Advice needed for plugin running background thread

[Phssthpok]

As described in another thread I'm thinking of writing a plugin to reset permissions on files in the auto-add directory so they don't get stuck there for weeks until I manually reset them. (The rights and wrongs of it are discussed extensively in that thread, but I feel like trying it anyway, as an exercise if nothing else.)

The idea is to have a plugin which spins off a background thread when Calibre starts up, which shuts down when Calibre shuts down. I was thinking of something along the following lines:

class MyPlugin(Plugin):
    keepRunning = True
    def threadBody():
        while keepRunning:
            ...
    def __init__(self):
        thread = new Thread(target=threadBody)
        thread.start()

Can anyone advise me:
(a) am I going about this in the right way -- that is, will this do what I want?
(b) what are the lifecycle issues I need to deal with (i.e. setting my keepRunning flag to False to shut down the thread in an orderly way; handling plugin reloads or whatever) and how do I deal with them?
(c) is there anything else I should know before I dive in (apart from RTFM, of course)?

I've never written a plugin before, so feel free to tell me I'm a complete idiot!

[kovidgoyal]

Create a user interface plugin start your thread in the genesis() method and shut it down in the shutting_down() method. And dont forget to set your thread as a daemon.

[Phssthpok]

Originally Posted by kovidgoyal

Create a user interface plugin start your thread in the genesis() method and shut it down in the shutting_down() method. And dont forget to set your thread as a daemon.

Thanks!

[Phssthpok]

Okay, this is what I came up with for anyone else who's interested. All it does is try to make any files in the auto-add directory readable and writable so that the auto-adder can process them, signal the auto-adder to process the files, and then sleep for 10 minutes. It can undoubtedly be improved but it's good enough for me for now.

[eschwartz]

Well, you could at least tell it to only mangle permissions for filetypes that calibre knows about and tries to add...

[Phssthpok]

Originally Posted by eschwartz

Well, you could at least tell it to only mangle permissions for filetypes that calibre knows about and tries to add...

Yeah, it's only a toy at the moment. Is there a list of filetypes that Calibre tries to add somewhere easily accessible? (I wouldn't want to hard-code it of course, as new formats will presumably come along sometime.) If so, it's easy enough to fix. And maybe the delay should be configurable, and so on.

Incidentally, does anyone ever put files they don't want Calibre to add in the auto-add directory? If so, why? And does this mean a manual clearing-out every so often, or what? (I only ever drop book files into my auto-add directory, and I assumed this was the norm for others too.)

[eschwartz]

The unsurprisingly-named and -located:

from calibre.ebooks import BOOK_EXTENSIONS

And some people use ~/Downloads as an auto-add folder.

...

How do I find these things out? I take a look at how calibre adds things, in calibre.gui2.add_to_library and calibre.gui2.auto_add

[Phssthpok]

Originally Posted by eschwartz

The unsurprisingly-named and -located:

from calibre.ebooks import BOOK_EXTENSIONS

And some people use ~/Downloads as an auto-add folder.

...

How do I find these things out? I take a look at how calibre adds things, in calibre.gui2.add_to_library and calibre.gui2.auto_add

Thanks!

...although I see the auto-adder ignores some of those file types, so probably I would be better off using "from calibre.gui2.auto-add import AUTO_ADDED" in this case?

[Phssthpok]

Originally Posted by eschwartz

Well, you could at least tell it to only mangle permissions for filetypes that calibre knows about and tries to add...

Here you go:

[PeterT]

You could also just mangle them for files that do NOT have the correct permissions.

[eschwartz]

Originally Posted by PeterT

You could also just mangle them for files that do NOT have the correct permissions.

Ah, but that would be a no-op change...

[Phssthpok]

Originally Posted by PeterT

You could also just mangle them for files that do NOT have the correct permissions.

Sigh; no rest for the wicked!

[Phssthpok]

Originally Posted by eschwartz

Ah, but that would be a no-op change...

Hmm, good point! Getting late where I am... Pity I read this after I got suckered into making the change... so I've undone it now. Good night all.

[eschwartz]

Checking for the pre-existing permissions only of files that are already slated to be added and cleaned up?

We don't care about preserving the mtime if it is being deleted, do we...

On the separate topic of efficiency, I had/have no qualms.
Anyway, you'd lose time when you stat the current permissions, and gain time if you can skip writing new permissions to an already-rw file.
You'd save time by not writing+deleting the flag file if only already-rw files are there.
Neither matters unless the plugin wakes up right after you add a rw file and before the auto-add finishes processing it. Unlikely timing.

With the extra (wasted?) stat calls, you might actually lose time. I'm not sure if os.stat is faster than os.chmod, if not then you always lose.

[kovidgoyal]

The list of file types calibre adds is based on a user preference, the logic for getting that list is

        if gprefs['auto_add_everything']:
            self.allowed = AllAllowed()
        else:
            self.allowed = AUTO_ADDED - frozenset(gprefs['blocked_auto_formats'])