KAFKA-19719: --no-initial-controllers should not assume kraft.version=1 (#20551)

Just because a controller node sets --no-initial-controllers flag does
not mean it is necessarily running kraft.version=1. The more precise
meaning is that the controller node being formatted does not know what
kraft version the cluster should be in, and therefore it is only safe to
assume kraft.version=0. Only by setting
--standalone,--initial-controllers, or --no-initial-controllers
AND not specifying the controller.quorum.voters static config, is it
known kraft.version > 0.

For example, it is a valid configuration (although confusing) to run a
static   quorum defined by controller.quorum.voters but have all the
controllers   format with --no-initial-controllers. In this case,
specifying --no-initial-controllers alongside a metadata version that
does not  support kraft.version=1 causes formatting to fail, which is
a  regression.

Additionally, the formatter should not check the kraft.version against
the release version, since kraft.version does not actually depend on any
release version. It should only check the kraft.version against the
static voters config/format arguments.

This PR also cleans up the integration test framework to match the
semantics of formatting an actual cluster.

Reviewers: TengYao Chi <kitingiao@gmail.com>, Kuan-Po Tseng
 <brandboat@gmail.com>, Chia-Ping Tsai <chia7712@gmail.com>, José
 Armando García Sancio <jsancio@apache.org>

core/src/main/scala/kafka/tools/StorageTool.scala

@@ -144,8 +144,9 @@ object StorageTool extends Logging {
       })
     val initialControllers = namespace.getString("initial_controllers")
     val isStandalone = namespace.getBoolean("standalone")
-    if (!config.quorumConfig.voters().isEmpty &&
+    val staticVotersEmpty = config.quorumConfig.voters().isEmpty
-      (Option(initialControllers).isDefined || isStandalone)) {
+    formatter.setHasDynamicQuorum(staticVotersEmpty)
+    if (!staticVotersEmpty && (Option(initialControllers).isDefined || isStandalone)) {
       throw new TerseFailure("You cannot specify " +
         QuorumConfig.QUORUM_VOTERS_CONFIG + " and format the node " +
         "with --initial-controllers or --standalone. " +
@@ -158,16 +159,13 @@ object StorageTool extends Logging {
     if (isStandalone) {
       formatter.setInitialControllers(createStandaloneDynamicVoters(config))
     }
-    if (namespace.getBoolean("no_initial_controllers")) {
+    if (!namespace.getBoolean("no_initial_controllers") &&
-      formatter.setNoInitialControllersFlag(true)
+      config.processRoles.contains(ProcessRole.ControllerRole) &&
-    } else {
+      staticVotersEmpty &&
-      if (config.processRoles.contains(ProcessRole.ControllerRole)) {
+      formatter.initialVoters().isEmpty) {
-        if (config.quorumConfig.voters().isEmpty && formatter.initialVoters().isEmpty) {
           throw new TerseFailure("Because " + QuorumConfig.QUORUM_VOTERS_CONFIG +
             " is not set on this controller, you must specify one of the following: " +
             "--standalone, --initial-controllers, or --no-initial-controllers.");
-        }
-      }
     }
     Option(namespace.getList("add_scram")).
       foreach(scramArgs => formatter.setScramArguments(scramArgs.asInstanceOf[util.List[String]]))
@@ -336,18 +334,21 @@ object StorageTool extends Logging {
 
     val reconfigurableQuorumOptions = formatParser.addMutuallyExclusiveGroup()
     reconfigurableQuorumOptions.addArgument("--standalone", "-s")
-      .help("Used to initialize a controller as a single-node dynamic quorum.")
+      .help("Used to initialize a controller as a single-node dynamic quorum. When setting this flag, " +
+        "the controller.quorum.voters config must not be set, and controller.quorum.bootstrap.servers is set instead.")
       .action(storeTrue())
 
     reconfigurableQuorumOptions.addArgument("--no-initial-controllers", "-N")
-      .help("Used to initialize a server without a dynamic quorum topology.")
+      .help("Used to initialize a server without specifying a dynamic quorum. When setting this flag, " +
+        "the controller.quorum.voters config should not be set, and controller.quorum.bootstrap.servers is set instead.")
       .action(storeTrue())
 
