HeartSaVioR commented on a change in pull request #19096: [SPARK-21869][SS] A
cached Kafka producer should not be closed if any task is using it - adds inuse
tracking.
URL: https://github.com/apache/spark/pull/19096#discussion_r272468707
##########
File path:
external/kafka-0-10-sql/src/main/scala/org/apache/spark/sql/kafka010/CachedKafkaProducer.scala
##########
@@ -40,81 +90,114 @@ private[kafka010] object CachedKafkaProducer extends
Logging {
"spark.kafka.producer.cache.timeout",
s"${defaultCacheExpireTimeout}ms")).getOrElse(defaultCacheExpireTimeout)
- private val cacheLoader = new CacheLoader[Seq[(String, Object)], Producer] {
- override def load(config: Seq[(String, Object)]): Producer = {
- val configMap = config.map(x => x._1 -> x._2).toMap.asJava
- createKafkaProducer(configMap)
+ private val cacheLoader = new CacheLoader[Seq[(String, Object)],
CachedKafkaProducer] {
+ override def load(params: Seq[(String, Object)]): CachedKafkaProducer = {
+ CachedKafkaProducer(kafkaParams = params)
}
}
- private val removalListener = new RemovalListener[Seq[(String, Object)],
Producer]() {
+ private val closeQueue = new ConcurrentLinkedQueue[CachedKafkaProducer]()
+
+ private val removalListener = new RemovalListener[Seq[(String, Object)],
CachedKafkaProducer]() {
override def onRemoval(
- notification: RemovalNotification[Seq[(String, Object)], Producer]):
Unit = {
- val paramsSeq: Seq[(String, Object)] = notification.getKey
- val producer: Producer = notification.getValue
- logDebug(
- s"Evicting kafka producer $producer params: $paramsSeq, due to
${notification.getCause}")
- close(paramsSeq, producer)
+ notification: RemovalNotification[Seq[(String, Object)],
CachedKafkaProducer]): Unit = {
+ val producer: CachedKafkaProducer = notification.getValue
+ if (producer.inUse()) {
+ logDebug(s"Evicting kafka producer $producer, due to
${notification.getCause}.")
+ // When `inuse` producer is evicted we wait for it to be released
before finally closing it.
+ closeQueue.add(producer)
+ producer.unCache()
+ } else {
+ close(producer)
+ }
}
}
- private lazy val guavaCache: LoadingCache[Seq[(String, Object)], Producer] =
+ private lazy val guavaCache: LoadingCache[Seq[(String, Object)],
CachedKafkaProducer] =
CacheBuilder.newBuilder().expireAfterAccess(cacheExpireTimeout,
TimeUnit.MILLISECONDS)
.removalListener(removalListener)
- .build[Seq[(String, Object)], Producer](cacheLoader)
-
- private def createKafkaProducer(producerConfiguration: ju.Map[String,
Object]): Producer = {
- val updatedKafkaProducerConfiguration =
- KafkaConfigUpdater("executor", producerConfiguration.asScala.toMap)
- .setAuthenticationConfigIfNeeded()
- .build()
- val kafkaProducer: Producer = new
Producer(updatedKafkaProducerConfiguration)
- logDebug(s"Created a new instance of KafkaProducer for
$updatedKafkaProducerConfiguration.")
- kafkaProducer
- }
+ .build[Seq[(String, Object)], CachedKafkaProducer](cacheLoader)
/**
* Get a cached KafkaProducer for a given configuration. If matching
KafkaProducer doesn't
* exist, a new KafkaProducer will be created. KafkaProducer is thread safe,
it is best to keep
* one instance per specified kafkaParams.
*/
- private[kafka010] def getOrCreate(kafkaParams: ju.Map[String, Object]):
Producer = {
- val paramsSeq: Seq[(String, Object)] = paramsToSeq(kafkaParams)
+ private[kafka010] def acquire(kafkaParamsMap: ju.Map[String, Object]):
CachedKafkaProducer = {
+ val paramsSeq: Seq[(String, Object)] = paramsToSeq(kafkaParamsMap)
try {
- guavaCache.get(paramsSeq)
+ val producer = this.synchronized {
+ val cachedKafkaProducer: CachedKafkaProducer =
guavaCache.get(paramsSeq)
+ cachedKafkaProducer.inUseCount.incrementAndGet()
+ logDebug(s"Granted producer $cachedKafkaProducer")
+ cachedKafkaProducer
+ }
+ producer
} catch {
- case e @ (_: ExecutionException | _: UncheckedExecutionException | _:
ExecutionError)
+ case e@(_: ExecutionException | _: UncheckedExecutionException | _:
ExecutionError)
if e.getCause != null =>
throw e.getCause
}
}
- private def paramsToSeq(kafkaParams: ju.Map[String, Object]): Seq[(String,
Object)] = {
- val paramsSeq: Seq[(String, Object)] = kafkaParams.asScala.toSeq.sortBy(x
=> x._1)
+ private def paramsToSeq(kafkaParamsMap: ju.Map[String, Object]):
Seq[(String, Object)] = {
+ val paramsSeq: Seq[(String, Object)] =
kafkaParamsMap.asScala.toSeq.sortBy(x => x._1)
paramsSeq
}
- /** For explicitly closing kafka producer */
- private[kafka010] def close(kafkaParams: ju.Map[String, Object]): Unit = {
- val paramsSeq = paramsToSeq(kafkaParams)
- guavaCache.invalidate(paramsSeq)
+ /* Release a kafka producer back to the kafka cache. We simply decrement
it's inuse count. */
+ private[kafka010] def release(producer: CachedKafkaProducer, failing:
Boolean): Unit = {
+ this.synchronized {
+ // It should be ok to call release multiple times on the same producer
object.
+ if (producer.inUse()) {
+ // So that we do not end up with -ve in-use counts.
+ producer.inUseCount.decrementAndGet()
+ logDebug(s"Released producer $producer.")
+ } else {
+ logWarning(s"Tried to release a not in use producer, $producer.")
+ }
+ if (failing) {
+ // If this producer is failing to write, we remove it from cache.
+ // So that it is re-created, eventually.
+ val cachedProducer = guavaCache.getIfPresent(producer.kafkaParams)
+ if (cachedProducer != null && cachedProducer.id == producer.id) {
+ logDebug(s"Invalidating a failing producer: $producer.")
+ guavaCache.invalidate(producer.kafkaParams)
+ }
+ }
+ }
+ if (!producer.inUse() && !producer.isCached) {
Review comment:
Could you point out which you don't understand my explanation of race
condition? Race condition is not a thing a test can reproduce consistently.
In short, `Adding producer to closeQueue` and `marking producer as uncached`
are not being done atomically given there's no synchronization in
`removalListener.onRemoval`. There's a case producer is added to closeQueue but
isCached is still `true` - race condition happens here.
In other words, suppose `inCount` in producer is exactly correct and
thread-safe: then why we need close queue? There should be "exactly only once"
when inUse = false, either `onRemoval` or `release`, then closeQueue doesn't be
needed and just closing the producer should work. `closeQueue` is just for
mitigation when synchronization of `inCount` is off, and looping closeQueue
every time when other producer is closing is not free.
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