Object
A lock file is a synchronization mechanism, like a Mutex, but it also allows inter-process synchronization (as opposed to only inter-thread synchronization within a single process).
Processes can obtain either a shared lock or an exclusive lock. It’s possible for multiple processes to obtain a shared lock on a file as long as no exclusive lock has been obtained by a process. If a process has obtained an exclusive lock, then no other processes can lock the file, whether they’re trying to obtain a shared lock or an exclusive lock.
Note that on JRuby, LockFile can only guarantee synchronization between threads if the different threads use the same LockFile object. Specifying the same filename is not enough.
Create a LockFile object. The lock file is initially not locked.
filename may point to a nonexistant file. In that case, the lock file will not be created until one’s trying to obtain a lock.
Note that LockFile will use this exact filename. So if filename is a relative filename, then the actual lock file that will be used depends on the current working directory.
# File lib/daemon_controller/lock_file.rb, line 51 51: def initialize(filename) 52: @filename = filename 53: end
Obtain an exclusive lock on the lock file, yield the given block, then unlock the lockfile. If the lock file was already locked (whether shared or exclusively) by another process/thread then this method will block until the lock file has been unlocked.
The lock file must be writable, otherwise an Errno::EACCESS exception will be raised.
# File lib/daemon_controller/lock_file.rb, line 62 62: def exclusive_lock 63: File.open(@filename, 'w') do |f| 64: if Fcntl.const_defined? :F_SETFD 65: f.fcntl(Fcntl::F_SETFD, Fcntl::FD_CLOEXEC) 66: end 67: f.flock(File::LOCK_EX) 68: yield 69: end 70: end
Try to obtain an exclusive lock on the lock file, similar to #. But unlike #, this method will raise AlreadyLocked if no lock can be obtained, instead of blocking.
If a lock can be obtained, then the given block will be yielded.
# File lib/daemon_controller/lock_file.rb, line 113 113: def try_exclusive_lock 114: File.open(@filename, 'w') do |f| 115: if Fcntl.const_defined? :F_SETFD 116: f.fcntl(Fcntl::F_SETFD, Fcntl::FD_CLOEXEC) 117: end 118: if f.flock(File::LOCK_EX | File::LOCK_NB) 119: yield 120: else 121: raise AlreadyLocked 122: end 123: end 124: end
Disabled; run with --debug to generate this.
Generated with the Darkfish Rdoc Generator 1.1.6.