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 <[email protected]> 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 <[email protected]> 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 <[email protected]>wrote: >> >>> Hi Tim, >>> >>> On 31 Jan 2013, at 10:45, Tim van Heugten <[email protected]> wrote: >>> >>> > Hi Gabriel, >>> > >>> > For the most part it is similar to what was send around recently on >>> this mailinglist, see: >>> > From Dave Beech <[email protected]> >>> > 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 >> >> >> >
