NPE observed intermittently in Editor when using HTTP Sink

[mohanvive]

Description:
Below NPE is observed when using event simulator. Seems like connection retry issue.

osgi>
osgi> [2020-01-09 14:55:01,468] ERROR {io.siddhi.core.stream.StreamJunction} - Error in 'Wait-Retry' after consuming events from Stream 'AbnormalGlucoseReadingStream', null. Hence, dropping event 'StreamEvent{ timestamp=1578561901467, beforeWindowData=null, onAfterWindowData=[1576829362, Alex, John], outputData=[1576829362, Get-1024, Level2, 10348, Alex John, 250.0], type=CURRENT, next=null}' java.lang.NullPointerException
	at io.siddhi.extension.io.http.sink.HttpSink.createClientConnector(HttpSink.java:1065)
	at io.siddhi.extension.io.http.sink.HttpSink.publish(HttpSink.java:597)
	at io.siddhi.core.stream.output.sink.Sink.publish(Sink.java:182)
	at io.siddhi.extension.map.json.sinkmapper.JsonSinkMapper.mapAndSend(JsonSinkMapper.java:209)
	at io.siddhi.core.stream.output.sink.SinkMapper.mapAndSend(SinkMapper.java:180)
	at io.siddhi.core.stream.output.sink.SinkCallback.receive(SinkCallback.java:55)
	at io.siddhi.core.stream.output.StreamCallback.receive(StreamCallback.java:100)
	at io.siddhi.core.stream.StreamJunction.sendEvent(StreamJunction.java:176)
	at io.siddhi.core.stream.StreamJunction$Publisher.send(StreamJunction.java:465)
	at io.siddhi.core.query.output.callback.InsertIntoStreamCallback.send(InsertIntoStreamCallback.java:56)
	at io.siddhi.core.query.output.ratelimit.OutputRateLimiter.sendToCallBacks(OutputRateLimiter.java:104)
	at io.siddhi.core.query.output.ratelimit.PassThroughOutputRateLimiter.process(PassThroughOutputRateLimiter.java:44)
	at io.siddhi.core.query.selector.QuerySelector.process(QuerySelector.java:97)
	at io.siddhi.core.query.processor.filter.FilterProcessor.process(FilterProcessor.java:58)
	at io.siddhi.core.query.input.ProcessStreamReceiver.processAndClear(ProcessStreamReceiver.java:182)
	at io.siddhi.core.query.input.ProcessStreamReceiver.process(ProcessStreamReceiver.java:89)
	at io.siddhi.core.query.input.ProcessStreamReceiver.receive(ProcessStreamReceiver.java:127)
	at io.siddhi.core.stream.StreamJunction.sendEvent(StreamJunction.java:199)
	at io.siddhi.core.stream.StreamJunction$Publisher.send(StreamJunction.java:474)
	at io.siddhi.core.stream.input.InputDistributor.send(InputDistributor.java:34)
	at io.siddhi.core.stream.input.InputEntryValve.send(InputEntryValve.java:45)
	at io.siddhi.core.stream.input.InputHandler.send(InputHandler.java:78)
	at io.siddhi.distribution.editor.core.internal.DebuggerEventStreamService.pushEvent(DebuggerEventStreamService.java:74)
	at io.siddhi.distribution.event.simulator.core.internal.generator.SingleEventGenerator.sendEvent(SingleEventGenerator.java:85)
	at io.siddhi.distribution.event.simulator.core.impl.SingleApiServiceImpl.runSingleSimulation(SingleApiServiceImpl.java:20)
	at io.siddhi.distribution.event.simulator.core.api.SingleApi.runSingleSimulation(SingleApi.java:72)
	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.wso2.msf4j.internal.router.HttpMethodInfo.invokeResource(HttpMethodInfo.java:187)
	at org.wso2.msf4j.internal.router.HttpMethodInfo.invoke(HttpMethodInfo.java:143)
	at org.wso2.msf4j.internal.MSF4JHttpConnectorListener.dispatchMethod(MSF4JHttpConnectorListener.java:218)
	at org.wso2.msf4j.internal.MSF4JHttpConnectorListener.lambda$onMessage$58(MSF4JHttpConnectorListener.java:129)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)

Siddhi App is give below

@App:name("Wait-Retry")

@App:description("Description of the plan")

-- Defines `GlucoseReadingStream` stream which contains events related to Glucose readings.
define stream GlucoseReadingStream (locationRoom string,
    locationBed string, timeStamp string, sensorID long,
    patientFirstName string, patientLastName string,
    sensorValue double);


-- If `HTTP` endpoint is unavailable then threads who bring events via `AbnormalGlucoseReadingStream` wait in `back-off and re-trying` mode.
-- Errors can be gracefully handled by configuring `on.error` parameter.
@sink(type = 'http', on.error='wait',
    publisher.url = "http://localhost:8080/logger",
    method = "POST",
    @map(type = 'json'))

define stream AbnormalGlucoseReadingStream
    (timeStampInLong long, locationRoom string,
    locationBed string, sensorID long,
    patientFullName string, sensorReadingValue double);


@info(name='abnormal-reading-identifier')
-- Identifies the abnomarl Glucose reading if `sensorValue > 220`
from GlucoseReadingStream[sensorValue > 220]
select math:parseLong(timeStamp) as timeStampInLong,
    locationRoom, locationBed, sensorID,

-- Concatenate string attributes `patientFirstName` and `patientLastName`
    str:concat(patientFirstName, " ", patientLastName)
        as patientFullName,

        sensorValue as sensorReadingValue
insert into AbnormalGlucoseReadingStream;