     reconfigurableQuorumOptions.addArgument("--initial-controllers", "-I")
-      .help("Used to initialize a server with a specific dynamic quorum topology. The argument " +
+      .help("Used to initialize a server with the specified dynamic quorum. The argument " +
         "is a comma-separated list of id@hostname:port:directory. The same values must be used to " +
         "format all nodes. For example:\n0@example.com:8082:JEXY6aqzQY-32P5TStzaFg,1@example.com:8083:" +
-        "MvDxzVmcRsaTz33bUuRU6A,2@example.com:8084:07R5amHmR32VDA6jHkGbTA\n")
+        "MvDxzVmcRsaTz33bUuRU6A,2@example.com:8084:07R5amHmR32VDA6jHkGbTA\n. When setting this flag, " +
+        "the controller.quorum.voters config must not be set, and controller.quorum.bootstrap.servers is set instead.")
       .action(store())
   }
 

core/src/test/java/kafka/server/ReconfigurableQuorumIntegrationTest.java

@@ -84,9 +84,8 @@ public class ReconfigurableQuorumIntegrationTest {
             new TestKitNodes.Builder().
                 setNumBrokerNodes(1).
                 setNumControllerNodes(1).
-                setFeature(KRaftVersion.FEATURE_NAME, KRaftVersion.KRAFT_VERSION_1.featureLevel()).
                 build()
-        ).build()) {
+        ).setStandalone(true).build()) {
             cluster.format();
             cluster.startup();
             try (Admin admin = Admin.create(cluster.clientProperties())) {
@@ -108,13 +107,23 @@ public class ReconfigurableQuorumIntegrationTest {
 
     @Test
     public void testRemoveController() throws Exception {
-        try (KafkaClusterTestKit cluster = new KafkaClusterTestKit.Builder(
+        final var nodes = new TestKitNodes.Builder().
-            new TestKitNodes.Builder().
+            setNumBrokerNodes(1).
-                setNumBrokerNodes(1).
+            setNumControllerNodes(3).
-                setNumControllerNodes(3).
+            build();
-                setFeature(KRaftVersion.FEATURE_NAME, KRaftVersion.KRAFT_VERSION_1.featureLevel()).
+
-                build()
+        final Map<Integer, Uuid> initialVoters = new HashMap<>();
-        ).build()) {
+        for (final var controllerNode : nodes.controllerNodes().values()) {
+            initialVoters.put(
+                controllerNode.id(),
+                controllerNode.metadataDirectoryId()
+            );
+        }
+
+        try (KafkaClusterTestKit cluster = new KafkaClusterTestKit.Builder(nodes).
+            setInitialVoterSet(initialVoters).
+            build()
+        ) {
             cluster.format();
             cluster.startup();
             try (Admin admin = Admin.create(cluster.clientProperties())) {
@@ -133,12 +142,22 @@ public class ReconfigurableQuorumIntegrationTest {
 
     @Test
     public void testRemoveAndAddSameController() throws Exception {
-        try (KafkaClusterTestKit cluster = new KafkaClusterTestKit.Builder(
+        final var nodes = new TestKitNodes.Builder().
-            new TestKitNodes.Builder().
+            setNumBrokerNodes(1).
-                setNumBrokerNodes(1).
+            setNumControllerNodes(4).
-                setNumControllerNodes(4).
+            build();
-                setFeature(KRaftVersion.FEATURE_NAME, KRaftVersion.KRAFT_VERSION_1.featureLevel()).
+
-                build()).build()
+        final Map<Integer, Uuid> initialVoters = new HashMap<>();
+        for (final var controllerNode : nodes.controllerNodes().values()) {
+            initialVoters.put(
+                controllerNode.id(),
+                controllerNode.metadataDirectoryId()
+            );
+        }
+
+        try (KafkaClusterTestKit cluster = new KafkaClusterTestKit.Builder(nodes).
+            setInitialVoterSet(initialVoters).
+            build()
         ) {
             cluster.format();
             cluster.startup();
@@ -173,7 +192,6 @@ public class ReconfigurableQuorumIntegrationTest {
         final var nodes = new TestKitNodes.Builder().
             setNumBrokerNodes(1).
             setNumControllerNodes(3).
-            setFeature(KRaftVersion.FEATURE_NAME, KRaftVersion.KRAFT_VERSION_1.featureLevel()).
             build();
         try (KafkaClusterTestKit cluster = new KafkaClusterTestKit.Builder(nodes).
             setConfigProp(QuorumConfig.QUORUM_AUTO_JOIN_ENABLE_CONFIG, true).
@@ -199,7 +217,6 @@ public class ReconfigurableQuorumIntegrationTest {
         final var nodes = new TestKitNodes.Builder().
             setNumBrokerNodes(1).
             setNumControllerNodes(3).
-            setFeature(KRaftVersion.FEATURE_NAME, KRaftVersion.KRAFT_VERSION_1.featureLevel()).
             build();
 
         // Configure the initial voters with one voter having a different directory ID.

