From 550eb3a46edc4819692be18ec0fa8be2b1c0d984 Mon Sep 17 00:00:00 2001
From: Momo Kornher <kornherm@amazon.co.uk>
Date: Tue, 3 Jun 2025 10:34:10 +0100
Subject: [PATCH] fix(toolkit-lib): tracing logs on watch action does not close
 immediately

---
 .../toolkit-lib/lib/api/logs-monitor/logs-monitor.ts  |  7 +++++--
 packages/@aws-cdk/toolkit-lib/lib/toolkit/toolkit.ts  |  3 +++
 .../@aws-cdk/toolkit-lib/test/actions/watch.test.ts   | 11 ++++++++---
 3 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/packages/@aws-cdk/toolkit-lib/lib/api/logs-monitor/logs-monitor.ts b/packages/@aws-cdk/toolkit-lib/lib/api/logs-monitor/logs-monitor.ts
index d1fb28796..b3da210e4 100644
--- a/packages/@aws-cdk/toolkit-lib/lib/api/logs-monitor/logs-monitor.ts
+++ b/packages/@aws-cdk/toolkit-lib/lib/api/logs-monitor/logs-monitor.ts
@@ -62,7 +62,9 @@ export class CloudWatchLogEventMonitor {
   private readonly pollingInterval: number = 2_000;
 
   public monitorId?: string;
+
   private readonly ioHelper: IoHelper;
+  private currentTick?: NodeJS.Timeout;
 
   constructor(props: CloudWatchLogEventMonitorProps) {
     this.startTime = props.startTime?.getTime() ?? Date.now();
@@ -80,8 +82,8 @@ export class CloudWatchLogEventMonitor {
       logGroupNames: this.logGroupNames(),
     }));
 
+    // tick schedules the next tick as well
     await this.tick();
-    this.scheduleNextTick();
   }
 
   /**
@@ -97,6 +99,7 @@ export class CloudWatchLogEventMonitor {
     const oldMonitorId = this.monitorId!;
     this.monitorId = undefined;
     this.startTime = Date.now();
+    clearTimeout(this.currentTick);
 
     await this.ioHelper.notify(IO.CDK_TOOLKIT_I5034.msg('Stopped monitoring log groups', {
       monitor: oldMonitorId,
@@ -140,7 +143,7 @@ export class CloudWatchLogEventMonitor {
       return;
     }
 
-    setTimeout(() => void this.tick(), this.pollingInterval);
+    this.currentTick = setTimeout(() => void this.tick(), this.pollingInterval);
   }
 
   private async tick(): Promise<void> {
diff --git a/packages/@aws-cdk/toolkit-lib/lib/toolkit/toolkit.ts b/packages/@aws-cdk/toolkit-lib/lib/toolkit/toolkit.ts
index e344c545c..2ba99bb6e 100644
--- a/packages/@aws-cdk/toolkit-lib/lib/toolkit/toolkit.ts
+++ b/packages/@aws-cdk/toolkit-lib/lib/toolkit/toolkit.ts
@@ -973,6 +973,9 @@ export class Toolkit extends CloudAssemblySourceBuilder {
 
     return {
       async dispose() {
+        // stop the logs monitor, if it exists
+        await cloudWatchLogMonitor?.deactivate();
+        // close the watcher itself
         await watcher.close();
         // Prevents Node from staying alive. There is no 'end' event that the watcher emits
         // that we can know it's definitely done, so best we can do is tell it to stop watching,
diff --git a/packages/@aws-cdk/toolkit-lib/test/actions/watch.test.ts b/packages/@aws-cdk/toolkit-lib/test/actions/watch.test.ts
index dfe850296..90337581c 100644
--- a/packages/@aws-cdk/toolkit-lib/test/actions/watch.test.ts
+++ b/packages/@aws-cdk/toolkit-lib/test/actions/watch.test.ts
@@ -161,7 +161,7 @@ describe('watch', () => {
     // GIVEN
     const cx = await builderFixture(toolkit, 'stack-with-role');
     ioHost.level = 'debug';
-    await toolkit.watch(cx, {
+    const watcher = await toolkit.watch(cx, {
       include: [],
       traceLogs: true,
     });
@@ -174,8 +174,13 @@ describe('watch', () => {
       cloudWatchLogMonitor: expect.anything(), // Not undefined
     }));
 
-    // Deactivate the cloudWatchLogMonitor that we created, otherwise the tests won't exit
-    (deploySpy.mock.calls[0]?.[2] as any).cloudWatchLogMonitor?.deactivate();
+    const logMonitorSpy = jest.spyOn((deploySpy.mock.calls[0]?.[2] as any).cloudWatchLogMonitor, 'deactivate');
+
+    // Deactivate the watcher and cloudWatchLogMonitor that we created, otherwise the tests won't exit
+    await watcher.dispose();
+
+    // ensure the log monitor has been closed
+    expect(logMonitorSpy).toHaveBeenCalled();
   });
 
   test('watch returns an object that can be used to stop the watch', async () => {