From: Patrick Steinhardt <ps@pks.im>
To: Taylor Blau <me@ttaylorr.com>
Cc: Junio C Hamano <gitster@pobox.com>,
git@vger.kernel.org, Elijah Newren <newren@gmail.com>,
"Eric W. Biederman" <ebiederm@gmail.com>,
Jeff King <peff@peff.net>
Subject: Re: [PATCH 7/7] builtin/merge-tree.c: implement support for `--write-pack`
Date: Tue, 10 Oct 2023 08:36:03 +0200 [thread overview]
Message-ID: <ZSTw04yxPg3NiBOs@tanuki> (raw)
In-Reply-To: <ZSQlgLDv+MrYmSp8@nand.local>
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On Mon, Oct 09, 2023 at 12:08:32PM -0400, Taylor Blau wrote:
> On Mon, Oct 09, 2023 at 12:54:12PM +0200, Patrick Steinhardt wrote:
> > In Gitaly, we usually set up quarantine directories for all operations
> > that create objects. This allows us to discard any newly written objects
> > in case either the RPC call gets cancelled or in case our access checks
> > determine that the change should not be allowed. The logic is rather
> > simple:
> >
> > 1. Create a new temporary directory.
> >
> > 2. Set up the new temporary directory as main object database via
> > the `GIT_OBJECT_DIRECTORY` environment variable.
> >
> > 3. Set up the main repository's object database via the
> > `GIT_ALTERNATE_OBJECT_DIRECTORIES` environment variable.
>
> Is there a reason not to run Git in the quarantine environment and list
> the main repository as an alternate via $GIT_DIR/objects/info/alternates
> instead of the GIT_ALTERNATE_OBJECT_DIRECTORIES environment variable?
The quarantine environment as we use it is really only a single object
database, so you cannot run Git inside of it directly.
> > 4. Execute Git commands that write objects with these environment
> > variables set up. The new objects will end up neatly contained in
> > the temporary directory.
> >
> > 5. Once done, either discard the temporary object database or
> > migrate objects into the main object daatabase.
>
> Interesting. I'm curious why you don't use the builtin tmp_objdir
> mechanism in Git itself. Do you need to run more than one command in the
> quarantine environment? If so, that makes sense that you'd want to have
> a scratch repository that lasts beyond the lifetime of a single process.
It's a mixture of things:
- Many commands simply don't set up a temporary object directory.
- We want to check the result after the objects have been generated.
Many of the commands don't provide hooks to do so in a reasonable
way. So we want to check the result _after_ the command has exited
already, and objects should not yet have been migrated into the
target object database at that point.
- Sometimes we indeed want to run multiple Git commands. We use this
e.g. for worktreeless rebases, where we run a succession of
commands to rebase every single commit.
So ultimately, our own quarantine directory sits at a conceptually
higher level than what Git commands would be able to provide.
> > I wonder whether this would be a viable approach for you, as well.
>
> I think that the main problem that we are trying to solve with this
> series is creating a potentially large number of loose objects. I think
> that you could do something like what you propose above, with a 'git
> repacks -adk' before moving its objects over back to the main repository.
Yeah, that's certainly possible. I had the feeling that there are two
different problems that we're trying to solve in this thread:
- The problem that the objects are of temporary nature. Regardless
of whether they are in a packfile or loose, it doesn't make much
sense to put them into the main object database as they would be
unreachable anyway and thus get pruned after some time.
- The problem that writing many loose objects can be slow.
My proposal only addresses the first problem.
> But since we're working in a single process only when doing a merge-tree
> operation, I think it is probably more expedient to write the pack's
> bytes directly.
If it's about efficiency and not about how we discard those objects
after the command has ran to completion then yes, I agree.