core/src/test/scala/integration/kafka/server/KRaftClusterTest.scala

@@ -1035,8 +1035,7 @@ class KRaftClusterTest {
     val cluster = new KafkaClusterTestKit.Builder(
       new TestKitNodes.Builder().
         setNumBrokerNodes(1).
-        setNumControllerNodes(1).
+        setNumControllerNodes(1).build()).setStandalone(true).build()
-        setFeature(KRaftVersion.FEATURE_NAME, 1.toShort).build()).build()
     try {
       cluster.format()
       cluster.startup()

core/src/test/scala/unit/kafka/tools/StorageToolTest.scala

@@ -605,19 +605,14 @@ Found problem:
               Seq("--release-version", "3.9-IV0"))).getMessage)
   }
 
-  @ParameterizedTest
+  @Test
-  @ValueSource(booleans = Array(false, true))
+  def testFormatWithNoInitialControllersSucceedsOnController(): Unit = {
-  def testFormatWithNoInitialControllersSucceedsOnController(setKraftVersionFeature: Boolean): Unit = {
     val availableDirs = Seq(TestUtils.tempDir())
     val properties = new Properties()
     properties.putAll(defaultDynamicQuorumProperties)
     properties.setProperty("log.dirs", availableDirs.mkString(","))
     val stream = new ByteArrayOutputStream()
     val arguments = ListBuffer[String]("--release-version", "3.9-IV0", "--no-initial-controllers")
-    if (setKraftVersionFeature) {
-      arguments += "--feature"
-      arguments += "kraft.version=1"
-    }
     assertEquals(0, runFormatCommand(stream, properties, arguments.toSeq))
     assertTrue(stream.toString().
       contains("Formatting metadata directory %s".format(availableDirs.head)),

docs/ops.html

@@ -4099,14 +4099,8 @@ Feature: metadata.version       SupportedMinVersion: 3.3-IV3    SupportedMaxVers
   <p>
     The static versus dynamic nature of the quorum is determined at the time of formatting.
     Specifically, the quorum will be formatted as dynamic if <code>controller.quorum.voters</code> is
-    <b>not</b> present, and if the software version is Apache Kafka 3.9 or newer. If you have
+    <b>not</b> present, and one of --standalone, --initial-controllers, or --no-initial-controllers is set.
-    followed the instructions earlier in this document, you will get a dynamic quorum.<p>
+    If you have followed the instructions earlier in this document, you will get a dynamic quorum.
-
-    If you would like the formatting process to fail if a dynamic quorum cannot be achieved, format your
-    controllers using the <code>--feature kraft.version=1</code>. (Note that you should not supply
-    this flag when formatting brokers -- only when formatting controllers.)<p>
-
-  <pre><code class="language-bash">$ bin/kafka-storage.sh format -t KAFKA_CLUSTER_ID --feature kraft.version=1 -c controller.properties</code></pre>
   <p>
   Note: To migrate from static voter set to dynamic voter set, please refer to the <a href="#kraft_upgrade">Upgrade</a> section.
 

metadata/src/main/java/org/apache/kafka/metadata/storage/Formatter.java

@@ -131,7 +131,7 @@ public class Formatter {
      * The initial KIP-853 voters.
      */
     private Optional<DynamicVoters> initialControllers = Optional.empty();
-    private boolean noInitialControllersFlag = false;
+    private boolean hasDynamicQuorum = false;
 
     public Formatter setPrintStream(PrintStream printStream) {
         this.printStream = printStream;
@@ -217,8 +217,8 @@ public class Formatter {
         return this;
     }
 
-    public Formatter setNoInitialControllersFlag(boolean noInitialControllersFlag) {
+    public Formatter setHasDynamicQuorum(boolean hasDynamicQuorum) {
-        this.noInitialControllersFlag = noInitialControllersFlag;
+        this.hasDynamicQuorum = hasDynamicQuorum;
         return this;
     }
 
@@ -227,7 +227,7 @@ public class Formatter {
     }
 
     boolean hasDynamicQuorum() {
-        return initialControllers.isPresent() || noInitialControllersFlag;
+        return hasDynamicQuorum;
     }
 
