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From Alex Karasulu <aok...@bellsouth.net>
Subject Re: Embedding Eve Was: To release or not to release?
Date Tue, 23 Nov 2004 18:25:16 GMT
Hey Henri,

Henri Yandell wrote:

>
>
> On Mon, 22 Nov 2004, Martin Wegner wrote:
>
>>> We definitely have embeddability in mind.  The core stuff will be POJO
>>> and we'll provide, or help with, wrappers for well-known containers.
>>
>>
>> Great.  What I hope happens is that once Eve is working and is 
>> embeddable
>> that the Jarkarta teams will start to think about moving configuration
>> information from static XML/property files to Eve.  By doing so we would
>
>
> Hope so, I want to kill simple-jndi, which is what I currently use as 
> a way to embed a JNDI server for local configuration. Though, a big 
> part is that it sits on top of static XML/property files.
>
> What kind of files would you make for Eve? 

Eve has a modular backend subsystem where you plug in any kind of 
database implementation that could forseeably use any kind of file 
format for storing information.  The default database that Eve's system 
partition uses is based on JDBM which is a Java based implementation of 
UNIX dbm. However note that the file formats are not the same between 
JDBM and UNIX dbm.  JDBM resembles Sleepycat's JE product more so than 
UNIX dbm.  It's basically an API for B+Trees on secondary storage.

Eve creates a set of these files for various indices and the master 
table for any partition.  So there will be several files within a folder 
corresponding to a partition that hangs off of the namespace.  For 
example ou=system is for the system partition.  Also note a file is 
created for each user specified index as well.  This is done basically 
to keep the master db separate which can be used to regenerate all these 
indices.  It's one of two files you can use to rebuild the entire 
database with.  Most indices can be generated from it.

> My todo list has: attach commons-configuration to directory-naming, 
> though I've no idea whether it's workable. Does Eve have this stuff 
> already?
>
No but it's an excellent fit.  Personally I would stick to the less 
heavy weight flat files in commons configuration for small data sets.  
When you're data grows beyond 10K and needs to be searchable this is 
where the power of the BTree comes in handy. 

Now this is for the default JDBM based database. 

Enrique and I have been talking about building a Prevayler partition 
which keeps all in memory.  This might be an excellent lighter 
alternative to the B+Tree based partition implementation.  I really 
think Prevalyer is worth looking at.  Again this would be for moderate 
to large data sets.

Alex


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