Realtime - Failed to persist merged index

Hi,
I’ve an 0.8.1 version with Kafka<->Realtime process.

After updating spec file with some new metrics and new datasource I’ve had this error for Realtime and segment wasn’t moved to Historical.

2016-09-20 04:10:57,313 ERROR i.d.s.r.p.RealtimePlumber [buck_bidding-2016-09-19T03:00:00.000-04:00-persist-n-merge] Failed to persist merged index[buck_bidding]: {class=io.druid.segment.realtime.plumber.RealtimePlumber, exceptionType=class java.lang.NullPointerException, exceptionMessage=null, interval=2016-09-19T03:00:00.000-04:00/2016-09-19T04:00:00.000-04:00}

java.lang.NullPointerException

at io.druid.query.aggregation.LongSumAggregator.combineValues(LongSumAggregator.java:39) ~[druid-processing-0.8.1.jar:0.8.1]

at io.druid.query.aggregation.LongSumAggregatorFactory.combine(LongSumAggregatorFactory.java:78) ~[druid-processing-0.8.1.jar:0.8.1]

at io.druid.segment.IndexMerger$RowboatMergeFunction.apply(IndexMerger.java:1242) ~[druid-processing-0.8.1.jar:0.8.1]

at io.druid.segment.IndexMerger$RowboatMergeFunction.apply(IndexMerger.java:1218) ~[druid-processing-0.8.1.jar:0.8.1]

at io.druid.collections.CombiningIterator.next(CombiningIterator.java:78) ~[druid-common-0.8.1.jar:0.8.1]

at io.druid.segment.IndexMerger.makeIndexFiles(IndexMerger.java:730) ~[druid-processing-0.8.1.jar:0.8.1]

at io.druid.segment.IndexMerger.merge(IndexMerger.java:336) ~[druid-processing-0.8.1.jar:0.8.1]

at io.druid.segment.IndexMerger.mergeQueryableIndex(IndexMerger.java:218) ~[druid-processing-0.8.1.jar:0.8.1]

at io.druid.segment.IndexMerger.mergeQueryableIndex(IndexMerger.java:207) ~[druid-processing-0.8.1.jar:0.8.1]

at io.druid.segment.realtime.plumber.RealtimePlumber$4.doRun(RealtimePlumber.java:444) [druid-server-0.8.1.jar:0.8.1]

at io.druid.common.guava.ThreadRenamingRunnable.run(ThreadRenamingRunnable.java:40) [druid-common-0.8.1.jar:0.8.1]

at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [?:1.8.0_60]

at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [?:1.8.0_60]

at java.lang.Thread.run(Thread.java:745) [?:1.8.0_60]

``

How can I try to solve the issue or remove this segment from the queue (every hour I’m receiving alerts) ?

Thanks,

Maurizio