[kafka] Add Kafka protocol compatibility configs (#592)

Author: dao-jun

fluss-common/src/main/java/com/alibaba/fluss/config/ConfigOptions.java

@@ -1373,6 +1373,28 @@ public class ConfigOptions {
                             "The datalake format used by Fluss to be as lake storage, such as Paimon, Iceberg, Hudi. "
                                     + "Now, only support Paimon.");
 
+    // ------------------------------------------------------------------------
+    //  ConfigOptions for fluss kafka
+    // ------------------------------------------------------------------------
+    public static final ConfigOption<Boolean> KAFKA_ENABLED =
+            key("kafka.enabled")
+                    .booleanType()
+                    .defaultValue(false)
+                    .withDescription(
+                            "Whether enable fluss kafka. Disabled by default. "
+                                    + "When this option is set to true, the fluss kafka will be enabled.");
+    public static final ConfigOption<Integer> KAFKA_PORT =
+            key("kafka.port")
+                    .intType()
+                    .defaultValue(9092)
+                    .withDescription("The port for fluss kafka. The default port is 9092.");
+    public static final ConfigOption<String> KAFKA_DATABASE =
+            key("kafka.database")
+                    .stringType()
+                    .defaultValue("_kafka")
+                    .withDescription(
+                            "The database for fluss kafka. The default database is '_kafka'.");
+
     /**
      * Compaction style for Fluss's kv, which is same to rocksdb's, but help use avoid including
      * rocksdb dependency when only need include this common module.

fluss-dist/src/main/resources/server.yaml

@@ -80,3 +80,10 @@ tablet-server.id: 0
 # fs.oss.endpoint: xxx
 # fs.oss.accessKeyId: xxx
 # fs.oss.accessKeySecret: xxx
+
+#==============================================================================
+# Fluss Kafka Configs
+#==============================================================================
+kafka.enabled: false
+kafka.port: 9092
+kafka.database: _kafka

fluss-kafka/pom.xml

@@ -46,5 +46,11 @@
             <groupId>org.slf4j</groupId>
             <artifactId>slf4j-api</artifactId>
         </dependency>
+        <dependency>
+            <groupId>com.alibaba.fluss</groupId>
+            <artifactId>fluss-common</artifactId>
+            <version>${project.version}</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 </project>

fluss-kafka/src/test/java/com/alibaba/fluss/kafka/KafkaConfigsTest.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) 2025 Alibaba Group Holding Ltd.
+ *
+ * Licensed 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 com.alibaba.fluss.kafka;
+
+import com.alibaba.fluss.config.ConfigOptions;
+import com.alibaba.fluss.config.Configuration;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class KafkaConfigsTest {
+    @Test
+    public void testFromMap() throws Exception {
+        Map<String, String> map = new HashMap<>();
+        map.put(ConfigOptions.KAFKA_ENABLED.key(), "true");
+        map.put(ConfigOptions.KAFKA_PORT.key(), "9093");
+        map.put(ConfigOptions.KAFKA_DATABASE.key(), "fluss");
+        Configuration configuration = Configuration.fromMap(map);
+
+        assertThat(configuration.getBoolean(ConfigOptions.KAFKA_ENABLED)).isTrue();
+        assertThat(configuration.getInt(ConfigOptions.KAFKA_PORT)).isEqualTo(9093);
+        assertThat(configuration.getString(ConfigOptions.KAFKA_DATABASE)).isEqualTo("fluss");
+    }
+
+    @Test
+    public void testFromDefault() throws Exception {
+        Configuration configuration = Configuration.fromMap(new HashMap<>());
+        assertThat(configuration.getBoolean(ConfigOptions.KAFKA_ENABLED)).isFalse();
+        assertThat(configuration.getInt(ConfigOptions.KAFKA_PORT)).isEqualTo(9092);
+        assertThat(configuration.getString(ConfigOptions.KAFKA_DATABASE)).isEqualTo("_kafka");
+    }
+}