fix: Enhance admin API health check reliability and error handling

scripts/post_deploy.py

@@ -244,8 +244,8 @@ def get_api_headers(config: ResourceConfig) -> Dict[str, str]:
     return headers
 
 
-async def check_admin_api_health(config: ResourceConfig, max_retries: int = 5, retry_delay: int = 10) -> bool:
-    """Check if the admin API is available with retry logic for cold starts."""
+async def check_admin_api_health(config: ResourceConfig, max_retries: int = 8, retry_delay: int = 20) -> bool:
+    """Check if the admin API is available with retry logic for cold starts and container restarts."""
     print_step("Checking admin API health...")
 
     async with httpx.AsyncClient(timeout=30.0) as client:
@@ -256,8 +256,32 @@ async def check_admin_api_health(config: ResourceConfig, max_retries: int = 5, r
                     headers=get_api_headers(config)
                 )
                 if response.status_code == 200:
-                    print_success("Admin API is healthy")
-                    return True
+                    # Validate the response is actually from the backend admin API,
+                    # not the frontend catch-all serving index.html
+                    try:
+                        data = response.json()
+                        if data.get("status") == "healthy":
+                            print_success("Admin API is healthy")
+                            return True
+                        else:
+                            print_warning(
+                                f"Attempt {attempt}/{max_retries}: Admin API returned unexpected JSON: {data}"
+                            )
+                    except (ValueError, json.JSONDecodeError):
+                        # Response is not JSON.
+                        # This means the API proxy is not forwarding requests to the backend.
+                        content_preview = response.text[:200]
+                        is_html = "<html" in content_preview.lower() or "<!doctype" in content_preview.lower()
+                        if is_html:
+                            print_warning(
+                                f"Attempt {attempt}/{max_retries}: Got HTML instead of JSON from /api/admin/health. "
+                                "The frontend proxy may not be forwarding requests to the backend. "
+                                "Check that BACKEND_URL is set in the App Service and that the backend container is running."
+                            )
+                        else:
+                            print_warning(
+                                f"Attempt {attempt}/{max_retries}: Admin API returned non-JSON response: {content_preview}"
+                            )
                 else:
                     print_warning(f"Attempt {attempt}/{max_retries}: Admin API returned {response.status_code}")
             except Exception as e:

src/App/server/server.js

@@ -22,40 +22,51 @@ const httpAgent = new http.Agent({
 
 // Proxy API requests to backend
 if (BACKEND_URL) {
-    app.use('/api', createProxyMiddleware({
-    target: BACKEND_URL,
-    changeOrigin: true,
-    pathRewrite: {
-        '^/': '/api/'
-    },
-    agent: httpAgent,
-    // Increase timeout for long-running requests (10 minutes)
-    proxyTimeout: 600000,
-    timeout: 600000,
-    // Support streaming responses (SSE)
-    onProxyRes: (proxyRes, req, res) => {
-        // Disable buffering for streaming responses
-        if (proxyRes.headers['content-type']?.includes('text/event-stream')) {
-            res.setHeader('Cache-Control', 'no-cache, no-store, must-revalidate');
-            res.setHeader('X-Accel-Buffering', 'no');
-            res.setHeader('Connection', 'keep-alive');
-            res.flushHeaders();
+    const apiProxy = createProxyMiddleware({
+        target: BACKEND_URL,
+        changeOrigin: true,
+        pathRewrite: {
+            '^/': '/api/'
+        },
+        agent: httpAgent,
+        // Increase timeout for long-running requests (10 minutes)
+        proxyTimeout: 600000,
+        timeout: 600000,
+        // Support streaming responses (SSE)
+        onProxyRes: (proxyRes, req, res) => {
+            // Disable buffering for streaming responses
+            if (proxyRes.headers['content-type']?.includes('text/event-stream')) {
+                res.setHeader('Cache-Control', 'no-cache, no-store, must-revalidate');
+                res.setHeader('X-Accel-Buffering', 'no');
+                res.setHeader('Connection', 'keep-alive');
+                res.flushHeaders();
+            }
+            // Log response for debugging
+            console.log(`Proxy response: ${req.method} ${req.path} -> ${proxyRes.statusCode}`);
+        },
+        onProxyReq: (proxyReq, req, res) => {
+            // Log request for debugging
+            console.log(`Proxy request: ${req.method} ${req.path}`);
+        },
+        onError: (err, req, res) => {
+            console.error('Proxy error:', err.message);
+            if (!res.headersSent) {
+                res.status(502).json({ error: 'Backend service unavailable', details: err.message });
+            }
         }
-        // Log response for debugging
-        console.log(`Proxy response: ${req.method} ${req.path} -> ${proxyRes.statusCode}`);
-    },
-    onProxyReq: (proxyReq, req, res) => {
-        // Log request for debugging
-        console.log(`Proxy request: ${req.method} ${req.path}`);
-    },
-    onError: (err, req, res) => {
-        console.error('Proxy error:', err.message);
-        if (!res.headersSent) {
-            res.status(502).json({ error: 'Backend service unavailable', details: err.message });
-        }
-    }
-}));
+    });
+    app.use('/api', apiProxy);
+} else {
+    // When BACKEND_URL is not set, return a clear error for API requests
+    // instead of letting them fall through to the SPA catch-all (which returns index.html with 200)
+    app.use('/api', (req, res) => {
+        res.status(503).json({
+            error: 'Backend not configured',
+            message: 'BACKEND_URL environment variable is not set. The API proxy is not available.',
+        });
+    });
 }
+
 // Serve static files from the build directory
 app.use(express.static(path.join(__dirname, 'static')));