我们正在使用Kryo对Kafka和Kafka之间的消息进行序列化/反序列化。旧版本的应用程序使用的是依赖于com.esotericsoftware.kryo.kryo-2.21.jar的Chill 0.6.0，而新版本的应用程序使用的是依赖于com.esotericsoftware.kryo-shaded-4.0.2.jar的Chill 0.9.5。
为了最大限度地减少停机时间，我们的应用程序的新版本需要能够读取由旧版本的应用程序写入的消息，但它失败了，并出现一个错误:
org.apache.kafka.common.errors.SerializationException: Error deserializing key/value for partition prod_2x02_external_entity_updates-0 at offset 8764198. If needed, please seek past the record to continue consumption.
Caused by: com.twitter.bijection.InversionFailure: Failed to invert: [B@14122f45
at com.twitter.bijection.InversionFailure$$anonfun$partialFailure$1.applyOrElse(InversionFailure.scala:43)
at com.twitter.bijection.InversionFailure$$anonfun$partialFailure$1.applyOrElse(InversionFailure.scala:42)
at scala.runtime.AbstractPartialFunction.apply(AbstractPartialFunction.scala:38)
at scala.util.Failure.recoverWith(Try.scala:236)
at com.twitter.bijection.Inversion$.attempt(Inversion.scala:32)
at com.X.backend.serialization.CustomKafkaKryoDeserializer.deserialize(KafkaKryoSerialization.scala:38)
at org.apache.kafka.common.serialization.Deserializer.deserialize(Deserializer.java:60)
at org.apache.kafka.clients.consumer.internals.Fetcher.parseRecord(Fetcher.java:1310)
at org.apache.kafka.clients.consumer.internals.Fetcher.access$3500(Fetcher.java:128)
at org.apache.kafka.clients.consumer.internals.Fetcher$CompletedFetch.fetchRecords(Fetcher.java:1541)
at org.apache.kafka.clients.consumer.internals.Fetcher$CompletedFetch.access$1700(Fetcher.java:1377)
at org.apache.kafka.clients.consumer.internals.Fetcher.fetchRecords(Fetcher.java:677)
at org.apache.kafka.clients.consumer.internals.Fetcher.fetchedRecords(Fetcher.java:632)
at org.apache.kafka.clients.consumer.KafkaConsumer.pollForFetches(KafkaConsumer.java:1315)
at org.apache.kafka.clients.consumer.KafkaConsumer.poll(KafkaConsumer.java:1248)
at org.apache.kafka.clients.consumer.KafkaConsumer.poll(KafkaConsumer.java:1216)
at com.X.common.kafka.KafkaSubscriber$$anonfun$brokerFound$1.applyOrElse(KafkaSubscriber.scala:163)
at akka.actor.Actor.aroundReceive(Actor.scala:535)
at akka.actor.Actor.aroundReceive$(Actor.scala:533)
at com.X.common.kafka.KafkaSubscriber.aroundReceive(KafkaSubscriber.scala:29)
at akka.actor.ActorCell.receiveMessage(ActorCell.scala:577)
at akka.actor.ActorCell.invoke(ActorCell.scala:547)
at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:270)
at akka.dispatch.Mailbox.run(Mailbox.scala:231)
at akka.dispatch.Mailbox.exec(Mailbox.scala:243)
at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056)
at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1692)
at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:175)
Caused by: com.esotericsoftware.kryo.KryoException: Unable to find class: com.X.backend.DashboardExternalEntities$ExtMessage
Serialization trace:
entity (com.X.backend.QueueMessageProtocol$ExternalEntityUpdated)
at com.esotericsoftware.kryo.util.DefaultClassResolver.readName(DefaultClassResolver.java:160)
at com.esotericsoftware.kryo.util.DefaultClassResolver.readClass(DefaultClassResolver.java:133)
at com.esotericsoftware.kryo.Kryo.readClass(Kryo.java:693)
at com.esotericsoftware.kryo.serializers.ObjectField.read(ObjectField.java:118)
at com.esotericsoftware.kryo.serializers.FieldSerializer.read(FieldSerializer.java:543)
at com.esotericsoftware.kryo.Kryo.readClassAndObject(Kryo.java:813)
at com.twitter.chill.SerDeState.readClassAndObject(SerDeState.java:61)
at com.twitter.chill.KryoPool.fromBytes(KryoPool.java:94)
at com.X.backend.serialization.CustomKafkaKryoDeserializer.$anonfun$deserialize$1(KafkaKryoSerialization.scala:38)
at com.twitter.bijection.Inversion$.$anonfun$attempt$1(Inversion.scala:32)
at scala.util.Try$.apply(Try.scala:213)
... 25 common frames omitted
Caused by: java.lang.ClassNotFoundException: com.X.backend.DashboardExternalEntities$ExtMessage
at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
at java.lang.ClassLoader.loadClass(ClassLoader.java:418)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:352)
at java.lang.ClassLoader.loadClass(ClassLoader.java:351)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:348)
at com.esotericsoftware.kryo.util.DefaultClassResolver.readName(DefaultClassResolver.java:154)
... 35 common frames omitted
基于此:https://github.com/EsotericSoftware/kryo/releases/tag/kryo-parent-4.0.0我实现了一个自定义的ScalaKryoInstantiator和相应的类来添加setOptimizedGenerics(true):
class CustomKafkaKryoDeserializer[M <: AnyRef] extends KafkaDeserializer[M] {
override def configure(configs: util.Map[String, _], isKey: Boolean): Unit = ()
override def close(): Unit = ()
override def deserialize(topic: String, data: Array[Byte]): M = {
Inversion.attempt(data) {
CustomKryoInstantiator.defaultPool.fromBytes(_)
}.get.asInstanceOf[M]
}
}
object CustomKryoInstantiator extends ScalaKryoInstantiator {
private val mutex = new AnyRef with Serializable // some serializable object
@transient private var kpool: Option[KryoPool] = None
def defaultPool: KryoPool = mutex.synchronized {
if (kpool.isEmpty) {
kpool = Some(KryoPool.withByteArrayOutputStream(guessThreads, new CustomKryoInstantiator))
}
kpool.get
}
private def guessThreads: Int = {
val cores = Runtime.getRuntime.availableProcessors
val GUESS_THREADS_PER_CORE = 4
GUESS_THREADS_PER_CORE * cores
}
}
class CustomKryoInstantiator extends EmptyScalaKryoInstantiator {
override def newKryo: KryoBase = {
val k = super.newKryo
k.getFieldSerializerConfig.setOptimizedGenerics(true)
val reg = new AllScalaRegistrar
reg(k)
k
}
}
，但我仍然得到相同的错误。是否有一种方法来读取消息，由Kryo 2.21序列化，与Kryo 4.0.2?消息类本身没有改变。
事实证明，消息包被重命名，因此Kryo无法找到正确的类。
然而，即使包重命名被恢复，Kryo 4.0.2和3.0.3无法反序列化被Kryo 2.21序列化的消息。
总之，我们决定用Protobuf代替Kryo，并编写一个MirrorMakerMessageHandler将Kafka消息从Chill-bijection 0.6.0 (Kryo 2.21)转换为Protobuf。