Hi all,
As mentioned on the E4 call today, I'd like to bring up the
idea of "lazy resources" once again.
I had mentioned this at the end of my E-Mail on Oct 7 already,
but it was somehow hidden beneath the other stuff.
The background is, I noticed that we were talking about pushing
down a variety of stuff from the Resource layer into the File
System Layer. Which might work for some stuff (like meta info,
and markers though I'd not be sure about the life cycle of markers
when a file gets renamed) and certainly won't work for others such
as delta notifications (which just won't work without state).
So I was wondering why we don't do it the other way round, and
allow a kind of IResource that is more loosely connected to the
Workspace (by means of having been visited before, like with an
external editor), and that's not eagerly refreshed like the resources
we know in the workspace.
Today, Resources are problematic with EFS-shared slow, remote,
huge file systems sice the eager deep refresh would generate
masses of data that's not necessary. We should think about a
kind (flag) of IResource that's more loosely connected to the
Workspace.
Does that make sense? - McQ argued that he's concerned about
making the (currently easily understood) resource model overly
complex, and about unclear user experience with such afeature.
I could imagine using Lazy Resources for
* Object files when no incremental build is desired
(we don't care about update notifications in this case)
* Static, frozen, read-only reference file systems where we
*know* nothing will change
In some sense, such a lazy resource is nothing other than
a Linked Resource to a file in a hidden project. Could we
solve this in a more elegant manner?
Discussion is opened, any thoughts?
Cheers,
--
Martin Oberhuber, Senior Member of Technical Staff, Wind River
Target Management Project Lead, DSDP PMC Member
http://www.eclipse.org/dsdp/tm
________________________________
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of
Oberhuber, Martin
Sent: Tuesday, October 07, 2008 7:16 PM
To: E4 developer list
Subject: [eclipse-incubator-e4-dev] [resources] File system
layerrequirements
Hi all,
I had some thoughts about the Strawman proposal, and the file
system
layer in particular.
*
We have a requirement to extend usability of Eclipse
tools beyond the Workspace. Bugs are open which request, for instance,
capabilities to Search files and folders outside the workspace, open
editors, add markers, ... apparently, we'll want to do all that on the
Filesystem layer.
*
Given that, the Filesystem layer must be stateless (we
cannot maintain state in memory for a tree that can become arbitrarily
large, since that wouldn't scale). The Filesystem layer must take its
information from the filesystem alone, and nowhere else. Which seems to
tie in nicely with ideas of having the FS layer RESTful.
*
If the Filesystem layer is stateless, we cannot push
down any resource deltas, since these require state ("before" vs "after"
the change). The Resources (Project) layer would remain the one which
holds state just as it does today.
*
I like the idea of pushing down metadata such that (a)
markers can live outside the workspace on FS objects, and (b) file
system capabilities for storing metadata such as Encoding or content
type can be leveraged. Perhaps that metadata layer could even be totally
separate from both FS Layer and Resource layer, linked with them through
URI as the identifier, and some resource delta callbacks for lifecycle
management. The other option is to leave it with the Resource layer, but
make it lazy (see below).
*
This brings up the question, where we really need to
beef up the FS layer? I actually don't see much need for this, except
for
(a) adding asynchronous support if needed ... though
that brings up other questions (see my other E-Mail), and
(b) adding an IFileStore#getCanonicalPath() API which we
clearly need for Alias resolution.
*
I think that we can not have full Alias Management on
the FS Layer, because:
1.) one requirement of Alias management is that given
some file X, you need to know "who else links to X?".
2.) Now that kind of "reverse lookup" of symbolic links
is not supported by file systems, so it must be solved in code.
3.) That, again, requires that clients have "expressed
interest" in X before, which is adding state to the file system, which
we cannot have on the FS layer.
I think that we need to keep Alias Management on the
Resource/Project layer, supported by the getCanonicalPath() API on the
FS layer. In order to still support Alias Management for items outside
the workspace (that have been looked at before), we'll probably want
some "lazy addition to Workspace" paradigm which adds files and folders
to the workspace as they are being visited (and probably removes them
again after some time with an LRU paradigm).
Now that being said, it looks for me as if the necessary
enhancements on the FS layer could even be done in the Eclipse 3.5
Stream (adding IFileStore#getCanonicalPath()).
Or am I missing any requirements on the FS Layer?
Cheers,
--
Martin Oberhuber, Senior Member of Technical Staff, Wind River
Target Management Project Lead, DSDP PMC Member
http://www.eclipse.org/dsdp/tm
.
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