[jira] [Updated] (NIFI-2841) SplitAvro Processor is Broken

2016-11-08 Thread Oleg Zhurakousky (JIRA) 

 [ 
https://issues.apache.org/jira/browse/NIFI-2841?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
 ]

Oleg Zhurakousky updated NIFI-2841:
---
Resolution: Fixed
Status: Resolved  (was: Patch Available)

> SplitAvro Processor is Broken
> -
>
> Key: NIFI-2841
> URL: https://issues.apache.org/jira/browse/NIFI-2841
> Project: Apache NiFi
>  Issue Type: Bug
>Reporter: David Hicks
>Assignee: Bryan Bende
>Priority: Critical
> Fix For: 1.1.0
>
> Attachments: NIFI-2841.patch
>
>
> This is largely the fault of the Avro DataFileStream reader, but it's making 
> the processor unusable.  The problem appears to occur when you make the 
> following series of calls (which happens because of the splitSize comparison):
> reader.next() -> returns last element
> reader.hasNext() -> returns false
> reader.hasNext() -> returns true
> reader.next() -> EOFException
> org.apache.nifi.processor.exception.ProcessException: IOException thrown from 
> SplitAvro[id=22e03ca4-0151-4474-92fc-040e1fe12ab9]: java.io.EOFException
>   at 
> org.apache.nifi.controller.repository.StandardProcessSession.write(StandardProcessSession.java:2013)
>  ~[na:na]
>   at 
> org.apache.nifi.processors.avro.SplitAvro$RecordSplitter$1.process(SplitAvro.java:250)
>  ~[nifi-avro-processors-0.7.0.jar:0.7.0]
>   at 
> org.apache.nifi.controller.repository.StandardProcessSession.read(StandardProcessSession.java:1851)
>  ~[na:na]
>   at 
> org.apache.nifi.controller.repository.StandardProcessSession.read(StandardProcessSession.java:1822)
>  ~[na:na]
>   at 
> org.apache.nifi.processors.avro.SplitAvro$RecordSplitter.split(SplitAvro.java:236)
>  ~[nifi-avro-processors-0.7.0.jar:0.7.0]
>   at 
> org.apache.nifi.processors.avro.SplitAvro.onTrigger(SplitAvro.java:202) 
> ~[nifi-avro-processors-0.7.0.jar:0.7.0]
>   at 
> org.apache.nifi.processor.AbstractProcessor.onTrigger(AbstractProcessor.java:27)
>  [nifi-api-0.7.0.jar:0.7.0]
>   at 
> org.apache.nifi.controller.StandardProcessorNode.onTrigger(StandardProcessorNode.java:1054)
>  [nifi-framework-core-0.7.0.jar:0.7.0]
>   at 
> org.apache.nifi.controller.tasks.ContinuallyRunProcessorTask.call(ContinuallyRunProcessorTask.java:136)
>  [nifi-framework-core-0.7.0.jar:0.7.0]
>   at 
> org.apache.nifi.controller.tasks.ContinuallyRunProcessorTask.call(ContinuallyRunProcessorTask.java:47)
>  [nifi-framework-core-0.7.0.jar:0.7.0]
>   at 
> org.apache.nifi.controller.scheduling.TimerDrivenSchedulingAgent$1.run(TimerDrivenSchedulingAgent.java:127)
>  [nifi-framework-core-0.7.0.jar:0.7.0]
>   at 
> java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) 
> [na:1.8.0_101]
>   at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308) 
> [na:1.8.0_101]
>   at 
> java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
>  [na:1.8.0_101]
>   at 
> java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
>  [na:1.8.0_101]
>   at 
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
>  [na:1.8.0_101]
>   at 
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
>  [na:1.8.0_101]
>   at java.lang.Thread.run(Thread.java:745) [na:1.8.0_101]
> Caused by: java.io.EOFException: null
>   at 
> org.apache.avro.io.BinaryDecoder.ensureBounds(BinaryDecoder.java:473) 
> ~[avro-1.7.7.jar:1.7.7]
>   at org.apache.avro.io.BinaryDecoder.readInt(BinaryDecoder.java:128) 
> ~[avro-1.7.7.jar:1.7.7]
>   at org.apache.avro.io.BinaryDecoder.readString(BinaryDecoder.java:259) 
> ~[avro-1.7.7.jar:1.7.7]
>   at 
> org.apache.avro.io.ResolvingDecoder.readString(ResolvingDecoder.java:201) 
> ~[avro-1.7.7.jar:1.7.7]
>   at 
> org.apache.avro.generic.GenericDatumReader.readString(GenericDatumReader.java:363)
>  ~[avro-1.7.7.jar:1.7.7]
>   at 
> org.apache.avro.generic.GenericDatumReader.readString(GenericDatumReader.java:355)
>  ~[avro-1.7.7.jar:1.7.7]
>   at 
> org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:157) 
> ~[avro-1.7.7.jar:1.7.7]
>   at 
> org.apache.avro.generic.GenericDatumReader.readField(GenericDatumReader.java:193)
>  ~[avro-1.7.7.jar:1.7.7]
>   at 
> org.apache.avro.generic.GenericDatumReader.readRecord(GenericDatumReader.java:183)
>  ~[avro-1.7.7.jar:1.7.7]
>   at 
> org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:151) 
> ~[avro-1.7.7.jar:1.7.7]
>   at 
> org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:142) 
> ~[avro-1.7.7.jar:1.7.7]
>   at org.apache.avro.file.DataFileStream.next(DataFileStream.java:233) 
> ~[avro-1.7.7.jar:1.7.7]
>   at 
>

