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Posted to dev@samza.apache.org by Jagadish Venkatraman <ja...@gmail.com> on 2016/09/01 02:49:45 UTC
Re: Review Request 51346: SAMZA-974 - Support finite datasources in
Samza that have a notion of End-Of-Stream
> 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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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
>
>