109 lines
2.8 KiB
Ruby
109 lines
2.8 KiB
Ruby
# typed: true # rubocop:todo Sorbet/StrictSigil
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# frozen_string_literal: true
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require "fcntl"
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# A lock file to prevent multiple Homebrew processes from modifying the same path.
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class LockFile
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class OpenFileChangedOnDisk < RuntimeError; end
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private_constant :OpenFileChangedOnDisk
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attr_reader :path
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sig { params(type: Symbol, locked_path: Pathname).void }
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def initialize(type, locked_path)
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@locked_path = locked_path
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lock_name = locked_path.basename.to_s
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@path = HOMEBREW_LOCKS/"#{lock_name}.#{type}.lock"
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@lockfile = nil
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end
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sig { void }
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def lock
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ignore_interrupts do
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next if @lockfile.present?
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path.dirname.mkpath
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begin
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lockfile = begin
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path.open(File::RDWR | File::CREAT)
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rescue Errno::EMFILE
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odie "The maximum number of open files on this system has been reached. " \
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"Use `ulimit -n` to increase this limit."
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end
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lockfile.fcntl(Fcntl::F_SETFD, Fcntl::FD_CLOEXEC)
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if lockfile.flock(File::LOCK_EX | File::LOCK_NB)
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# This prevents a race condition in case the file we locked doesn't exist on disk anymore, e.g.:
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#
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# 1. Process A creates and opens the file.
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# 2. Process A locks the file.
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# 3. Process B opens the file.
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# 4. Process A unlinks the file.
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# 5. Process A unlocks the file.
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# 6. Process B locks the file.
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# 7. Process C creates and opens the file.
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# 8. Process C locks the file.
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# 9. Process B and C hold locks to files with different inode numbers. 💥
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if !path.exist? || lockfile.stat.ino != path.stat.ino
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lockfile.close
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raise OpenFileChangedOnDisk
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end
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@lockfile = lockfile
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next
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end
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rescue OpenFileChangedOnDisk
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retry
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end
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lockfile.close
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raise OperationInProgressError, @locked_path
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end
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end
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sig { params(unlink: T::Boolean).void }
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def unlock(unlink: false)
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ignore_interrupts do
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next if @lockfile.nil?
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@path.unlink if unlink
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@lockfile.flock(File::LOCK_UN)
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@lockfile.close
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@lockfile = nil
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end
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end
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def with_lock
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lock
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yield
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ensure
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unlock
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end
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end
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# A lock file for a formula.
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class FormulaLock < LockFile
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sig { params(rack_name: String).void }
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def initialize(rack_name)
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super(:formula, HOMEBREW_CELLAR/rack_name)
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end
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end
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# A lock file for a cask.
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class CaskLock < LockFile
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sig { params(cask_token: String).void }
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def initialize(cask_token)
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super(:cask, HOMEBREW_PREFIX/"Caskroom/#{cask_token}")
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end
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end
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# A lock file for a download.
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class DownloadLock < LockFile
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sig { params(download_path: Pathname).void }
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def initialize(download_path)
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super(:download, download_path)
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end
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end
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