NPE observed in uniqueExternalTimeBatch

[dilini-muthumala]

Description:
Following issue was observed in wso2am-analytics-2.1.0 . The issue occurs from the uniqueExternalTimeBatch window, used in the execution plan APIMAnalytics-RequestSummarizer-RequestSummarizer-realtime1.siddhiql

This error was continuously printed many times, on the server start up.

Another thing to note is that this execution plan uses multiple uniqueExternalTimeBatch windows.

TID: [-1234] [] [2019-08-19 10:42:44,443] ERROR {org.wso2.siddhi.core.query.processor.stream.AbstractStreamProcessor} - Dropping event chunk EventChunk{first=StreamEvent{timestamp=1566204163947, beforeWindowData=[1566204164000_samuel--healthcheck:vv1, 1566204164000], onAfterWindowData=[4], outputData=[samuel--healthcheck:vv1, carbon.super, null], type=CURRENT, next=null}}, error in processing org.wso2.siddhi.core.query.processor.stream.window.UniqueExternalTimeBatchWindowProcessor, null {org.wso2.siddhi.core.query.processor.stream.AbstractStreamProcessor}
java.lang.NullPointerException
 at org.wso2.siddhi.core.event.stream.StreamEventCloner.copyStreamEvent(StreamEventCloner.java:46)
 at org.wso2.siddhi.core.query.processor.stream.window.UniqueExternalTimeBatchWindowProcessor.appendToOutputChunk(UniqueExternalTimeBatchWindowProcessor.java:311)
 at org.wso2.siddhi.core.query.processor.stream.window.UniqueExternalTimeBatchWindowProcessor.process(UniqueExternalTimeBatchWindowProcessor.java:205)
 at org.wso2.siddhi.core.query.processor.stream.window.WindowProcessor.processEventChunk(WindowProcessor.java:57)
 at org.wso2.siddhi.core.query.processor.stream.AbstractStreamProcessor.process(AbstractStreamProcessor.java:101)
 at org.wso2.siddhi.core.query.input.stream.single.EntryValveProcessor.process(EntryValveProcessor.java:47)
 at org.wso2.siddhi.core.query.input.ProcessStreamReceiver.processAndClear(ProcessStreamReceiver.java:154)
 at org.wso2.siddhi.core.query.input.ProcessStreamReceiver.process(ProcessStreamReceiver.java:80)
 at org.wso2.siddhi.core.query.input.ProcessStreamReceiver.receive(ProcessStreamReceiver.java:102)
 at org.wso2.siddhi.core.stream.StreamJunction.sendEvent(StreamJunction.java:127)
 at org.wso2.siddhi.core.stream.StreamJunction$Publisher.send(StreamJunction.java:328)
 at org.wso2.siddhi.core.query.output.callback.InsertIntoStreamCallback.send(InsertIntoStreamCallback.java:46)
 at org.wso2.siddhi.core.query.output.ratelimit.OutputRateLimiter.sendToCallBacks(OutputRateLimiter.java:78)
 at org.wso2.siddhi.core.query.output.ratelimit.PassThroughOutputRateLimiter.process(PassThroughOutputRateLimiter.java:40)
 at org.wso2.siddhi.core.query.selector.QuerySelector.processNoGroupBy(QuerySelector.java:121)
 at org.wso2.siddhi.core.query.selector.QuerySelector.process(QuerySelector.java:86)
 at org.wso2.siddhi.core.query.input.ProcessStreamReceiver.processAndClear(ProcessStreamReceiver.java:154)
 at org.wso2.siddhi.core.query.input.ProcessStreamReceiver.process(ProcessStreamReceiver.java:80)
 at org.wso2.siddhi.core.query.input.ProcessStreamReceiver.receive(ProcessStreamReceiver.java:102)
 at org.wso2.siddhi.core.stream.StreamJunction.sendEvent(StreamJunction.java:127)
 at org.wso2.siddhi.core.stream.StreamJunction$Publisher.send(StreamJunction.java:328)
 at org.wso2.siddhi.core.query.output.callback.InsertIntoStreamCallback.send(InsertIntoStreamCallback.java:46)
 at org.wso2.siddhi.core.query.output.ratelimit.OutputRateLimiter.sendToCallBacks(OutputRateLimiter.java:78)