     public BootstrapMetadata bootstrapMetadata() {
@@ -337,8 +337,8 @@ public class Formatter {
     /**
      * Calculate the effective feature level for kraft.version. In order to keep existing
      * command-line invocations of StorageTool working, we default this to 0 if no dynamic
-     * voter quorum arguments were provided. As a convenience, if dynamic voter quorum arguments
+     * voter quorum arguments were provided. As a convenience, if the static voters config is
-     * were passed, we set the latest kraft.version. (Currently there is only 1 non-zero version).
+     * empty, we set the latest kraft.version. (Currently there is only 1 non-zero version).
      *
      * @param configuredKRaftVersionLevel   The configured level for kraft.version
      * @return                              The effective feature level.
@@ -348,20 +348,19 @@ public class Formatter {
             if (configuredKRaftVersionLevel.get() == 0) {
                 if (hasDynamicQuorum()) {
                     throw new FormatterException(
-                        "Cannot set kraft.version to " +
+                        "Cannot set kraft.version to 0 if controller.quorum.voters is empty and one of the flags " +
-                        configuredKRaftVersionLevel.get() +
+                        "--standalone, --initial-controllers, or --no-initial-controllers is used. For dynamic " +
-                        " if one of the flags --standalone, --initial-controllers, or --no-initial-controllers is used. " +
+                        "controllers support, try removing the --feature flag for kraft.version."
-                        "For dynamic controllers support, try removing the --feature flag for kraft.version."
                     );
                 }
             } else {
                 if (!hasDynamicQuorum()) {
                     throw new FormatterException(
-                        "Cannot set kraft.version to " +
+                        "Cannot set kraft.version to " + configuredKRaftVersionLevel.get() +
-                        configuredKRaftVersionLevel.get() +
+                        " unless controller.quorum.voters is empty and one of the flags --standalone, " +
-                        " unless one of the flags --standalone, --initial-controllers, or --no-initial-controllers is used. " +
+                        "--initial-controllers, or --no-initial-controllers is used. " +
-                        "For dynamic controllers support, try using one of --standalone, --initial-controllers, or " +
+                        "For dynamic controllers support, try using one of --standalone, --initial-controllers, " +
-                        "--no-initial-controllers."
+                        "or --no-initial-controllers and removing controller.quorum.voters."
                     );
                 }
             }

metadata/src/test/java/org/apache/kafka/metadata/storage/FormatterTest.java

@@ -32,6 +32,7 @@ import org.apache.kafka.server.common.ApiMessageAndVersion;
 import org.apache.kafka.server.common.EligibleLeaderReplicasVersion;
 import org.apache.kafka.server.common.Feature;
 import org.apache.kafka.server.common.GroupVersion;
+import org.apache.kafka.server.common.KRaftVersion;
 import org.apache.kafka.server.common.MetadataVersion;
 import org.apache.kafka.server.common.TestFeatureVersion;
 import org.apache.kafka.server.common.TransactionVersion;
@@ -200,6 +201,7 @@ public class FormatterTest {
             String newDirectoryId = Uuid.randomUuid().toString();
             formatter1.formatter
                 .setInitialControllers(DynamicVoters.parse("1@localhost:8020:" + originalDirectoryId))
+                .setHasDynamicQuorum(true)
                 .run();
             assertEquals("Bootstrap metadata: " + formatter1.formatter.bootstrapMetadata() +
                     "\nFormatting dynamic metadata voter directory " + testEnv.directory(0) +
@@ -422,13 +424,14 @@ public class FormatterTest {
         try (TestEnv testEnv = new TestEnv(2)) {
             FormatterContext formatter1 = testEnv.newFormatter();
             if (specifyKRaftVersion) {
-                formatter1.formatter.setFeatureLevel("kraft.version", (short) 1);
+                formatter1.formatter.setFeatureLevel(KRaftVersion.FEATURE_NAME, (short) 1);
             }
             formatter1.formatter.setUnstableFeatureVersionsEnabled(true);
             formatter1.formatter.setInitialControllers(DynamicVoters.
                 parse("1@localhost:8020:4znU-ou9Taa06bmEJxsjnw"));
+            formatter1.formatter.setHasDynamicQuorum(true);
             formatter1.formatter.run();
-            assertEquals((short) 1, formatter1.formatter.featureLevels.getOrDefault("kraft.version", (short) 0));
+            assertEquals((short) 1, formatter1.formatter.featureLevels.get(KRaftVersion.FEATURE_NAME));
             assertEquals(List.of(
                 "Bootstrap metadata: " + formatter1.formatter.bootstrapMetadata(),
                 String.format("Formatting data directory %s with %s %s.",
@@ -456,49 +459,66 @@ public class FormatterTest {
     public void testFormatWithInitialVotersFailsWithOlderKraftVersion() throws Exception {
         try (TestEnv testEnv = new TestEnv(2)) {
             FormatterContext formatter1 = testEnv.newFormatter();
-            formatter1.formatter.setFeatureLevel("kraft.version", (short) 0);
+            formatter1.formatter.setFeatureLevel(KRaftVersion.FEATURE_NAME, (short) 0);
             formatter1.formatter.setUnstableFeatureVersionsEnabled(true);
             formatter1.formatter.setInitialControllers(DynamicVoters.
                     parse("1@localhost:8020:4znU-ou9Taa06bmEJxsjnw"));
+            formatter1.formatter.setHasDynamicQuorum(true);
             assertTrue(formatter1.formatter.hasDynamicQuorum());
             assertEquals(
-                "Cannot set kraft.version to 0 if one of the flags --standalone, --initial-controllers, or " +
+                "Cannot set kraft.version to 0 if controller.quorum.voters is empty " +
-                "--no-initial-controllers is used. For dynamic controllers support, try removing the " +
+                "and one of the flags --standalone, --initial-controllers, or --no-initial-controllers is used. " +
-                "--feature flag for kraft.version.",
+                "For dynamic controllers support, try removing the --feature flag for kraft.version.",
                 assertThrows(FormatterException.class, formatter1.formatter::run).getMessage()
             );
         }
     }
 