[jira] [Updated] (NIFI-2841) SplitAvro Processor is Broken

2016-10-03 Thread Bryan Bende (JIRA) 

 [ 
https://issues.apache.org/jira/browse/NIFI-2841?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
 ]

Bryan Bende updated NIFI-2841:
--
Fix Version/s: 1.1.0

> SplitAvro Processor is Broken
> -
>
> Key: NIFI-2841
> URL: https://issues.apache.org/jira/browse/NIFI-2841
> Project: Apache NiFi
>  Issue Type: Bug
>Reporter: David Hicks
>Priority: Critical
> Fix For: 1.1.0
>
> Attachments: NIFI-2841.patch
>
>
> This is largely the fault of the Avro DataFileStream reader, but it's making 
> the processor unusable.  The problem appears to occur when you make the 
> following series of calls (which happens because of the splitSize comparison):
> reader.next() -> returns last element
> reader.hasNext() -> returns false
> reader.hasNext() -> returns true
> reader.next() -> EOFException
> org.apache.nifi.processor.exception.ProcessException: IOException thrown from 
> SplitAvro[id=22e03ca4-0151-4474-92fc-040e1fe12ab9]: java.io.EOFException
>   at 
> org.apache.nifi.controller.repository.StandardProcessSession.write(StandardProcessSession.java:2013)
>  ~[na:na]
>   at 
> org.apache.nifi.processors.avro.SplitAvro$RecordSplitter$1.process(SplitAvro.java:250)
>  ~[nifi-avro-processors-0.7.0.jar:0.7.0]
>   at 
> org.apache.nifi.controller.repository.StandardProcessSession.read(StandardProcessSession.java:1851)
>  ~[na:na]
>   at 
> org.apache.nifi.controller.repository.StandardProcessSession.read(StandardProcessSession.java:1822)
>  ~[na:na]
>   at 
> org.apache.nifi.processors.avro.SplitAvro$RecordSplitter.split(SplitAvro.java:236)
>  ~[nifi-avro-processors-0.7.0.jar:0.7.0]
>   at 
> org.apache.nifi.processors.avro.SplitAvro.onTrigger(SplitAvro.java:202) 
> ~[nifi-avro-processors-0.7.0.jar:0.7.0]
>   at 
> org.apache.nifi.processor.AbstractProcessor.onTrigger(AbstractProcessor.java:27)
>  [nifi-api-0.7.0.jar:0.7.0]
>   at 
> org.apache.nifi.controller.StandardProcessorNode.onTrigger(StandardProcessorNode.java:1054)
>  [nifi-framework-core-0.7.0.jar:0.7.0]
>   at 
> org.apache.nifi.controller.tasks.ContinuallyRunProcessorTask.call(ContinuallyRunProcessorTask.java:136)
>  [nifi-framework-core-0.7.0.jar:0.7.0]
>   at 
> org.apache.nifi.controller.tasks.ContinuallyRunProcessorTask.call(ContinuallyRunProcessorTask.java:47)
>  [nifi-framework-core-0.7.0.jar:0.7.0]
>   at 
> org.apache.nifi.controller.scheduling.TimerDrivenSchedulingAgent$1.run(TimerDrivenSchedulingAgent.java:127)
>  [nifi-framework-core-0.7.0.jar:0.7.0]
>   at 
> java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) 
> [na:1.8.0_101]
>   at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308) 
> [na:1.8.0_101]
>   at 
> java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
>  [na:1.8.0_101]
>   at 
> java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
>  [na:1.8.0_101]
>   at 
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
>  [na:1.8.0_101]
>   at 
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
>  [na:1.8.0_101]
>   at java.lang.Thread.run(Thread.java:745) [na:1.8.0_101]
> Caused by: java.io.EOFException: null
>   at 
> org.apache.avro.io.BinaryDecoder.ensureBounds(BinaryDecoder.java:473) 
> ~[avro-1.7.7.jar:1.7.7]
>   at org.apache.avro.io.BinaryDecoder.readInt(BinaryDecoder.java:128) 
> ~[avro-1.7.7.jar:1.7.7]
>   at org.apache.avro.io.BinaryDecoder.readString(BinaryDecoder.java:259) 
> ~[avro-1.7.7.jar:1.7.7]
>   at 
> org.apache.avro.io.ResolvingDecoder.readString(ResolvingDecoder.java:201) 
> ~[avro-1.7.7.jar:1.7.7]
>   at 
> org.apache.avro.generic.GenericDatumReader.readString(GenericDatumReader.java:363)
>  ~[avro-1.7.7.jar:1.7.7]
>   at 
> org.apache.avro.generic.GenericDatumReader.readString(GenericDatumReader.java:355)
>  ~[avro-1.7.7.jar:1.7.7]
>   at 
> org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:157) 
> ~[avro-1.7.7.jar:1.7.7]
>   at 
> org.apache.avro.generic.GenericDatumReader.readField(GenericDatumReader.java:193)
>  ~[avro-1.7.7.jar:1.7.7]
>   at 
> org.apache.avro.generic.GenericDatumReader.readRecord(GenericDatumReader.java:183)
>  ~[avro-1.7.7.jar:1.7.7]
>   at 
> org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:151) 
> ~[avro-1.7.7.jar:1.7.7]
>   at 
> org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:142) 
> ~[avro-1.7.7.jar:1.7.7]
>   at org.apache.avro.file.DataFileStream.next(DataFileStream.java:233) 
> ~[avro-1.7.7.jar:1.7.7]
>   at 
> org.apache.nifi.processors.avro.SplitAvro$RecordSplitter$1$1.process(SplitAvro.java:259)
>

