Before this change, when cache.GetFn was called on a file rather than a
directory, two cache entries would be added (the file + its parent) but only one
of them would get pinned if the caller then called Pin(f). This left the other
one exposed to expiration if the ci.FsCacheExpireDuration was reached. This was
problematic because both entries point to the same Fs, and if one entry expires
while the other is pinned, the Shutdown method gets erroneously called on an Fs
that is still in use.
An example of the problem showed up in the Hasher backend, which uses the
Shutdown method to stop the bolt db used to store hashes. If a command was run
on a Hasher file (ex. `rclone md5sum --download hasher:somelargefile.zip`) and
hashing the file took longer than the --fs-cache-expire-duration (5m by default), the
bolt db was stopped before the hashing operation completed, resulting in an
error.
This change fixes the issue by ensuring that:
1. only one entry is added to the cache (the file's parent, not the file).
2. future lookups correctly find the entry regardless of whether they are called
with the parent name or one of its children.
3. fs.ErrorIsFile is returned when (and only when) fsString points to a file
(preserving the fix from 8d5bc7f28b).
Note that f.Root() should always point to the parent dir as of c69eb84573
Before this patch, when an alias backend was created it would be
renamed to be canonical and in the process Shutdown would be called on
it. This was particularly noticeable with the dropbox backend which
gave this error when uploading files after the backend was Shutdown.
Failed to copy: upload failed: batcher is shutting down
This patch fixes the cache Rename code not to finalize objects if the
object that is being overwritten is the same as the existing object.
See: https://forum.rclone.org/t/upload-failed-batcher-is-shutting-down/33900
This change ensures we call the Shutdown method on backends when
they drop out of the fs/cache and at program exit.
Some backends implement the optional fs.Shutdowner interface. Until now,
Shutdown is only checked and called, when a backend is wrapped (e.g.
crypt, compress, ...).
To have a general way to perform operations at the end of the backend
lifecycle with proper error handling, we can call Shutdown at cache
clear time.
We add a finalize hook to the cache which will be called when values
drop out of the cache.
Previous discussion: https://forum.rclone.org/t/31336
This commit makes the previously statically configured fs cache configurable.
It introduces two parameters `--fs-cache-expire-duration` and
`--fs-cache-expire-interval` to control the caching of the items.
It also adds new interfaces to lib/cache to set these.
