From: Florian Achleitner <florian.achleitner.2.6.31@gmail.com>
To: Jonathan Nieder <jrnieder@gmail.com>
Cc: Florian Achleitner <florian.achleitner.2.6.31@gmail.com>,
git@vger.kernel.org, David Michael Barr <davidbarr@google.com>,
Sverre Rabbelier <srabbelier@gmail.com>,
Jeff King <peff@peff.net>, Johannes Sixt <j.sixt@viscovery.net>
Subject: Re: [RFC 1/4 v2] Implement a basic remote helper for svn in C.
Date: Mon, 30 Jul 2012 10:12:06 +0200 [thread overview]
Message-ID: <3225988.4e4jhmQGr7@flomedio> (raw)
In-Reply-To: <20120728070030.GC4739@burratino>
On Saturday 28 July 2012 02:00:31 Jonathan Nieder wrote:
> Thanks for explaining. Now we've discussed a few different approproaches,
> none of which is perfect.
>
> a. use --cat-blob-fd, no FIFO
>
> Doing this unconditionally would break platforms that don't support
> --cat-blob-fd=(descriptor >2), like Windows, so we'd have to:
>
> * Make it conditional --- only do it (1) we are not on Windows and
> (2) the remote helper requests backflow by advertising the
> import-bidi capability.
>
> * Let the remote helper know what's going on by using
> "import-bidi" instead of "import" in the command stream to
> initiate the import.
Generally I like your prefered solution.
I think there's one problem:
The pipe needs to be created before the fork, so that the fd can be inherited.
There is no way of creating it if the remote-helper advertises a capability,
because it is already forked then. This would work with fifos, though.
We could:
- add a capability: bidi-import.
- make transport-helper create a fifo if the helper advertises it.
- add a command for remote-helpers, like 'bidi-import <pipename>' that makes
the remote helper open the fifo at <pipename> and use it.
- fast-import is forked after the helper, so we do already know if there will
be a back-pipe. If yes, open it in transport-helper and pass the fd as command
line argument cat-blob-fd.
--> fast-import wouldn't need to be changed, but we'd use a fifo, and we get
rid of the env-vars.
(I guess it could work on windows too).
What do you think?
>
> b. use envvars to pass around FIFO path
>
> This complicates the fast-import interface and makes debugging hard.
> It would be nice to avoid this if we can, but in case we can't, it's
> nice to have the option available.
>
> c. transport-helper.c uses FIFO behind the scenes.
>
> Like (a), except it would require a fast-import tweak (boo) and
> would work on Windows (yea)
>
> d. use --cat-blob-fd with FIFO
>
> Early scripted remote-svn prototypes did this to fulfill "fetch"
> requests.
>
> It has no advantage over "use --cat-blob-fd, no FIFO" except being
> easier to implement as a shell script. I'm listing this just for
> comparison; since (a) looks better in every way, I don't see any
> reason to pursue this one.
>
> Since avoiding deadlocks with bidirectional communication is always a
> little subtle, it would be nice for this to be implemented once in
> transport-helper.c rather than each remote helper author having to
> reimplement it again. As a result, my knee-jerk ranking is a > c >
> b > d.
>
> Sane?
> Jonathan
next prev parent reply other threads:[~2012-07-30 8:12 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-04 17:20 [RFC 0/4] Florian Achleitner
2012-06-04 17:20 ` [RFC 1/4] Implement a basic remote helper vor svn in C Florian Achleitner
2012-06-04 17:20 ` [RFC 2/4] Integrate remote-svn into svn-fe/Makefile Florian Achleitner
2012-06-04 17:20 ` [RFC 3/4] Add svndump_init_fd to allow reading dumps from arbitrary FDs Florian Achleitner
2012-06-04 17:20 ` [RFC 4/4] Add cat-blob report pipe from fast-import to remote-helper Florian Achleitner
2012-06-05 1:33 ` David Michael Barr
2012-06-05 6:56 ` Jeff King
2012-06-05 7:07 ` David Michael Barr
2012-06-05 8:14 ` Jeff King
2012-06-05 22:16 ` Florian Achleitner
2012-06-06 13:43 ` Jeff King
2012-06-06 21:04 ` Florian Achleitner
2012-06-05 8:51 ` Johannes Sixt
2012-06-05 9:07 ` Jeff King
2012-06-05 22:17 ` Florian Achleitner
2012-06-05 9:09 ` Johannes Sixt
2012-06-05 1:21 ` [RFC 3/4] Add svndump_init_fd to allow reading dumps from arbitrary FDs David Michael Barr
2012-06-29 7:49 ` [RFC 0/4 v2] Florian Achleitner
2012-06-29 7:54 ` [RFC 1/4 v2] Implement a basic remote helper for svn in C Florian Achleitner
2012-07-02 11:07 ` Jonathan Nieder
2012-07-06 0:30 ` Jonathan Nieder
2012-07-06 10:39 ` Florian Achleitner
2012-07-26 8:31 ` Florian Achleitner
2012-07-26 9:08 ` Jonathan Nieder
2012-07-26 16:16 ` Florian Achleitner
2012-07-28 7:00 ` Jonathan Nieder
2012-07-30 8:12 ` Florian Achleitner [this message]
2012-07-30 8:29 ` Jonathan Nieder
2012-07-30 13:55 ` Florian Achleitner
2012-07-30 16:55 ` Jonathan Nieder
2012-07-31 19:31 ` Florian Achleitner
2012-07-31 22:43 ` Jonathan Nieder
2012-08-01 8:25 ` Florian Achleitner
2012-08-01 19:42 ` Jonathan Nieder
2012-08-12 10:06 ` Florian Achleitner
2012-08-12 16:12 ` Jonathan Nieder
2012-08-12 19:39 ` Florian Achleitner
2012-08-12 20:10 ` Jonathan Nieder
2012-08-12 19:36 ` Jonathan Nieder
2012-07-26 17:29 ` Junio C Hamano
2012-07-30 8:12 ` Florian Achleitner
2012-07-26 9:45 ` Steven Michalske
[not found] ` <358E6F1E-8BAD-4F82-B270-0233AB86EF66@gmail.com>
2012-07-26 11:40 ` Jonathan Nieder
2012-07-26 14:28 ` Florian Achleitner
2012-07-26 14:54 ` Jonathan Nieder
2012-07-27 7:23 ` Florian Achleitner
2012-07-28 6:54 ` Jonathan Nieder
2012-06-29 7:58 ` [RFC 2/4 v2] Integrate remote-svn into svn-fe/Makefile Florian Achleitner
2012-06-29 7:59 ` [RFC 3/4 v2] Add svndump_init_fd to allow reading dumps from arbitrary FDs Florian Achleitner
2012-06-29 8:00 ` [RFC 4/4 v2] Add cat-blob report fifo from fast-import to remote-helper Florian Achleitner
2012-07-21 12:45 ` [RFC 4/4 v3] " Florian Achleitner
2012-07-21 14:48 ` Jonathan Nieder
2012-07-21 15:24 ` Florian Achleitner
2012-07-21 15:44 ` Jonathan Nieder
2012-07-22 21:03 ` Florian Achleitner
2012-07-22 21:24 ` Jonathan Nieder
2012-07-21 15:58 ` Jonathan Nieder
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