App Config 6.0 bug fixes

sdk/spring/spring-cloud-azure-appconfiguration-config/src/main/java/com/azure/spring/cloud/appconfiguration/config/implementation/AppConfigurationApplicationSettingPropertySource.java

@@ -116,11 +116,11 @@ private void handleKeyVaultReference(String key, SecretReferenceConfigurationSet
             KeyVaultSecret secret = keyVaultClientFactory.getClient("https://" + uri.getHost()).getSecret(uri);
             properties.put(key, secret.getValue());
         } catch (URISyntaxException e) {
-            LOGGER.error(String.format("Error Retrieving Key Vault Entry for key %s.", key));
+            LOGGER.error("Error Retrieving Key Vault Entry for key {}.", key);
             throw new InvalidConfigurationPropertyValueException(key, "<Redacted>",
                 "Invalid URI found in JSON property field 'uri' unable to parse.");
         } catch (RuntimeException e) {
-            LOGGER.error(String.format("Error Retrieving Key Vault Entry for key %s.", key));
+            LOGGER.error("Error Retrieving Key Vault Entry for key {}.", key);
             throw e;
         }
     }

sdk/spring/spring-cloud-azure-appconfiguration-config/src/main/java/com/azure/spring/cloud/appconfiguration/config/implementation/AppConfigurationFeatureManagementPropertySource.java

@@ -32,7 +32,8 @@ class AppConfigurationFeatureManagementPropertySource extends EnumerableProperty
 
     @Override
     public String[] getPropertyNames() {
-        if (featureFlagLoader != null && !featureFlagLoader.getFeatureFlags().isEmpty()) {
+        if (featureFlagLoader != null && featureFlagLoader.getFeatureFlags() != null 
+            && !featureFlagLoader.getFeatureFlags().isEmpty()) {
             return new String[] { FEATURE_FLAG_KEY };
         }
         return new String[0];

sdk/spring/spring-cloud-azure-appconfiguration-config/src/main/java/com/azure/spring/cloud/appconfiguration/config/implementation/AppConfigurationKeyVaultClientFactory.java

@@ -15,9 +15,9 @@
  * Vault host.
  */
 class AppConfigurationKeyVaultClientFactory {
-
     /**
      * Cache of secret client managers by Key Vault host.
+     */
     private final Map<String, AppConfigurationSecretClientManager> keyVaultClients;
 
     /**

sdk/spring/spring-cloud-azure-appconfiguration-config/src/main/java/com/azure/spring/cloud/appconfiguration/config/implementation/AppConfigurationPropertySource.java

@@ -5,7 +5,6 @@
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.Set;
 
 import org.springframework.boot.context.properties.source.InvalidConfigurationPropertyValueException;
 import org.springframework.core.env.EnumerablePropertySource;
@@ -23,6 +22,8 @@
 abstract class AppConfigurationPropertySource extends EnumerablePropertySource<AppConfigurationReplicaClient> {
 
     /**
+     * Cache for storing configuration properties retrieved from Azure App Configuration.
+     */
     protected final Map<String, Object> properties = new LinkedHashMap<>();
 
     /**
@@ -39,7 +40,7 @@ abstract class AppConfigurationPropertySource extends EnumerablePropertySource<A
     AppConfigurationPropertySource(String name, AppConfigurationReplicaClient replicaClient) {
         // The context alone does not uniquely define a PropertySource, append storeName
         // and label to uniquely define a PropertySource
-        super(name);
+        super(name, replicaClient);
         this.replicaClient = replicaClient;
     }
 
@@ -50,13 +51,14 @@ abstract class AppConfigurationPropertySource extends EnumerablePropertySource<A
      */
     @Override
     public String[] getPropertyNames() {
-        Set<String> keySet = properties.keySet();
-        return keySet.toArray(new String[keySet.size()]);
+        return properties.keySet().toArray(String[]::new);
     }
 
     /**
      * Returns the value of the specified property.
      * 
+     * @param name the name of the property to retrieve
+     * @return the value of the property, or null if not found
      */
     @Override
     public Object getProperty(String name) {
@@ -70,11 +72,19 @@ public Object getProperty(String name) {
      * @return comma-separated string of labels, or empty string if null/empty
      */
     protected static String getLabelName(String[] labelFilters) {
-        if (labelFilters == null) {
+        if (labelFilters == null || labelFilters.length == 0) {
             return "";
         }
         return String.join(",", labelFilters);
     }
 
