KAFKA-16770; [2/2] Coalesce records into bigger batches

clients/src/main/java/org/apache/kafka/common/record/MemoryRecordsBuilder.java

@@ -870,6 +870,18 @@ public boolean hasRoomFor(long timestamp, ByteBuffer key, ByteBuffer value, Head
         return this.writeLimit >= estimatedBytesWritten() + recordSize;
     }
 
+    /**
+     * Check if we have room for a given number of bytes.
+     */
+    public boolean hasRoomFor(int estimatedRecordsSize) {
+        if (isFull()) return false;
+        return this.writeLimit >= estimatedBytesWritten() + estimatedRecordsSize;
+    }
+
+    public int maxAllowedBytes() {
+        return this.writeLimit - this.batchHeaderSizeInBytes;
+    }
+
     public boolean isClosed() {
         return builtRecords != null;
     }

core/src/main/scala/kafka/server/BrokerServer.scala

@@ -570,6 +570,7 @@ class BrokerServer(
       val serde = new CoordinatorRecordSerde
       val groupCoordinatorConfig = new GroupCoordinatorConfig(
         config.groupCoordinatorNumThreads,
+        config.groupCoordinatorAppendLingerMs,
         config.consumerGroupSessionTimeoutMs,
         config.consumerGroupHeartbeatIntervalMs,
         config.consumerGroupMaxSize,

core/src/main/scala/kafka/server/KafkaConfig.scala

@@ -278,6 +278,7 @@ object KafkaConfig {
       .define(GroupCoordinatorConfig.GROUP_COORDINATOR_REBALANCE_PROTOCOLS_CONFIG, LIST, GroupCoordinatorConfig.GROUP_COORDINATOR_REBALANCE_PROTOCOLS_DEFAULT,
         ValidList.in(Utils.enumOptions(classOf[GroupType]):_*), MEDIUM, GroupCoordinatorConfig.GROUP_COORDINATOR_REBALANCE_PROTOCOLS_DOC)
       .define(GroupCoordinatorConfig.GROUP_COORDINATOR_NUM_THREADS_CONFIG, INT, GroupCoordinatorConfig.GROUP_COORDINATOR_NUM_THREADS_DEFAULT, atLeast(1), MEDIUM, GroupCoordinatorConfig.GROUP_COORDINATOR_NUM_THREADS_DOC)
+      .define(GroupCoordinatorConfig.GROUP_COORDINATOR_APPEND_LINGER_MS_CONFIG, INT, GroupCoordinatorConfig.GROUP_COORDINATOR_APPEND_LINGER_MS_DEFAULT, atLeast(0), MEDIUM, GroupCoordinatorConfig.GROUP_COORDINATOR_APPEND_LINGER_MS_DOC)
       // Internal configuration used by integration and system tests.
       .defineInternal(GroupCoordinatorConfig.NEW_GROUP_COORDINATOR_ENABLE_CONFIG, BOOLEAN, GroupCoordinatorConfig.NEW_GROUP_COORDINATOR_ENABLE_DEFAULT, null, MEDIUM, GroupCoordinatorConfig.NEW_GROUP_COORDINATOR_ENABLE_DOC)
 
@@ -948,6 +949,7 @@ class KafkaConfig private(doLog: Boolean, val props: java.util.Map[_, _], dynami
   val isNewGroupCoordinatorEnabled = getBoolean(GroupCoordinatorConfig.NEW_GROUP_COORDINATOR_ENABLE_CONFIG) ||
     groupCoordinatorRebalanceProtocols.contains(GroupType.CONSUMER)
   val groupCoordinatorNumThreads = getInt(GroupCoordinatorConfig.GROUP_COORDINATOR_NUM_THREADS_CONFIG)
+  val groupCoordinatorAppendLingerMs = getInt(GroupCoordinatorConfig.GROUP_COORDINATOR_APPEND_LINGER_MS_CONFIG)
 
   /** Consumer group configs */
   val consumerGroupSessionTimeoutMs = getInt(GroupCoordinatorConfig.CONSUMER_GROUP_SESSION_TIMEOUT_MS_CONFIG)

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

@@ -57,6 +57,10 @@ public class GroupCoordinatorConfig {
             Arrays.stream(Group.GroupType.values()).map(Group.GroupType::toString).collect(Collectors.joining(",")) + ". " +
             "The " + Group.GroupType.CONSUMER + " rebalance protocol is in early access and therefore must not be used in production.";
     public static final List<String> GROUP_COORDINATOR_REBALANCE_PROTOCOLS_DEFAULT = Collections.singletonList(Group.GroupType.CLASSIC.toString());
+    public final static String GROUP_COORDINATOR_APPEND_LINGER_MS_CONFIG = "group.coordinator.append.linger.ms";
+    public final static String GROUP_COORDINATOR_APPEND_LINGER_MS_DOC = "The duration in milliseconds that the coordinator will " +
+        "wait for writes to accumulate before flushing them to disk. Transactional writes are not accumulated.";
+    public final static int GROUP_COORDINATOR_APPEND_LINGER_MS_DEFAULT = 10;
 
     public final static String GROUP_COORDINATOR_NUM_THREADS_CONFIG = "group.coordinator.threads";
     public final static String GROUP_COORDINATOR_NUM_THREADS_DOC = "The number of threads used by the group coordinator.";
@@ -164,6 +168,12 @@ public class GroupCoordinatorConfig {
      */
     public final int numThreads;
 
+    /**
+     * The duration in milliseconds that the coordinator will wait for writes to
+     * accumulate before flushing them to disk.
+     */
+    public final int appendLingerMs;
+
     /**
      * The consumer group session timeout in milliseconds.
      */
@@ -259,6 +269,7 @@ public class GroupCoordinatorConfig {
 
     public GroupCoordinatorConfig(
         int numThreads,
+        int appendLingerMs,
         int consumerGroupSessionTimeoutMs,
         int consumerGroupHeartbeatIntervalMs,
         int consumerGroupMaxSize,
@@ -277,6 +288,7 @@ public GroupCoordinatorConfig(
         CompressionType compressionType
     ) {
         this.numThreads = numThreads;
+        this.appendLingerMs = appendLingerMs;
         this.consumerGroupSessionTimeoutMs = consumerGroupSessionTimeoutMs;
         this.consumerGroupHeartbeatIntervalMs = consumerGroupHeartbeatIntervalMs;
         this.consumerGroupMaxSize = consumerGroupMaxSize;

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

@@ -182,12 +182,12 @@ public GroupCoordinatorService build() {
                     .withPartitionWriter(writer)
                     .withLoader(loader)
                     .withCoordinatorShardBuilderSupplier(supplier)
-                    .withTime(time)
                     .withDefaultWriteTimeOut(Duration.ofMillis(config.offsetCommitTimeoutMs))
                     .withCoordinatorRuntimeMetrics(coordinatorRuntimeMetrics)
                     .withCoordinatorMetrics(groupCoordinatorMetrics)
                     .withSerializer(new CoordinatorRecordSerde())
                     .withCompression(Compression.of(config.compressionType).build())
+                    .withAppendLingerMs(config.appendLingerMs)
                     .build();
 
             return new GroupCoordinatorService(