Object
A Lock is used to lock a data source so that not more than one output stream can access a data source at one time. It is possible that locks could be disabled. For example a read only index stored on a CDROM would have no need for a lock.
You can use a lock in two ways. Firstly:
write_lock = @directory.make_lock(LOCK_NAME) write_lock.obtain(WRITE_LOCK_TIME_OUT) ... # Do your file modifications # ... write_lock.release()
Alternatively you could use the while locked method. This ensures that the lock will be released once processing has finished.
write_lock = @directory.make_lock(LOCK_NAME) write_lock.while_locked(WRITE_LOCK_TIME_OUT) do ... # Do your file modifications # ... end
Returns true if the lock has been obtained.
static VALUE frb_lock_is_locked(VALUE self) { Lock *lock; GET_LOCK(lock, self); return lock->is_locked(lock) ? Qtrue : Qfalse; }
Obtain a lock. Returns true if lock was successfully obtained. Make sure the lock is released using Lock#release. Otherwise you’ll be left with a stale lock file.
The timeout defaults to 1 second and 5 attempts are made to obtain the lock. If you’re doing large batch updates on the index with multiple processes you may need to increase the lock timeout but 1 second will be substantial in most cases.
timeout |
seconds to wait to obtain lock before timing out and returning false |
return |
true if lock was successfully obtained. Raises a Lock::LockError otherwise. |
static VALUE frb_lock_obtain(int argc, VALUE *argv, VALUE self) { VALUE rtimeout; int timeout = 1; Lock *lock; GET_LOCK(lock, self); if (rb_scan_args(argc, argv, "01", &rtimeout) > 0) { timeout = FIX2INT(rtimeout); } /* TODO: use the lock timeout */ if (!lock->obtain(lock)) { rb_raise(cLockError, "could not obtain lock: #%s", lock->name); } return Qtrue; }
Release the lock. This should only be called by the process which obtains the lock.
static VALUE frb_lock_release(VALUE self) { Lock *lock; GET_LOCK(lock, self); lock->release(lock); return self; }
Run the code in a block while a lock is obtained, automatically releasing the lock when the block returns.
See Lock#obtain for more information on lock timeout.
timeout |
seconds to wait to obtain lock before timing out and returning false |
return |
true if lock was successfully obtained. Raises a Lock::LockError otherwise. |
static VALUE frb_lock_while_locked(int argc, VALUE *argv, VALUE self) { VALUE rtimeout; int timeout = 1; Lock *lock; GET_LOCK(lock, self); if (rb_scan_args(argc, argv, "01", &rtimeout) > 0) { timeout = FIX2INT(rtimeout); } if (!lock->obtain(lock)) { rb_raise(cLockError, "could not obtain lock: #%s", lock->name); } rb_yield(Qnil); lock->release(lock); return Qtrue; }
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