From: Lars Schneider <larsxschneider@gmail.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: "Torsten Bögershausen" <tboegi@web.de>, git <git@vger.kernel.org>,
"Jeff King" <peff@peff.net>, "Stefan Beller" <sbeller@google.com>,
"Jakub Narębski" <jnareb@gmail.com>,
"Martin-Louis Bright" <mlbright@gmail.com>,
ramsay@ramsayjones.plus.com
Subject: Re: [PATCH v8 00/11] Git filter protocol
Date: Mon, 3 Oct 2016 19:35:19 +0200 [thread overview]
Message-ID: <56FAEF34-6A31-4E10-9671-F890796EF5A6@gmail.com> (raw)
In-Reply-To: <xmqqvax974dl.fsf@gitster.mtv.corp.google.com>
> On 03 Oct 2016, at 19:02, Junio C Hamano <gitster@pobox.com> wrote:
>
> Lars Schneider <larsxschneider@gmail.com> writes:
>
>>> If the filter process refuses to die forever when Git told it to
>>> shutdown (by closing the pipe to it, for example), that filter
>>> process is simply buggy. I think we want users to become aware of
>>> that, instead of Git leaving it behind, which essentially is to
>>> sweep the problem under the rug.
>>>
>>> I agree with what Peff said elsewhere in the thread; if a filter
>>> process wants to take time to clean things up while letting Git
>>> proceed, it can do its own process management, but I think it is
>>> sensible for Git to wait the filter process it directly spawned.
>>
>> To realize the approach above I prototyped the run-command patch below:
>>
>> I added an "exit_timeout" variable to the "child_process" struct.
>> On exit, Git will close the pipe to the process and wait "exit_timeout"
>> seconds until it kills the child process. If "exit_timeout" is negative
>> then Git will wait until the process is done.
>
>> If we use that in the long running filter process, then we could make
>> the timeout even configurable. E.g. with "filter.<driver>.process-timeout".
>>
>> What do you think about this solution?
>
> Is such a configuration (or timeout in general) necessary? I
> suspect that a need for timeout, especially needing timeout and
> needing to get killed that happens so often to require a
> configuration variable, is a sign of something else seriously wrong.
>
> What's the justification for a filter to _require_ getting killed
> all the time when it is spawned? Otherwise you wouldn't configure
> "this driver does not die when told, so we need a timeout" variable.
> Is it a sign of the flaw in the protocol to talk to it? e.g. Git
> has a way to tell it to die, but it somehow is very hard to hear
> from filter's end and honor that request?
>
> I think that we would need some timeout in the mechanism, but not to
> be used for "killing".
>
> You would decide to "kill" an filter process in two cases: the
> filter is buggy and refuses to die when Git tells it to exit, or the
> code in Git waiting for its death is somehow miscounting its
> children, and thought it told to die one process but in fact it
> didn't (perhaps it told somebody else to die), or it thought it
> hasn't seen the child die when in fact it already did.
Agreed.
> Calling kill(2) and exiting would hide these two kind of bugs from
> end users. Not doing so would give the end users a hung Git, which
> is a VERY GOOD thing. Otherwise you would not notice bugs and lose
> the opportunity to diagnose and fix it.
Aha. I assumed that a hung Git because of a buggy filter would be a no-no.
Thanks for this clarification.
> The timeout would be good for you to give a message "filter process
> running the script '%s' is not exiting; I am waiting for it". The
> user is still left with a hung Git, and can then see if that process
> is hanging around. If it is, then we found a buggy filter. Or we
> found a buggy Git. Either needs to be fixed. I do not think it
> would help anybody by doing a kill(2) to sweep possible bugs under
> the rug.
