refactor: cleanup sync

donut-sync/src/app.controller.ts

@@ -19,15 +19,25 @@ export class AppController {
     return { status: "ok" };
   }
 
+  // `storageEndpoint` is the host clients are handed in presigned URLs. The
+  // server cannot tell whether a client can reach it, so report it and let
+  // whoever is debugging a failing sync compare it against their network.
+  // Self-hosted only — see getDiagnosticStorageEndpoint.
   @Get("readyz")
-  async getReadiness(): Promise<{ status: string; s3: boolean }> {
+  async getReadiness(): Promise<{
+    status: string;
+    s3: boolean;
+    storageEndpoint?: string;
+  }> {
     const s3Ready = await this.syncService.checkS3Connectivity();
+    const storageEndpoint = this.syncService.getDiagnosticStorageEndpoint();
+    const diagnostic = storageEndpoint ? { storageEndpoint } : {};
     if (!s3Ready) {
       throw new HttpException(
-        { status: "not ready", s3: false },
+        { status: "not ready", s3: false, ...diagnostic },
         HttpStatus.SERVICE_UNAVAILABLE,
       );
     }
-    return { status: "ready", s3: true };
+    return { status: "ready", s3: true, ...diagnostic };
   }
 }