     @Test
-    public void testFormatWithoutInitialVotersFailsWithNewerKraftVersion() throws Exception {
+    public void testFormatWithStaticQuorumFailsWithNewerKraftVersion() throws Exception {
         try (TestEnv testEnv = new TestEnv(2)) {
             FormatterContext formatter1 = testEnv.newFormatter();
-            formatter1.formatter.setFeatureLevel("kraft.version", (short) 1);
+            formatter1.formatter.setFeatureLevel(KRaftVersion.FEATURE_NAME, (short) 1);
             formatter1.formatter.setUnstableFeatureVersionsEnabled(true);
             assertFalse(formatter1.formatter.hasDynamicQuorum());
             assertEquals(
-                "Cannot set kraft.version to 1 unless one of the flags --standalone, --initial-controllers, or " +
+                "Cannot set kraft.version to 1 unless controller.quorum.voters is empty and " +
-                "--no-initial-controllers is used. For dynamic controllers support, try using one of " +
+                "one of the flags --standalone, --initial-controllers, or --no-initial-controllers is used. " +
-                "--standalone, --initial-controllers, or --no-initial-controllers.",
+                "For dynamic controllers support, try using one of --standalone, --initial-controllers, " +
+                "or --no-initial-controllers and removing controller.quorum.voters.",
                 assertThrows(FormatterException.class, formatter1.formatter::run).getMessage()
             );
         }
     }
 
     @Test
-    public void testFormatWithInitialVotersFailsWithOlderMetadataVersion() throws Exception {
+    public void testFormatWithInitialVotersWithOlderMetadataVersion() throws Exception {
         try (TestEnv testEnv = new TestEnv(2)) {
             FormatterContext formatter1 = testEnv.newFormatter();
             formatter1.formatter.setReleaseVersion(MetadataVersion.IBP_3_8_IV0);
-            formatter1.formatter.setFeatureLevel("kraft.version", (short) 1);
+            formatter1.formatter.setFeatureLevel(KRaftVersion.FEATURE_NAME, (short) 1);
             formatter1.formatter.setInitialControllers(DynamicVoters.
                     parse("1@localhost:8020:4znU-ou9Taa06bmEJxsjnw"));
             formatter1.formatter.setUnstableFeatureVersionsEnabled(true);
-            assertEquals("kraft.version could not be set to 1 because it depends on " +
+            formatter1.formatter.setHasDynamicQuorum(true);
-                "metadata.version level 21",
+            formatter1.formatter.run();
-                    assertThrows(IllegalArgumentException.class,
+            assertEquals((short) 1, formatter1.formatter.featureLevels.get(KRaftVersion.FEATURE_NAME));
-                        formatter1.formatter::run).getMessage());
+        }
+    }
+
+    @ParameterizedTest
+    @ValueSource(booleans = {false, true})
+    public void testFormatWithNoInitialControllersWithOlderMetadataVersion(boolean hasDynamicQuorum) throws Exception {
+        try (TestEnv testEnv = new TestEnv(2)) {
+            FormatterContext formatter1 = testEnv.newFormatter();
+            formatter1.formatter.setReleaseVersion(MetadataVersion.IBP_3_8_IV0);
+            formatter1.formatter.setHasDynamicQuorum(hasDynamicQuorum);
+            formatter1.formatter.run();
+            if (hasDynamicQuorum) {
+                assertEquals((short) 1, formatter1.formatter.featureLevels.get(KRaftVersion.FEATURE_NAME));
+            } else {
+                assertEquals((short) 0, formatter1.formatter.featureLevels.get(KRaftVersion.FEATURE_NAME));
+            }
         }
     }
 
