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#
# Author:: Daniel DeLeo (<dan@opscode.com>)
# Copyright:: Copyright (c) 2012 Opscode, Inc.
# License:: Apache License, Version 2.0
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
require 'chef/mixin/create_path'
require 'fcntl'
if Chef::Platform.windows?
require 'chef/win32/mutex'
end
require 'chef/config'
require 'chef/exceptions'
require 'timeout'
class Chef
# == 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.
class RunLock
include Chef::Mixin::CreatePath
attr_reader :runlock
attr_reader :mutex
attr_reader :runlock_file
# Create a new instance of RunLock
# === Arguments
# * :lockfile::: the full path to the lockfile.
def initialize(lockfile)
@runlock_file = lockfile
@runlock = nil
@mutex = nil
@runpid = nil
end
# Acquire the system-wide lock. Will block indefinitely if another process
# already has the lock and Chef::Config[:run_lock_timeout] is
# not set. Otherwise will block for Chef::Config[:run_lock_timeout]
# 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.
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
#
# 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.
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
#
# Waits until acquiring the system-wide lock.
#
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
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
# Release the system-wide lock.
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
private
def reset
@runlock = nil
@mutex = nil
@runpid = nil
end
# Since flock mechanism doesn't exist on windows we are using
# platform Mutex.
# We are creating a "Global" mutex here so that non-admin
# users can not DoS chef-client by creating the same named
# mutex we are using locally.
# Mutex name is case-sensitive contrary to other things in
# windows. "\" is the only invalid character.
def acquire_win32_mutex
@mutex = Chef::ReservedNames::Win32::Mutex.new("Global\\#{runlock_file.gsub(/[\\]/, "/").downcase}")
mutex.test
end
def runpid
@runpid ||= runlock.read.strip
end
def timeout_given?
!time_to_wait.nil?
end
def time_to_wait
Chef::Config[:run_lock_timeout]
end
def exit_from_timeout
rp = runpid
release # Just to be on the safe side...
raise Chef::Exceptions::RunLockTimeout.new(time_to_wait, rp)
end
end
end
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