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[PATCH 07/11] multi-pack-index: prepare 'repack' subcommand

From
Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>
Date
Jun 10, 2019, 23:35 UTC
Message-ID
<1776e36f1952cb6ed7fea73e90167134285c331b.1560209720.git.gitgitgadget@gmail.com>
In-Reply-To
<pull.261.git.gitgitgadget@gmail.com>
From: Derrick Stolee <dstolee@microsoft.com>

In an environment where the multi-pack-index is useful, it is due to many pack-files and an inability to repack the object store into a single pack-file. However, it is likely that many of these pack-files are rather small, and could be repacked into a slightly larger pack-file without too much effort. It may also be important to ensure the object store is highly available and the repack operation does not interrupt concurrent git commands.

Introduce a 'repack' subcommand to 'git multi-pack-index' that takes a '--batch-size' option. The subcommand will inspect the multi-pack-index for referenced pack-files whose size is smaller than the batch size, until collecting a list of pack-files whose sizes sum to larger than the batch size. Then, a new pack-file will be created containing the objects from those pack-files that are referenced by the multi-pack-index. The resulting pack is likely to actually be smaller than the batch size due to compression and the fact that there may be objects in the pack- files that have duplicate copies in other pack-files.

The current change introduces the command-line arguments, and we add a test that ensures we parse these options properly. Since we specify a small batch size, we will guarantee that future implementations do not change the list of pack-files.

In addition, we hard-code the modified times of the packs in the pack directory to ensure the list of packs sorted by modified time matches the order if sorted by size (ascending). This will be important in a future test.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 Documentation/git-multi-pack-index.txt | 17 +++++++++++++++++
 builtin/multi-pack-index.c             | 12 ++++++++++--
 midx.c                                 |  5 +++++
 midx.h                                 |  1 +
 t/t5319-multi-pack-index.sh            | 20 +++++++++++++++++++-
 5 files changed, 52 insertions(+), 3 deletions(-)
diff --git a/Documentation/git-multi-pack-index.txt b/Documentation/git-multi-pack-index.txt
index 6186c4c936..233b2b7862 100644
--- a/Documentation/git-multi-pack-index.txt
+++ b/Documentation/git-multi-pack-index.txt
@@ -36,6 +36,23 @@ expire::
 	have no objects referenced by the MIDX. Rewrite the MIDX file
 	afterward to remove all references to these pack-files.
 
+repack::
+	Create a new pack-file containing objects in small pack-files
+	referenced by the multi-pack-index. If the size given by the
+	`--batch-size=<size>` argument is zero, then create a pack
+	containing all objects referenced by the multi-pack-index. For
+	a non-zero batch size, Select the pack-files by examining packs
+	from oldest-to-newest, computing the "expected size" by counting
+	the number of objects in the pack referenced by the
+	multi-pack-index, then divide by the total number of objects in
+	the pack and multiply by the pack size. We select packs with
+	expected size below the batch size until the set of packs have
+	total expected size at least the batch size. If the total size
+	does not reach the batch size, then do nothing. If a new pack-
+	file is created, rewrite the multi-pack-index to reference the
+	new pack-file. A later run of 'git multi-pack-index expire' will
+	delete the pack-files that were part of this batch.
+
 
 EXAMPLES
 --------
diff --git a/builtin/multi-pack-index.c b/builtin/multi-pack-index.c
index ad10d40512..b1ea1a6aa1 100644
--- a/builtin/multi-pack-index.c
+++ b/builtin/multi-pack-index.c
@@ -6,12 +6,13 @@
 #include "trace2.h"
 
 static char const * const builtin_multi_pack_index_usage[] = {
-	N_("git multi-pack-index [--object-dir=<dir>] (write|verify|expire)"),
+	N_("git multi-pack-index [--object-dir=<dir>] (write|verify|expire|repack --batch-size=<size>)"),
 	NULL
 };
 
 static struct opts_multi_pack_index {
 	const char *object_dir;
+	unsigned long batch_size;
 } opts;
 
 int cmd_multi_pack_index(int argc, const char **argv,
@@ -20,6 +21,8 @@ int cmd_multi_pack_index(int argc, const char **argv,
 	static struct option builtin_multi_pack_index_options[] = {
 		OPT_FILENAME(0, "object-dir", &opts.object_dir,
 		  N_("object directory containing set of packfile and pack-index pairs")),
+		OPT_MAGNITUDE(0, "batch-size", &opts.batch_size,
+		  N_("during repack, collect pack-files of smaller size into a batch that is larger than this size")),
 		OPT_END(),
 	};
 
@@ -43,6 +46,11 @@ int cmd_multi_pack_index(int argc, const char **argv,
 
 	trace2_cmd_mode(argv[0]);
 
+	if (!strcmp(argv[0], "repack"))
+		return midx_repack(the_repository, opts.object_dir, (size_t)opts.batch_size);
+	if (opts.batch_size)
+		die(_("--batch-size option is only for 'repack' subcommand"));
+
 	if (!strcmp(argv[0], "write"))
 		return write_midx_file(opts.object_dir);
 	if (!strcmp(argv[0], "verify"))
@@ -50,5 +58,5 @@ int cmd_multi_pack_index(int argc, const char **argv,
 	if (!strcmp(argv[0], "expire"))
 		return expire_midx_packs(the_repository, opts.object_dir);
 
