refactor(heart): bind class methods and make beat async (#5142)

* feat: set up new test for beat twice

* refactor: make Heart.beat() async

This allows us to properly await heart.beat() in our tests and remove
the HACK I added before.

* refactor: bind heart methods .beat and .alive

This allows the functions to maintain access to the Heart instance (or
`this`) even when they are passed to other functions. We do this because
we pass both `isActive` and `beat` to `heartbeatTimer`.

* feat(heart): add test to ensure no warnings called

* fixup!: revert setTimeout for heartbeatTimer

* fixup!: return promise in beat

src/node/heart.ts

@@ -9,7 +9,10 @@ export class Heart {
   private heartbeatInterval = 60000
   public lastHeartbeat = 0
 
-  public constructor(private readonly heartbeatPath: string, private readonly isActive: () => Promise<boolean>) {}
+  public constructor(private readonly heartbeatPath: string, private readonly isActive: () => Promise<boolean>) {
+    this.beat = this.beat.bind(this)
+    this.alive = this.alive.bind(this)
+  }
 
   public alive(): boolean {
     const now = Date.now()
@@ -20,20 +23,22 @@ export class Heart {
    * timeout and start or reset a timer that keeps running as long as there is
    * activity. Failures are logged as warnings.
    */
-  public beat(): void {
+  public async beat(): Promise<void> {
     if (this.alive()) {
       return
     }
 
     logger.trace("heartbeat")
-    fs.writeFile(this.heartbeatPath, "").catch((error) => {
-      logger.warn(error.message)
-    })
     this.lastHeartbeat = Date.now()
     if (typeof this.heartbeatTimer !== "undefined") {
       clearTimeout(this.heartbeatTimer)
     }
     this.heartbeatTimer = setTimeout(() => heartbeatTimer(this.isActive, this.beat), this.heartbeatInterval)
+    try {
+      return await fs.writeFile(this.heartbeatPath, "")
+    } catch (error: any) {
+      logger.warn(error.message)
+    }
   }
 
   /**

src/node/routes/index.ts

@@ -56,6 +56,8 @@ export const register = async (app: App, args: DefaultedArgs): Promise<Disposabl
     // /healthz|/healthz/ needs to be excluded otherwise health checks will make
     // it look like code-server is always in use.
     if (!/^\/healthz\/?$/.test(req.url)) {
+      // NOTE@jsjoeio - intentionally not awaiting the .beat() call here because
+      // we don't want to slow down the request.
       heart.beat()
     }