[GitHub] spark pull request #22138: [SPARK-25151][SS] Apply Apache Commons Pool to Ka...

[gaborgsomogyi <gi...@git.apache.org>]

Github user gaborgsomogyi commented on a diff in the pull request:

    https://github.com/apache/spark/pull/22138#discussion_r214813543
  
    --- Diff: external/kafka-0-10-sql/src/main/scala/org/apache/spark/sql/kafka010/InternalKafkaConsumerPool.scala ---
    @@ -0,0 +1,241 @@
    +/*
    + * 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 java.util.concurrent.ConcurrentHashMap
    +
    +import org.apache.commons.pool2.{BaseKeyedPooledObjectFactory, PooledObject, SwallowedExceptionListener}
    +import org.apache.commons.pool2.impl.{DefaultEvictionPolicy, DefaultPooledObject, GenericKeyedObjectPool, GenericKeyedObjectPoolConfig}
    +
    +import org.apache.spark.SparkEnv
    +import org.apache.spark.internal.Logging
    +import org.apache.spark.sql.kafka010.InternalKafkaConsumerPool._
    +import org.apache.spark.sql.kafka010.KafkaDataConsumer.CacheKey
    +
    +/**
    + * Provides object pool for [[InternalKafkaConsumer]] which is grouped by [[CacheKey]].
    + *
    + * This class leverages [[GenericKeyedObjectPool]] internally, hence providing methods based on
    + * the class, and same contract applies: after using the borrowed object, you must either call
    + * returnObject() if the object is healthy to return to pool, or invalidateObject() if the object
    + * should be destroyed.
    + *
    + * The soft capacity of pool is determined by "spark.sql.kafkaConsumerCache.capacity" config value,
    + * and the pool will have reasonable default value if the value is not provided.
    + * (The instance will do its best effort to respect soft capacity but it can exceed when there's
    + * a borrowing request and there's neither free space nor idle object to clear.)
    + *
    + * This class guarantees that no caller will get pooled object once the object is borrowed and
    + * not yet returned, hence provide thread-safety usage of non-thread-safe [[InternalKafkaConsumer]]
    + * unless caller shares the object to multiple threads.
    + */
    +private[kafka010] class InternalKafkaConsumerPool(
    +    objectFactory: ObjectFactory,
    +    poolConfig: PoolConfig) {
    +
    +  // the class is intended to have only soft capacity
    +  assert(poolConfig.getMaxTotal < 0)
    +
    +  private lazy val pool = {
    +    val internalPool = new GenericKeyedObjectPool[CacheKey, InternalKafkaConsumer](
    +      objectFactory, poolConfig)
    +    internalPool.setSwallowedExceptionListener(CustomSwallowedExceptionListener)
    +    internalPool
    +  }
    +
    +  /**
    +   * Borrows [[InternalKafkaConsumer]] object from the pool. If there's no idle object for the key,
    +   * the pool will create the [[InternalKafkaConsumer]] object.
    +   *
    +   * If the pool doesn't have idle object for the key and also exceeds the soft capacity,
    +   * pool will try to clear some of idle objects.
    +   *
    +   * Borrowed object must be returned by either calling returnObject or invalidateObject, otherwise
    +   * the object will be kept in pool as active object.
    +   */
    +  def borrowObject(key: CacheKey, kafkaParams: ju.Map[String, Object]): InternalKafkaConsumer = {
    +    updateKafkaParamForKey(key, kafkaParams)
    +
    +    if (getTotal == poolConfig.getSoftMaxTotal()) {
    +      pool.clearOldest()
    +    }
    +
    +    pool.borrowObject(key)
    +  }
    +
    +  /** Returns borrowed object to the pool. */
    +  def returnObject(consumer: InternalKafkaConsumer): Unit = {
    +    pool.returnObject(extractCacheKey(consumer), consumer)
    +  }
    +
    +  /** Invalidates (destroy) borrowed object to the pool. */
    +  def invalidateObject(consumer: InternalKafkaConsumer): Unit = {
    +    pool.invalidateObject(extractCacheKey(consumer), consumer)
    +  }
    +
    +  /** Invalidates all idle consumers for the key */
    +  def invalidateKey(key: CacheKey): Unit = {
    +    pool.clear(key)
    +  }
    +
    +  /**
    +   * Closes the keyed object pool. Once the pool is closed,
    +   * borrowObject will fail with [[IllegalStateException]], but returnObject and invalidateObject
    +   * will continue to work, with returned objects destroyed on return.
    +   *
    +   * Also destroys idle instances in the pool.
    +   */
    +  def close(): Unit = {
    +    pool.close()
    +  }
    +
    +  def getNumIdle: Int = pool.getNumIdle
    +
    +  def getNumIdle(key: CacheKey): Int = pool.getNumIdle(key)
    +
    +  def getNumActive: Int = pool.getNumActive
    +
    +  def getNumActive(key: CacheKey): Int = pool.getNumActive(key)
    +
    +  def getTotal: Int = getNumIdle + getNumActive
    +
    +  def getTotal(key: CacheKey): Int = getNumIdle(key) + getNumActive(key)
    +
    +  private def updateKafkaParamForKey(key: CacheKey, kafkaParams: ju.Map[String, Object]): Unit = {
    +    // We can assume that kafkaParam should not be different for same cache key,
    --- End diff --
    
    Then why not enforce it?


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