Add entry formatter to do conversions between MemoryRecords and ByteB…

…uf (#280)

Currently, KoP has some significant performance overhead in the conversion between Kafka's records and Pulsar's messages. For pure Kafka users, i.e. no Pulsar client is involved, the conversion is unnecessary.

So this PR provides a config `entry.format` to specify if the entry's format can be accepted by Pulsar clients. And a `EntryFormatter` is used to do the format conversion instead of static methods of `MessageRecordUtils`.

In future, we'll implement a new `EntryFormatter` to avoid this conversion so that the performance can be improved a lot. After that, users can choose whether to support Pulsar clients for KoP.

kafka-impl/conf/kop.conf

@@ -71,6 +71,16 @@ offsetsTopicNumPartitions=8
 # Maximum number of entries that are read from cursor once per time
 maxReadEntriesNum=5
 
+# The format of an entry. The default value is pulsar.
+# Optional values: [pulsar]
+#
+# pulsar:
+#   When KoP receives messages from kafka producer, it will serialize these messages to
+#   the format so that pulsar consumer can read directly.
+#   When KoP sends entries to kafka consumer, it will treat each entry as pulsar's
+#   format and deserialize each entry to kafka's format.
+entry.format=pulsar
+
 ### --- KoP SSL configs--- ###
 
 # Kafka ssl configuration map with: SSL_PROTOCOL_CONFIG = ssl.protocol

kafka-impl/conf/kop_standalone.conf

@@ -71,6 +71,16 @@ offsetsTopicNumPartitions=8
 # Maximum number of entries that are read from cursor once per time
 maxReadEntriesNum=1
 
+# The format of an entry. The default value is pulsar.
+# Optional values: [pulsar]
+#
+# pulsar:
+#   When KoP receives messages from kafka producer, it will serialize these messages to
+#   the format so that pulsar consumer can read directly.
+#   When KoP sends entries to kafka consumer, it will treat each entry as pulsar's
+#   format and deserialize each entry to kafka's format.
+entry.format=pulsar
+
 ### --- KoP SSL configs--- ###
 
 # Kafka ssl configuration map with: SSL_PROTOCOL_CONFIG = ssl.protocol

kafka-impl/src/main/java/io/streamnative/pulsar/handlers/kop/KafkaRequestHandler.java

@@ -29,6 +29,8 @@
 import io.streamnative.pulsar.handlers.kop.coordinator.group.GroupCoordinator;
 import io.streamnative.pulsar.handlers.kop.coordinator.group.GroupMetadata.GroupOverview;
 import io.streamnative.pulsar.handlers.kop.coordinator.group.GroupMetadata.GroupSummary;
+import io.streamnative.pulsar.handlers.kop.format.EntryFormatter;
+import io.streamnative.pulsar.handlers.kop.format.EntryFormatterFactory;
 import io.streamnative.pulsar.handlers.kop.offset.OffsetAndMetadata;
 import io.streamnative.pulsar.handlers.kop.security.SaslAuthenticator;
 import io.streamnative.pulsar.handlers.kop.utils.CoreUtils;
@@ -157,6 +159,8 @@ public class KafkaRequestHandler extends KafkaCommandDecoder {
     private final int sslPort;
     private final int defaultNumPartitions;
     public final int maxReadEntriesNum;
+    @Getter
+    private final EntryFormatter entryFormatter;
 
     private final Map<TopicPartition, PendingProduceQueue> pendingProduceQueueMap = new ConcurrentHashMap<>();
 
@@ -184,6 +188,7 @@ public KafkaRequestHandler(PulsarService pulsarService,
         this.topicManager = new KafkaTopicManager(this);
         this.defaultNumPartitions = kafkaConfig.getDefaultNumPartitions();
         this.maxReadEntriesNum = kafkaConfig.getMaxReadEntriesNum();
+        this.entryFormatter = EntryFormatterFactory.create(kafkaConfig.getEntryFormat());
     }
 