@@ -519,6 +539,7 @@ public class FormatterTest {
             formatter1.formatter.setFeatureLevel(EligibleLeaderReplicasVersion.FEATURE_NAME, (short) 1);
             formatter1.formatter.setInitialControllers(DynamicVoters.
                 parse("1@localhost:8020:4znU-ou9Taa06bmEJxsjnw"));
+            formatter1.formatter.setHasDynamicQuorum(true);
             if (metadataVersion.isAtLeast(MetadataVersion.IBP_4_0_IV1)) {
                 assertDoesNotThrow(formatter1.formatter::run);
             } else {
@@ -530,20 +551,14 @@ public class FormatterTest {
         }
     }
 
-    @ParameterizedTest
+    @Test
-    @ValueSource(booleans = {false, true})
+    public void testFormatWithNoInitialControllers() throws Exception {
-    public void testFormatWithNoInitialControllers(boolean specifyKRaftVersion) throws Exception {
         try (TestEnv testEnv = new TestEnv(2)) {
             FormatterContext formatter1 = testEnv.newFormatter();
-            if (specifyKRaftVersion) {
-                formatter1.formatter.setFeatureLevel("kraft.version", (short) 1);
-            }
             formatter1.formatter.setUnstableFeatureVersionsEnabled(true);
-            formatter1.formatter.setNoInitialControllersFlag(true);
+            assertFalse(formatter1.formatter.hasDynamicQuorum());
-            assertTrue(formatter1.formatter.hasDynamicQuorum());
-
             formatter1.formatter.run();
-            assertEquals((short) 1, formatter1.formatter.featureLevels.getOrDefault("kraft.version", (short) 0));
+            assertEquals((short) 0, formatter1.formatter.featureLevels.get(KRaftVersion.FEATURE_NAME));
             assertEquals(List.of(
                     "Bootstrap metadata: " + formatter1.formatter.bootstrapMetadata(),
                     String.format("Formatting data directory %s with %s %s.",
@@ -564,38 +579,4 @@ public class FormatterTest {
             assertNotNull(logDirProps1);
         }
     }
-
-    @Test
-    public void testFormatWithoutNoInitialControllersFailsWithNewerKraftVersion() throws Exception {
-        try (TestEnv testEnv = new TestEnv(2)) {
-            FormatterContext formatter1 = testEnv.newFormatter();
-            formatter1.formatter.setFeatureLevel("kraft.version", (short) 1);
-            formatter1.formatter.setUnstableFeatureVersionsEnabled(true);
-            formatter1.formatter.setNoInitialControllersFlag(false);
-            assertFalse(formatter1.formatter.hasDynamicQuorum());
-            assertEquals(
-                "Cannot set kraft.version to 1 unless one of the flags --standalone, --initial-controllers, or " +
-                "--no-initial-controllers is used. For dynamic controllers support, try using one of " +
-                "--standalone, --initial-controllers, or --no-initial-controllers.",
-                assertThrows(FormatterException.class, formatter1.formatter::run).getMessage()
-            );
-        }
-    }
-
-    @Test
-    public void testFormatWithNoInitialControllersFailsWithOlderKraftVersion() throws Exception {
-        try (TestEnv testEnv = new TestEnv(2)) {
-            FormatterContext formatter1 = testEnv.newFormatter();
-            formatter1.formatter.setFeatureLevel("kraft.version", (short) 0);
-            formatter1.formatter.setUnstableFeatureVersionsEnabled(true);
-            formatter1.formatter.setNoInitialControllersFlag(true);
-            assertTrue(formatter1.formatter.hasDynamicQuorum());
-            assertEquals(
-                "Cannot set kraft.version to 0 if one of the flags --standalone, --initial-controllers, or " +
-                "--no-initial-controllers is used. For dynamic controllers support, try removing the " +
-                "--feature flag for kraft.version.",
-                assertThrows(FormatterException.class, formatter1.formatter::run).getMessage()
-            );
-        }
-    }
 }

server-common/src/main/java/org/apache/kafka/server/common/KRaftVersion.java

@@ -72,12 +72,7 @@ public enum KRaftVersion implements FeatureVersion {
 
     @Override
     public Map<String, Short> dependencies() {
-        if (this.featureLevel == 0) {
+        return Map.of();
-            return Map.of();
-        } else {
-            return Map.of(
-                MetadataVersion.FEATURE_NAME, MetadataVersion.IBP_3_9_IV0.featureLevel());
-        }
     }
 
     public boolean isAtLeast(KRaftVersion otherVersion) {

test-common/test-common-runtime/src/main/java/org/apache/kafka/common/test/KafkaClusterTestKit.java

