chore: add reason to app restart log (#33930)

packages/apps-engine/src/server/runtime/deno/LivenessManager.ts

@@ -132,7 +132,7 @@ export class LivenessManager {
 
                 if (reason === 'timeout' && this.pingTimeoutConsecutiveCount >= this.options.consecutiveTimeoutLimit) {
                     this.debug('Subprocess failed to respond to pings %d consecutive times. Attempting restart...', this.options.consecutiveTimeoutLimit);
-                    this.restartProcess();
+                    this.restartProcess('Too many pings timed out');
                     return false;
                 }
 
@@ -164,17 +164,21 @@ export class LivenessManager {
             return;
         }
 
+        let reason: string;
+
         // Otherwise we try to restart the subprocess, if possible
         if (signal) {
             this.debug('App has been killed (%s). Attempting restart #%d...', signal, this.restartCount + 1);
+            reason = `App has been killed with signal ${signal}`;
         } else {
             this.debug('App has exited with code %d. Attempting restart #%d...', exitCode, this.restartCount + 1);
+            reason = `App has exited with code ${exitCode}`;
         }
 
-        this.restartProcess();
+        this.restartProcess(reason);
     }
 
-    private restartProcess() {
+    private restartProcess(reason: string) {
         if (this.restartCount >= this.options.maxRestarts) {
             this.debug('Limit of restarts reached (%d). Aborting restart...', this.options.maxRestarts);
             this.controller.stopApp();
@@ -184,6 +188,7 @@ export class LivenessManager {
         this.pingTimeoutConsecutiveCount = 0;
         this.restartCount++;
         this.restartLog.push({
+            reason,
             restartedAt: new Date(),
             source: 'liveness-manager',
             pid: this.subprocess.pid,