Re: Processes with open handles to unlinked files

I commented:
Some programs will deliberately create temporary files and unlink them
immediately, to ensure that if anything is killed or crashes, the
[temporary file is deleted].

Tony Lawrence replied:
Yes, of course: I do that myself. But what I meant was what process is
so sloppy that it matters?

I might have a couple of files hanging about for a few minutes, but not
enough that I'm concerned about disk space (certainly not nowadays
anyway!). And those processes WILL end, and the space will be
reclaimed - this sounds like he's got some runaway rogue..

I said:
"Temporary" files might not be *that* temporary, or that small,
especially if the temporary files contain per-session database tables
and the program is querying a large (separate and persistent) database.

Tony objected:
If that were the case, then obviously you wouldn't be looking to kill
off processes ordinarily, now would you?

I think you're assuming either a single-user machine here, or one where
the users co-operate on the use of the machine. It's quite possible that
the only way the administrator normally knows what the machine is
running is by using the provided tools.

If the process is doing legitimate work, why on earth would he be
looking to kill it? And if not, then why is it still running? Why
hasn't it finished on its own?

No, something is very, very wrong here. Do *you* have systems where
you have to ordinarily and regularly use lsof to find unlinked open
files? Where that's an accepted and ordinary part of administering
the system?

OK -- say that I've got a system where a number of users are running
long-running reports against a database. One of them may have been
misprogrammed, or the user might have (by mistake) chosen options that
require a huge amount of run-time and disk space. Because these reports
*are* long-running anyway, the users have got used to leaving them to
run and continue working in other sessions. These users are
non-technical, and may not notice that their program is taking a lot
longer to run than they expect. They might not know how long it should
take -- they may have intended to run it with unusual parameters.

Now the filesystem where temporary unlinked files is held is becoming
full. Which of those reports are responsible?

(When I first came to one job, I was asked I could make a particular
report run any faster. I asked "how long does it take", and was told
"three days". Rewriting the application and retuning the box got that
down to fifteen minutes).

Hope this helps,

James.

--
E-mail: james@ | You will stop at nothing to reach your objective, but
aprilcottage.co.uk | only because your brakes are defective.
.

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