_server
 
         const call = (event) =>
             new Promise((resolve) => handler(event, context, (err, response) => resolve(response)))