Re: [jbosscache-dev] Pulling the FileCacheLoader from 3.0.0
Manik Surtani wrote:
On 1 Apr 2008, at 16:38, Brian Stansberry wrote:
>>
>> Re: FileChannel, locking is less important since I have implemented
>> locking on a per-Fqn basis in the FCL [1] - agreed the FileChannel
>> stuff may be better, but it's a less urgent need since locking isn't
>> a problem with the FCL anymore.
>
> If the FCL is used with a shared=true you need to coordinate access to
> the filesystem.
Unless I'm mistaken, the FileChannel lock won't do that either?
Platform dependent. From the javadoc of java.nio.channels.FileLock:
"Platform dependencies
This file-locking API is intended to map directly to the native locking
facility of the underlying operating system. Thus the locks held on a
file should be visible to all programs that have access to the file,
regardless of the language in which those programs are written.
Whether or not a lock actually prevents another program from accessing
the content of the locked region is system-dependent and therefore
unspecified.
...
Some network filesystems permit file locking to be used with
memory-mapped files only when the locked regions are page-aligned and a
whole multiple of the underlying hardware's page size. Some network
filesystems do not implement file locks on regions that extend past a
certain position, often 230 or 231. In general, great care should be
taken when locking files that reside on network filesystems."
--
Manik Surtani
Lead, JBoss Cache
manik(a)jboss.org
--
Brian Stansberry
Lead, AS Clustering
JBoss, a division of Red Hat
brian.stansberry(a)redhat.com