[jira] [Updated] (NIFI-2841) SplitAvro Processor is Broken

2016-09-29 Thread Bryan Bende (JIRA) 

 [ 
https://issues.apache.org/jira/browse/NIFI-2841?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
 ]

Bryan Bende updated NIFI-2841:
--
Attachment: NIFI-2841.patch

The attached patch should avoid making two consecutive calls to 
reader.hasNext(), although I would really like to reproduce the problem to know 
for sure that this solves it. Existing unit tests still pass.

I know there has been one other change to SplitAvro after the 1.0.0 release, so 
if you wanted to try this out you could apply this patch to master and do a 
build of that, and then take the updated Avro NAR.

> SplitAvro Processor is Broken
> -
>
> Key: NIFI-2841
> URL: https://issues.apache.org/jira/browse/NIFI-2841
> Project: Apache NiFi
>  Issue Type: Bug
>Reporter: David Hicks
>Priority: Critical
> Attachments: NIFI-2841.patch
>
>
> This is largely the fault of the Avro DataFileStream reader, but it's making 
> the processor unusable.  The problem appears to occur when you make the 
> following series of calls (which happens because of the splitSize comparison):
> reader.next() -> returns last element
> reader.hasNext() -> returns false
> reader.hasNext() -> returns true
> reader.next() -> EOFException
> org.apache.nifi.processor.exception.ProcessException: IOException thrown from 
> SplitAvro[id=22e03ca4-0151-4474-92fc-040e1fe12ab9]: java.io.EOFException
>   at 
> org.apache.nifi.controller.repository.StandardProcessSession.write(StandardProcessSession.java:2013)
>  ~[na:na]
>   at 
> org.apache.nifi.processors.avro.SplitAvro$RecordSplitter$1.process(SplitAvro.java:250)
>  ~[nifi-avro-processors-0.7.0.jar:0.7.0]
>   at 
> org.apache.nifi.controller.repository.StandardProcessSession.read(StandardProcessSession.java:1851)
>  ~[na:na]
>   at 
> org.apache.nifi.controller.repository.StandardProcessSession.read(StandardProcessSession.java:1822)
>  ~[na:na]
>   at 
> org.apache.nifi.processors.avro.SplitAvro$RecordSplitter.split(SplitAvro.java:236)
>  ~[nifi-avro-processors-0.7.0.jar:0.7.0]
>   at 
> org.apache.nifi.processors.avro.SplitAvro.onTrigger(SplitAvro.java:202) 
> ~[nifi-avro-processors-0.7.0.jar:0.7.0]
>   at 
> org.apache.nifi.processor.AbstractProcessor.onTrigger(AbstractProcessor.java:27)
>  [nifi-api-0.7.0.jar:0.7.0]
>   at 
> org.apache.nifi.controller.StandardProcessorNode.onTrigger(StandardProcessorNode.java:1054)
>  [nifi-framework-core-0.7.0.jar:0.7.0]
>   at 
> org.apache.nifi.controller.tasks.ContinuallyRunProcessorTask.call(ContinuallyRunProcessorTask.java:136)
