[Glass] protect temporary files

[Otto Behrens]

Thanks everyone. I opted for a read lock as a mutex. I release the lock in
an ensure block. This appears to be the simplest as I cannot rely on
transactions at the point in time when this is invoked. Let's see
what happens.

Otto Behrens

+27 82 809 2375
[image: FINWorks]
[image: FINWorks] <http://za.linkedin.com/in/waltherbehrens>
www.finworks.biz

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On Fri, Jun 2, 2023 at 6:04 PM Norm Green via Glass <
glass at lists.gemtalksystems.com> wrote:

> Hi Otto,
>
> There is file locking protocol in GsFile under category #locking. There
> are several caveats and restrictions so be sure to read the methods
> carefully. Also note that file locking over NFS is buggy and should not be
> relied upon. If your zip files are on NFS you could create a local (not on
> NFS) 1 byte file with a known name in a known location and lock it when the
> zip file is in use.
>
> There are other ways to do this as well as James says. For example, you
> could also use a shared counter (in class System) as your lock bit and use
> a KeyValueDictionary to map the file name to the shared counter ID.
>
> Norm Green
>
> On 6/2/2023 5:09 AM, Otto Behrens via Glass wrote:
>
> Hi,
>
> We have zipped files (references stored in GemStone with
> MAExternalFileModel) that we use in an operation, for example to merge PDF
> data (with PDFTk) or serve to the user via the web server, while it is
> temporarily unzipped. The code is something like this:
>
> operation: aBlock
>   tempFile := f unzip.
>   ^ [ aBlock value: tempFile ] ensure: [ tempFile remove ]
>
> We have on occasion multiple sessions that do operations on the same file,
> which causes a problem. We would like to protect the operation with a
> semaphore or something like that.
>
> Is a Semaphore the way to solve this or is there a better alternative?
>
> If we use Semaphore and store it on our file object, we cannot commit
> because we cannot persist the semaphore instVar. According to the
> programming guide, "if you need to encapsulate objects that should not be
> persistent, such as semaphores, within object structures that do need to be
> persistent and shared".
>
> I am unsure how to structure this or if this is a good idea. Can anyone
> please help?
>
> Kind regards
>
> Otto Behrens
>
> +27 82 809 2375
> [image: FINWorks]
>
>
>
> [image: FINWorks] <http://za.linkedin.com/in/waltherbehrens>
> www.finworks.biz
>
> Disclaimer & Confidentiality Note: This email is intended solely for the
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> than the addressee in respect of any opinions, conclusions, advice or other
> information contained in this email.
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