Thumbnail cache not writeable?

[drubb]

I've installed a new instance of Calibre Web and copied my existing Calibre library to /library. This works fine so far. However, when I upload new books, no thumbnails can be generated. Here's what I can see in the logs:

[2023-01-03 16:33:19,257]  INFO {cps.fs:41} Failed to create path /app/code/calibre-web/cps/cache (Permission denied).
[2023-01-03 16:33:19,374]  INFO {cps.fs:41} Failed to create path /app/code/calibre-web/cps/cache (Permission denied).
[2023-01-03 16:39:24,997]  INFO {cps.fs:41} Failed to create path /app/code/calibre-web/cps/cache (Permission denied).
[2023-01-03 16:39:24,998] ERROR {cps:1457} Exception on /cover/1921/sm [GET]
Traceback (most recent call last):
  File "/usr/local/lib/python3.8/dist-packages/flask/app.py", line 2073, in wsgi_app
    response = self.full_dispatch_request()
  File "/usr/local/lib/python3.8/dist-packages/flask/app.py", line 1518, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/usr/local/lib/python3.8/dist-packages/flask/app.py", line 1516, in full_dispatch_request
    rv = self.dispatch_request()
  File "/usr/local/lib/python3.8/dist-packages/flask/app.py", line 1502, in dispatch_request
    return self.ensure_sync(self.view_functions[rule.endpoint])(**req.view_args)
  File "/app/code/calibre-web/cps/usermanagement.py", line 35, in decorated_view
    return login_required(func)(*args, **kwargs)
  File "/usr/local/lib/python3.8/dist-packages/flask_login/utils.py", line 303, in decorated_view
    return current_app.ensure_sync(func)(*args, **kwargs)
  File "/app/code/calibre-web/cps/web.py", line 1122, in get_cover
    return get_book_cover(book_id, cover_resolution)
  File "/app/code/calibre-web/cps/helper.py", line 705, in get_book_cover
    return get_book_cover_internal(book, use_generic_cover_on_failure=True, resolution=resolution)
  File "/app/code/calibre-web/cps/helper.py", line 722, in get_book_cover_internal
    if cache.get_cache_file_exists(thumbnail.filename, CACHE_TYPE_THUMBNAILS):
  File "/app/code/calibre-web/cps/fs.py", line 69, in get_cache_file_exists
    path = self.get_cache_file_path(filename, cache_type)
  File "/app/code/calibre-web/cps/fs.py", line 66, in get_cache_file_path
    return join(self.get_cache_file_dir(filename, cache_type), filename) if filename else None
  File "/app/code/calibre-web/cps/fs.py", line 55, in get_cache_file_dir
    path = join(self.get_cache_dir(cache_type), filename[:2])
  File "/app/code/calibre-web/cps/fs.py", line 39, in get_cache_dir
    makedirs(self._cache_dir)
  File "/usr/lib/python3.8/os.py", line 223, in makedirs
    mkdir(name, mode)
OSError: [Errno 30] Read-only file system: '/app/code/calibre-web/cps/cache'

Seems that Calibre Web wants to cache thumbnails in /app/code/calibre-web/cps/cache, and afaik the code folder for Cloudron apps isn't writeable.

Are there any settings to choose the cache location or disable thumbnail caching?

Generating original cover images works fine, e.g. /cover/1922/og exists, but cover/1922/sm doesn't.

Thx a lot!

[jdaviescoates]

@drubb I think I've hit this issue previously, can't fully remember but I think it was something to do with folder/file permissions - have a look in the File Manager for your Calibre App to check they've all got the correct permissions (Owner should be cloudron)

[nebulon]

This post is deleted!

[nebulon]

I tried to reproduce this, but I couldn't. At least in my instances this /app/code/calibre-web/cps/cache directory does not exist and is also not attempted to be created. But I only have pdfs currently to test with, so maybe this is related specific formats?

[jdaviescoates]

@nebulon said in Thumbnail cache not writeable?:

I tried to reproduce this, but I couldn't. At least in my instances this /app/code/calibre-web/cps/cache directory does not exist and is also not attempted to be created. But I only have pdfs currently to test with, so maybe this is related specific formats?

Just checked and it doesn't exist in mine either (with lots of epubs, mobis and pdfs)

[robi]

@jdaviescoates of course not, it's RO.

[nebulon]

Is there any more info on this and can someone reproduce this?

[hpz24]

Hi,
I got the same error after installing the calibre-web instance yesterday and moving(!) my existing database to the cloudron instance.
And yes, the cache directory does not exist for me either.

May 24 08:13:29 OSError: [Errno 30] Read-only file system: '/app/code/calibre-web/cps/cache'
May 24 08:13:29 OSError: [Errno 30] Read-only file system: '/app/code/calibre-web/cps/cache'
May 24 08:13:29 OSError: [Errno 30] Read-only file system: '/app/code/calibre-web/cps/cache'
May 24 08:13:29 Traceback (most recent call last):
May 24 08:13:29 Traceback (most recent call last):
May 24 08:13:29 [2025-05-24 06:13:29,905] INFO {cps.fs:41} Failed to create path /app/code/calibre-web/cps/cache (Permission denied).

[girish]

@hpz24 I couldn't reproduce it myself but there is a CACHE_DIR env var to be set . It defaults to BASE_DIR/cps/cache per upstream code. I have set this variable in the latest package, can you update and check?

[hpz24]

Works perfectly!
All thumbnails are there, thx a lot!