>  [nifi-framework-core-0.7.0.jar:0.7.0]
>   at 
> org.apache.nifi.controller.tasks.ContinuallyRunProcessorTask.call(ContinuallyRunProcessorTask.java:47)
>  [nifi-framework-core-0.7.0.jar:0.7.0]
>   at 
> org.apache.nifi.controller.scheduling.TimerDrivenSchedulingAgent$1.run(TimerDrivenSchedulingAgent.java:127)
>  [nifi-framework-core-0.7.0.jar:0.7.0]
>   at 
> java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) 
> [na:1.8.0_101]
>   at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308) 
> [na:1.8.0_101]
>   at 
> java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
>  [na:1.8.0_101]
>   at 
> java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
>  [na:1.8.0_101]
>   at 
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
>  [na:1.8.0_101]
>   at 
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
>  [na:1.8.0_101]
>   at java.lang.Thread.run(Thread.java:745) [na:1.8.0_101]
> Caused by: java.io.EOFException: null
>   at 
> org.apache.avro.io.BinaryDecoder.ensureBounds(BinaryDecoder.java:473) 
> ~[avro-1.7.7.jar:1.7.7]
>   at org.apache.avro.io.BinaryDecoder.readInt(BinaryDecoder.java:128) 
> ~[avro-1.7.7.jar:1.7.7]
>   at org.apache.avro.io.BinaryDecoder.readString(BinaryDecoder.java:259) 
> ~[avro-1.7.7.jar:1.7.7]
>   at 
> org.apache.avro.io.ResolvingDecoder.readString(ResolvingDecoder.java:201) 
> ~[avro-1.7.7.jar:1.7.7]
>   at 
> org.apache.avro.generic.GenericDatumReader.readString(GenericDatumReader.java:363)
>  ~[avro-1.7.7.jar:1.7.7]
>   at 
> org.apache.avro.generic.GenericDatumReader.readString(GenericDatumReader.java:355)
>  ~[avro-1.7.7.jar:1.7.7]
>   at 
> org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:157) 
> ~[avro-1.7.7.jar:1.7.7]
>   at 
> org.apache.avro.generic.GenericDatumReader.readField(GenericDatumReader.java:193)
>  ~[avro-1.7.7.jar:1.7.7]
>   at 
> org.apache.avro.generic.GenericDatumReader.readRecord(GenericDatumReader.java:183)
>  ~[avro-1.7.7.jar:1.7.7]
>   at 
>

[jira] [Updated] (NIFI-2841) SplitAvro Processor is Broken

2016-09-29 Thread David Hicks (JIRA) 

 [ 
https://issues.apache.org/jira/browse/NIFI-2841?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
 ]

David Hicks updated NIFI-2841:
--
Description: 
This is largely the fault of the Avro DataFileStream reader, but it's making 
the processor unusable.  The problem appears to occur when you make the 
following series of calls (which happens because of the splitSize comparison):
reader.next() -> returns last element
reader.hasNext() -> returns false
reader.hasNext() -> returns true
reader.next() -> EOFException

