Question

使用kafka-streams 0.10.0.0，我在转发消息时会定期在StreamTask中看到空指针异常。它在调用的10％到50％之间变化。 NPE发生在这种方法中：

public <K, V> void forward(K key, V value) {
    ProcessorNode thisNode = currNode;
    try {
        for (ProcessorNode childNode : (List<ProcessorNode<K, V>>) thisNode.children()) {
            currNode = childNode;
            childNode.process(key, value);
        }
    } finally {
        currNode = thisNode;
    }
}

在某些情况下， thisNode 字段似乎为空。知道可能导致这种情况的原因吗？堆栈跟踪在下面。

[ERROR] 2016-08-21 14:50:39.288 [StreamThread-1] StreamedMetricMeter - Forwarding failed
java.lang.NullPointerException
    at org.apache.kafka.streams.processor.internals.StreamTask.forward(StreamTask.java:336) ~[kafka-streams-0.10.0.0.jar:?]
    at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:187) ~[kafka-streams-0.10.0.0.jar:?]
    at com.heliosapm.streams.metrics.processors.AbstractStreamedMetricProcessor.forward(AbstractStreamedMetricProcessor.java:552) [classes/:?]
    at com.heliosapm.streams.metrics.processors.impl.StreamedMetricMeter.doProcess(StreamedMetricMeter.java:89) [classes/:?]
    at com.heliosapm.streams.metrics.processors.impl.StreamedMetricMeter.doProcess(StreamedMetricMeter.java:1) [classes/:?]
    at com.heliosapm.streams.metrics.processors.AbstractStreamedMetricProcessor.process(AbstractStreamedMetricProcessor.java:166) [classes/:?]
    at org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:68) [kafka-streams-0.10.0.0.jar:?]
    at org.apache.kafka.streams.processor.internals.StreamTask.forward(StreamTask.java:338) [kafka-streams-0.10.0.0.jar:?]
    at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:187) [kafka-streams-0.10.0.0.jar:?]
    at org.apache.kafka.streams.processor.internals.SourceNode.process(SourceNode.java:64) [kafka-streams-0.10.0.0.jar:?]
    at org.apache.kafka.streams.processor.internals.StreamTask.process(StreamTask.java:174) [kafka-streams-0.10.0.0.jar:?]
    at org.apache.kafka.streams.processor.internals.StreamThread.runLoop(StreamThread.java:320) [kafka-streams-0.10.0.0.jar:?]
    at org.apache.kafka.streams.processor.internals.StreamThread.run(StreamThread.java:218) [kafka-streams-0.10.0.0.jar:?]

Answer 1

问题是我的ProcessorSupplier在每次调用get时都返回了同一个Processor实例。反过来，Kafka Streams引擎试图创建多个处理器实例，毫无疑问我创建了一个多线程垃圾箱火。注意同样粗心.... ProcessorSupplier.get（）应该在每次调用时返回一个处理器的新实例。

Kafka Streams处理器上下文中的周期性NPE

1 个答案: