fix: enhance client ID retry logic for backend requests and improve error handling

src/main/java/cz/trask/adfs/context/ProcessHandler.java

@@ -33,12 +33,6 @@ public class ProcessHandler extends BaseContextHandler {
                 return;
             }
 
-            int index = clientIdIndex.get() % clientIds.size();
-            String currentClientId = clientIds.get(index);
-
-            TokenPayloadIdp token = tokenService.getToken(currentClientId);
-            String accessToken = token.getAccessToken();
-
             String backendBaseUrl = appConfig.getBackendUrl();
             if (backendBaseUrl == null || backendBaseUrl.isBlank()) {
                 logger.error("backend_url is not configured");
@@ -84,34 +78,50 @@ public class ProcessHandler extends BaseContextHandler {
                 body = exchange.getRequestBody().readAllBytes();
             }
 
-            logger.info("Forwarding {} request to backend: {} (Client ID: {})", method, targetUrl, currentClientId);
+            BackendResponse backendResponse = null;
-            BackendResponse backendResponse = callBackend(targetUrl, method, exchange.getRequestHeaders(), body, accessToken);
+            int maxAttempts = clientIds.size();
+            for (int attempt = 1; attempt <= maxAttempts; attempt++) {
+                int index = clientIdIndex.get() % clientIds.size();
+                if (index < 0) index += clientIds.size();
+                String currentClientId = clientIds.get(index);
 
-            int retryCount = 0;
+                if (attempt > 1) {
-            int maxRetries = clientIds.size() - 1;
+                    logger.info("Retrying request to backend with next Client ID: {} (attempt {}/{})", currentClientId, attempt, maxAttempts);
-            while (backendResponse.statusCode == 429 && retryCount < maxRetries) {
-                retryCount++;
-                int nextIndex = clientIdIndex.incrementAndGet() % clientIds.size();
-                String retryClientId = clientIds.get(nextIndex);
-                
-                logger.warn("Backend returned 429. Retrying ({}/{}) with next client ID: {}...", 
-                        retryCount, maxRetries, retryClientId);
-                
-                token = tokenService.getToken(retryClientId);
-                accessToken = token.getAccessToken();
-
-                logger.info("Retrying request to backend with new token (Client ID: {})", retryClientId);
-                backendResponse = callBackend(targetUrl, method, exchange.getRequestHeaders(), body, accessToken);
                 }
 
-            if (backendResponse.statusCode == 429) {
+                try {
+                    TokenPayloadIdp token = tokenService.getToken(currentClientId);
+                    String accessToken = token.getAccessToken();
+
+                    backendResponse = callBackend(targetUrl, method, exchange.getRequestHeaders(), body, accessToken);
+                    
+                    if (backendResponse.statusCode != 429) {
+                        break; // Success or fatal backend error, exit loop
+                    }
+
+                    logger.warn("Backend returned 429 Too Many Requests for Client ID: {}. Switching to next identity.", currentClientId);
+                } catch (Exception e) {
+                    logger.warn("Failed to process request with Client ID: {}: {}", currentClientId, e.getMessage());
+                    if (attempt == maxAttempts) {
+                        throw e; // Last identity failed, propagate exception
+                    }
+                    // Else, treat as retryable failure and move to next identity
+                    backendResponse = new BackendResponse(429, null, null);
+                }
+                
+                clientIdIndex.incrementAndGet();
+            }
+
+            if (backendResponse != null && backendResponse.statusCode == 429) {
                 logger.error("Throttling limit reached. Exhausted all {} identities and backend still returns 429.", clientIds.size());
                 sendError(exchange, 429, ERR_TOO_MANY_REQUESTS, 
-                        "All configured client identities are currently throttled by the backend after " + retryCount + " retries.");
+                        "All configured client identities are currently throttled by the backend after " + maxAttempts + " attempts.");
                 return;
             }
 
+            if (backendResponse != null) {
                 sendResponse(exchange, backendResponse.statusCode, backendResponse.contentType, backendResponse.body);
+            }
 
         } catch (IllegalArgumentException e) {
             sendError(exchange, 400, ERR_INVALID_CONFIG, e.getMessage());

src/main/resources/config.yaml

@@ -14,6 +14,7 @@ adfs:
   audience: "https://fs.komercpoj.loc/adfs/oauth2/token"
   resource: "urn:kamma:api"
   clientIds:
+    - "db2edf05-7af2-4523-97f9-39f930afc634a"
     - "db2edf05-7af2-4523-97f9-39f930afc634"
   certificate: "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"
   privateKey: "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"