Flink Kryo 序列化器，因為找不到 Chill 序列化器

Question

有時會引發此錯誤並關閉任務管理器。 我用過 org.apache.flink.shaded.jackson2.com.fasterxml.jackson.databind.JsonNode

WARN  org.apache.flink.api.java.typeutils.runtime.kryo.KryoSerializer  - Falling back to default Kryo serializer because Chill serializer couldn't be found.
    java.lang.reflect.InvocationTargetException
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.apache.flink.api.java.typeutils.runtime.kryo.KryoSerializer.getKryoInstance(KryoSerializer.java:436)
        at org.apache.flink.api.java.typeutils.runtime.kryo.KryoSerializer.checkKryoInitialized(KryoSerializer.java:454)
        at org.apache.flink.api.java.typeutils.runtime.kryo.KryoSerializer.deserialize(KryoSerializer.java:337)
        at org.apache.flink.api.common.typeutils.CompositeSerializer.deserialize(CompositeSerializer.java:151)
        at org.apache.flink.contrib.streaming.state.ttl.RocksDbTtlCompactFiltersManager$ListElementFilter.nextElementLastAccessTimestamp(RocksDbTtlCompactFiltersManager.java:202)
        at org.apache.flink.contrib.streaming.state.ttl.RocksDbTtlCompactFiltersManager$ListElementFilter.nextUnexpiredOffset(RocksDbTtlCompactFiltersManager.java:189)
    Caused by: java.lang.ClassNotFoundException: scala/Function0
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Class.java:348)
        at com.twitter.chill.KryoBase.$anonfun$functions$1(KryoBase.scala:41)
        at com.twitter.chill.KryoBase.$anonfun$functions$1$adapted(KryoBase.scala:41)
        at scala.collection.TraversableLike.$anonfun$map$1(TraversableLike.scala:233)
        at scala.collection.immutable.Range.foreach(Range.scala:155)
        at scala.collection.TraversableLike.map(TraversableLike.scala:233)
        at scala.collection.TraversableLike.map$(TraversableLike.scala:226)
        at scala.collection.AbstractTraversable.map(Traversable.scala:104)
        at com.twitter.chill.KryoBase.<init>(KryoBase.scala:41)
        at org.apache.flink.runtime.types.EmptyFlinkScalaKryoInstantiator.newKryo(FlinkScalaKryoInstantiator.scala:45)
        at org.apache.flink.runtime.types.FlinkScalaKryoInstantiator.newKryo(FlinkScalaKryoInstantiator.scala:82)
        ... 10 more
    Exception in thread "Thread-9" java.lang.IllegalArgumentException: classLoader cannot be null.
        at com.esotericsoftware.kryo.Kryo.setClassLoader(Kryo.java:975)
        at org.apache.flink.api.java.typeutils.runtime.kryo.KryoSerializer.checkKryoInitialized(KryoSerializer.java:477)
        at org.apache.flink.api.java.typeutils.runtime.kryo.KryoSerializer.deserialize(KryoSerializer.java:337)
        at org.apache.flink.api.common.typeutils.CompositeSerializer.deserialize(CompositeSerializer.java:151)
        at org.apache.flink.contrib.streaming.state.ttl.RocksDbTtlCompactFiltersManager$ListElementFilter.nextElementLastAccessTimestamp(RocksDbTtlCompactFiltersManager.java:202)
        at org.apache.flink.contrib.streaming.state.ttl.RocksDbTtlCompactFiltersManager$ListElementFilter.nextUnexpiredOffset(RocksDbTtlCompactFiltersManager.java:189)

Answer 1

這可能是在本機壓縮線程的上下文中沒有用戶類加載器的問題。

作為一種解決方法，我建議使用帶有簡單元素的列表狀態，該元素類型在序列化時具有固定的字節長度。 那將是原始類型和 POJO，如果可能的話，可能會實現自定義的固定長度序列化程序。 然后 Kryo 序列化器不必在 TTL 清理中調用，並且需要用戶類加載器。