I could achieve that with this run-command patch:
http://public-inbox.org/git/E9946E9F-6EE5-492B-B122-9078CEB88044@gmail.com/
(I'll remove the "timeout after x seconds" parts and keep the "wait until
done" part with stderr output)
Thanks,
Lars
next prev parent reply other threads:[~2016-10-03 17:35 UTC|newest]
Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-20 19:02 [PATCH v8 00/11] Git filter protocol larsxschneider
2016-09-20 19:02 ` [PATCH v8 01/11] pkt-line: rename packet_write() to packet_write_fmt() larsxschneider
2016-09-24 21:14 ` Jakub Narębski
2016-09-26 18:49 ` Lars Schneider
2016-09-28 23:15 ` Jakub Narębski
2016-09-20 19:02 ` [PATCH v8 02/11] pkt-line: extract set_packet_header() larsxschneider
2016-09-24 21:22 ` Jakub Narębski
2016-09-26 18:53 ` Lars Schneider
2016-09-20 19:02 ` [PATCH v8 03/11] run-command: move check_pipe() from write_or_die to run_command larsxschneider
2016-09-24 22:12 ` Jakub Narębski
2016-09-26 16:13 ` Lars Schneider
2016-09-26 16:21 ` Jakub Narębski
2016-09-20 19:02 ` [PATCH v8 04/11] pkt-line: add packet_write_fmt_gently() larsxschneider
2016-09-24 22:27 ` Jakub Narębski
2016-09-20 19:02 ` [PATCH v8 05/11] pkt-line: add packet_flush_gently() larsxschneider
2016-09-24 22:56 ` Jakub Narębski
2016-09-20 19:02 ` [PATCH v8 06/11] pkt-line: add packet_write_gently() larsxschneider
2016-09-25 11:26 ` Jakub Narębski
2016-09-26 19:21 ` Lars Schneider
2016-09-27 8:39 ` Jeff King
2016-09-27 19:33 ` Jakub Narębski
2016-09-20 19:02 ` [PATCH v8 07/11] pkt-line: add functions to read/write flush terminated packet streams larsxschneider
2016-09-25 13:46 ` Jakub Narębski
2016-09-26 20:23 ` Lars Schneider
2016-09-27 8:14 ` Lars Schneider
2016-09-27 9:00 ` Jeff King
2016-09-27 12:10 ` Lars Schneider
2016-09-27 12:13 ` Jeff King
2016-09-20 19:02 ` [PATCH v8 08/11] convert: quote filter names in error messages larsxschneider
2016-09-25 14:03 ` Jakub Narębski
2016-09-20 19:02 ` [PATCH v8 09/11] convert: modernize tests larsxschneider
2016-09-25 14:43 ` Jakub Narębski
2016-09-20 19:02 ` [PATCH v8 10/11] convert: make apply_filter() adhere to standard Git error handling larsxschneider
2016-09-25 14:47 ` Jakub Narębski
2016-09-20 19:02 ` [PATCH v8 11/11] convert: add filter.<driver>.process option larsxschneider
2016-09-26 22:41 ` Jakub Narębski
2016-09-30 18:56 ` Lars Schneider
2016-10-04 20:50 ` Jakub Narębski
2016-10-06 13:16 ` Lars Schneider
2016-09-27 15:37 ` Jakub Narębski
2016-09-30 19:38 ` Lars Schneider
2016-10-04 21:00 ` Jakub Narębski
2016-10-06 21:27 ` Lars Schneider
2016-09-28 23:14 ` Jakub Narębski
2016-10-01 15:34 ` Lars Schneider
2016-10-04 21:34 ` Jakub Narębski
2016-09-28 21:49 ` [PATCH v8 00/11] Git filter protocol Junio C Hamano
2016-09-29 10:28 ` Lars Schneider
2016-09-29 11:57 ` Torsten Bögershausen
2016-09-29 16:57 ` Junio C Hamano
2016-09-29 17:57 ` Lars Schneider
2016-09-29 18:18 ` Torsten Bögershausen
2016-09-29 18:38 ` Johannes Sixt
2016-09-29 21:27 ` Junio C Hamano
2016-10-01 18:59 ` Lars Schneider
2016-10-01 20:48 ` Jakub Narębski
2016-10-03 17:13 ` Lars Schneider
2016-10-04 19:04 ` Jakub Narębski
2016-10-06 13:13 ` Lars Schneider
2016-10-06 16:01 ` Jeff King
2016-10-06 17:17 ` Junio C Hamano
2016-10-03 17:02 ` Junio C Hamano
2016-10-03 17:35 ` Lars Schneider [this message]
2016-10-04 12:11 ` Jeff King
2016-10-04 16:47 ` Junio C Hamano
2016-09-29 18:02 ` Jeff King
2016-09-29 21:19 ` Junio C Hamano
2016-09-29 20:50 ` Lars Schneider
2016-09-29 21:12 ` Junio C Hamano
2016-09-29 20:59 ` Jakub Narębski
2016-09-29 21:17 ` Junio C Hamano
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