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From Jagadish Venkatraman <jagadish1...@gmail.com>
Subject Re: Review Request 51346: SAMZA-974 - Support finite datasources in Samza that have a notion of End-Of-Stream
Date Thu, 01 Sep 2016 02:49:45 GMT


> On Aug. 26, 2016, 7:51 p.m., Chris Pettitt wrote:
> > samza-api/src/main/java/org/apache/samza/system/IncomingMessageEnvelope.java, line
31
> > <https://reviews.apache.org/r/51346/diff/4/?file=1486375#file1486375line31>
> >
> >     How likely are we to collide with this? Thats the problem with using a user
definable token. I see two options:
> >     
> >     If null is not supported (and thus not usable by user-defined implementations)
I would use that and mark it as reserved.
> >     
> >     Otherwise I would probably do something more to make this unlikely to collide
(call me paranoid). Something like use a NUL byte as the first character and document that
offsets with such an encoding are reserved. I would also check that this sort of string doesn't
make it to user code in the task.
> 
> Jagadish Venkatraman wrote:
>     Returning a null is not possible (because a null offset could mean that we don't
have messages at this moment instead of meaning end-of-stream. While we should poll again
when a consumer returns null, we should not for the END_OF_STREAM case.) Hence, I was hoping
to use a special offset.
>     
>     I like your suggestion of using a NUL byte as the first character (and calling that
out). I'll update the RB with that.

There seem to be inter-operability versions of strings in Java vs strings in scala (esp -
around handling NUL bytes in the string- Scala appears to strip out NUL bytes). Hence, I've
used a "SAMZA_INTERNAL_END_OF_STREAM" as a string. Let me know if there's a better way to
handle this.


- Jagadish


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https://reviews.apache.org/r/51346/#review147015
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On Aug. 30, 2016, 12:32 a.m., Jagadish Venkatraman wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/51346/
> -----------------------------------------------------------
> 
> (Updated Aug. 30, 2016, 12:32 a.m.)
> 
> 
> Review request for samza, Boris Shkolnik, Chris Pettitt, Yi Pan (Data Infrastructure),
Navina Ramesh, and Xinyu Liu.
> 
> 
> Repository: samza
> 
> 
> Description
> -------
> 
> Samza currently works with unbounded data sources (kafka streams). However, for bounded
data sources like HDFS files, snapshot files which are not infinite, we need a notion of 'end-of-stream'.

> 
> This is a step towards realizing a 'finite' Samza job that terminates once data processing
is complete.(as opposed to an infinite stream job that keeps running)  
> 
> RB changes:
> - New interface for EndOfStreamListener
> - New 'end-of-stream' state in the state-machine of AsyncStreamTask (Invariant: When
end-of-stream is reached there are no buffered messages, no-callbacks are in-flight and no-window
or commit call shall be in progress)
> - Changes to allow clean shut-downs of the tasks/container/job for end-of-stream.
> 
> Design Doc and Implementation Notes: https://issues.apache.org/jira/secure/attachment/12825119/ProposalforEndofStreaminSamza.pdf
> 
> 
> Diffs
> -----
> 
>   build.gradle 1d4eb74b1294318db8454631ddd0901596121ab2 
>   samza-api/src/main/java/org/apache/samza/system/IncomingMessageEnvelope.java cc860cf7eb4d514736913c1dceaa80534b61d71a

>   samza-api/src/main/java/org/apache/samza/system/SystemStreamPartitionIterator.java
a8f858aa7e4f4ce436f450cf439fe1a102983c64 
>   samza-api/src/main/java/org/apache/samza/task/EndOfStreamListenerTask.java PRE-CREATION

>   samza-core/src/main/java/org/apache/samza/task/AsyncRunLoop.java a510bb0c5914c772438930d27f100b4d360c1296

>   samza-core/src/main/java/org/apache/samza/task/AsyncStreamTaskAdapter.java 1fc645673b7547b642830df5639c0b4fcd11c0d5

>   samza-core/src/main/scala/org/apache/samza/container/TaskInstance.scala 89f6857014489aba2db4129bc2e26dfec5b10652

>   samza-core/src/test/java/org/apache/samza/task/TestAsyncRunLoop.java ca913dea79fecbcecdfd1010dc794318055c5764

> 
> Diff: https://reviews.apache.org/r/51346/diff/
> 
> 
> Testing
> -------
> 
> Unit tests to test scenarios for inorder processing, out-of-order processing and commit
semantics.
> 
> 
> Thanks,
> 
> Jagadish Venkatraman
> 
>


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