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From "Massimilian Mattetti" <MASSI...@il.ibm.com>
Subject Re: java.lang.NoClassDefFoundError with fields of custom Filter
Date Thu, 07 Jul 2016 17:49:54 GMT
Hi Jim,

the approach of using namespace from HDFS looks promising. I need to 
investigate a little on how it works but I guess I will take your advice.
Thank you.

Cheers,
Massimiliano




From:   James Hughes <jnh5y@virginia.edu>
To:     user@accumulo.apache.org
Date:   07/07/2016 08:28 PM
Subject:        Re: java.lang.NoClassDefFoundError with fields of custom 
Filter



Hi Massimiliano, 

I'm a fan of producing uber jars for this kind of thing; we do that for 
GeoMesa.  There is one gotcha which can come up:  if you have several uber 
jars in lib/ext, they can collide in rather unexpected ways.

There are two options to call out:

First, Accumulo has support for loading jars from HDFS into namespaces.  
With that, you could have various namespaces for different versions or 
different collections of iterator projects.  If you are sharing a dev 
cloud with other projects or co-workers working on the same project that 
can be helpful since it would avoid restarts, etc.  Big thumbs-up for this 
approach!

Second, rather than having an uber jar, you could build up zip files with 
the various jars you need for your iterators and unzip them in lib/ext.  
If you did that for multiple competing iterator projects, you'd avoid 
duplication of code inside uber-jars.  Also, you'd be able to see if there 
are 8 versions of Log4J and Guava in lib/ext...;)  It wouldn't be as 
powerful as the namespace, but there's something nice about having a 
low-tech approach.

Others will likely have varied experiences; I'm not sure if there's an 
established 'best practice' here.

Cheers,

Jim

On Thu, Jul 7, 2016 at 12:56 PM, Massimilian Mattetti <MASSIMIL@il.ibm.com
> wrote:
Thanks for your prompt response, you are right Jim. There is a static 
dependency to Log4J in my lexicoder. Adding the Log4J Jar to the classpath 
solved the problem.
Would you suggest to use an Uber Jar to avoid this kind of problems?

Regards,
Massimiliano




From:        James Hughes <jnh5y@virginia.edu>
To:        user@accumulo.apache.org
Date:        07/07/2016 06:25 PM
Subject:        Re: java.lang.NoClassDefFoundError with fields of custom 
Filter




Hi Massimilian, 

As a quick note, your error says that it could not initialize class 
accumulo.lexicoders.MyLexicoder.  Did you provide all the dependencies for 
your class on Accumulo's classpath?  

That exception (or similar) can occur if there is a static block in your 
MyLexicoder class which can't run properly.

Cheers,

Jim


On Thu, Jul 7, 2016 at 11:19 AM, Massimilian Mattetti <MASSIMIL@il.ibm.com
> wrote:
Hi,

I have implemented a custom filter and a custom lexicoder. Both this two 
classes are packed in the same jar that has been deployed under the 
directory $ACCUMULO_HOME/lib/extof my Accumulo servers (version 1.7.1). 
The lexicoder is used by the filter to get the real object from the 
accumulo value and test some conditions on it. When I tried to scan the 
table applying this filter I got the following exception:

Caused by: java.lang.NoClassDefFoundError: Could not initialize class 
accumulo.lexicoders.MyLexicoder
        at accumulo.filters.MyFilter.<init>(MyFilter.java:24)
        at sun.reflect.GeneratedConstructorAccessor9.newInstance(Unknown 
Source)
        at 
sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
        at java.lang.Class.newInstance(Class.java:442)
        at 
org.apache.accumulo.core.iterators.IteratorUtil.loadIterators(IteratorUtil.java:261)
        at 
org.apache.accumulo.core.iterators.IteratorUtil.loadIterators(IteratorUtil.java:237)
        at 
org.apache.accumulo.core.iterators.IteratorUtil.loadIterators(IteratorUtil.java:218)
        at 
org.apache.accumulo.core.iterators.IteratorUtil.loadIterators(IteratorUtil.java:205)
        at 
org.apache.accumulo.tserver.tablet.ScanDataSource.createIterator(ScanDataSource.java:193)
        at 
org.apache.accumulo.tserver.tablet.ScanDataSource.iterator(ScanDataSource.java:127)
        at 
org.apache.accumulo.core.iterators.system.SourceSwitchingIterator.seek(SourceSwitchingIterator.java:180)
        at 
org.apache.accumulo.tserver.tablet.Tablet.nextBatch(Tablet.java:880)
        at 
org.apache.accumulo.tserver.tablet.Scanner.read(Scanner.java:98)
        at 
org.apache.accumulo.tserver.scan.NextBatchTask.run(NextBatchTask.java:69)
        at 
org.apache.htrace.wrappers.TraceRunnable.run(TraceRunnable.java:57)
        ... 4 more


 I do not undestand how it is possible that the class loader is able to 
find the filter and no the lexicoder. Am I missing something?

Thanks,
Massimiliano









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