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From: Lars Schneider <larsxschneider@gmail.com>
To: Jeff King <peff@peff.net>
Cc: git@vger.kernel.org, gitster@pobox.com, jnareb@gmail.com,
	tboegi@web.de, mlbright@gmail.com, e@80x24.org
Subject: Re: [PATCH v4 07/12] run-command: add clean_on_exit_handler
Date: Thu, 4 Aug 2016 01:09:57 +0200	[thread overview]
Message-ID: <74C2CEA6-EAAB-406F-8B37-969654955413@gmail.com> (raw)
In-Reply-To: <20160803225313.pk3tfe5ovz4y3i7l@sigill.intra.peff.net>


> On 04 Aug 2016, at 00:53, Jeff King <peff@peff.net> wrote:
> 
> On Thu, Aug 04, 2016 at 12:15:46AM +0200, Lars Schneider wrote:
> 
>>> I'm not clear on why we want this cleanup filter. It looks like you use
>>> it in the final patch to send an explicit shutdown to any filters we
>>> start. But I see two issues with that:
>>> 
>>> 1. This shutdown may come at any time, and you have no idea what state
>>>    the protocol conversation with the filter is in. You could be in
>>>    the middle of sending another pkt-line, or in a sequence of non-command
>>>    pkt-lines where "shutdown" is not recognized.
>> 
>> Maybe I am missing something, but I don't think that can happen because 
>> the cleanup callback is *only* executed if Git exits normally without error. 
>> In that case we would be in a sane protocol state, no?
> 
> OK, then maybe I am doubly missing the point. I thought this cleanup was
> here to hit the case where we call die() and git exits unexpectedly.
> 
> If you only want to cover the "we are done, no errors, goodbye" case,
> then why don't you just write shutdown when we're done?

I think I tried that at some point but the filter code is called from
multiple places and therefore I looked into atexit() (via run-command)
and it seemed easier. Do you have a place in mind where you would call 
the shutdown after all blobs are processed explicitly?


> I realize you may have multiple filters, but I don't think it should be
> run-command's job to iterate over them. You are presumably keeping a
> list of active filters, and should have a function to iterate over that.

Yes, that would be easy.


> Or better yet, do not require a shutdown at all. The filter sees EOF and
> knows there is nothing more to do. If we are in the middle of an
> operation, then it knows git died. If not, then presumably git had
> nothing else to say (and really, it is not the filter's business if git
> saw an error or not).

EOF? The filter is supposed to process multiple files. How would one EOF
indicate that we are done?


> Though...
> 
>> Thanks. The shutdown command is not intended to be a mechanism to tell
>> the filter that everything went well. At this point - as you mentioned -
>> the filter already received all data in the right way. The shutdown
>> command is intended to give the filter some time to perform some post
>> processing before Git returns.
>> 
>> See here for some brainstorming how this feature could be useful
>> in filters similar to Git LFS:
>> https://github.com/github/git-lfs/issues/1401#issuecomment-236133991
> 
> OK, so it is not really "tell the filter to shutdown" but "I am done
> with you, filter, but I will wait for you to tell me you are all done,
> so that I can tell the user".

Correct!


> I'm not sure if calling that "shutdown" makes sense, though. It's almost
> more of a checkpoint (and I wonder if git would ever want to
> "checkpoint" without hanging up the connection).

OK, I agree that the naming might not be ideal. But "checkpoint" does not
convey that it is only executed once after all blobs are filtered?!

I understand that Git might not want to wait for the filter...

- Lars

  reply	other threads:[~2016-08-03 23:10 UTC|newest]