Patrick
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next prev parent reply other threads:[~2023-10-10 6:36 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-06 22:01 [PATCH 0/7] merge-ort: implement support for packing objects together Taylor Blau
2023-10-06 22:01 ` [PATCH 1/7] bulk-checkin: factor out `format_object_header_hash()` Taylor Blau
2023-10-06 22:01 ` [PATCH 2/7] bulk-checkin: factor out `prepare_checkpoint()` Taylor Blau
2023-10-06 22:01 ` [PATCH 3/7] bulk-checkin: factor out `truncate_checkpoint()` Taylor Blau
2023-10-06 22:01 ` [PATCH 4/7] bulk-checkin: factor our `finalize_checkpoint()` Taylor Blau
2023-10-06 22:02 ` [PATCH 5/7] bulk-checkin: introduce `index_blob_bulk_checkin_incore()` Taylor Blau
2023-10-06 22:02 ` [PATCH 6/7] bulk-checkin: introduce `index_tree_bulk_checkin_incore()` Taylor Blau
2023-10-07 3:07 ` Eric Biederman
2023-10-09 1:31 ` Taylor Blau
2023-10-06 22:02 ` [PATCH 7/7] builtin/merge-tree.c: implement support for `--write-pack` Taylor Blau
2023-10-06 22:35 ` Junio C Hamano
2023-10-06 23:02 ` Taylor Blau
2023-10-08 7:02 ` Elijah Newren
2023-10-08 16:04 ` Taylor Blau
2023-10-08 17:33 ` Jeff King
2023-10-09 1:37 ` Taylor Blau
2023-10-09 20:21 ` Jeff King
2023-10-09 17:24 ` Junio C Hamano
2023-10-09 10:54 ` Patrick Steinhardt
2023-10-09 16:08 ` Taylor Blau
2023-10-10 6:36 ` Patrick Steinhardt [this message]
2023-10-17 16:31 ` [PATCH v2 0/7] merge-ort: implement support for packing objects together Taylor Blau
2023-10-17 16:31 ` [PATCH v2 1/7] bulk-checkin: factor out `format_object_header_hash()` Taylor Blau
2023-10-17 16:31 ` [PATCH v2 2/7] bulk-checkin: factor out `prepare_checkpoint()` Taylor Blau
2023-10-17 16:31 ` [PATCH v2 3/7] bulk-checkin: factor out `truncate_checkpoint()` Taylor Blau
2023-10-17 16:31 ` [PATCH v2 4/7] bulk-checkin: factor our `finalize_checkpoint()` Taylor Blau
2023-10-17 16:31 ` [PATCH v2 5/7] bulk-checkin: introduce `index_blob_bulk_checkin_incore()` Taylor Blau
2023-10-18 2:18 ` Junio C Hamano
2023-10-18 16:34 ` Taylor Blau
2023-10-17 16:31 ` [PATCH v2 6/7] bulk-checkin: introduce `index_tree_bulk_checkin_incore()` Taylor Blau
2023-10-17 16:31 ` [PATCH v2 7/7] builtin/merge-tree.c: implement support for `--write-pack` Taylor Blau
2023-10-18 17:07 ` [PATCH v3 00/10] merge-ort: implement support for packing objects together Taylor Blau
2023-10-18 17:07 ` [PATCH v3 01/10] bulk-checkin: factor out `format_object_header_hash()` Taylor Blau
2023-10-18 17:07 ` [PATCH v3 02/10] bulk-checkin: factor out `prepare_checkpoint()` Taylor Blau
2023-10-18 17:07 ` [PATCH v3 03/10] bulk-checkin: factor out `truncate_checkpoint()` Taylor Blau
2023-10-18 17:07 ` [PATCH v3 04/10] bulk-checkin: factor out `finalize_checkpoint()` Taylor Blau
2023-10-18 17:08 ` [PATCH v3 05/10] bulk-checkin: extract abstract `bulk_checkin_source` Taylor Blau
2023-10-18 23:10 ` Junio C Hamano
2023-10-19 15:19 ` Taylor Blau
2023-10-19 17:55 ` Junio C Hamano
2023-10-18 17:08 ` [PATCH v3 06/10] bulk-checkin: implement `SOURCE_INCORE` mode for `bulk_checkin_source` Taylor Blau
2023-10-18 17:08 ` [PATCH v3 07/10] bulk-checkin: generify `stream_blob_to_pack()` for arbitrary types Taylor Blau
2023-10-18 17:08 ` [PATCH v3 08/10] bulk-checkin: introduce `index_blob_bulk_checkin_incore()` Taylor Blau
2023-10-18 23:18 ` Junio C Hamano
2023-10-19 15:30 ` Taylor Blau
2023-10-18 17:08 ` [PATCH v3 09/10] bulk-checkin: introduce `index_tree_bulk_checkin_incore()` Taylor Blau
2023-10-18 17:08 ` [PATCH v3 10/10] builtin/merge-tree.c: implement support for `--write-pack` Taylor Blau
2023-10-18 18:32 ` [PATCH v4 00/17] bloom: changed-path Bloom filters v2 (& sundries) Taylor Blau
2023-10-18 18:32 ` [PATCH v4 01/17] t/t4216-log-bloom.sh: harden `test_bloom_filters_not_used()` Taylor Blau