 at org.wso2.siddhi.core.query.output.ratelimit.PassThroughOutputRateLimiter.process(PassThroughOutputRateLimiter.java:40)
 at org.wso2.siddhi.core.query.selector.QuerySelector.processNoGroupBy(QuerySelector.java:121)
 at org.wso2.siddhi.core.query.selector.QuerySelector.process(QuerySelector.java:86)
 at org.wso2.siddhi.core.query.input.ProcessStreamReceiver.processAndClear(ProcessStreamReceiver.java:154)
 at org.wso2.siddhi.core.query.input.ProcessStreamReceiver.process(ProcessStreamReceiver.java:80)
 at org.wso2.siddhi.core.query.input.ProcessStreamReceiver.receive(ProcessStreamReceiver.java:102)
 at org.wso2.siddhi.core.stream.StreamJunction.sendEvent(StreamJunction.java:127)
 at org.wso2.siddhi.core.stream.StreamJunction$Publisher.send(StreamJunction.java:328)
 at org.wso2.siddhi.core.query.output.callback.InsertIntoStreamCallback.send(InsertIntoStreamCallback.java:46)
 at org.wso2.siddhi.core.query.output.ratelimit.OutputRateLimiter.sendToCallBacks(OutputRateLimiter.java:78)
 at org.wso2.siddhi.core.query.output.ratelimit.PassThroughOutputRateLimiter.process(PassThroughOutputRateLimiter.java:40)
 at org.wso2.siddhi.core.query.selector.QuerySelector.processInBatchGroupBy(QuerySelector.java:251)
 at org.wso2.siddhi.core.query.selector.QuerySelector.process(QuerySelector.java:78)
 at org.wso2.siddhi.core.query.processor.stream.window.ExternalTimeBatchWindowProcessor.process(ExternalTimeBatchWindowProcessor.java:203)
 at org.wso2.siddhi.core.query.processor.stream.window.WindowProcessor.processEventChunk(WindowProcessor.java:57)
 at org.wso2.siddhi.core.query.processor.stream.AbstractStreamProcessor.process(AbstractStreamProcessor.java:101)
 at org.wso2.siddhi.core.query.input.stream.single.EntryValveProcessor.process(EntryValveProcessor.java:47)
 at org.wso2.siddhi.core.query.input.ProcessStreamReceiver.processAndClear(ProcessStreamReceiver.java:154)
 at org.wso2.siddhi.core.query.input.ProcessStreamReceiver.process(ProcessStreamReceiver.java:80)
 at org.wso2.siddhi.core.query.input.ProcessStreamReceiver.receive(ProcessStreamReceiver.java:150)
 at org.wso2.siddhi.core.stream.StreamJunction.sendData(StreamJunction.java:219)
 at org.wso2.siddhi.core.stream.StreamJunction.access$200(StreamJunction.java:47)
 at org.wso2.siddhi.core.stream.StreamJunction$Publisher.send(StreamJunction.java:348)
 at org.wso2.siddhi.core.stream.input.InputDistributor.send(InputDistributor.java:49)
 at org.wso2.siddhi.core.stream.input.InputEntryValve.send(InputEntryValve.java:59)
 at org.wso2.siddhi.core.stream.input.InputHandler.send(InputHandler.java:51)
 at org.wso2.carbon.event.processor.core.internal.listener.SiddhiInputEventDispatcher.sendEvent(SiddhiInputEventDispatcher.java:39)
 at org.wso2.carbon.event.processor.core.internal.listener.AbstractSiddhiInputEventDispatcher.consumeEvent(AbstractSiddhiInputEventDispatcher.java:104)
 at org.wso2.carbon.event.stream.core.internal.EventJunction.sendEvent(EventJunction.java:146)
 at org.wso2.carbon.event.receiver.core.internal.management.QueueInputEventDispatcher$QueueInputEventDispatcherWorker.run(QueueInputEventDispatcher.java:146)
 at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
 at java.util.concurrent.FutureTask.run(FutureTask.java:266)
 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
 at java.lang.Thread.run(Thread.java:748)

Affected Product Version:
wso2am-analytics-2.1.0
Siddhi 3.1.2