org.apache.nifi.processor.exception.ProcessException: IOException thrown from 
SplitAvro[id=22e03ca4-0151-4474-92fc-040e1fe12ab9]: java.io.EOFException
at 
org.apache.nifi.controller.repository.StandardProcessSession.write(StandardProcessSession.java:2013)
 ~[na:na]
at 
org.apache.nifi.processors.avro.SplitAvro$RecordSplitter$1.process(SplitAvro.java:250)
 ~[nifi-avro-processors-0.7.0.jar:0.7.0]
at 
org.apache.nifi.controller.repository.StandardProcessSession.read(StandardProcessSession.java:1851)
 ~[na:na]
at 
org.apache.nifi.controller.repository.StandardProcessSession.read(StandardProcessSession.java:1822)
 ~[na:na]
at 
org.apache.nifi.processors.avro.SplitAvro$RecordSplitter.split(SplitAvro.java:236)
 ~[nifi-avro-processors-0.7.0.jar:0.7.0]
at 
org.apache.nifi.processors.avro.SplitAvro.onTrigger(SplitAvro.java:202) 
~[nifi-avro-processors-0.7.0.jar:0.7.0]
at 
org.apache.nifi.processor.AbstractProcessor.onTrigger(AbstractProcessor.java:27)
 [nifi-api-0.7.0.jar:0.7.0]
at 
org.apache.nifi.controller.StandardProcessorNode.onTrigger(StandardProcessorNode.java:1054)
 [nifi-framework-core-0.7.0.jar:0.7.0]
at 
org.apache.nifi.controller.tasks.ContinuallyRunProcessorTask.call(ContinuallyRunProcessorTask.java:136)
 [nifi-framework-core-0.7.0.jar:0.7.0]
at 
org.apache.nifi.controller.tasks.ContinuallyRunProcessorTask.call(ContinuallyRunProcessorTask.java:47)
 [nifi-framework-core-0.7.0.jar:0.7.0]
at 
org.apache.nifi.controller.scheduling.TimerDrivenSchedulingAgent$1.run(TimerDrivenSchedulingAgent.java:127)
 [nifi-framework-core-0.7.0.jar:0.7.0]
at 
java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) 
[na:1.8.0_101]
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308) 
[na:1.8.0_101]
at 
java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
 [na:1.8.0_101]
at 
java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
 [na:1.8.0_101]
at 
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) 
[na:1.8.0_101]
at 
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) 
[na:1.8.0_101]
at java.lang.Thread.run(Thread.java:745) [na:1.8.0_101]
Caused by: java.io.EOFException: null
at 
org.apache.avro.io.BinaryDecoder.ensureBounds(BinaryDecoder.java:473) 
~[avro-1.7.7.jar:1.7.7]
at org.apache.avro.io.BinaryDecoder.readInt(BinaryDecoder.java:128) 
~[avro-1.7.7.jar:1.7.7]
at org.apache.avro.io.BinaryDecoder.readString(BinaryDecoder.java:259) 
~[avro-1.7.7.jar:1.7.7]
at 
org.apache.avro.io.ResolvingDecoder.readString(ResolvingDecoder.java:201) 
~[avro-1.7.7.jar:1.7.7]
at 
org.apache.avro.generic.GenericDatumReader.readString(GenericDatumReader.java:363)
 ~[avro-1.7.7.jar:1.7.7]
at 
org.apache.avro.generic.GenericDatumReader.readString(GenericDatumReader.java:355)
 ~[avro-1.7.7.jar:1.7.7]
at 
org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:157) 
~[avro-1.7.7.jar:1.7.7]
at 
org.apache.avro.generic.GenericDatumReader.readField(GenericDatumReader.java:193)
 ~[avro-1.7.7.jar:1.7.7]
at 
org.apache.avro.generic.GenericDatumReader.readRecord(GenericDatumReader.java:183)
 ~[avro-1.7.7.jar:1.7.7]
at 
org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:151) 
~[avro-1.7.7.jar:1.7.7]
at 
org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:142) 
~[avro-1.7.7.jar:1.7.7]
at org.apache.avro.file.DataFileStream.next(DataFileStream.java:233) 
~[avro-1.7.7.jar:1.7.7]
at 
org.apache.nifi.processors.avro.SplitAvro$RecordSplitter$1$1.process(SplitAvro.java:259)
 ~[nifi-avro-processors-0.7.0.jar:0.7.0]
at 
org.apache.nifi.controller.repository.StandardProcessSession.write(StandardProcessSession.java:1998)
 ~[na:na]
... 17 common frames omitted


  was:
This is largely the fault of the Avro DataFileStream reader, but it's making 
the processor unusable.  The problem appears to occur when you make the 
following series of calls (which happens because of the splitSize comparison):
reader.next() -> returns last element
reader.hasNext() -> returns false
reader.hasNext() ->