Class: Chef::RunLock

Inherits:
Object
  • Object
show all
Includes:
Mixin::CreatePath
Defined in:
lib/chef/run_lock.rb

Overview

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.

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from Mixin::CreatePath

#create_path

Constructor Details

#initialize(lockfile) ⇒ RunLock

Create a new instance of RunLock

Arguments

  • :lockfile:

    the full path to the lockfile.


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# File 'lib/chef/run_lock.rb', line 46

def initialize(lockfile)
  @runlock_file = lockfile
  @runlock = nil
  @mutex = nil
  @runpid = nil
end

Instance Attribute Details

#mutexObject (readonly)

Returns the value of attribute mutex


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# File 'lib/chef/run_lock.rb', line 40

def mutex
  @mutex
end

#runlockObject (readonly)

Returns the value of attribute runlock


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# File 'lib/chef/run_lock.rb', line 39

def runlock
  @runlock
end

#runlock_fileObject (readonly)

Returns the value of attribute runlock_file


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# File 'lib/chef/run_lock.rb', line 41

def runlock_file
  @runlock_file
end

Instance Method Details

#acquireObject

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.


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# File 'lib/chef/run_lock.rb', line 64

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
      exit_from_timeout
    end
  else
    wait unless test
  end
end

#acquire_lockObject


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# File 'lib/chef/run_lock.rb', line 140

def acquire_lock
  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

#create_lockObject


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# File 'lib/chef/run_lock.rb', line 133

def create_lock
  # ensure the runlock_file path exists
  create_path(File.dirname(runlock_file))
  @runlock = File.open(runlock_file, "a+")
end

#releaseObject

Release the system-wide lock.


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# File 'lib/chef/run_lock.rb', line 117

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_pidObject


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# File 'lib/chef/run_lock.rb', line 107

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

#testObject

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.


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# File 'lib/chef/run_lock.rb', line 90

def test
  create_lock
  acquire_lock
end

#waitObject

Waits until acquiring the system-wide lock.


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# File 'lib/chef/run_lock.rb', line 98

def wait
  Chef::Log.warn("#{Chef::Dist::PRODUCT} #{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