Thread overview: 120+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20160727000605.49982-1-larsxschneider%40gmail.com/>
2016-07-29 23:37 ` [PATCH v3 00/10] Git filter protocol larsxschneider
2016-07-29 23:37   ` [PATCH v3 01/10] pkt-line: extract set_packet_header() larsxschneider
2016-07-30 10:30     ` Jakub Narębski
2016-08-01 11:33       ` Lars Schneider
2016-08-03 20:05         ` Jakub Narębski
2016-08-05 11:52           ` Lars Schneider
2016-07-29 23:37   ` [PATCH v3 02/10] pkt-line: add direct_packet_write() and direct_packet_write_data() larsxschneider
2016-07-30 10:49     ` Jakub Narębski
2016-08-01 12:00       ` Lars Schneider
2016-08-03 20:12         ` Jakub Narębski
2016-08-05 12:02           ` Lars Schneider
2016-07-29 23:37   ` [PATCH v3 03/10] pkt-line: add packet_flush_gentle() larsxschneider
2016-07-30 12:04     ` Jakub Narębski
2016-08-01 12:28       ` Lars Schneider
2016-07-31 20:36     ` Torstem Bögershausen
2016-07-31 21:45       ` Lars Schneider
2016-08-02 19:56         ` Torsten Bögershausen
2016-08-05  9:59           ` Lars Schneider
2016-07-29 23:37   ` [PATCH v3 04/10] pkt-line: call packet_trace() only if a packet is actually send larsxschneider
2016-07-30 12:29     ` Jakub Narębski
2016-08-01 12:18       ` Lars Schneider
2016-08-03 20:15         ` Jakub Narębski
2016-07-29 23:37   ` [PATCH v3 05/10] pack-protocol: fix maximum pkt-line size larsxschneider
2016-07-30 13:58     ` Jakub Narębski
2016-08-01 12:23       ` Lars Schneider
2016-07-29 23:37   ` [PATCH v3 06/10] run-command: add clean_on_exit_handler larsxschneider
2016-07-30  9:50     ` Johannes Sixt
2016-08-01 11:14       ` Lars Schneider
2016-08-02  5:53         ` Johannes Sixt
2016-08-02  7:41           ` Lars Schneider
2016-07-29 23:37   ` [PATCH v3 07/10] convert: quote filter names in error messages larsxschneider
2016-07-29 23:37   ` [PATCH v3 08/10] convert: modernize tests larsxschneider
2016-07-29 23:38   ` [PATCH v3 09/10] convert: generate large test files only once larsxschneider
2016-07-29 23:38   ` [PATCH v3 10/10] convert: add filter.<driver>.process option larsxschneider
2016-07-30 22:05     ` Jakub Narębski
2016-07-31  9:42       ` Jakub Narębski
2016-07-31 19:49         ` Lars Schneider
2016-07-31 22:59           ` Jakub Narębski
2016-08-01 13:32       ` Lars Schneider
2016-08-03 18:30         ` Designing the filter process protocol (was: Re: [PATCH v3 10/10] convert: add filter.<driver>.process option) Jakub Narębski
2016-08-05 10:32           ` Lars Schneider
2016-08-06 18:24           ` Lars Schneider
2016-08-03 22:47         ` [PATCH v3 10/10] convert: add filter.<driver>.process option Jakub Narębski
2016-07-31 22:19     ` Jakub Narębski
2016-08-01 17:55       ` Lars Schneider
2016-08-04  0:42         ` Jakub Narębski
2016-08-03 13:10       ` Lars Schneider
2016-08-04 10:18         ` Jakub Narębski
2016-08-05 13:20           ` Lars Schneider
2016-08-03 16:42   ` [PATCH v4 00/12] Git filter protocol larsxschneider
2016-08-03 16:42     ` [PATCH v4 01/12] pkt-line: extract set_packet_header() larsxschneider
2016-08-03 20:18       ` Junio C Hamano
2016-08-03 21:12         ` Jeff King
2016-08-03 21:27           ` Jeff King
2016-08-04 16:14           ` Junio C Hamano
2016-08-05 14:55             ` Lars Schneider
2016-08-05 16:31               ` Junio C Hamano
2016-08-05 17:31             ` Lars Schneider
2016-08-05 17:41               ` Junio C Hamano
2016-08-03 21:56         ` Lars Schneider
2016-08-03 16:42     ` [PATCH v4 02/12] pkt-line: add direct_packet_write() and direct_packet_write_data() larsxschneider
2016-08-03 16:42     ` [PATCH v4 03/12] pkt-line: add packet_flush_gentle() larsxschneider
2016-08-03 21:39       ` Jeff King
