[Broker] Fix create the dynamic configuration resource if not exist

pulsar-broker-common/src/main/java/org/apache/pulsar/broker/resources/DynamicConfigurationResources.java

@@ -40,8 +40,8 @@ public CompletableFuture<Optional<Map<String, String>>> getDynamicConfigurationA
         return getAsync(BROKER_SERVICE_CONFIGURATION_PATH);
     }
 
-    public Map<String, String> getDynamicConfiguration() throws MetadataStoreException {
-        return get(BROKER_SERVICE_CONFIGURATION_PATH).orElse(Collections.emptyMap());
+    public Optional<Map<String, String>> getDynamicConfiguration() throws MetadataStoreException {
+        return get(BROKER_SERVICE_CONFIGURATION_PATH);
     }
 
     public void setDynamicConfigurationWithCreate(

pulsar-broker/src/main/java/org/apache/pulsar/broker/admin/impl/BrokersBase.java

@@ -181,7 +181,7 @@ public void deleteDynamicConfiguration(@PathParam("configName") String configNam
     public Map<String, String> getAllDynamicConfigurations() throws Exception {
         validateSuperUserAccess();
         try {
-            return dynamicConfigurationResources().getDynamicConfiguration();
+            return dynamicConfigurationResources().getDynamicConfiguration().orElseGet(Maps::newHashMap);
         } catch (RestException e) {
             LOG.error("[{}] couldn't find any configuration in zk {}", clientAppId(), e.getMessage(), e);
             throw e;

pulsar-broker/src/main/java/org/apache/pulsar/broker/service/BrokerService.java

@@ -2296,9 +2296,16 @@ private void validateConfigKey(String key) {
      */
     private void updateDynamicServiceConfiguration() {
         Optional<Map<String, String>> configCache = Optional.empty();
+
         try {
-            configCache =
-                    Optional.of(pulsar().getPulsarResources().getDynamicConfigResources().getDynamicConfiguration());
+            configCache  =
+                    pulsar().getPulsarResources().getDynamicConfigResources().getDynamicConfiguration();
+
+            // create dynamic-config if not exist.
+            if (!configCache.isPresent()) {
+                pulsar().getPulsarResources().getDynamicConfigResources()
+                        .setDynamicConfigurationWithCreate(n -> Maps.newHashMap());
+            }
         } catch (Exception e) {
             log.warn("Failed to read dynamic broker configuration", e);
         }

pulsar-broker/src/test/java/org/apache/pulsar/broker/admin/AdminApiDynamicConfigurationsTest.java

@@ -0,0 +1,72 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.pulsar.broker.admin;
+
+import static org.junit.Assert.fail;
+import static org.testng.Assert.assertEquals;
+import static org.testng.Assert.assertNotNull;
+import java.util.Map;
+import javax.ws.rs.core.Response;
+import lombok.extern.slf4j.Slf4j;
+import org.apache.pulsar.broker.auth.MockedPulsarServiceBaseTest;
+import org.apache.pulsar.client.admin.PulsarAdminException;
+import org.testng.annotations.AfterMethod;
+import org.testng.annotations.BeforeMethod;
+import org.testng.annotations.Test;
+
+@Slf4j
+@Test(groups = "broker")
+public class AdminApiDynamicConfigurationsTest extends MockedPulsarServiceBaseTest {
+    @BeforeMethod
+    @Override
+    public void setup() throws Exception {
+        super.internalSetup();
+    }
+
+    @AfterMethod(alwaysRun = true)
+    @Override
+    public void cleanup() throws Exception {
+        super.internalCleanup();
+    }
+
+    @Test
+    public void TestGetAllDynamicConfigurations() throws Exception {
+        Map<String,String> configs = admin.brokers().getAllDynamicConfigurations();
+        assertNotNull(configs);
+    }
+
+    @Test
+    public void TestDeleteDynamicConfiguration() throws Exception {
+        admin.brokers().deleteDynamicConfiguration("dispatcherMinReadBatchSize");
+    }
+
+    @Test
+    public void TestDeleteInvalidDynamicConfiguration() {
+        try {
+            admin.brokers().deleteDynamicConfiguration("errorName");
+            fail("exception should be thrown");
+        } catch (Exception e) {
+            if (e instanceof PulsarAdminException) {
+                assertEquals(((PulsarAdminException) e).getStatusCode(), Response.Status.PRECONDITION_FAILED.getStatusCode());
+            } else {
+                fail("PulsarAdminException should be thrown");
+            }
+        }
+    }
+}