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c45af94dbc
We normally try to avoid having two auto-gc operations run at the same time, because it wastes resources. This was done long ago in64a99eb47(gc: reject if another gc is running, unless --force is given, 2013-08-08). When we do a detached auto-gc, we run the ref-related commands _before_ detaching, to avoid confusing lock contention. This was done by62aad1849(gc --auto: do not lock refs in the background, 2014-05-25). These two features do not interact well. The pre-detach operations are run before we check the gc.pid lock, meaning that on a busy repository we may run many of them concurrently. Ideally we'd take the lock before spawning any operations, and hold it for the duration of the program. This is tricky, though, with the way the pid-file interacts with the daemonize() process. Other processes will check that the pid recorded in the pid-file still exists. But detaching causes us to fork and continue running under a new pid. So if we take the lock before detaching, the pid-file will have a bogus pid in it. We'd have to go back and update it with the new pid after detaching. We'd also have to play some tricks with the tempfile subsystem to tweak the "owner" field, so that the parent process does not clean it up on exit, but the child process does. Instead, we can do something a bit simpler: take the lock only for the duration of the pre-detach work, then detach, then take it again for the post-detach work. Technically, this means that the post-detach lock could lose to another process doing pre-detach work. But in the long run this works out. That second process would then follow-up by doing post-detach work. Unless it was in turn blocked by a third process doing pre-detach work, and so on. This could in theory go on indefinitely, as the pre-detach work does not repack, and so need_to_gc() will continue to trigger. But in each round we are racing between the pre- and post-detach locks. Eventually, one of the post-detach locks will win the race and complete the full gc. So in the worst case, we may racily repeat the pre-detach work, but we would never do so simultaneously (it would happen via a sequence of serialized race-wins). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
123 lines
3.6 KiB
Bash
Executable file
123 lines
3.6 KiB
Bash
Executable file
#!/bin/sh
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test_description='basic git gc tests
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'
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. ./test-lib.sh
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test_expect_success 'gc empty repository' '
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git gc
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'
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test_expect_success 'gc does not leave behind pid file' '
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git gc &&
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test_path_is_missing .git/gc.pid
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'
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test_expect_success 'gc --gobbledegook' '
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test_expect_code 129 git gc --nonsense 2>err &&
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test_i18ngrep "[Uu]sage: git gc" err
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'
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test_expect_success 'gc -h with invalid configuration' '
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mkdir broken &&
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(
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cd broken &&
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git init &&
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echo "[gc] pruneexpire = CORRUPT" >>.git/config &&
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test_expect_code 129 git gc -h >usage 2>&1
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) &&
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test_i18ngrep "[Uu]sage" broken/usage
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'
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test_expect_success 'gc is not aborted due to a stale symref' '
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git init remote &&
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(
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cd remote &&
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test_commit initial &&
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git clone . ../client &&
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git branch -m develop &&
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cd ../client &&
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git fetch --prune &&
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git gc
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)
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'
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test_expect_success 'auto gc with too many loose objects does not attempt to create bitmaps' '
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test_config gc.auto 3 &&
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test_config gc.autodetach false &&
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test_config pack.writebitmaps true &&
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# We need to create two object whose sha1s start with 17
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# since this is what git gc counts. As it happens, these
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# two blobs will do so.
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test_commit 263 &&
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test_commit 410 &&
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# Our first gc will create a pack; our second will create a second pack
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git gc --auto &&
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ls .git/objects/pack | sort >existing_packs &&
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test_commit 523 &&
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test_commit 790 &&
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git gc --auto 2>err &&
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test_i18ngrep ! "^warning:" err &&
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ls .git/objects/pack/ | sort >post_packs &&
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comm -1 -3 existing_packs post_packs >new &&
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comm -2 -3 existing_packs post_packs >del &&
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test_line_count = 0 del && # No packs are deleted
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test_line_count = 2 new # There is one new pack and its .idx
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'
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run_and_wait_for_auto_gc () {
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# We read stdout from gc for the side effect of waiting until the
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# background gc process exits, closing its fd 9. Furthermore, the
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# variable assignment from a command substitution preserves the
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# exit status of the main gc process.
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# Note: this fd trickery doesn't work on Windows, but there is no
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# need to, because on Win the auto gc always runs in the foreground.
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doesnt_matter=$(git gc --auto 9>&1)
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}
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test_expect_success 'background auto gc does not run if gc.log is present and recent but does if it is old' '
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test_commit foo &&
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test_commit bar &&
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git repack &&
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test_config gc.autopacklimit 1 &&
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test_config gc.autodetach true &&
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echo fleem >.git/gc.log &&
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test_must_fail git gc --auto 2>err &&
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test_i18ngrep "^error:" err &&
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test_config gc.logexpiry 5.days &&
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test-chmtime =-345600 .git/gc.log &&
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test_must_fail git gc --auto &&
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test_config gc.logexpiry 2.days &&
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run_and_wait_for_auto_gc &&
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ls .git/objects/pack/pack-*.pack >packs &&
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test_line_count = 1 packs
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'
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test_expect_success 'background auto gc respects lock for all operations' '
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# make sure we run a background auto-gc
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test_commit make-pack &&
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git repack &&
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test_config gc.autopacklimit 1 &&
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test_config gc.autodetach true &&
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# create a ref whose loose presence we can use to detect a pack-refs run
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git update-ref refs/heads/should-be-loose HEAD &&
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test_path_is_file .git/refs/heads/should-be-loose &&
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# now fake a concurrent gc that holds the lock; we can use our
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# shell pid so that it looks valid.
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hostname=$(hostname || echo unknown) &&
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printf "$$ %s" "$hostname" >.git/gc.pid &&
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# our gc should exit zero without doing anything
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run_and_wait_for_auto_gc &&
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test_path_is_file .git/refs/heads/should-be-loose
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'
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# DO NOT leave a detached auto gc process running near the end of the
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# test script: it can run long enough in the background to racily
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# interfere with the cleanup in 'test_done'.
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test_done
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