2016-08-03 22:56         ` [PATCH 0/7] minor trace fixes and cosmetic improvements Jeff King
2016-08-03 22:56           ` [PATCH 1/7] trace: handle NULL argument in trace_disable() Jeff King
2016-08-03 22:58           ` [PATCH 2/7] trace: stop using write_or_whine_pipe() Jeff King
2016-08-03 22:58           ` [PATCH 3/7] trace: use warning() for printing trace errors Jeff King
2016-08-04 20:41             ` Junio C Hamano
2016-08-04 21:21               ` Jeff King
2016-08-04 21:28                 ` Junio C Hamano
2016-08-05  7:56                   ` Jeff King
2016-08-05  7:59                   ` Christian Couder
2016-08-05 18:41                     ` Junio C Hamano
2016-08-03 23:00           ` [PATCH 4/7] trace: cosmetic fixes for error messages Jeff King
2016-08-04 20:42             ` Junio C Hamano
2016-08-05  8:00               ` Jeff King
2016-08-03 23:00           ` [PATCH 5/7] trace: correct variable name in write() error message Jeff King
2016-08-03 23:01           ` [PATCH 6/7] trace: disable key after write error Jeff King
2016-08-04 20:45             ` Junio C Hamano
2016-08-04 21:22               ` Jeff King
2016-08-05  7:58                 ` Jeff King
2016-08-03 23:01           ` [PATCH 7/7] write_or_die: drop write_or_whine_pipe() Jeff King
2016-08-03 23:04           ` [PATCH 0/7] minor trace fixes and cosmetic improvements Jeff King
2016-08-04 16:16         ` [PATCH v4 03/12] pkt-line: add packet_flush_gentle() Junio C Hamano
2016-08-03 16:42     ` [PATCH v4 04/12] pkt-line: call packet_trace() only if a packet is actually send larsxschneider
2016-08-03 16:42     ` [PATCH v4 05/12] pkt-line: add functions to read/write flush terminated packet streams larsxschneider
2016-08-03 16:42     ` [PATCH v4 06/12] pack-protocol: fix maximum pkt-line size larsxschneider
2016-08-03 16:42     ` [PATCH v4 07/12] run-command: add clean_on_exit_handler larsxschneider
2016-08-03 21:24       ` Jeff King
2016-08-03 22:15         ` Lars Schneider
2016-08-03 22:53           ` Jeff King
2016-08-03 23:09             ` Lars Schneider [this message]
2016-08-03 23:15               ` Jeff King
2016-08-05 13:08                 ` Lars Schneider
2016-08-05 21:19                   ` Torsten Bögershausen
2016-08-05 21:50                     ` Lars Schneider
2016-08-03 16:42     ` [PATCH v4 08/12] convert: quote filter names in error messages larsxschneider
2016-08-03 16:42     ` [PATCH v4 09/12] convert: modernize tests larsxschneider
2016-08-03 16:42     ` [PATCH v4 10/12] convert: generate large test files only once larsxschneider
2016-08-03 16:42     ` [PATCH v4 11/12] convert: add filter.<driver>.process option larsxschneider
2016-08-03 17:45       ` Junio C Hamano
2016-08-03 21:48         ` Lars Schneider
2016-08-03 22:46           ` Jeff King
2016-08-05 12:53             ` Lars Schneider
2016-08-03 20:29       ` Junio C Hamano
2016-08-03 21:37         ` Lars Schneider
2016-08-03 21:43           ` Junio C Hamano
2016-08-03 22:01             ` Lars Schneider
2016-08-05 21:34       ` Torsten Bögershausen
2016-08-05 21:49         ` Lars Schneider
2016-08-05 22:06         ` Junio C Hamano
2016-08-05 22:27           ` Jeff King
2016-08-06 11:55             ` Lars Schneider
2016-08-06 12:14               ` Jeff King
2016-08-06 18:19                 ` Lars Schneider
2016-08-08 15:02                   ` Jeff King
2016-08-08 16:21                     ` Lars Schneider
2016-08-08 16:26                       ` Jeff King
2016-08-06 20:40           ` Torsten Bögershausen
2016-08-03 16:42     ` [PATCH v4 12/12] convert: add filter.<driver>.process shutdown command option larsxschneider

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