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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.
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
attr_reader :runlock
attr_reader :runlock_file
# 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`
def initialize(config)
@runlock_file = config[:lockfile] || "#{config[:file_cache_path]}/chef-client-running.pid"
@runlock = nil
end
# 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)).
def acquire
@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 the system-wide lock.
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
private
def reset
@runlock = nil
end
end
end
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