-	die(_("unrecognized verb: %s"), argv[0]);
+	die(_("unrecognized subcommand: %s"), argv[0]);
 }
diff --git a/midx.c b/midx.c
index 9b0b4c1520..fbed8a8adb 100644
--- a/midx.c
+++ b/midx.c
@@ -1226,3 +1226,8 @@ int expire_midx_packs(struct repository *r, const char *object_dir)
 	string_list_clear(&packs_to_drop, 0);
 	return result;
 }
+
+int midx_repack(struct repository *r, const char *object_dir, size_t batch_size)
+{
+	return 0;
+}
diff --git a/midx.h b/midx.h
index 505f1431b7..f0ae656b5d 100644
--- a/midx.h
+++ b/midx.h
@@ -51,6 +51,7 @@ int write_midx_file(const char *object_dir);
 void clear_midx_file(struct repository *r);
 int verify_midx_file(struct repository *r, const char *object_dir);
 int expire_midx_packs(struct repository *r, const char *object_dir);
+int midx_repack(struct repository *r, const char *object_dir, size_t batch_size);
 
 void close_midx(struct multi_pack_index *m);
 
diff --git a/t/t5319-multi-pack-index.sh b/t/t5319-multi-pack-index.sh
index 12570fe7ac..133d5b7068 100755
--- a/t/t5319-multi-pack-index.sh
+++ b/t/t5319-multi-pack-index.sh
@@ -398,7 +398,8 @@ test_expect_success 'setup expire tests' '
 		git pack-objects --revs .git/objects/pack/pack-E <<-EOF &&
 		refs/heads/E
 		EOF
-		git multi-pack-index write
+		git multi-pack-index write &&
+		cp -r .git/objects/pack .git/objects/pack-backup
 	)
 '
 
@@ -432,4 +433,21 @@ test_expect_success 'expire removes unreferenced packs' '
 	)
 '
 
+test_expect_success 'repack with minimum size does not alter existing packs' '
+	(
+		cd dup &&
+		rm -rf .git/objects/pack &&
+		mv .git/objects/pack-backup .git/objects/pack &&
+		touch -m -t 201901010000 .git/objects/pack/pack-D* &&
+		touch -m -t 201901010001 .git/objects/pack/pack-C* &&
+		touch -m -t 201901010002 .git/objects/pack/pack-B* &&
+		touch -m -t 201901010003 .git/objects/pack/pack-A* &&
+		ls .git/objects/pack >expect &&
+		MINSIZE=$(ls -l .git/objects/pack/*pack | awk "{print \$5;}" | sort -n | head -n 1) &&
+		git multi-pack-index repack --batch-size=$MINSIZE &&
+		ls .git/objects/pack >actual &&
+		test_cmp expect actual
+	)
+'
+
 test_done

-- 
gitgitgadget
Previous: Derrick Stolee via GitGitGadgetNext: Derrick Stolee via GitGitGadget
Message 10 of 29 in “Create 'expire' and 'repack' verbs for git-multi-pack-index”
  1. 00/11 Create 'expire' and 'repack' verbs for git-multi-pack-indexDerrick Stolee via GitGitGadget, Jun 10, 2019
  2. 01/11 repack: refactor pack deletion for future useDerrick Stolee via GitGitGadget, Jun 10, 2019
  3. 02/11 Docs: rearrange subcommands for multi-pack-indexDerrick Stolee via GitGitGadget, Jun 10, 2019
  4. 03/11 multi-pack-index: prepare for 'expire' subcommandDerrick Stolee via GitGitGadget, Jun 10, 2019
  5. 05/11 midx: refactor permutation logic and pack sortingDerrick Stolee via GitGitGadget, Jun 10, 2019
  6. 10/11 midx: add test that 'expire' respects .keep filesDerrick Stolee via GitGitGadget, Jun 10, 2019
  7. 11/11 t5319-multi-pack-index.sh: test batch size zeroDerrick Stolee via GitGitGadget, Jun 10, 2019
  8. 08/11 midx: implement midx_repack()Derrick Stolee via GitGitGadget, Jun 10, 2019
  9. 04/11 midx: simplify computation of pack name lengthsDerrick Stolee via GitGitGadget, Jun 10, 2019
  10. 07/11 multi-pack-index: prepare 'repack' subcommandDerrick Stolee via GitGitGadget, Jun 10, 2019
  11. 09/11 multi-pack-index: test expire while adding packsDerrick Stolee via GitGitGadget, Jun 10, 2019
  12. 06/11 multi-pack-index: implement 'expire' subcommandDerrick Stolee via GitGitGadget, Jun 10, 2019
  13. Junio C HamanoJun 11, 2019
  14. t5319: don't trip over a user name with whitespaceJohannes Sixt, Jun 30, 2019
  15. Eric SunshineJun 30, 2019
  16. Johannes SixtJun 30, 2019
  17. Jeff KingJun 30, 2019
  18. Johannes SixtJul 1, 2019
  19. Jeff KingJul 1, 2019
  20. SZEDER GáborJul 1, 2019
  21. Derrick StoleeJul 1, 2019
  22. Johannes SchindelinJul 1, 2019
  23. Derrick StoleeJul 1, 2019
  24. Johannes SixtJul 1, 2019
  25. Derrick StoleeJul 1, 2019
  26. Jeff KingJul 1, 2019
  27. SZEDER GáborJul 1, 2019
  28. Andreas SchwabJul 1, 2019
  29. Junio C HamanoJul 1, 2019

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