Github user tdas commented on a diff in the pull request:
https://github.com/apache/spark/pull/15102#discussion_r81930531
--- Diff:
external/kafka-0-10-sql/src/main/scala/org/apache/spark/sql/kafka010/KafkaSource.scala
---
@@ -0,0 +1,396 @@
+/*
+ * 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.sql.kafka010
+
+import java.{util => ju}
+
+import scala.collection.JavaConverters._
+import scala.util.control.NonFatal
+
+import org.apache.kafka.clients.consumer.{Consumer, KafkaConsumer}
+import
org.apache.kafka.clients.consumer.internals.NoOpConsumerRebalanceListener
+import org.apache.kafka.common.TopicPartition
+
+import org.apache.spark.SparkContext
+import org.apache.spark.internal.Logging
+import org.apache.spark.scheduler.ExecutorCacheTaskLocation
+import org.apache.spark.sql._
+import org.apache.spark.sql.execution.streaming._
+import org.apache.spark.sql.kafka010.KafkaSource._
+import org.apache.spark.sql.types._
+import org.apache.spark.util.UninterruptibleThread
+
+/**
+ * A [[Source]] that uses Kafka's own [[KafkaConsumer]] API to reads data
from Kafka. The design
+ * for this source is as follows.
+ *
+ * - The [[KafkaSourceOffset]] is the custom [[Offset]] defined for this
source that contains
+ * a map of TopicPartition -> offset. Note that this offset is 1 +
(available offset). For
+ * example if the last record in a Kafka topic "t", partition 2 is
offset 5, then
+ * KafkaSourceOffset will contain TopicPartition("t", 2) -> 6. This is
done keep it consistent
+ * with the semantics of `KafkaConsumer.position()`.
+ *
+ * - The [[ConsumerStrategy]] class defines which Kafka topics and
partitions should be read
+ * by this source. These strategies directly correspond to the different
consumption options
+ * in . This class is designed to return a configured [[KafkaConsumer]]
that is used by the
+ * [[KafkaSource]] to query for the offsets. See the docs on
+ * [[org.apache.spark.sql.kafka010.KafkaSource.ConsumerStrategy]] for
more details.
+ *
+ * - The [[KafkaSource]] written to do the following.
+ *
+ * - As soon as the source is created, the pre-configured KafkaConsumer
returned by the
+ * [[ConsumerStrategy]] is used to query the initial offsets that this
source should
+ * start reading from. This used to create the first batch.
+ *
+ * - `getOffset()` uses the KafkaConsumer to query the latest available
offsets, which are
+ * returned as a [[KafkaSourceOffset]].
+ *
+ * - `getBatch()` returns a DF that reads from the 'start offset' until
the 'end offset' in
+ * for each partition. The end offset is excluded to be consistent
with the semantics of
+ * [[KafkaSourceOffset]] and `KafkaConsumer.position()`.
+ *
+ * - The DF returned is based on [[KafkaSourceRDD]] which is constructed
such that the
+ * data from Kafka topic + partition is consistently read by the same
executors across
+ * batches, and cached KafkaConsumers in the executors can be reused
efficiently. See the
+ * docs on [[KafkaSourceRDD]] for more details.
+ *
+ * Zero data lost is not guaranteed when topics are deleted. If zero data
lost is critical, the user
+ * must make sure all messages in a topic have been processed when
deleting a topic.
+ *
+ * There is a known issue caused by KAFKA-1894: the query using
KafkaSource maybe cannot be stopped.
+ * To avoid this issue, you should make sure stopping the query before
stopping the Kafka brokers
+ * and not use wrong broker addresses.
+ */
+private[kafka010] case class KafkaSource(
+ sqlContext: SQLContext,
+ consumerStrategy: ConsumerStrategy,
+ executorKafkaParams: ju.Map[String, Object],
+ sourceOptions: Map[String, String],
+ metadataPath: String,
+ failOnDataLoss: Boolean)
+ extends Source with Logging {
+
+ private val sc = sqlContext.sparkContext
+
+ private val pollTimeoutMs =
sourceOptions.getOrElse("kafkaConsumer.pollTimeoutMs", "512").toLong
+
+ private val maxOffsetFetchAttempts =
+ sourceOptions.getOrElse("fetchOffset.numRetries", "3").toInt
+
+ private val offsetFetchAttemptIntervalMs =
+ sourceOptions.getOrElse("fetchOffset.retryIntervalMs", "10").toLong
+
+ /**
+ * A KafkaConsumer used in the driver to query the latest Kafka offsets.
This only queries the
+ * offsets and never commits them.
+ */
+ private val consumer = consumerStrategy.createConsumer()
+
+ /**
+ * Lazy set initialPartitionOffsets to make sure only call
`KafkaConsumer.poll` in
+ * StreamExecutionThread. Otherwise, interrupting a thread running
`KafkaConsumer.poll` may hang
+ * forever (KAFKA-1894).
+ */
+ private lazy val initialPartitionOffsets = {
+ val metadataLog = new
HDFSMetadataLog[KafkaSourceOffset](sqlContext.sparkSession, metadataPath)
+ metadataLog.get(0).getOrElse {
+ val offsets = KafkaSourceOffset(fetchPartitionOffsets(seekToEnd =
false))
+ metadataLog.add(0, offsets)
+ logInfo(s"Initial offsets: $offsets")
+ offsets
+ }.partitionToOffsets
+ }
+
+ override def schema: StructType = KafkaSource.kafkaSchema
+
+ /** Returns the maximum available offset for this source. */
+ override def getOffset: Option[Offset] = {
+ // Make sure initialPartitionOffsets is set
--- End diff --
nit: is set --> is initialized
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