Re: Create an exclusive lock on an IFS file?

On 11/3/2014 11:18 AM, CRPence wrote:

Currently I'm looking at using this code to make the lock.

IFSRandomAccessFile lockFile = new IFSRandomAccessFile(as400,
LOCKFILE, "rw");

IFSKey lockKey = lockFile.lock(0L, 10L);

I would think more appropriate, including the optional fourth
argument [int shareOption] for the open request, using the value of
SHARE_NONE; i.e. preventing an open by any other process\thread
irrespective that other thread properly implementing the
keyed-locking scheme.?

Assuming I understand what you are saying, I'm not especially worried about another process trying to read or lock the LOCKFILE in question. The chances of another application trying to use the same file in the IFS is vanishingly slim.

Also, I am unsure of the default for the optional fifth argument
[int existenceOption] for the open request, but possibly the value
OPEN_OR_FAIL is desirable if the semaphore is implemented as a "lock
on *a known* IFS file" [emphasis mine].?

The file in question should *NOT* exist. If it does, then reason would the application left the file behind accidentally (aborted, killed, etc, before cleanup). I've changed my code to be the following:

file = new IFSFile(as400, LOCKFILE_NAME);

lockFile = new IFSRandomAccessFile(file, "rw",
IFSRandomAccessFile.SHARE_ALL,
IFSRandomAccessFile.OPEN_OR_CREATE);

lockKey = lockFile.lock(0L, 10L);

(the above code is actually encapsulated in a class)

This way, once the lock is no longer needed, I perform the unlock and then delete the lock file.

david