forked from the-distro/infra
133 lines
4.4 KiB
Bash
133 lines
4.4 KiB
Bash
#!/usr/bin/env bash
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set +o errexit
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# Copyright (C) 2022 The Android Open Source Project
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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usage() { # exit code
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cat <<-EOF
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NAME
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git-gc-preserve - Run git gc and preserve old packs to avoid races for JGit
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SYNOPSIS
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git gc-preserve
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DESCRIPTION
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Runs git gc and can preserve old packs to avoid races with concurrently
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executed commands in JGit.
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This command uses custom git config options to configure if preserved packs
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from the last run of git gc should be pruned and if packs should be preserved.
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This is similar to the implementation in JGit [1] which is used by
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JGit to avoid errors [2] in such situations.
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The command prevents concurrent runs of the command on the same repository
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by acquiring an exclusive file lock on the file
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"\$repopath/gc-preserve.pid"
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If it cannot acquire the lock it fails immediately with exit code 3.
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Failure Exit Codes
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1: General failure
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2: Couldn't determine repository path. If the current working directory
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is outside of the working tree of the git repository use git option
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--git-dir to pass the root path of the repository.
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E.g.
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$ git --git-dir ~/git/foo gc-preserve
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3: Another process already runs $0 on the same repository
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[1] https://git.eclipse.org/r/c/jgit/jgit/+/87969
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[2] https://git.eclipse.org/r/c/jgit/jgit/+/122288
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CONFIGURATION
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"pack.prunepreserved": if set to "true" preserved packs from the last gc run
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are pruned before current packs are preserved.
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"pack.preserveoldpacks": if set to "true" current packs will be hard linked
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to objects/pack/preserved before git gc is executed. JGit will
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fallback to the preserved packs in this directory in case it comes
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across missing objects which might be caused by a concurrent run of
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git gc.
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EOF
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exit "$1"
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}
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# acquire file lock, unlock when the script exits
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lock() { # repo
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readonly LOCKFILE="$1/gc-preserve.pid"
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test -f "$LOCKFILE" || touch "$LOCKFILE"
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exec 9> "$LOCKFILE"
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if flock -nx 9; then
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echo -n "$$ $USER@$(hostname)" >&9
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trap unlock EXIT
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else
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echo "$0 is already running"
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exit 3
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fi
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}
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unlock() {
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# only delete if the file descriptor 9 is open
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if { : >&9 ; } &> /dev/null; then
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rm -f "$LOCKFILE"
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fi
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# close the file handle to release file lock
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exec 9>&-
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}
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# prune preserved packs if pack.prunepreserved == true
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prune_preserved() { # repo
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configured=$(git --git-dir="$1" config --get pack.prunepreserved)
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if [ "$configured" != "true" ]; then
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return 0
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fi
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local preserved=$1/objects/pack/preserved
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if [ -d "$preserved" ]; then
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printf "Pruning old preserved packs: "
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count=$(find "$preserved" -name "*.old-pack" | wc -l)
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rm -rf "$preserved"
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echo "$count, done."
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fi
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}
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# preserve packs if pack.preserveoldpacks == true
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preserve_packs() { # repo
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configured=$(git --git-dir="$1" config --get pack.preserveoldpacks)
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if [ "$configured" != "true" ]; then
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return 0
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fi
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local packdir=$1/objects/pack
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pushd "$packdir" >/dev/null || exit 1
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mkdir -p preserved
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printf "Preserving packs: "
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count=0
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for file in pack-*{.pack,.idx} ; do
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ln -f "$file" preserved/"$(get_preserved_packfile_name "$file")"
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if [[ "$file" == pack-*.pack ]]; then
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((count++))
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fi
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done
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echo "$count, done."
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popd >/dev/null || exit 1
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}
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# pack-0...2.pack to pack-0...2.old-pack
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# pack-0...2.idx to pack-0...2.old-idx
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get_preserved_packfile_name() { # packfile > preserved_packfile
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local old=${1/%\.pack/.old-pack}
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old=${old/%\.idx/.old-idx}
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echo "$old"
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}
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# main
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while [ $# -gt 0 ] ; do
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case "$1" in
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-u|-h) usage 0 ;;
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esac
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shift
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done
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args=$(git rev-parse --sq-quote "$@")
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repopath=$(git rev-parse --git-dir)
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if [ -z "$repopath" ]; then
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usage 2
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fi
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lock "$repopath"
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prune_preserved "$repopath"
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preserve_packs "$repopath"
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git gc ${args:+"$args"} || { EXIT_CODE="$?"; echo "git gc failed"; exit "$EXIT_CODE"; }
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