Github user tdas commented on a diff in the pull request:
https://github.com/apache/spark/pull/11863#discussion_r68549572
--- Diff:
external/kafka-0-10/src/main/scala/org/apache/spark/streaming/kafka/ConsumerStrategy.scala
---
@@ -0,0 +1,164 @@
+/*
+ * 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 java.{ util => ju }
+
+import scala.collection.JavaConverters._
+import scala.reflect.ClassTag
+
+import org.apache.kafka.clients.consumer._
+import org.apache.kafka.common.TopicPartition
+
+/**
+ * Choice of how to create and configure underlying Kafka Consumers on
driver and executors.
+ * Kafka 0.10 consumers can require additional, sometimes complex, setup
after object
+ * instantiation. This interface encapsulates that process, and allows it
to be checkpointed.
+ * @tparam K type of Kafka message key
+ * @tparam V type of Kafka message value
+ */
+trait ConsumerStrategy[K, V] {
+ /**
+ * Kafka <a
href="http://kafka.apache.org/documentation.htmll#newconsumerconfigs";>
+ * configuration parameters</a> to be used on executors. Requires
"bootstrap.servers" to be set
+ * with Kafka broker(s) specified in host1:port1,host2:port2 form.
+ */
+ def executorKafkaParams: ju.Map[String, Object]
+
+ /**
+ * Must return a fully configured Kafka Consumer, including subscribed
or assigned topics.
+ * This consumer will be used on the driver to query for offsets only,
not messages.
+ * @param currentOffsets A map from TopicPartition to offset, indicating
how far the driver
+ * has successfully read. Will be empty on initial start, possibly
non-empty on restart from
+ * checkpoint.
+ * TODO: is strategy or dstream responsible for seeking on checkpoint
restart
+ */
+ def onStart(currentOffsets: Map[TopicPartition, Long]): Consumer[K, V]
+}
+
+/**
+ * Subscribe to a collection of topics.
+ * @param topics collection of topics to subscribe
+ * @param kafkaParams Kafka
+ * <a
href="http://kafka.apache.org/documentation.htmll#newconsumerconfigs";>
+ * configuration parameters</a> to be used on driver. The same parameters
will be used on executors,
+ * with minor automatic modifications applied.
+ * Requires "bootstrap.servers" to be set
+ * with Kafka broker(s) specified in host1:port1,host2:port2 form.
+ */
+case class Subscribe[K: ClassTag, V: ClassTag](
+ topics: ju.Collection[java.lang.String],
+ kafkaParams: ju.Map[String, Object]
+ ) extends ConsumerStrategy[K, V] {
+
+ def executorKafkaParams: ju.Map[String, Object] = kafkaParams
+
+ def onStart(currentOffsets: Map[TopicPartition, Long]): Consumer[K, V] =
{
+ val consumer = new KafkaConsumer[K, V](kafkaParams)
+ consumer.subscribe(topics)
+ consumer
+ }
+}
+
+object Subscribe {
--- End diff --
Please add some basic docs on the object ("e.g. Helper object for creating
[[Subscribe]] strategy") and create as that will be an entry point as well,
especially in Scala docs.
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