     @Override
@@ -600,8 +605,8 @@ protected void handleProduceRequest(KafkaHeaderAndRequest produceHar,
 
             MemoryRecords records = (MemoryRecords) entry.getValue();
             String fullPartitionName = KopTopic.toString(topicPartition);
-            PendingProduce pendingProduce =
-                    new PendingProduce(partitionResponse, topicManager, fullPartitionName, records, executor);
+            PendingProduce pendingProduce = new PendingProduce(partitionResponse, topicManager, fullPartitionName,
+                    entryFormatter, records, executor);
             PendingProduceQueue queue =
                     pendingProduceQueueMap.computeIfAbsent(topicPartition, ignored -> new PendingProduceQueue());
             queue.add(pendingProduce);

kafka-impl/src/main/java/io/streamnative/pulsar/handlers/kop/KafkaServiceConfiguration.java

@@ -249,4 +249,9 @@ public class KafkaServiceConfiguration extends ServiceConfiguration {
     )
     private int maxReadEntriesNum = 5;
 
+    @FieldContext(
+            category = CATEGORY_KOP,
+            doc = "The format of an entry. Default: pulsar. Optional: [pulsar]"
+    )
+    private String entryFormat = "pulsar";
 }

kafka-impl/src/main/java/io/streamnative/pulsar/handlers/kop/MessageFetchContext.java

@@ -13,7 +13,6 @@
  */
 package io.streamnative.pulsar.handlers.kop;
 
-import static io.streamnative.pulsar.handlers.kop.utils.MessageRecordUtils.entriesToRecords;
 import static org.apache.kafka.common.protocol.CommonFields.THROTTLE_TIME_MS;
 
 import com.google.common.collect.Lists;
@@ -322,9 +321,7 @@ private void readMessagesInternal(KafkaHeaderAndRequest fetch,
                             } else if (apiVersion <= 3) {
                                 magic = RecordBatch.MAGIC_VALUE_V1;
                             }
-                            MemoryRecords records;
-                            // by default kafka is produced message in batched mode.
-                            records = entriesToRecords(entries, magic);
+                            final MemoryRecords records = requestHandler.getEntryFormatter().decode(entries, magic);
 
                             partitionData = new FetchResponse.PartitionData(
                                 Errors.NONE,

kafka-impl/src/main/java/io/streamnative/pulsar/handlers/kop/PendingProduce.java

@@ -14,14 +14,13 @@
 package io.streamnative.pulsar.handlers.kop;
 
 import io.netty.buffer.ByteBuf;
-import io.streamnative.pulsar.handlers.kop.utils.MessageRecordUtils;
+import io.streamnative.pulsar.handlers.kop.format.EntryFormatter;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.ExecutorService;
 import lombok.extern.slf4j.Slf4j;
 import org.apache.kafka.common.protocol.Errors;
 import org.apache.kafka.common.record.MemoryRecords;
-import org.apache.kafka.common.record.Record;
 import org.apache.kafka.common.requests.ProduceResponse.PartitionResponse;
 import org.apache.pulsar.broker.service.persistent.PersistentTopic;
 
@@ -42,12 +41,13 @@ public class PendingProduce {
     public PendingProduce(CompletableFuture<PartitionResponse> responseFuture,
                           KafkaTopicManager topicManager,
                           String partitionName,
+                          EntryFormatter entryFormatter,
                           MemoryRecords memoryRecords,
                           ExecutorService executor) {
         this.responseFuture = responseFuture;
         this.topicManager = topicManager;
         this.partitionName = partitionName;
-        this.numMessages = parseNumMessages(memoryRecords);
+        this.numMessages = EntryFormatter.parseNumMessages(memoryRecords);
 
