From: Lea Wiemann <lewiemann@gmail.com>
To: Jakub Narebski <jnareb@gmail.com>
Cc: git@vger.kernel.org
Subject: Re: [PATCH] gitweb: use Git.pm, and use its parse_rev method for git_get_head_hash
Date: Sat, 31 May 2008 14:39:58 +0200 [thread overview]
Message-ID: <4841471E.2070302@gmail.com> (raw)
In-Reply-To: <m3lk1q24nb.fsf@localhost.localdomain>
Jakub Narebski wrote:
> But I'm not sure for example [that] parsing subroutines [that parse the
> output of the git commands should be in Git.pm].
>
> [...] IMVHO caching command output is bad idea. I'd rather have gitweb
> cache _parsed_ data (i.e. Perl structures).
Yes, I agree with you that parsed data should be cached, but for that
reason I think that the subroutine that parse git's output should be in
Git.pm, not in Gitweb:
If you want to cache parsed data, you need the caching layer in between
the application (= Gitweb) and the repository access layer (= command
output parsing), or you would have to insert cache code at every call to
the repository access layer. So you end up with these layers:
(Layer 0: Front-end [HTML] caching.)
Layer 1: Application (Gitweb)
Layer 2: Back-end caching
Layer 3: Repository access (command parsing)
Layer 4: Calls to the git binary
Layer 3 and 4 are application-independent (i.e. not Gitweb specific),
and since they form a usable API, they might as well be written as a
separate API rather than lumped together with Gitweb. Git.pm is a start
of such an API (it does layer 4 and a little bit of layer 3), so it
seems natural for me to extend it.
Layer 2 is application-independent as well, so it can become an extra
class in Git.pm or a separate module. (It should stay independent of
layers 3 and 4).
We may need to have an explicitly implemented layer 0 (front-end
caching) in Gitweb for at least a subset of pages (like project pages),
but we'll see if that's necessary.
> Caching git command output (something like IPC::Cmd::Cached?)
> would only repeat bad I/O patterns of git commands.
I hope you're not assuming that the back-end cache will reside on disk
-- the problem is IO throughput, so having a cache on disk can really
only work for a front-end cache. For the back-end cache, we *will* have
to use a memory cache (or no cache at all).
> P.S. Here it is what could go [from Gitweb] to Git.pm: [snip]
Good points, I agree those should eventually be moved to Git.pm. (They
are not my priority at the moment, since I really want to implement
caching. So unless they move naturally as part of my refactoring, I'll
leave them in Gitweb for now.)
-- Lea
next prev parent reply other threads:[~2008-05-31 12:41 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-05-30 23:00 [PATCH] gitweb: use Git.pm, and use its parse_rev method for git_get_head_hash Lea Wiemann
2008-05-30 23:03 ` Lea Wiemann
2008-05-31 9:40 ` Jakub Narebski
2008-05-31 12:39 ` Lea Wiemann [this message]
2008-06-01 22:19 ` Jakub Narebski
2008-06-02 5:35 ` Junio C Hamano
2008-06-02 9:29 ` Petr Baudis
2008-06-02 21:32 ` Jakub Narebski
2008-06-02 22:31 ` Lea Wiemann
2008-05-31 13:04 ` Petr Baudis
2008-05-31 14:19 ` [PATCH v2] " Lea Wiemann
2008-05-31 14:34 ` Lea Wiemann
2008-06-01 8:23 ` Junio C Hamano
2008-06-01 15:44 ` Lea Wiemann
2008-06-01 21:33 ` Junio C Hamano
2008-06-01 22:16 ` [PATCH] test-lib.sh: set PERL5LIB instead of GITPERLLIB Lea Wiemann
2008-06-02 5:17 ` Junio C Hamano
2008-06-02 14:08 ` Lea Wiemann
2008-06-02 14:13 ` [PATCH v2] " Lea Wiemann
2008-06-02 20:01 ` Junio C Hamano
2008-06-02 22:19 ` Lea Wiemann
2008-06-03 0:20 ` [PATCH] " Lea Wiemann
2008-06-01 23:18 ` [PATCH v2] gitweb: use Git.pm, and use its parse_rev method for git_get_head_hash Lea Wiemann
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