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Date: Thu, 18 Jun 2009 14:38:23 -0700
Message-ID: <2bacf5dd0906181438x41d67446j3e17ad3dbaa604b1@mail.gmail.com>
Subject: Re: [vfs] MemcachedFilesCache for Google App Engine (object
	serialization)
From: "ralph.goers @dslextreme.com" <ralph.goers@dslextreme.com>
To: Commons Developers List <dev@commons.apache.org>
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No. The instructions are in
https://svn.apache.org/repos/asf/commons/proper/vfs/trunk/xdocs/testing.xml.


Ralph

On Thu, Jun 18, 2009 at 9:18 AM, Vince Bonfanti <vbonfanti@gmail.com> wrote:

> I'm finished with my changes to support serialization of AbstractFileName
> and AbstractFileObject. The unit tests that are executed via "mvn test" are
> all passing. I tried to do "mvn site:stage" as you suggest, but got
> out-of-memory errors. Is this the documentation I need to follow to run the
> external server tests?
>
>  http://commons.apache.org/vfs/testserver.html
>
> Thanks.
> On Thu, Jun 4, 2009 at 6:40 PM, Ralph Goers <ralph.goers@dslextreme.com
> >wrote:
>
> > Wow.  I'm interested to see if you can really get this to work. Just make
> > sure that after you get the existing unit tests to pass that the
> functional
> > tests that require external servers also pass - if you do a mvn
> site:stage
> > you will see the documentation on how to do that.
> >
> > VFS-245 is opened against AbstractFileName and probably needs to be dealt
> > with in the context of what you are doing.
> >
> >
> > On Jun 4, 2009, at 2:22 PM, Vince Bonfanti wrote:
> >
> > I'm investigating creating a memcached-based FilesCache implementation
> for
> >> use with Google App Engine. The basic obstacle is that this requires
> that
> >> all objects that are used as keys or values must be serializable. Before
> I
> >> go too far down this path, I'd like to know if this is a reasonable
> thing
> >> to
> >> do (or consider doing). Any thoughts or guidance would be greatly
> >> appreciated.
> >>
> >> Background info: the Google App Engine (GAE) environment is inherently
> >> distributed, where an unknown number of multiple instances of your
> >> servlet-based web application will be running at the same time. The
> GaeVFS
> >> project (http://gaevfs.appspot.com) implements a VFS plugin on top of
> the
> >> GAE datastore; this is needed because the "real" filesystem within GAE
> is
> >> read-only, so GaeVFS provides a writeable filesystem for use by
> >> applications. It seems that for proper operation of VFS, the FilesCache
> >> implementation used by GaeVFS should (must?) also be inherently
> >> distributed.
> >> Fortunately, GAE supplies a memcached API that will be perfect for this
> >> use
> >> (if I can solve the serialization problem).
> >>
> >> Here's my first cut at what classes I'd need to make serializable and
> some
> >> notes on which fields might be marked transient:
> >>
> >> *AbstractFileName*
> >> serialized fields: scheme (String), absPath (String), type (FileType)
> >> transient fields: uri, baseName, rootUri, extension, decodedPath
> >>
> >> *FileType*
> >> serialized fields: name (String), hasChildren (boolean), hasContent
> >> (boolean), hasAttrs (boolean)
> >> transient fields: none
> >>
> >> *AbstractFileObject*
> >> serialized fields: name (AbstractFileName), content (DefaultFileContent)
> >> transient fields: fs (AbstractFileSystem),  operation (FileOperations),
> >> attached (boolean), type (FileType), parent (FileObject), children
> >> (FileName[]), objects (List)
> >>
> >> It's very important the the fs (AbstractFileSystem) field be transient
> to
> >> limit the number of other classes that need to be made serializable. It
> >> looks like files are always retrieved from the files cache via the
> >> AbstractFileSystem.getFileFromCache() method; if so then the "fs" field
> of
> >> AbstractFileObject can be restored within this method and doesn't need
> to
> >> be
> >> serialized. We'll need to define a package-scope
> >> AbstractFileObject.setFileSystem() method to support this. Or, this
> could
> >> be
> >> done within the MemcachedFilesCache.getFile() method before returning
> the
> >> FileObject (but then we'd need a FileObject.setFileSystem method, or do
> >> some
> >> not-very-nice type casting).
> >>
> >> *DefaultFileContent
> >> *serialized fields: file (AbstractFileObject), attrs (Map), roAttrs
> (Map),
> >> fileContentInfo (FileContentInfo), fileContentInfoFactory
> >> (FileContentInfoFactory), openStreams (int)
> >> transient fields: threadData (ThreadLocal)
> >> question: what types do the "attrs" and "roAttrs" maps contain? are
> these
> >> serializable?
> >>
> > attrs and roAttrs contain attributes specific to the file system. For
> > example, Webdav contains what you would get back from a PROPFIND method.
> The
> > Jar file system seems to return values found in the jar manifest., etc.
> The
> > values I found would all be Strings but I can't guarantee it.
> >
> >>
> >> question: FileContentInfo and FileContentInforFactory are interfaces,
> what
> >> are the implementations of these?
> >>
> > DefaultFileContentInfo, FileContentInfoFileNameFactory,
> > HttpFileContentInfoFactory, MimeFileContentInfoFactory and
> > WebdavFileContentInfoFactory.
> >
> >
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> >
>

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