From: Imran M Yousuf <imyousuf@gmail.com>
To: "Shawn O. Pearce" <spearce@spearce.org>
Cc: git@vger.kernel.org, egit-dev@eclipse.org,
Imran M Yousuf <imyousuf@smartitengineering.com>
Subject: Re: [JGit-io-RFC-PATCH v2 2/4] Add JGit IO SPI and default implementation
Date: Tue, 13 Oct 2009 08:30:45 +0700 [thread overview]
Message-ID: <7bfdc29a0910121830y4dc9b3efpe17860e04457988d@mail.gmail.com> (raw)
In-Reply-To: <20091012145741.GM9261@spearce.org>
On Mon, Oct 12, 2009 at 9:57 PM, Shawn O. Pearce <spearce@spearce.org> wrote:
> imyousuf@gmail.com wrote:
>> The SPI mainly focus's in providing an API to JGit to be able to perform
>> similar operations to that of java.io.File. All direct I/O is based on the
>> java.io.Input/OutputStream classes.
>>
>> Different JGit IO SPI provider is designed to be URI scheme based and thus
>> the default implementation is that of "file" scheme. SPI provider will be
<snip />
> I think this may be a bit in the wrong direction for what we are
> trying to accomplish.
>
> A number of people really want to map Git onto what is essentially
> Google's BigTable schema. Aside from Google's own BigTable product
> (which I want to use Git on at work, because it would vastly simplfiy
> my system administration duties at $DAYJOB) there is Cassandra and
> Hadoop HBase which implement the same schema semantics.
>
> None of those systems implement file streams, they implement cell
> storage in a non-transactional system with a semi-dynamic schema.
>
> Some people have built transactional semantics on top of these
> storage layers, e.g. Google AppEngine provides multiple row
> transactions through some magic sauce layered on top of BigTable.
> I'm sure people will build similar tools on top of Cassandra
> and HBase.
>
> Where I'm trying to go with this is that things that are stored
> in files on the filesystem in traditional Git wouldn't normally be
> mapped into "byte streams" in a BigTable-ish system, or even the
> JDBC-ish system you were describing.
>
> For .git/config we might want to map config variable names into
> keys in the table, with values stored in cells. This makes it
> easier to query or edit the data.
>
> Fortunately, "Config" is abstract enough that we could subclass
> it with a CassandraConfig and simply use that instance when on a
> based Cassandra storage system. No file streams required. Ditto
> for a JdbcConfig.
>
Firstly, I am sorry but I am not intelligent enough to perceive, how
do the user decide which instance of Config to use? I personally think
that there is no API to achieve what you just mentioned :(; i.e. the
user will have know CassandraConfig directly. Secondly, I instead was
thinking of porting JGit for that matter to any system supporting
streams (not any specific sub-class of them), such HBase/BigTable or
HDFS anything.... Thirdly, I think we actually have several task in
hand and I would state them as -
1. First introduce the I/O API such that it completely replaces java.io.File
2. Secondly segregate persistence of for config (or config like
objects) and introduce a SPI for them for smarter storage.
I am not thinking of storing "only" the bare content of a git
repository, but I intent to be able to also store the versioned
contents it self as well. If we choose the above 2 steps I mentioned I
am of the opinion that we will be able
to achieve both our ideas. In addition I hope that if one day Git
itself introduces a similar I/O API then Git can also support the I/O
SPI implementations JGit will.
Waiting eagerly to learn what you think :).
Best regards,
Imran
> For RefDatabase, we'd want to do the same and avoid the concept of
> packed-refs altogether. Each Ref should go into its own row in a
> Cassandra storage system, and essentially act as a loose object.
> Ditto with JDBC.
>
> We'd probably never need to read-or-write the info/refs or
> objects/info/packs listings.
>
> And I think that's everything that a bare repository needs, aside
> from ObjectDatabase, which is already mostly abstract anyway.
>
> --
> Shawn.
>
--
Imran M Yousuf
Entrepreneur & Software Engineer
Smart IT Engineering
Dhaka, Bangladesh
Email: imran@smartitengineering.com
Blog: http://imyousuf-tech.blogs.smartitengineering.com/
Mobile: +880-1711402557
next prev parent reply other threads:[~2009-10-13 1:37 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-10-11 14:07 [JGit-io-RFC-PATCH v2 1/4] Introduce a new module for IO SPI of JGit imyousuf
2009-10-11 14:07 ` [JGit-io-RFC-PATCH v2 2/4] Add JGit IO SPI and default implementation imyousuf
2009-10-11 14:07 ` [JGit-io-RFC-PATCH v2 3/4] Incorporate current FileSystem Util implementations to the SPI imyousuf
2009-10-11 14:07 ` [JGit-io-RFC-PATCH v2 4/4] Add locking capability to the IO SPI based on Java Concurrency Lock API imyousuf
2009-10-12 14:57 ` [JGit-io-RFC-PATCH v2 2/4] Add JGit IO SPI and default implementation Shawn O. Pearce
2009-10-13 1:30 ` Imran M Yousuf [this message]
2009-10-13 15:15 ` Shawn O. Pearce
2009-10-13 15:59 ` Imran M Yousuf
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