         this.topicFuture = topicManager.getTopic(partitionName).exceptionally(e -> {
             log.error("Failed to getTopic for partition '{}': {}", partitionName, e);
@@ -58,10 +58,7 @@ public PendingProduce(CompletableFuture<PartitionResponse> responseFuture,
             log.error("Failed to compute ByteBuf for partition '{}': {}", partitionName, e);
             return null;
         });
-        executor.execute(() -> {
-            ByteBuf byteBuf = MessageRecordUtils.recordsToByteBuf(memoryRecords, this.numMessages);
-            this.byteBufFuture.complete(byteBuf);
-        });
+        executor.execute(() -> byteBufFuture.complete(entryFormatter.encode(memoryRecords, numMessages)));
         this.offsetFuture = new CompletableFuture<>();
     }
 
@@ -119,12 +116,4 @@ public void publishMessages() {
             byteBuf.release();
         });
     }
-
-    private static int parseNumMessages(MemoryRecords records) {
-        int n = 0;
-        for (Record ignored : records.records()) {
-            n++;
-        }
-        return n;
-    }
 }

kafka-impl/src/main/java/io/streamnative/pulsar/handlers/kop/format/EntryFormatter.java

@@ -0,0 +1,63 @@
+/**
+ * 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 io.streamnative.pulsar.handlers.kop.format;
+
+import io.netty.buffer.ByteBuf;
+import java.util.List;
+
+import org.apache.bookkeeper.mledger.Entry;
+import org.apache.kafka.common.record.MemoryRecords;
+import org.apache.kafka.common.record.MutableRecordBatch;
+
+
+/**
+ * The formatter for conversion between Kafka records and Bookie entries.
+ */
+public interface EntryFormatter {
+
+    /**
+     * Encode Kafka records to a ByteBuf.
+     *
+     * @param records messages with Kafka's format
+     * @param numMessages the number of messages
+     * @return the ByteBuf of an entry that is to be written to Bookie
+     */
+    ByteBuf encode(final MemoryRecords records, final int numMessages);
+
+    /**
+     * Decode a stream of entries to Kafka records.
+     *
+     * @param entries the list of entries
+     * @param magic the Kafka record batch's magic value
+     * @return the Kafka records
+     */
+    MemoryRecords decode(final List<Entry> entries, final byte magic);
+
+    /**
+     * Get the number of messages from MemoryRecords.
+     * Since MemoryRecords doesn't provide a way to get the number of messages. We need to iterate over the whole
+     * MemoryRecords object. So we use a helper method to get the number of messages that can be passed to
+     * {@link EntryFormatter#encode(MemoryRecords, int)} and metrics related methods as well.
+     *
+     * @param records messages with Kafka's format
+     * @return the number of messages
+     */
+    static int parseNumMessages(final MemoryRecords records) {
+        int numMessages = 0;
+        for (MutableRecordBatch batch : records.batches()) {
+            numMessages += (batch.lastOffset() - batch.baseOffset() + 1);
+        }
+        return numMessages;
+    }
+}

kafka-impl/src/main/java/io/streamnative/pulsar/handlers/kop/format/EntryFormatterFactory.java

@@ -0,0 +1,40 @@
+/**
+ * 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 io.streamnative.pulsar.handlers.kop.format;
+
+/**
+ * Factory of EntryFormatter.
+ *
+ * @see EntryFormatter
+ */
+public class EntryFormatterFactory {
+
+    enum EntryFormat {
+        PULSAR
+    }
+
+    public static EntryFormatter create(final String format) {
+        try {
+            EntryFormat entryFormat = Enum.valueOf(EntryFormat.class, format.toUpperCase());
+            switch (entryFormat) {
+                case PULSAR:
+                    return new PulsarEntryFormatter();
+                default:
+                    throw new Exception("No EntryFormatter for " + entryFormat);
+            }
+        } catch (Exception e) {
+            throw new IllegalArgumentException("Unsupported entry.format '" + format + "': " + e.getMessage());
+        }
+    }
+}