feat: add stop function to allow shutting down the debug agent (#1147)

Author: mctavish

src/agent/debuglet.ts

@@ -187,6 +187,7 @@ export interface FindFilesResult {
 export class Debuglet extends EventEmitter {
   private debug: Debug;
   private v8debug: DebugApi | null;
+  private started: boolean;
   private running: boolean;
   private project: string | null;
   private controller: Controller | null;
@@ -241,6 +242,9 @@ export class Debuglet extends EventEmitter {
      */
     this.v8debug = null;
 
+    /** @private {boolean} */
+    this.started = false;
+
     /** @private {boolean} */
     this.running = false;
 
@@ -351,6 +355,7 @@ export class Debuglet extends EventEmitter {
    * @private
    */
   async start(): Promise<void> {
+    this.started = true;
     const stat = util.promisify(fs.stat);
 
     try {
@@ -734,6 +739,10 @@ export class Debuglet extends EventEmitter {
     }
 
     setTimeout(() => {
+      if (!this.running) {
+        this.logger.info('Debuglet is stopped; not registering');
+        return;
+      }
       assert(that.controller);
       if (!that.running) {
         onError(new Error('Debuglet not running'));
@@ -785,6 +794,10 @@ export class Debuglet extends EventEmitter {
   }
 
   startListeningForBreakpoints_(): void {
+    if (!this.running) {
+      this.logger.info('Debuglet is stopped; not listening for breakpoints');
+      return;
+    }
     assert(this.controller);
     // TODO: Handle the case where this.debuggee is null or not properly registered.
     this.controller.subscribeToBreakpoints(
@@ -1072,16 +1085,30 @@ export class Debuglet extends EventEmitter {
   }
 
   /**
-   * Stops the Debuglet. This is for testing purposes only. Stop should only be
-   * called on a agent that has started (i.e. emitted the 'started' event).
-   * Calling this while the agent is initializing may not necessarily stop all
-   * pending operations.
+   * Stops the Debuglet.
+   *
+   * Stop should only be called on a agent that has started.
    */
   stop(): void {
+    if (this.running) {
+      this.stopController();
+    } else {
+      if (!this.started) {
+        this.logger.info('Attempt to stop Debuglet before it was started');
+        return;
+      }
+      this.on('started', () => {
+        this.stopController();
+      });
+    }
+  }
+
+  stopController(): void {
     assert(this.controller);
     assert.ok(this.running, 'stop can only be called on a running agent');
     this.logger.debug('Stopping Debuglet');
     this.running = false;
+    this.started = false;
     this.controller.stop();
     this.emit('stopped');
   }

src/agent/firebase-controller.ts

@@ -349,7 +349,7 @@ export class FirebaseController implements Controller {
     debuglog(`starting to mark every ${this.markActivePeriodMsec} ms`);
     this.markActiveInterval = setInterval(() => {
       this.markDebuggeeActive();
-    }, this.markActivePeriodMsec);
+    }, this.markActivePeriodMsec).unref();
   }
 
   /**

src/index.ts

@@ -23,7 +23,7 @@ import * as util from 'util';
 const debuglog = util.debuglog('cdbg');
 
 // Singleton.
-let debuglet: Debuglet;
+let debuglet: Debuglet | undefined;
 
 /**
  * Start the Debug agent that will make your application available for debugging
@@ -86,3 +86,14 @@ function mergeConfigs<T>(options: T & {debug?: T}): T {
 export function get(): Debuglet | undefined {
   return debuglet;
 }
+
+/**
+ * Cleanly shut down the debug agent.
+ *
+ * This will free up all resources.  It may be necessary to call this to allow
+ * your process to shut down cleanly.
+ */
+export function stop(): void {
+  debuglet?.stop();
+  debuglet = undefined;
+}

system-test/fixtures/sample/src/allowExpressions.ts

@@ -13,3 +13,4 @@
 
 import * as debug from '@google-cloud/debug-agent';
 debug.start({allowExpressions: true});
+debug.stop();

system-test/fixtures/sample/src/allowExpressionsJs.js

@@ -14,3 +14,4 @@
 require('@google-cloud/debug-agent').start({
   allowExpressions: true,
 });
+require('@google-cloud/debug-agent').stop();

system-test/fixtures/sample/src/completeServiceContext.ts

@@ -19,3 +19,4 @@ debug.start({
     version: 'Some version',
   },
 });
+debug.stop();

system-test/fixtures/sample/src/firebase.ts

@@ -0,0 +1,16 @@
+// Copyright 2023 Google LLC
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import * as debug from '@google-cloud/debug-agent';
+debug.start({useFirebase: true});
+debug.stop();

system-test/fixtures/sample/src/import.ts

@@ -13,3 +13,4 @@
 
 import * as debug from '@google-cloud/debug-agent';
 debug.start();
+debug.stop();

system-test/fixtures/sample/src/noargs.ts

@@ -13,3 +13,4 @@
 
 import * as debug from '@google-cloud/debug-agent';
 debug.start();
+debug.stop();

system-test/fixtures/sample/src/partialCapture.ts

@@ -17,3 +17,4 @@ debug.start({
     maxFrames: 1,
   },
 });
+debug.stop();