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From Tim van Heugten <sti...@gmail.com>
Subject Re: MemPipeline and context
Date Tue, 05 Feb 2013 14:38:33 GMT
Hmmm,

So we had a mistake in our code that emitted the data in both branches
before union2.
*And*, the crunch union also *failed to merge the data* in some
circumstance. My side-remark about not seeing the join happen was actually
bang on.. :-/

So the question now becomes, when does a union ignore one of its incoming
branches?
Apparently with materialization in the right spots we can force the correct
pipeline(*).

Cheers,

Tim van Heugten


*) Thereby exposing our bug, seemingly data duplication. But just to be
clear, this is actually the *correct* behavior.


On Tue, Feb 5, 2013 at 3:18 PM, Tim van Heugten <stimme@gmail.com> wrote:

> Hi,
>
> It turns out the data in the two branches that are unioned in union2 is
> not mutually exclusive (counter to what I was expecting). Probably we
> should expect data duplication.
>
> However, this does still not explain why sometimes we find data
> duplication and sometimes we don't.
>
> Will keep you posted,
>
> Tim
>
>
> On Tue, Feb 5, 2013 at 11:32 AM, Tim van Heugten <stimme@gmail.com> wrote:
>
>> Hi Gabriel,
>>
>> I've been unsuccessful so far to reproduce the issue in a controlled
>> environment. As said, its fragile, maybe the types involved play a role, so
>> when I tried to simplify those I broke the failure condition.
>> I decide it's time to try providing more information without giving an
>> explicit example.
>>
>> The pipeline we build is illustrated here: http://yuml.me/8ef99512.
>> Depending on where we materialize the data occurs twice in UP.
>> The EITPI job filters the exact opposite of the filter branch. In PWR
>> only data from EITPI is passed through, while the PITP data is used to
>> modify it.
>> Below you find the job names as executed when dataduplication occurs,
>> materializations occur before BTO(*) and after UP.
>>
>> "Avro(target/stored/sIPhase)+EITPI+GBK+PITEI+Avro(/tmp/crunch655004156/p4)"
>>
>> "[[Avro(target/stored/sIPhase)+PITP]/[Avro(/tmp/crunch655004156/p4)]]+GBK+PWR+UnionCollectionWrapper+Avro(/tmp/crunch655004156/p2)"
>>
>> "[[Avro(target/stored/sIPhase)+PITP]/[Avro(/tmp/crunch655004156/p4)]]+GBK+PWR+BTO+Avro(/tmp/crunch655004156/p8)"
>>
>> "[[Avro(target/stored/sIPhase)+S0+BTO]/[Avro(/tmp/crunch655004156/p8)]]+GBK+UP+Avro(/tmp/crunch655004156/p6)"
>> "Avro(/tmp/crunch655004156/p6)+GetData+Avro(/tmp/crunch655004156/p10)"
>> "Avro(/tmp/crunch655004156/p6)+GetTraces+Avro(target/trace-dump/traces)"
>>
>> Here are the jobs performed when materialization is added between BTO and
>> gbk:
>>
>> "Avro(target/stored/sIPhase)+EITPI+GBK+PITEI+Avro(/tmp/crunch-551174870/p4)"
>>
>> "[[Avro(target/stored/sIPhase)+PITP]/[Avro(/tmp/crunch-551174870/p4)]]+GBK+PWR+UnionCollectionWrapper+Avro(/tmp/crunch-551174870/p2)"
>>
>> "[[Avro(target/stored/sIPhase)+PITP]/[Avro(/tmp/crunch-551174870/p4)]]+GBK+PWR+BTO+Avro(/tmp/crunch-551174870/p6)"
>> "Avro(/tmp/crunch-551174870/p6)+GBK+UP+Avro(/tmp/crunch-551174870/p8)"
>> "Avro(/tmp/crunch-551174870/p8)+GetData+Avro(/tmp/crunch-551174870/p10)"
>> "Avro(/tmp/crunch-551174870/p8)+GetTraces+Avro(target/trace-dump/traces)"
>>
>> Without changing changing anything else, the added materialization fixes
>> the issue of data duplication.
>>
>> If you have any clues how I can extract a clean working example I'm happy
>> to hear.
>>
>>
>> *) This materialization probably explains the second job, however, where
>> the filtered data is joined is lost on me. This is not the cause though,
>> with just one materialize at the end, after UP, the data count still
>> doubled. The jobs then look like this:
>>
>> "Avro(target/stored/sIPhase)+EITPI+GBK+PITEI+Avro(/tmp/crunch369510677/p4)"
>>
>> "[[Avro(target/stored/sIPhase)+PITP]/[Avro(/tmp/crunch369510677/p4)]]+GBK+PWR+BTO+Avro(/tmp/crunch369510677/p6)"
>>
>> "[[Avro(target/stored/sIPhase)+S0+BTO]/[Avro(/tmp/crunch369510677/p6)]]+GBK+UP+Avro(/tmp/crunch369510677/p2)"
>> "Avro(/tmp/crunch369510677/p2)+GetTraces+Avro(target/trace-dump/traces)"
>> "Avro(/tmp/crunch369510677/p2)+GetData+Avro(/tmp/crunch369510677/p8)"
>>
>> BR,
>>
>> Tim van Heugten
>>
>>
>> On Thu, Jan 31, 2013 at 9:27 PM, Gabriel Reid <gabriel.reid@gmail.com>wrote:
>>
>>> Hi Tim,
>>>
>>> On 31 Jan 2013, at 10:45, Tim van Heugten <stimme@gmail.com> wrote:
>>>
>>> > Hi Gabriel,
>>> >
>>> > For the most part it is similar to what was send around recently on
>>> this mailinglist, see:
>>> > From  Dave Beech <d...@paraliatech.com>
>>> > Subject       Question about mapreduce job planner
>>> > Date  Tue, 15 Jan 2013 11:41:42 GMT
>>> >
>>> > So, the common path before multiple outputs branch is executed twice.
>>> Sometimes the issues seem related to unions though, i.e. multiple inputs.
>>> We seem to have been troubled by a grouped table parallelDo on a
>>> table-union-gbk that got its data twice (all grouped doubled in size).
>>> Inserting a materialize between the union and groupByKey solved the issue.
>>> >
>>> > These issues seem very fragile (so they're fixed easily by changing
>>> something that's irrelevant to the output), so usually we just add or
>>> remove a materialization to make it run again.
>>> > I'll see if I can cleanly reproduce the data duplication issue later
>>> this week.
>>>
>>> Ok, that would be great if you could replicate it in a small test,
>>> thanks!
>>>
>>> - Gabriel
>>
>>
>>
>

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