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From: Jeff King <peff@peff.net>
To: Jonathan Tan <jonathantanmy@google.com>
Cc: gitster@pobox.com, git@vger.kernel.org
Subject: Re: [RFC PATCH] Modify fetch-pack to no longer die on error?
Date: Tue, 28 Jul 2020 16:08:47 -0400	[thread overview]
Message-ID: <20200728200847.GA1019822@coredump.intra.peff.net> (raw)
In-Reply-To: <20200728192350.352978-1-jonathantanmy@google.com>

On Tue, Jul 28, 2020 at 12:23:50PM -0700, Jonathan Tan wrote:

> > For this particular case, with the performance and all, I agree that
> > the stupid and robust approach would be the best.
> 
> I'm concerned that we will be painting ourselves into a corner here - I
> have been appreciating the richer interface that a C call provides us,
> compared to sub-processes where we have to communicate through a single
> input stream and a single output stream. For example, "wanted-refs" and
> [...]

Yeah, that's a compelling reason. I'd have thought for this use case you
could just say "hey, make sure these objects exist", which doesn't
require a lot of communication. But often when I think things like that
and start coding, it turns out to be much more complicated. So I am
perfectly willing to believe you that it doesn't apply here. And even
if it did, you're right that we may run into other spots that do need to
pass back more information, but benefit from more lib-ified code that
doesn't die().

Just to play devil's advocate for a moment...

> (Also, I think that debugging within a process is easier than debugging
> across processes, but that might not be a concern that other people
> share.)

This is definitely true sometimes, but I think is sometimes the
opposite. When we push things out to a sub-process, then the interface
between the two processes has to be well-defined (e.g., writing results
to a file with a particular format). And that can make debugging easier,
because you can pick up from that intermediate state (munging it in the
middle, or even generating it from scratch for testing).

Likewise, that can result in a more flexible and robust system from the
perspective of users. If we had invented "git log" first, we probably
wouldn't have "git rev-list | git diff-tree --stdin" at all. But having
that as two separate tools is sometimes useful for people doing things
_besides_ log, since it gives different entry points to the code.

That said, I think I could buy the argument that "fetch" works pretty
well as a basic building block for users. It's pretty rare to actually
use fetch-pack as a distinct operation. This is all a monolith vs module
tradeoff question, and the tradeoff around modularity for fetch isn't
that compelling.

-Peff

  reply	other threads:[~2020-07-28 20:09 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-24 22:38 Jonathan Tan
2020-07-24 23:07 ` Junio C Hamano
2020-07-24 23:11 ` Junio C Hamano
2020-07-25 21:41   ` Jeff King
2020-07-25 23:01     ` Junio C Hamano
2020-07-27 17:11       ` Jeff King
2020-07-28 19:23       ` Jonathan Tan
2020-07-28 20:08         ` Jeff King [this message]
2020-07-29 18:53           ` Jonathan Tan
2020-07-29 19:29             ` Jeff King
2020-07-29 19:02           ` Junio C Hamano
2020-07-29 22:55             ` Jonathan Tan
2020-08-05  1:20 ` [RFC PATCH 0/7] Lazy fetch with subprocess Jonathan Tan
2020-08-05  1:20   ` [RFC PATCH 1/7] fetch-pack: allow NULL negotiator->add_tip Jonathan Tan
2020-08-05 19:53     ` Junio C Hamano
2020-08-07 20:53       ` Jonathan Tan
2020-08-05  1:20   ` [RFC PATCH 2/7] fetch-pack: allow NULL negotiator->known_common Jonathan Tan
2020-08-05 20:08     ` Junio C Hamano
2020-08-05 22:11       ` Junio C Hamano
2020-08-07 20:59         ` Jonathan Tan
2020-08-05  1:20   ` [RFC PATCH 3/7] negotiator/null: add null fetch negotiator Jonathan Tan
2020-08-05  1:20   ` [RFC PATCH 4/7] fetch: --stdin Jonathan Tan
2020-08-05 20:33     ` Junio C Hamano
2020-08-07 21:10       ` Jonathan Tan
2020-08-07 21:58         ` Junio C Hamano
2020-08-07 21:10       ` Jonathan Tan
2020-08-05  1:20   ` [RFC PATCH 5/7] fetch: submodule config Jonathan Tan
2020-08-05  1:20   ` [RFC PATCH 6/7] fetch: only populate existing_refs if needed Jonathan Tan
2020-08-05  1:20   ` [RFC PATCH 7/7] promisor-remote: use subprocess to fetch Jonathan Tan
2020-08-11 22:52 ` [PATCH v2 0/7] Lazy fetch with subprocess Jonathan Tan
2020-08-11 22:52   ` [PATCH v2 1/7] negotiator/null: add null fetch negotiator Jonathan Tan
2020-08-12 12:55     ` Derrick Stolee
2020-08-12 16:44       ` Junio C Hamano
2020-08-12 17:29         ` Jonathan Tan
2020-08-11 22:52   ` [PATCH v2 2/7] fetch: allow refspecs specified through stdin Jonathan Tan
2020-08-11 22:52   ` [PATCH v2 3/7] fetch: avoid reading submodule config until needed Jonathan Tan
2020-08-12 17:34     ` Junio C Hamano
2020-08-11 22:52   ` [PATCH v2 4/7] fetch: only populate existing_refs if needed Jonathan Tan
2020-08-12 18:06     ` Junio C Hamano
2020-08-11 22:52   ` [PATCH v2 5/7] fetch-pack: do not lazy-fetch during ref iteration Jonathan Tan
2020-08-12 18:25     ` Junio C Hamano
2020-08-11 22:52   ` [PATCH v2 6/7] promisor-remote: lazy-fetch objects in subprocess Jonathan Tan
2020-08-12 18:28     ` Junio C Hamano
2020-08-11 22:52   ` [PATCH v2 7/7] fetch-pack: remove no_dependents code Jonathan Tan
2020-08-12 12:51   ` [PATCH v2 0/7] Lazy fetch with subprocess Derrick Stolee
2020-08-18  4:01 ` [PATCH v3 " Jonathan Tan
2020-08-18  4:01   ` [PATCH v3 1/7] negotiator/noop: add noop fetch negotiator Jonathan Tan
2020-08-18  4:01   ` [PATCH v3 2/7] fetch: allow refspecs specified through stdin Jonathan Tan
2020-08-18  4:01   ` [PATCH v3 3/7] fetch: avoid reading submodule config until needed Jonathan Tan
2020-08-18  4:01   ` [PATCH v3 4/7] fetch: only populate existing_refs if needed Jonathan Tan
2020-08-18  4:01   ` [PATCH v3 5/7] fetch-pack: do not lazy-fetch during ref iteration Jonathan Tan
2020-08-18  4:01   ` [PATCH v3 6/7] promisor-remote: lazy-fetch objects in subprocess Jonathan Tan
2020-08-18  4:01   ` [PATCH v3 7/7] fetch-pack: remove no_dependents code Jonathan Tan
2020-08-18 19:56   ` [PATCH v3 0/7] Lazy fetch with subprocess Junio C Hamano
2020-08-18 22:32     ` Junio C Hamano
2020-08-18 23:36       ` [PATCH] fixup! promisor-remote: lazy-fetch objects in subprocess Jonathan Tan
2020-08-18 23:57         ` Junio C Hamano

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