Re: [RFC/PATCH 3/3] gitweb: Fill project details lazily when caching

[Jakub Narebski <jnareb@gmail.com>]

On Tue, 18 March 2008, Petr Baudis wrote:
> On Mon, Mar 17, 2008 at 04:09:30PM +0100, Jakub Narebski wrote:
>>
>> If caching is turned on project details can be filled in already from
>> the cache.  When refreshing project info details for all project (when
>> cache is stale and has to be refreshed) generate projects info only if
>> modification time (as returned by lstat()) of projects repository
>> gitdir changed.
>> 
>> This way we can avoid hitting repository refs, object database and
>> repository config at the cost of additional lstat.
>> 
>> Signed-off-by: Jakub Narebski <jnareb@gmail.com>
>> ---
>> This is an idea for further improvement of 'projects list caching'.
>> Could you please: 
>> 
>>  1.) comment if it is a good idea, or why it works, or why it
>>      couldn't work :),  
> 
> The idea is nice, but I'm surely missing something obvious again - why
> do you use lstat() as opposed to stat()?

Because in my home installation of gitweb (for tests) I have 
/home/local/scm/git.git symlinked to /home/jnareb/git/.git
And I want to follow changes in repository; link itself doesn't
change.

> And more importantly, the mtime 
> of projects repository unfortunately does not reflect almost any
> changes per se; you would need to check mtime of description file,
> config file and the refs instead.

Well, I had hopes that because git uses "write to temporary file, rename
temporary file to final name" to have atomic file writes any change in
git repository would be reflected in mtime of topdir / GIT_DIR. I have
checked it superficially... by doing a fetch, and a commit. But while
both fetch and commit manipulate files in top dir (FETCH_HEAD, ORIG_HEAD,
COMMIT_EDITMSG) it is not the case for push, unfortunately. If all
pushes would result in pack transfer, it would be enough to watch for
GIT_DIR/objects/pack/ directory.

I think that nothing short of inotify or equivalent would work: it is
just too many files/directories to watch for changes... I hope I am
mistaken here...

-- 
Jakub Narebski
Poland