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From koeninger <...@git.apache.org>
Subject [GitHub] spark pull request #15102: [SPARK-17346][SQL] Add Kafka source for Structure...
Date Tue, 27 Sep 2016 01:40:40 GMT
Github user koeninger commented on a diff in the pull request:

    https://github.com/apache/spark/pull/15102#discussion_r80607882
  
    --- Diff: external/kafka-0-10-sql/src/main/scala/org/apache/spark/sql/kafka010/CachedKafkaConsumer.scala
---
    @@ -0,0 +1,155 @@
    +/*
    + * 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 org.apache.kafka.clients.consumer.{ConsumerConfig, ConsumerRecord, KafkaConsumer}
    +import org.apache.kafka.common.TopicPartition
    +
    +import org.apache.spark.{SparkEnv, SparkException, TaskContext}
    +import org.apache.spark.internal.Logging
    +
    +
    +/**
    + * Consumer of single topicpartition, intended for cached reuse.
    + * Underlying consumer is not threadsafe, so neither is this,
    + * but processing the same topicpartition and group id in multiple threads is usually
bad anyway.
    + */
    +private[kafka010] case class CachedKafkaConsumer private(
    +    topicPartition: TopicPartition,
    +    kafkaParams: ju.Map[String, Object]) extends Logging {
    +
    +  private val consumer = {
    +    val c = new KafkaConsumer[Array[Byte], Array[Byte]](kafkaParams)
    +    val tps = new ju.ArrayList[TopicPartition]()
    +    tps.add(topicPartition)
    +    c.assign(tps)
    +    c
    +  }
    +
    +  /**
    +   * Timeout for polls to the consumer. Since the data should be already available, the
poll
    +   * should get the data immediately, and the timeout value should not matter as long
as it is
    +   * generous and does not cause timeout when there are not issues.
    +   */
    +  private val pollTimeoutMs = 60 * 1000
    +
    +  /** Iterator to the already fetch data */
    +  private var fetchedData = ju.Collections.emptyIterator[ConsumerRecord[Array[Byte],
Array[Byte]]]
    +  private var nextOffsetInFetchedData = -2L
    +
    +  /**
    +   * Get the record for the given offset, waiting up to timeout ms if IO is necessary.
    +   * Sequential forward access will use buffers, but random access will be horribly inefficient.
    +   */
    +  def get(offset: Long): ConsumerRecord[Array[Byte], Array[Byte]] = {
    +    logDebug(s"Get $topicPartition nextOffset $nextOffsetInFetchedData requested $offset")
    +    if (offset != nextOffsetInFetchedData) {
    +      logInfo(s"Initial fetch for $topicPartition $offset")
    +      seek(offset)
    +      poll()
    +    }
    +
    +    if (!fetchedData.hasNext()) { poll() }
    +    assert(fetchedData.hasNext(),
    +      s"Failed to get records for $topicPartition $offset after polling for $pollTimeoutMs")
    +    var record = fetchedData.next()
    +
    +    if (record.offset != offset) {
    +      logInfo(s"Buffer miss for $topicPartition $offset")
    +      seek(offset)
    +      poll()
    --- End diff --
    
    Nor is the timeout used here


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