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
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.
This adds a context.Context parameter to NewFs and related calls.
This is necessary as part of reading config from the context -
backends need to be able to read the global config.
Before this change, if the cache was given a source `remote:file` it
stored `remote:` with the error `fs.ErrorIsFile` attached. This meant
that if it `remote:` was subsequently looked up it would return the
`fs.ErrorIsFile` error.
This broke `moveto remote:file remote:file2` as moveto would lookup
`remote:` from the second argument and erroneously get the
`fs.ErrorIsFile` error.
This likely broke other commands too.
This was broken in
4c9836035 fs/cache: Add Pin and Unpin and canonicalised lookup
Which was released in v1.52.0
The fix is to make a new cache entry for `remote:` with no error
attached in the case that the original call returned `fs.ErrorIsFile`.
Before this change we stored cached Fs under the config string the
user gave us. As the result of fs.ConfigString() can often be
different after the backend has canonicalised the paths this meant
that we could not look up backends in the cache reliably.
After this change we store cached Fs under their config string as
returned from fs.ConfigString(f) after the Fs has been created. We
also store a map of user to canonical names (where they are different)
so the users can look up Fs under the names they passed to rclone too.
This change along with Pin and Unpin is necessary so we can look up
the Fs in use reliably in the `backend/command` remote control
interface.