2023-10-18 18:32 ` [PATCH v4 02/17] revision.c: consult Bloom filters for root commits Taylor Blau
2023-10-18 18:32 ` [PATCH v4 03/17] commit-graph: ensure Bloom filters are read with consistent settings Taylor Blau
2023-10-18 18:32 ` [PATCH v4 04/17] gitformat-commit-graph: describe version 2 of BDAT Taylor Blau
2023-10-18 18:32 ` [PATCH v4 05/17] t/helper/test-read-graph.c: extract `dump_graph_info()` Taylor Blau
2023-10-18 18:32 ` [PATCH v4 06/17] bloom.h: make `load_bloom_filter_from_graph()` public Taylor Blau
2023-10-18 18:32 ` [PATCH v4 07/17] t/helper/test-read-graph: implement `bloom-filters` mode Taylor Blau
2023-10-18 18:32 ` [PATCH v4 08/17] t4216: test changed path filters with high bit paths Taylor Blau
2023-10-18 18:32 ` [PATCH v4 09/17] repo-settings: introduce commitgraph.changedPathsVersion Taylor Blau
2023-10-18 18:32 ` [PATCH v4 10/17] commit-graph: new filter ver. that fixes murmur3 Taylor Blau
2023-10-18 18:33 ` [PATCH v4 11/17] bloom: annotate filters with hash version Taylor Blau
2023-10-18 18:33 ` [PATCH v4 12/17] bloom: prepare to discard incompatible Bloom filters Taylor Blau
2023-10-18 18:33 ` [PATCH v4 13/17] commit-graph.c: unconditionally load " Taylor Blau
2023-10-18 18:33 ` [PATCH v4 14/17] commit-graph: drop unnecessary `graph_read_bloom_data_context` Taylor Blau
2023-10-18 18:33 ` [PATCH v4 15/17] object.h: fix mis-aligned flag bits table Taylor Blau
2023-10-18 18:33 ` [PATCH v4 16/17] commit-graph: reuse existing Bloom filters where possible Taylor Blau
2023-10-18 18:33 ` [PATCH v4 17/17] bloom: introduce `deinit_bloom_filters()` Taylor Blau
2023-10-18 23:26 ` [PATCH v4 00/17] bloom: changed-path Bloom filters v2 (& sundries) Junio C Hamano
2023-10-20 17:27 ` Taylor Blau
2023-10-23 20:22 ` SZEDER Gábor
2023-10-30 20:24 ` Taylor Blau
2024-01-16 22:08 ` [PATCH v5 " Taylor Blau
2024-01-16 22:09 ` [PATCH v5 01/17] t/t4216-log-bloom.sh: harden `test_bloom_filters_not_used()` Taylor Blau
2024-01-16 22:09 ` [PATCH v5 02/17] revision.c: consult Bloom filters for root commits Taylor Blau
2024-01-16 22:09 ` [PATCH v5 03/17] commit-graph: ensure Bloom filters are read with consistent settings Taylor Blau
2024-01-16 22:09 ` [PATCH v5 04/17] gitformat-commit-graph: describe version 2 of BDAT Taylor Blau
2024-01-16 22:09 ` [PATCH v5 05/17] t/helper/test-read-graph.c: extract `dump_graph_info()` Taylor Blau
2024-01-16 22:09 ` [PATCH v5 06/17] bloom.h: make `load_bloom_filter_from_graph()` public Taylor Blau
2024-01-16 22:09 ` [PATCH v5 07/17] t/helper/test-read-graph: implement `bloom-filters` mode Taylor Blau
2024-01-16 22:09 ` [PATCH v5 08/17] t4216: test changed path filters with high bit paths Taylor Blau
2024-01-16 22:09 ` [PATCH v5 09/17] repo-settings: introduce commitgraph.changedPathsVersion Taylor Blau
2024-01-29 21:26 ` SZEDER Gábor
2024-01-29 23:58 ` Taylor Blau
2024-01-16 22:09 ` [PATCH v5 10/17] commit-graph: new Bloom filter version that fixes murmur3 Taylor Blau
2024-01-16 22:09 ` [PATCH v5 11/17] bloom: annotate filters with hash version Taylor Blau
2024-01-16 22:09 ` [PATCH v5 12/17] bloom: prepare to discard incompatible Bloom filters Taylor Blau
2024-01-16 22:09 ` [PATCH v5 13/17] commit-graph.c: unconditionally load " Taylor Blau
2024-01-16 22:09 ` [PATCH v5 14/17] commit-graph: drop unnecessary `graph_read_bloom_data_context` Taylor Blau
2024-01-16 22:09 ` [PATCH v5 15/17] object.h: fix mis-aligned flag bits table Taylor Blau
2024-01-16 22:09 ` [PATCH v5 16/17] commit-graph: reuse existing Bloom filters where possible Taylor Blau
2024-01-16 22:09 ` [PATCH v5 17/17] bloom: introduce `deinit_bloom_filters()` Taylor Blau
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