KAFKA-14363; Add new `group-coordinator` module (KIP-848) (#12827)

Introduce new group-coordinator module that will host the future new group coordinator as part of KIP-848.

Reviewers: Ismael Juma <ismael@juma.me.uk>

build.gradle

@@ -865,10 +865,12 @@ project(':core') {
     api libs.scalaLibrary
 
     implementation project(':server-common')
+    implementation project(':group-coordinator')
     implementation project(':metadata')
     implementation project(':raft')
     implementation project(':storage')
 
+
     implementation libs.argparse4j
     implementation libs.jacksonDatabind
     implementation libs.jacksonModuleScala
@@ -896,6 +898,7 @@ project(':core') {
     compileOnly libs.log4j
 
     testImplementation project(':clients').sourceSets.test.output
+    testImplementation project(':group-coordinator').sourceSets.test.output
     testImplementation project(':metadata').sourceSets.test.output
     testImplementation project(':raft').sourceSets.test.output
     testImplementation project(':server-common').sourceSets.test.output
@@ -1222,6 +1225,40 @@ project(':metadata') {
   }
 }
 
+project(':group-coordinator') {
+  archivesBaseName = "kafka-group-coordinator"
+
+  dependencies {
+    implementation project(':server-common')
+    implementation project(':clients')
+    implementation libs.slf4jApi
+
+    testImplementation project(':clients').sourceSets.test.output
+    testImplementation project(':server-common').sourceSets.test.output
+    testImplementation libs.junitJupiter
+    testImplementation libs.mockitoCore
+
+    testRuntimeOnly libs.slf4jlog4j
+  }
+
+  sourceSets {
+    main {
+      java {
+        srcDirs = ["src/generated/java", "src/main/java"]
+      }
+    }
+    test {
+      java {
+        srcDirs = ["src/generated/java", "src/test/java"]
+      }
+    }
+  }
+
+  javadoc {
+    enabled = false
+  }
+}
+
 project(':examples') {
   archivesBaseName = "kafka-examples"
 

group-coordinator/.gitignore

@@ -0,0 +1 @@
+/bin/

group-coordinator/src/main/java/org/apache/kafka/coordinator/group/GroupCoordinator.java

@@ -0,0 +1,21 @@
+/*
+ * 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.kafka.coordinator.group;
+
+public interface GroupCoordinator {
+}

group-coordinator/src/test/resources/log4j.properties

@@ -0,0 +1,22 @@
+# 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.
+log4j.rootLogger=DEBUG, stdout
+
+log4j.appender.stdout=org.apache.log4j.ConsoleAppender
+log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
+log4j.appender.stdout.layout.ConversionPattern=[%d] %p %m (%c:%L)%n
+
+log4j.logger.org.apache.kafka=DEBUG
+log4j.logger.org.apache.zookeeper=WARN

settings.gradle

@@ -25,6 +25,7 @@ include 'clients',
     'core',
     'examples',
     'generator',
+    'group-coordinator',
     'jmh-benchmarks',
     'log4j-appender',
     'metadata',