-    protected abstract void initProperties(List<String> trim, Context context) throws InvalidConfigurationPropertyValueException;
+    /**
+     * Initializes the properties for this property source by loading them from Azure App Configuration.
+     * 
+     * @param trim list of key prefixes to trim from configuration keys
+     * @param context the context for loading properties, may contain additional metadata
+     * @throws InvalidConfigurationPropertyValueException if there are issues with the configuration properties
+     */
+    protected abstract void initProperties(List<String> trim, Context context)
+        throws InvalidConfigurationPropertyValueException;
 }

sdk/spring/spring-cloud-azure-appconfiguration-config/src/main/java/com/azure/spring/cloud/appconfiguration/config/implementation/AppConfigurationReplicaClient.java

@@ -50,6 +50,7 @@ class AppConfigurationReplicaClient {
     /**
      * Holds Configuration Client and info needed to manage backoff.
      * @param endpoint client endpoint
+     * @param originClient origin client identifier
      * @param client Configuration Client to App Configuration store
      */
     AppConfigurationReplicaClient(String endpoint, String originClient, ConfigurationClient client) {
@@ -105,6 +106,7 @@ String getOriginClient() {
      * @param label String value of the watch key, use \0 for null.
      * @param context Azure SDK context for request correlation
      * @return The first returned configuration.
+     * @throws HttpResponseException if the request fails
      */
     ConfigurationSetting getWatchKey(String key, String label, Context context)
         throws HttpResponseException {
@@ -212,8 +214,9 @@ List<ConfigurationSetting> listSettingSnapshot(String snapshotName, Context cont
     }
 
     boolean checkWatchKeys(SettingSelector settingSelector, Context context) {
-        List<PagedResponse<ConfigurationSetting>> results = client.listConfigurationSettings(settingSelector, context)
-            .streamByPage().filter(pagedResponse -> pagedResponse.getStatusCode() != 304).toList();
+        List<PagedResponse<ConfigurationSetting>> results = client
+            .listConfigurationSettings(settingSelector, context)
+            .streamByPage().filter(pagedResponse -> pagedResponse.getStatusCode() != HTTP_NOT_MODIFIED).toList();
         return results.size() > 0;
     }
 
@@ -227,7 +230,14 @@ void updateSyncToken(String syncToken) {
         }
     }
 
-    private HttpResponseException hanndleHttpResponseException(HttpResponseException e) {
+    /**
+     * Handles HTTP response exceptions by determining if they are retryable.
+     * 
+     * @param e the HTTP response exception to handle
+     * @return an AppConfigurationStatusException for retryable errors, or the original exception for non-retryable
+     * errors
+     */
+    private HttpResponseException handleHttpResponseException(HttpResponseException e) {
         if (e.getResponse() != null) {
             int statusCode = e.getResponse().getStatusCode();
 

sdk/spring/spring-cloud-azure-appconfiguration-config/src/main/java/com/azure/spring/cloud/appconfiguration/config/implementation/AppConfigurationReplicaClientFactory.java

@@ -31,7 +31,7 @@ public class AppConfigurationReplicaClientFactory {
     AppConfigurationReplicaClientFactory(AppConfigurationReplicaClientsBuilder clientBuilder,
         List<ConfigStore> configStores, ReplicaLookUp replicaLookUp) {
         this.configStores = configStores;
-        if (CONNECTIONS.size() == 0) {
+        if (CONNECTIONS.isEmpty()) {
             for (ConfigStore store : configStores) {
                 ConnectionManager manager = new ConnectionManager(clientBuilder, store, replicaLookUp);
                 CONNECTIONS.put(manager.getMainEndpoint(), manager);
@@ -51,9 +51,11 @@ public Map<String, ConnectionManager> getConnections() {
     /**
      * Returns available replica clients for a given configuration store.
      * 
+     * @param originEndpoint identifier of the store (primary endpoint)
+     * @return list of available replica clients for the store
      */
     List<AppConfigurationReplicaClient> getAvailableClients(String originEndpoint) {
-        return CONNECTIONS.get(originEndpoint).getAvailableClients();
+        return getAvailableClients(originEndpoint, false);
     }
 
     /**
@@ -73,7 +75,7 @@ List<AppConfigurationReplicaClient> getAvailableClients(String originEndpoint, B
      * @param originEndpoint identifier of the store (primary endpoint)
      * @param endpoint the specific replica endpoint that failed
      */
-    void backoffClientClient(String originEndpoint, String endpoint) {
+    void backoffClient(String originEndpoint, String endpoint) {
         CONNECTIONS.get(originEndpoint).backoffClient(endpoint);
     }
 
