Class: LockFile Private

Inherits:
Object show all
Defined in:
lock_file.rb

Overview

This class is part of a private API. This class may only be used in the Homebrew/brew repository. Third parties should avoid using this class if possible, as it may be removed or changed without warning.

A lock file to prevent multiple Homebrew processes from modifying the same path.

Direct Known Subclasses

CaskLock, DownloadLock, FormulaLock

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(type, locked_path) ⇒ void

This method is part of a private API. This method may only be used in the Homebrew/brew repository. Third parties should avoid using this method if possible, as it may be removed or changed without warning.

Parameters:



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# File 'lock_file.rb', line 14

def initialize(type, locked_path)
  @locked_path = locked_path
  lock_name = locked_path.basename.to_s
  @path = HOMEBREW_LOCKS/"#{lock_name}.#{type}.lock"
  @lockfile = nil
end

Instance Attribute Details

#path ⇒ Object (readonly)

This method is part of a private API. This method may only be used in the Homebrew/brew repository. Third parties should avoid using this method if possible, as it may be removed or changed without warning. 



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# File 'lock_file.rb', line 11

def path
  @path
end

Instance Method Details

#lock ⇒ void

This method is part of a private API. This method may only be used in the Homebrew/brew repository. Third parties should avoid using this method if possible, as it may be removed or changed without warning.

This method returns an undefined value.



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# File 'lock_file.rb', line 22

def lock
  ignore_interrupts do
    next if @lockfile.present?

    path.dirname.mkpath

    begin
      lockfile = begin
        path.open(File::RDWR | File::CREAT)
      rescue Errno::EMFILE
        odie "The maximum number of open files on this system has been reached. " \
             "Use `ulimit -n` to increase this limit."
      end
      lockfile.fcntl(Fcntl::F_SETFD, Fcntl::FD_CLOEXEC)

      if lockfile.flock(File::LOCK_EX | File::LOCK_NB)
        # This prevents a race condition in case the file we locked doesn't exist on disk anymore, e.g.:
        #
        # 1. Process A creates and opens the file.
        # 2. Process A locks the file.
        # 3. Process B opens the file.
        # 4. Process A unlinks the file.
        # 5. Process A unlocks the file.
        # 6. Process B locks the file.
        # 7. Process C creates and opens the file.
        # 8. Process C locks the file.
        # 9. Process B and C hold locks to files with different inode numbers. 💥
        if !path.exist? || lockfile.stat.ino != path.stat.ino
          lockfile.close
          raise OpenFileChangedOnDisk
        end

        @lockfile = lockfile
        next
      end
    rescue OpenFileChangedOnDisk
      retry
    end

    lockfile.close
    raise OperationInProgressError, @locked_path
  end
end

#unlock(unlink: false) ⇒ void

This method is part of a private API. This method may only be used in the Homebrew/brew repository. Third parties should avoid using this method if possible, as it may be removed or changed without warning.

This method returns an undefined value.

Parameters:

  • unlink (Boolean) (defaults to: false) 


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# File 'lock_file.rb', line 67

def unlock(unlink: false)
  ignore_interrupts do
    next if @lockfile.nil?

    @path.unlink if unlink
    @lockfile.flock(File::LOCK_UN)
    @lockfile.close
    @lockfile = nil
  end
end

#with_lock ⇒ Object

This method is part of a private API. This method may only be used in the Homebrew/brew repository. Third parties should avoid using this method if possible, as it may be removed or changed without warning. 



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# File 'lock_file.rb', line 78

def with_lock
  lock
  yield
ensure
  unlock
end