@@ -45,7 +45,6 @@ import org.apache.kafka.raft.DynamicVoters;
 import org.apache.kafka.raft.MetadataLogConfig;
 import org.apache.kafka.raft.QuorumConfig;
 import org.apache.kafka.server.common.ApiMessageAndVersion;
-import org.apache.kafka.server.common.KRaftVersion;
 import org.apache.kafka.server.config.KRaftConfigs;
 import org.apache.kafka.server.config.ServerConfigs;
 import org.apache.kafka.server.fault.FaultHandler;
@@ -182,18 +181,31 @@ public class KafkaClusterTestKit implements AutoCloseable {
             props.putIfAbsent(INTER_BROKER_LISTENER_NAME_CONFIG, brokerListenerName);
             props.putIfAbsent(KRaftConfigs.CONTROLLER_LISTENER_NAMES_CONFIG, controllerListenerName);
 
-            StringBuilder quorumVoterStringBuilder = new StringBuilder();
+            if (!standalone && initialVoterSet.isEmpty()) {
-            String prefix = "";
+                StringBuilder quorumVoterStringBuilder = new StringBuilder();
-            for (int nodeId : nodes.controllerNodes().keySet()) {
+                String prefix = "";
-                quorumVoterStringBuilder.append(prefix).
+                for (int nodeId : nodes.controllerNodes().keySet()) {
-                    append(nodeId).
+                    quorumVoterStringBuilder.append(prefix).
-                    append("@").
+                        append(nodeId).
-                    append("localhost").
+                        append("@").
-                    append(":").
+                        append("localhost").
-                    append(socketFactoryManager.getOrCreatePortForListener(nodeId, controllerListenerName));
+                        append(":").
-                prefix = ",";
+                        append(socketFactoryManager.getOrCreatePortForListener(nodeId, controllerListenerName));
+                    prefix = ",";
+                }
+                props.put(QuorumConfig.QUORUM_VOTERS_CONFIG, quorumVoterStringBuilder.toString());
+            } else {
+                StringBuilder bootstrapServersStringBuilder = new StringBuilder();
+                String prefix = "";
+                for (int nodeId : nodes.controllerNodes().keySet()) {
+                    bootstrapServersStringBuilder.append(prefix).
+                        append("localhost").
+                        append(":").
+                        append(socketFactoryManager.getOrCreatePortForListener(nodeId, controllerListenerName));
+                    prefix = ",";
+                }
+                props.put(QuorumConfig.QUORUM_BOOTSTRAP_SERVERS_CONFIG, bootstrapServersStringBuilder.toString());
             }
-            props.put(QuorumConfig.QUORUM_VOTERS_CONFIG, quorumVoterStringBuilder.toString());
 
