Fix repository-azure for empty settings on reload (#79559)

Today when reloading settings, if the repository-azure plugin is
installed and no repositories of type "azure" are defined, the
repository-azure plugin will throw an exception that no client
configurations are specified, and it will not process the update (thus,
leaving the definition of existing repositories). This behavior has the
impact that if the repository-azure plugin is installed, but no
repositories of type "azure" are defined, then any attempt to reload
settings will receive an exception. This behavior appears to be legacy,
and is not mirrored in the other cloud service provider repository
plugins. This commit removes that behavior. This enables installing the
repository-azure plugin by default, without requiring that a repository
of type "azure" be configured.

Author: jasontedor

plugins/repository-azure/src/main/java/org/elasticsearch/repositories/azure/AzureRepositoryPlugin.java

@@ -9,17 +9,16 @@
 package org.elasticsearch.repositories.azure;
 
 import com.azure.core.util.serializer.JacksonAdapter;
+
 import org.apache.lucene.util.SetOnce;
 import org.elasticsearch.client.Client;
 import org.elasticsearch.cluster.metadata.IndexNameExpressionResolver;
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.io.stream.NamedWriteableRegistry;
 import org.elasticsearch.common.settings.Setting;
 import org.elasticsearch.common.settings.Settings;
-import org.elasticsearch.common.settings.SettingsException;
-import org.elasticsearch.core.TimeValue;
 import org.elasticsearch.common.util.BigArrays;
-import org.elasticsearch.xcontent.NamedXContentRegistry;
+import org.elasticsearch.core.TimeValue;
 import org.elasticsearch.env.Environment;
 import org.elasticsearch.env.NodeEnvironment;
 import org.elasticsearch.indices.recovery.RecoverySettings;
@@ -33,6 +32,7 @@
 import org.elasticsearch.threadpool.ScalingExecutorBuilder;
 import org.elasticsearch.threadpool.ThreadPool;
 import org.elasticsearch.watcher.ResourceWatcherService;
+import org.elasticsearch.xcontent.NamedXContentRegistry;
 
 import java.util.Arrays;
 import java.util.Collection;
@@ -132,9 +132,6 @@ public static ExecutorBuilder<?> nettyEventLoopExecutorBuilder(Settings settings
     public void reload(Settings settings) {
         // secure settings should be readable
         final Map<String, AzureStorageSettings> clientsSettings = AzureStorageSettings.load(settings);
-        if (clientsSettings.isEmpty()) {
-            throw new SettingsException("If you want to use an azure repository, you need to define a client configuration.");
-        }
         AzureStorageService storageService = azureStoreService.get();
         assert storageService != null;
         storageService.refreshSettings(clientsSettings);

plugins/repository-azure/src/test/java/org/elasticsearch/repositories/azure/AzureStorageServiceTests.java

@@ -9,6 +9,7 @@
 package org.elasticsearch.repositories.azure;
 
 import com.azure.storage.common.policy.RequestRetryOptions;
+
 import org.elasticsearch.common.settings.MockSecureSettings;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.settings.SettingsException;
@@ -163,14 +164,14 @@ public void testReinitClientEmptySettings() throws IOException {
             final AzureStorageService azureStorageService = plugin.azureStoreService.get();
             AzureBlobServiceClient client11 = azureStorageService.client("azure1", LocationMode.PRIMARY_ONLY);
             assertThat(client11.getSyncClient().getAccountUrl(), equalTo("https://myaccount1.blob.core.windows.net"));
-            // reinit with empty settings
-            final SettingsException e = expectThrows(SettingsException.class, () -> plugin.reload(Settings.EMPTY));
-            assertThat(e.getMessage(), is("If you want to use an azure repository, you need to define a client configuration."));
+            // reinit with empty settings is okay
+            plugin.reload(Settings.EMPTY);
             // existing client untouched
             assertThat(client11.getSyncClient().getAccountUrl(), equalTo("https://myaccount1.blob.core.windows.net"));
-            // new client also untouched
-            AzureBlobServiceClient client21 = azureStorageService.client("azure1", LocationMode.PRIMARY_ONLY);
-            assertThat(client21.getSyncClient().getAccountUrl(), equalTo("https://myaccount1.blob.core.windows.net"));
+            // client is no longer registered
+            final SettingsException e =
+                expectThrows(SettingsException.class, () -> azureStorageService.client("azure1", LocationMode.PRIMARY_ONLY));
+            assertThat(e.getMessage(), equalTo("Unable to find client with name [azure1]"));
         }
     }