@@ -98,10 +100,9 @@ Map<String, AppConfigurationStoreHealth> getHealth() {
      */
     String findOriginForEndpoint(String endpoint) {
         for (ConfigStore store : configStores) {
-            for (String replica : store.getEndpoints()) {
-                if (replica.equals(endpoint)) {
-                    return store.getEndpoint();
-                }
+            List<String> replicas = store.getEndpoints();
+            if (replicas != null && replicas.contains(endpoint)) {
+                return store.getEndpoint();
             }
         }
         return endpoint;

sdk/spring/spring-cloud-azure-appconfiguration-config/src/main/java/com/azure/spring/cloud/appconfiguration/config/implementation/AzureAppConfigDataLoader.java

@@ -7,6 +7,7 @@
 import java.io.IOException;
 import java.time.Instant;
 import java.util.ArrayList;
+import java.util.Iterator;
 import java.util.List;
 
 import org.apache.commons.logging.Log;
@@ -125,20 +126,21 @@ public ConfigData load(ConfigDataLoaderContext context, AzureAppConfigDataResour
 
             boolean reloadFailed = false;
             boolean pushRefresh = false;
+            Exception lastException = null;
             PushNotification notification = resource.getMonitoring().getPushNotification();
             if ((notification.getPrimaryToken() != null
                 && StringUtils.hasText(notification.getPrimaryToken().getName()))
                 || (notification.getSecondaryToken() != null
                     && StringUtils.hasText(notification.getPrimaryToken().getName()))) {
                 pushRefresh = true;
             }
-            requestContext = new Context("refresh", resource.isRefresh()).addData(PUSH_REFRESH,
-                pushRefresh);
-
             // Feature Management needs to be set in the last config store.
+            requestContext = new Context("refresh", resource.isRefresh()).addData(PUSH_REFRESH, pushRefresh);
+
+            Iterator<AppConfigurationReplicaClient> clientIterator = clients.iterator();
 
-            for (AppConfigurationReplicaClient client : clients) {
-                sourceList = new ArrayList<>();
+            while (clientIterator.hasNext()) {
+                AppConfigurationReplicaClient client = clientIterator.next();
 
                 if (reloadFailed
                     && !AppConfigurationRefreshUtil.refreshStoreCheck(client,
@@ -167,19 +169,31 @@ public ConfigData load(ConfigDataLoaderContext context, AzureAppConfigDataResour
 
                         storeState.setState(resource.getEndpoint(), watchKeysSettings, monitoring.getRefreshInterval());
                     }
-                    storeState.setLoadState(resource.getEndpoint(), true);
+                    storeState.setLoadState(resource.getEndpoint(), true); // Success - configuration loaded, exit loop
+                    lastException = null;
+                    // Break out of the loop since we have successfully loaded configuration
+                    break;
                 } catch (AppConfigurationStatusException e) {
                     reloadFailed = true;
-                    replicaClientFactory.backoffClientClient(resource.getEndpoint(), client.getEndpoint());
+                    replicaClientFactory.backoffClient(resource.getEndpoint(), client.getEndpoint());
+                    lastException = e;
+                    // Log the specific replica failure with context
+                    logReplicaFailure(client, "status exception", clientIterator.hasNext(), e);
                 } catch (Exception e) {
-                    failedToGeneratePropertySource(e);
-
-                    // Not a retriable error
-                    break;
-                }
-                if (sourceList.size() > 0) {
-                    break;
+                    // Store the exception to potentially use if all replicas fail
+                    lastException = e; // Log the specific replica failure with context
+                    logReplicaFailure(client, "exception", clientIterator.hasNext(), e);
                 }
+            } // Check if all replicas failed
+            if (lastException != null && !resource.isRefresh()) {
+                // During startup, if all replicas failed, fail the application
+                logger.error("Azure App Configuration failed to load configuration during startup for store: "
+                    + resource.getEndpoint() + ". Application cannot start without required configuration.");
+                failedToGeneratePropertySource(lastException);
+            } else if (lastException != null && resource.isRefresh()) {
+                // During refresh, log warning but don't fail the application
+                logger.warn("Azure App Configuration failed during refresh for store: "
+                    + resource.getEndpoint() + ". Continuing with existing configuration.");
             }
         }
 
@@ -256,15 +270,36 @@ private List<FeatureFlags> createFeatureFlags(AppConfigurationReplicaClient clie
         return featureFlagWatchKeys;
     }
 