             // reduce log cleaner offset map memory usage
             props.putIfAbsent(CleanerConfig.LOG_CLEANER_DEDUPE_BUFFER_SIZE_PROP, "2097152");
@@ -277,7 +289,7 @@ public class KafkaClusterTestKit implements AutoCloseable {
                         Time.SYSTEM,
                         new Metrics(),
                         CompletableFuture.completedFuture(QuorumConfig.parseVoterConnections(config.quorumConfig().voters())),
-                        List.of(),
+                        QuorumConfig.parseBootstrapServers(config.quorumConfig().bootstrapServers()),
                         faultHandlerFactory,
                         socketFactoryManager.getOrCreateSocketFactory(node.id())
                     );
@@ -305,7 +317,7 @@ public class KafkaClusterTestKit implements AutoCloseable {
                             Time.SYSTEM,
                             new Metrics(),
                             CompletableFuture.completedFuture(QuorumConfig.parseVoterConnections(config.quorumConfig().voters())),
-                            List.of(),
+                            QuorumConfig.parseBootstrapServers(config.quorumConfig().bootstrapServers()),
                             faultHandlerFactory,
                             socketFactoryManager.getOrCreateSocketFactory(node.id())
                         );
@@ -467,8 +479,6 @@ public class KafkaClusterTestKit implements AutoCloseable {
                 return;
             }
             formatter.setReleaseVersion(nodes.bootstrapMetadata().metadataVersion());
-            formatter.setFeatureLevel(KRaftVersion.FEATURE_NAME,
-                nodes.bootstrapMetadata().featureLevel(KRaftVersion.FEATURE_NAME));
             formatter.setUnstableFeatureVersionsEnabled(true);
             formatter.setIgnoreFormatted(false);
             formatter.setControllerListenerName(controllerListenerName);
@@ -477,53 +487,43 @@ public class KafkaClusterTestKit implements AutoCloseable {
             } else {
                 formatter.setMetadataLogDirectory(Optional.empty());
             }
-            if (nodes.bootstrapMetadata().featureLevel(KRaftVersion.FEATURE_NAME) > 0) {
+            StringBuilder dynamicVotersBuilder = new StringBuilder();
-                StringBuilder dynamicVotersBuilder = new StringBuilder();
+            String prefix = "";
-                String prefix = "";
+            if (standalone) {
-                if (standalone) {
+                if (nodeId == TestKitDefaults.BROKER_ID_OFFSET + TestKitDefaults.CONTROLLER_ID_OFFSET) {
-                    if (nodeId == TestKitDefaults.CONTROLLER_ID_OFFSET) {
+                    final var controllerNode = nodes.controllerNodes().get(nodeId);
-                        final var controllerNode = nodes.controllerNodes().get(nodeId);
+                    dynamicVotersBuilder.append(
-                        dynamicVotersBuilder.append(
+                        String.format(
-                            String.format(
+                            "%d@localhost:%d:%s",
-                                "%d@localhost:%d:%s",
+                            controllerNode.id(),
-                                controllerNode.id(),
+                            socketFactoryManager.
-                                socketFactoryManager.
+                                getOrCreatePortForListener(controllerNode.id(), controllerListenerName),
-                                    getOrCreatePortForListener(controllerNode.id(), controllerListenerName),
+                            controllerNode.metadataDirectoryId()
-                                controllerNode.metadataDirectoryId()
+                        )
-                            )
+                    );
-                        );
-                        formatter.setInitialControllers(DynamicVoters.parse(dynamicVotersBuilder.toString()));
-                    } else {
-                        formatter.setNoInitialControllersFlag(true);
-                    }
-                } else if (initialVoterSet.isPresent()) {
-                    for (final var controllerNode : initialVoterSet.get().entrySet()) {
-                        final var voterId = controllerNode.getKey();
-                        final var voterDirectoryId = controllerNode.getValue();
-                        dynamicVotersBuilder.append(prefix);
-                        prefix = ",";
-                        dynamicVotersBuilder.append(
-                            String.format(
-                                "%d@localhost:%d:%s",
-                                voterId,
-                                socketFactoryManager.
-                                    getOrCreatePortForListener(voterId, controllerListenerName),
-                                voterDirectoryId
-                            )
-                        );
-                    }
-                    formatter.setInitialControllers(DynamicVoters.parse(dynamicVotersBuilder.toString()));
-                } else {
-                    for (TestKitNode controllerNode : nodes.controllerNodes().values()) {
-                        int port = socketFactoryManager.
-                            getOrCreatePortForListener(controllerNode.id(), controllerListenerName);
-                        dynamicVotersBuilder.append(prefix);
-                        prefix = ",";
-                        dynamicVotersBuilder.append(String.format("%d@localhost:%d:%s",
-                            controllerNode.id(), port, controllerNode.metadataDirectoryId()));
-                    }
                     formatter.setInitialControllers(DynamicVoters.parse(dynamicVotersBuilder.toString()));
                 }
+                // when the nodeId != TestKitDefaults.CONTROLLER_ID_OFFSET, the node is formatting with
+                // the --no-initial-controllers flag
+                formatter.setHasDynamicQuorum(true);
+            } else if (initialVoterSet.isPresent()) {
+                for (final var controllerNode : initialVoterSet.get().entrySet()) {
+                    final var voterId = controllerNode.getKey();
+                    final var voterDirectoryId = controllerNode.getValue();
+                    dynamicVotersBuilder.append(prefix);
+                    prefix = ",";
+                    dynamicVotersBuilder.append(
+                        String.format(
+                            "%d@localhost:%d:%s",
+                            voterId,
+                            socketFactoryManager.
+                                getOrCreatePortForListener(voterId, controllerListenerName),
+                            voterDirectoryId
+                        )
+                    );
+                }
+                formatter.setInitialControllers(DynamicVoters.parse(dynamicVotersBuilder.toString()));
+                formatter.setHasDynamicQuorum(true);
             }
             formatter.run();
         } catch (Exception e) {

test-common/test-common-runtime/src/main/java/org/apache/kafka/common/test/TestKitNodes.java

@@ -93,11 +93,6 @@ public class TestKitNodes {
             return this;
         }
 
-        public Builder setFeature(String featureName, short level) {
-            this.bootstrapMetadata = bootstrapMetadata.copyWithFeatureRecord(featureName, level);
-            return this;
-        }
-
         public Builder setCombined(boolean combined) {
             this.combined = combined;
             return this;