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From Renato Marroquín Mogrovejo <renatoj.marroq...@gmail.com>
Subject Re: Should MongoDB know about Utf8?
Date Fri, 10 Oct 2014 13:52:56 GMT
They are deserialized out of Mongo but as a set of MongoResult objects and
not as WebPages.


2014-10-10 15:17 GMT+02:00 Tyler Palsulich <tpalsulich@gmail.com>:

> > MongoDb doesn’t support Serializable interface.
>
> You're right. My mistake. Even if it was, Utf8 implementing Serializable
> isn't an option.
>
> > I end up with a bunch of MongoResults instead of WebPages
>
> Are the WebPages "serialized" into Mongo, but not out of Mongo?
>
> Tyler
>
> On Fri, Oct 10, 2014 at 5:37 AM, Renato Marroquín Mogrovejo <
> renatoj.marroquin@gmail.com> wrote:
>
> > Hi guys,
> >
> > So I have just tried putting and getting elements (Nutch's WebPage)
> > entries specifically and everything works fine. So this is confusing, I
> > guess Nutch is doing something in the middle there that may have to do
> with
> > the mapping file or something like it. Because I tried changing the key
> > type (from String to Utf8) and gave an unrelated error saying that the
> > collection hadn't been defined (which is not true), I would have expected
> > to get a classCastException. And the other weird thing is that when
> > performing a get using a query object I end up with a bunch of
> MongoResults
> > instead of WebPages. I think that is bug (or . . . a feature) that we are
> > not aware of. Maybe Damian can help us out here.
> > I will keep on pocking around, but gora-mongodb is getting the data in,
> > and it is able to take it out.
> >
> >
> > Renato M.
> >
> > 2014-10-10 9:17 GMT+02:00 Kiril Menshikov <post@kiril.me>:
> >
> >> Tyler,
> >>
> >> MongoDb doesn’t support Serializable interface. BasicBSONEncoder has
> >> direct class checks. Unfortunately it's not enough to make Utf8
> >> serializable.
> >>
> >> -Kiril
> >>
> >> On Oct 9, 2014, at 21:44, Lewis John Mcgibbney <
> lewis.mcgibbney@gmail.com>
> >> wrote:
> >>
> >> > Hi Folks,
> >> > Whilst in the muddle of upgrading Nutch 2.3-SNAPSHOT to use Gora 0.5
> >> we've run into a problem when implementing the gora-mongodb stuff.
> >> > The issue is described within the Jira issue [0]. This being said,
> >> Kiril (CC'd) has stated quite clearly why this is happening. This is a
> >> consequence of the following lines of the Nutch code base
> >> >
> >> >
> >>
> https://github.com/apache/nutch/blob/2.x/src/java/org/apache/nutch/fetcher/FetcherJob.java#L218
> >> >
> >> >
> >>
> https://github.com/apache/nutch/blob/2.x/src/java/org/apache/nutch/parse/ParserJob.java#L274
> >> >
> >> >
> >>
> https://github.com/apache/nutch/blob/2.x/src/java/org/apache/nutch/crawl/DbUpdaterJob.java#L128
> >> >
> >> > and results in the following stack trace
> >> > java.lang.IllegalArgumentException: can't serialize class
> >> org.apache.avro.util.Utf8
> >> > at
> org.bson.BasicBSONEncoder._putObjectField(BasicBSONEncoder.java:284)
> >> > at org.bson.BasicBSONEncoder.putObject(BasicBSONEncoder.java:185)
> >> > at org.bson.BasicBSONEncoder.putObject(BasicBSONEncoder.java:131)
> >> > at com.mongodb.DefaultDBEncoder.writeObject(DefaultDBEncoder.java:33)
> >> > at com.mongodb.OutMessage.putObject(OutMessage.java:289)
> >> > at com.mongodb.OutMessage.writeQuery(OutMessage.java:211)
> >> > at com.mongodb.OutMessage.query(OutMessage.java:86)
> >> > at com.mongodb.DBCollectionImpl.find(DBCollectionImpl.java:81)
> >> > at com.mongodb.DBCollectionImpl.find(DBCollectionImpl.java:66)
> >> > at com.mongodb.DBCursor._check(DBCursor.java:458)
> >> > at com.mongodb.DBCursor._hasNext(DBCursor.java:546)
> >> > at com.mongodb.DBCursor.hasNext(DBCursor.java:571)
> >> > at
> >>
> org.apache.gora.mongodb.query.MongoDBResult.nextInner(MongoDBResult.java:69)
> >> > at org.apache.gora.query.impl.ResultBase.next(ResultBase.java:114)
> >> > at
> >>
> org.apache.gora.mapreduce.GoraRecordReader.nextKeyValue(GoraRecordReader.java:119)
> >> > at
> >>
> org.apache.hadoop.mapred.MapTask$NewTrackingRecordReader.nextKeyValue(MapTask.java:531)
> >> > at
> >> org.apache.hadoop.mapreduce.MapContext.nextKeyValue(MapContext.java:67)
> >> > at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:144)
> >> > at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:764)
> >> > at org.apache.hadoop.mapred.MapTask.run(MapTask.java:364)
> >> > at
> >>
> org.apache.hadoop.mapred.LocalJobRunner$Job$MapTaskRunnable.run(LocalJobRunner.java:223)
> >> > at
> >> java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
> >> > at java.util.concurrent.FutureTask.run(FutureTask.java:262)
> >> > at
> >>
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
> >> > at
> >>
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
> >> > at java.lang.Thread.run(Thread.java:744)
> >> >
> >> > The cause is the following line (example from FetcherJob):
> >> > filter.getOperands().add(new Utf8(batchId));
> >> >
> >> > During serialization MongoDB doesn't know about Utf8 type.
> >> >
> >> > My question is now... should we remove the Utf8 from Nutch, or should
> >> gora-mongodb handle this silently?
> >> >
> >> > Thanks for reading.
> >> > Lewis
> >> >
> >> > [0] https://issues.apache.org/jira/browse/NUTCH-1843
> >> >
> >> > --
> >> > Lewis
> >>
> >>
> >
>

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