+    /**
+     * Logs a replica failure with contextual information about the failure scenario and available replicas.
+     *
+     * @param client the replica client that failed
+     * @param exceptionType a brief description of the exception type (e.g., "status exception", "exception")
+     * @param hasMoreReplicas whether there are additional replicas available to try
+     * @param exception the exception that caused the failure
+     */
+    private void logReplicaFailure(AppConfigurationReplicaClient client, String exceptionType,
+        boolean hasMoreReplicas, Exception exception) {
+        String scenario = resource.isRefresh() ? "refresh" : "startup";
+        String nextAction = hasMoreReplicas ? "Trying next replica." : "No more replicas available.";
+
+        logger.warn("Azure App Configuration replica " + client.getEndpoint()
+            + " failed during " + scenario + " with " + exceptionType + ". "
+            + nextAction + " Store: " + resource.getEndpoint(), exception);
+    }
+
+    /**
+     * Introduces a delay before throwing exceptions during startup to prevent fast crash loops.
+     */
     private void delayException() {
         Instant currentDate = Instant.now();
-        Instant preKillTIme = START_DATE.plusSeconds(PREKILL_TIME);
-        if (currentDate.isBefore(preKillTIme)) {
-            long diffInMillies = Math.abs(preKillTIme.toEpochMilli() - currentDate.toEpochMilli());
+        Instant preKillTime = START_DATE.plusSeconds(PREKILL_TIME);
+        if (currentDate.isBefore(preKillTime)) {
+            long diffInMillies = Math.abs(preKillTime.toEpochMilli() - currentDate.toEpochMilli());
             try {
                 Thread.sleep(diffInMillies);
             } catch (InterruptedException e) {
-                logger.error("Failed to wait before fast fail.");
+                Thread.currentThread().interrupt(); // Restore interrupted status
             }
         }
     }

sdk/spring/spring-cloud-azure-appconfiguration-config/src/main/java/com/azure/spring/cloud/appconfiguration/config/implementation/AzureAppConfigDataLocationResolver.java

@@ -56,22 +56,29 @@ public boolean isResolvable(ConfigDataLocationResolverContext context, ConfigDat
         if (!location.hasPrefix(PREFIX)) {
             return false;
         }
-        Boolean hasEndpoint = StringUtils.hasText(context.getBinder()
-            .bind(AppConfigurationProperties.CONFIG_PREFIX + ".stores[0].endpoint", String.class)
-            .orElse(""));
-        Boolean hasConnectionString = StringUtils.hasText(context.getBinder()
-            .bind(AppConfigurationProperties.CONFIG_PREFIX + ".stores[0].connection-string", String.class)
-            .orElse(""));
-        Boolean hasEndpoints = StringUtils.hasText(context.getBinder()
-            .bind(AppConfigurationProperties.CONFIG_PREFIX + ".stores[0].endpoints", String.class)
-            .orElse(""));
-        Boolean hasConnectionStrings = StringUtils.hasText(context.getBinder()
-            .bind(AppConfigurationProperties.CONFIG_PREFIX + ".stores[0].connection-strings", String.class)
-            .orElse(""));
-
-        return (hasEndpoint || hasConnectionString || hasEndpoints || hasConnectionStrings);
+
+        // Check if the configuration properties for Azure App Configuration are present
+        return hasValidStoreConfiguration(context.getBinder());
+    }
+
+    /**
+     * Checks if the required configuration properties for Azure App Configuration are present.
+     * 
+     * @param binder the binder to check for properties
+     * @return true if at least one of the required properties is present, false otherwise
+     */
+    private boolean hasValidStoreConfiguration(Binder binder) {
+        // Check if any of the required properties for Azure App Configuration stores are present
+        String configPrefix = AppConfigurationProperties.CONFIG_PREFIX + ".stores[0].";
+
+        return hasNonEmptyProperty(binder, configPrefix + "endpoint")
+            || hasNonEmptyProperty(binder, configPrefix + "connection-string")
+            || hasNonEmptyProperty(binder, configPrefix + "endpoints")
+            || hasNonEmptyProperty(binder, configPrefix + "connection-strings");
     }
 
+    private boolean hasNonEmptyProperty(Binder binder, String propertyPath) {
+        return StringUtils.hasText(binder.bind(propertyPath, String.class).orElse(""));
     }
 
     /**
@@ -105,6 +112,12 @@ public List<AzureAppConfigDataResource> resolveProfileSpecific(
         AppConfigurationProperties properties = loadProperties(resolverContext);
         List<AzureAppConfigDataResource> locations = new ArrayList<>();
 
+        if (properties.getStores() == null || properties.getStores().isEmpty()) {
+            throw new ConfigDataLocationNotFoundException(location,
+                "No Azure App Configuration stores are configured. Please check your application properties.",
+                new IllegalStateException("No stores configured"));
+        }
+
         for (ConfigStore store : properties.getStores()) {
             locations.add(
                 new AzureAppConfigDataResource(store, profiles, START_UP.get(), properties.getRefreshInterval()));