File locking supported on all platforms?

[Stefan Reich]

Hmm that's what I feared. So to be really sure I should do an actual test.
Maybe I can get away with doing two locks on the same file within one JVM
for testing the feature? I should try that.

Thanks

On Sat, 11 Jul 2020 at 12:10, Jonas Konrad <me at yawk.at> wrote:

> I think it should just fail silently / without error, that's what fcntl
> does at least. I'm not sure if there's a good way to determine whether
> locking will actually work.
>
> - Jonas
>
> On 7/11/20 11:47 AM, Stefan Reich wrote:
> > Hi Jonas,
> >
> > what would happen if I try to lock a file on these platforms? Can I
> > reliably detect this case? That would already help a lot.
> >
> > The use case is ensuring a database's consistency which I now do over a
> > socket protocol, but file locks would be faster and more reliable.
> >
> > Stefan
> >
> > On Sat, 11 Jul 2020 at 11:45, Jonas Konrad <me at yawk.at
> > <mailto:me at yawk.at>> wrote:
> >
> >     Hey,
> >
> >     Some file systems on Linux, eg old NFS, do not support locking at
> all.
> >
> >     - Jonas
> >
> >     On 7/11/20 11:36 AM, Stefan Reich wrote:
> >      > Hi,
> >      >
> >      > a quick question regarding file locks in Java. I seem to remember
> >      > reading somewhere that this feature isn't guaranteed to work on
> all
> >      > platforms. However, I can now find no mention of that e.g. here
> >      >
> >     <
> https://docs.oracle.com/javase/7/docs/api/java/nio/channels/FileLock.html
> >.
> >      >
> >      > The page does list that numerous special assumptions may fail, for
> >      > example that programs which /don't/ lock a file are prevented from
> >      > changing it when it is locked by another program.
> >      >
> >      > However, I only care about the basic feature, namely that one
> >     local file
> >      > cannot be locked by two Java programs at once and will cause one
> >     of them
> >      > to throw an exception.
> >      >
> >      > Is this guaranteed to work everywhere?
> >      >
> >      > Many greetings
> >      > Stefan
> >      >
> >      > --
> >      > Stefan Reich
> >      > BotCompany.de // Java-based operating systems
> >
> >
> >
> > --
> > Stefan Reich
> > BotCompany.de // Java-based operating systems
>


-- 
Stefan Reich
BotCompany.de // Java-based operating systems
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