Class: Chef::RunLock

Inherits:
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(config) ⇒ RunLock

Create a new instance of RunLock

Arguments

  • config:

    This will generally be the ‘Chef::Config`, but any Hash-like

    object with Symbol keys will work. See ‘Parameters’ section.

Parameters/Config

  • :lockfile:

    if set, this will be used as the full path to the lockfile.

  • :file_cache_path:

    if ‘:lockfile` is not set, the lock file will be

    named “chef-client-running.pid” and be placed in the directory given by ‘:file_cache_path`



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# File 'lib/chef/run_lock.rb', line 43

def initialize(config)
  @runlock_file = config[:lockfile] || "#{config[:file_cache_path]}/chef-client-running.pid"
  @runlock = nil
end

Instance Attribute Details

#runlock ⇒ Object (readonly)

Returns the value of attribute runlock.



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# File 'lib/chef/run_lock.rb', line 31

def runlock
  @runlock
end

#runlock_file ⇒ Object (readonly)

Returns the value of attribute runlock_file.



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# File 'lib/chef/run_lock.rb', line 32

def runlock_file
  @runlock_file
end

Instance Method Details

#acquire ⇒ Object

Acquire the system-wide lock. Will block indefinitely if another process already has the lock.

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

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



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# File 'lib/chef/run_lock.rb', line 54

def acquire
  # ensure the runlock_file path exists
  create_path(File.dirname(runlock_file))
  @runlock = File.open(runlock_file,'w+')
  unless runlock.flock(File::LOCK_EX|File::LOCK_NB)
    # Another chef client running...
    runpid = runlock.read.strip.chomp
    Chef::Log.info("Chef client #{runpid} is running, will wait for it to finish and then run.")
    runlock.flock(File::LOCK_EX)
  end
  # We grabbed the run lock.  Save the pid.
  runlock.truncate(0)
  runlock.rewind # truncate doesn't reset position to 0.
  runlock.write(Process.pid.to_s)
end

#release ⇒ Object

Release the system-wide lock.



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# File 'lib/chef/run_lock.rb', line 71

def release
  if runlock
    runlock.flock(File::LOCK_UN)
    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