Github user tdas commented on a diff in the pull request:
https://github.com/apache/spark/pull/3798#discussion_r23972523
--- Diff:
external/kafka/src/main/scala/org/apache/spark/streaming/kafka/KafkaCluster.scala
---
@@ -0,0 +1,338 @@
+/*
+ * 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.spark.streaming.kafka
+
+import scala.util.control.NonFatal
+import scala.util.Random
+import scala.collection.mutable.ArrayBuffer
+import java.util.Properties
+import kafka.api._
+import kafka.common.{ErrorMapping, OffsetMetadataAndError,
TopicAndPartition}
+import kafka.consumer.{ConsumerConfig, SimpleConsumer}
+
+/**
+ * Convenience methods for interacting with a Kafka cluster.
+ * @param kafkaParams Kafka <a
href="http://kafka.apache.org/documentation.html#configuration";>
+ * configuration parameters</a>.
+ * Requires "metadata.broker.list" or "bootstrap.servers" to be set with
Kafka broker(s),
+ * NOT zookeeper servers, specified in host1:port1,host2:port2 form
+ */
+private[spark]
+class KafkaCluster(val kafkaParams: Map[String, String]) extends
Serializable {
+ import KafkaCluster.{Err, LeaderOffset}
+
+ val seedBrokers: Array[(String, Int)] =
+ kafkaParams.get("metadata.broker.list")
+ .orElse(kafkaParams.get("bootstrap.servers"))
+ .getOrElse(throw new Exception("Must specify metadata.broker.list or
bootstrap.servers"))
+ .split(",").map { hp =>
+ val hpa = hp.split(":")
+ (hpa(0), hpa(1).toInt)
+ }
+
+ // ConsumerConfig isn't serializable
+ @transient private var _config: ConsumerConfig = null
+
+ def config: ConsumerConfig = this.synchronized {
+ if (_config == null) {
+ _config = KafkaCluster.consumerConfig(kafkaParams)
+ }
+ _config
+ }
+
+ def connect(host: String, port: Int): SimpleConsumer =
+ new SimpleConsumer(host, port, config.socketTimeoutMs,
+ config.socketReceiveBufferBytes, config.clientId)
+
+ def connectLeader(topic: String, partition: Int): Either[Err,
SimpleConsumer] =
+ findLeader(topic, partition).right.map(hp => connect(hp._1, hp._2))
+
+ // Metadata api
+ // scalastyle:off
+ //
https://cwiki.apache.org/confluence/display/KAFKA/A+Guide+To+The+Kafka+Protocol#AGuideToTheKafkaProtocol-MetadataAPI
+ // scalastyle:on
+
+ def findLeader(topic: String, partition: Int): Either[Err, (String,
Int)] = {
+ val req = TopicMetadataRequest(TopicMetadataRequest.CurrentVersion,
+ 0, config.clientId, Seq(topic))
+ val errs = new Err
+ withBrokers(Random.shuffle(seedBrokers), errs) { consumer =>
+ val resp: TopicMetadataResponse = consumer.send(req)
+ resp.topicsMetadata.find(_.topic == topic).flatMap { tm:
TopicMetadata =>
+ tm.partitionsMetadata.find(_.partitionId == partition)
+ }.foreach { pm: PartitionMetadata =>
+ pm.leader.foreach { leader =>
+ return Right((leader.host, leader.port))
+ }
+ }
+ }
+ Left(errs)
+ }
+
+ def findLeaders(
+ topicAndPartitions: Set[TopicAndPartition]
+ ): Either[Err, Map[TopicAndPartition, (String, Int)]] = {
+ val topics = topicAndPartitions.map(_.topic)
+ getPartitionMetadata(topics).right.flatMap { tms: Set[TopicMetadata] =>
+ val result = tms.flatMap { tm: TopicMetadata =>
--- End diff --
Its not obvious what this loop is doing. What is the result? leaders?
The loop is also nested quite deep to understand.
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