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Chef::RunLock

Chef::RunLock

Provides an interface for acquiring and releasing a system-wide exclusive lock.

Used by Chef::Client to ensure only one instance of chef-client (or solo) is modifying the system at a time.

Attributes

mutex[R]
runlock[R]
runlock_file[R]

Public Class Methods

new(lockfile) click to toggle source

Create a new instance of RunLock

Arguments

  • :lockfile:

    the full path to the lockfile.

# File lib/chef/run_lock.rb, line 45
def initialize(lockfile)
  @runlock_file = lockfile
  @runlock = nil
  @mutex = nil
  @runpid = nil
end

Public Instance Methods

acquire() click to toggle source

Acquire the system-wide lock. Will block indefinitely if another process already has the lock and Chef::Config is not set. Otherwise will block for Chef::Config seconds and exit if the lock is not acquired.

Each call to acquire should have a corresponding call to release.

The implementation is based on File#flock (see also: flock(2)).

Either acquire() or test() methods should be called in order to get the ownership of run_lock.

# File lib/chef/run_lock.rb, line 63
def acquire
  if timeout_given?
    begin
      Timeout::timeout(time_to_wait) do
        unless test
          if time_to_wait > 0.0
            wait
          else
            exit_from_timeout
          end
        end
      end
    rescue Timeout::Error => e
      exit_from_timeout
    end
  else
    wait unless test
  end
end
release() click to toggle source

Release the system-wide lock.

# File lib/chef/run_lock.rb, line 135
def release
  if runlock
    if Chef::Platform.windows?
      mutex.release
    else
      runlock.flock(File::LOCK_UN)
    end
    runlock.close
    # Don't unlink the pid file, if another chef-client was waiting, it
    # won't be recreated. Better to leave a "dead" pid file than not have
    # it available if you need to break the lock.
    reset
  end
end
save_pid() click to toggle source
# File lib/chef/run_lock.rb, line 125
def save_pid
  runlock.truncate(0)
  runlock.rewind # truncate doesn't reset position to 0.
  runlock.write(Process.pid.to_s)
  # flush the file fsync flushes the system buffers
  # in addition to ruby buffers
  runlock.fsync
end
test() click to toggle source

Tests and if successful acquires the system-wide lock. Returns true if the lock is acquired, false otherwise.

Either acquire() or test() methods should be called in order to get the ownership of run_lock.

# File lib/chef/run_lock.rb, line 89
def test
  # ensure the runlock_file path exists
  create_path(File.dirname(runlock_file))
  @runlock = File.open(runlock_file,'a+')

  if Chef::Platform.windows?
    acquire_win32_mutex
  else
    # If we support FD_CLOEXEC, then use it.
    # NB: ruby-2.0.0-p195 sets FD_CLOEXEC by default, but not
    # ruby-1.8.7/1.9.3
    if Fcntl.const_defined?('F_SETFD') && Fcntl.const_defined?('FD_CLOEXEC')
      runlock.fcntl(Fcntl::F_SETFD, runlock.fcntl(Fcntl::F_GETFD, 0) | Fcntl::FD_CLOEXEC)
    end
    # Flock will return 0 if it can acquire the lock otherwise it
    # will return false
    if runlock.flock(File::LOCK_NB|File::LOCK_EX) == 0
      true
    else
      false
    end
  end
end
wait() click to toggle source

Waits until acquiring the system-wide lock.

# File lib/chef/run_lock.rb, line 116
def wait
  Chef::Log.warn("Chef client #{runpid} is running, will wait for it to finish and then run.")
  if Chef::Platform.windows?
    mutex.wait
  else
    runlock.flock(File::LOCK_EX)
  end
end

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