E-book viewer in Calibre 5.22.1 hangs forever on new books

[lkstrummer]

Opening new epubs loads the "Preparing book for first read, please wait" message on the e-book viewer. However, the viewer hangs forever and the book doesn't open. No error message is generated either as it hangs indefinitely.

Previously opened epubs will still open as usual unless there's another instance of the e-book viewer trying to open another epub for the first time (and hanging indefinitely). Two or more instances of epubs that have previously been opened will still continue to open normally. The process is only disrupted by an instance of the e-book viewer preparing an epub for the first read and hanging.

In the case of the previously opened epub that won't open with an instance of the e-book viewer that is hanging on a new book, an error message is generated. The error message:

WindowsError: [Error 32] The process cannot access the file because it is being used by another process.: u'C:\\Users\\xxxxx\\AppData\\Local\\calibre-cache\\ev2\\metadata.json'

I've searched for a solution to this error and was pointed towards making an exception to the cache folder in my antivirus (avast). I've done so and I also turned off Avast to both repair and reinstall the latest calibre 5.22.1. However, this error with the e-book viewer persists.

[kovidgoyal]

reboot in safe mode and see if the error goes away.

[lkstrummer]

So it seems that it hangs for a long time rather than endlessly when opening a new epub for the first time. It takes roughly 10-15 minutes to load a new epub (again, 'new' as in previously unopened). My mistake previously was closing the instance that was hanging on opening the new epub and then trying to reopen the same file and then the behavior repeating. However, waiting the duration of the 10-15 minutes to open the e-book fixes this flaw, at least temporarily.

Once the new epub is opened and that particular instance of the viewer closed (and all instances closed, as well) further epubs opened for the first time don't require this time premium. They open in just seconds even when they're the only active instance of the viewer. The viewer hanging flaw is temporarily fixed.

I say temporarily because once this was "fixed" yesterday and further new and preloaded epubs were opening just fine I closed all instances. However, when I tried to open another 'new' epub today, the behavior repeated, meaning the long hanging time before everything was 'fixed' again. So it seems that the viewer is building some temporary cache that either only valid for some x amount of time or is disappearing after x amount of time, forcing the viewer to (slowly) build it again.

My test files are all already in my calibre library. I use Avast antivirus with an behavior exception for the calibre cache folder located in Appdata. I don't use Avast's ransomware shield which restricts writing to certain files. I also use Comodo firewall in Safe mode with the extraneous features disabled (HIPS, Website Filtering, Auto-containment, VirusScope)

[lkstrummer]

Kovid, I did reboot in Safe Mode (without networking) and the the problem exists there as well. New books take a very long time ~10 minutes~ to load, after which subsequent new books and pre-loaded books load normally up to some time less than 24 hours. After this period expires without active instances (I believe) open, the long load time problem reappears. I also believe that each new instance opened in the absence of other instances in this refraction period seems to reset the clock, thereby extending the time to this less than 24 hr period before the problem emerges again.

Again, it seems like some cache is being constantly rebuilt and expiring very quickly.

[BetterRed]

Try giving calibre a dedicated location for its caches via CALIBRE_CACHE_DIRECTORY

See ==>> Environment variables

If that works it's probably an over-zealous third party %appdata% clean up utility.

BR

[zandonov]

I solved this problem by cleaning the temp folder on my Win 11 PC.

In search type: Disk Cleanup and select temporary files.

You can select also other options to save disk space, but if you are not sure what is what just keep them unselected

[JSWolf]

Originally Posted by zandonov

I solved this problem by cleaning the temp folder on my Win 11 PC.

In search type: Disk Cleanup and select temporary files.

You can select also other options to save disk space, but if you are not sure what is what just keep them unselected

You solve the problem by installing the latest calibre 8 instead of 5.22.1.

[DNSB]

Ummm... Jon, the OP (@lkstrummer) had this issue with calibre 5.22.1 when they posted in 2021. The person (@zandonov) you are responding to does not mention what version of calibre they are using.