This allows reads to only read part of the file and it keeps on disk a
cache of what parts of each file have been loaded.
File data itself is kept in sparse files.
When a file has its modtime set while it is open we delay setting the
modtime until the file is closed.
The file is then uploaded in Flush. In Release we check the cached
file has been uploaded by comparing modtimes and or hashes and upload
it again if it has changed.
Before this change we forgot to change the time on the cached file
when we updated the time file on the object, so this mean that Release
reset the time to the wrong time and uploaded the file again on
remotes which don't support hashes (eg crypt).
The fix was to set the modtime of the cached file at the same time we
set the modtime of the remote object. This means that the files check
as identical in Release so it doesn't try to upload the file.
This means that we avoid a double upload and the modtime is correct.
See: https://forum.rclone.org/t/modification-time-with-vfs-cache/13906/8
Before this change, renaming an open file when using the VFS cache was
delayed until the file was closed. This meant that the file was not
readable after a rename even though it is was in the cache.
After this change we rename the local cache file and the in memory
cache, delaying only the rename of the file in object storage.
See: https://forum.rclone.org/t/xen-orchestra-ebadf-bad-file-descriptor-write/13104
If a file handle is duplicated with dup() and the duplicate handle is
flushed, rclone will go ahead and close the file, making the original
file handle stale. This change removes the close() call from Flush() and
replaces it with FlushWrites() so that the file only gets closed when
Release() is called. The new FlushWrites method takes care of actually
writing the file back to the underlying storage.
Fixes#3381
- Change rclone/fs interfaces to accept context.Context
- Update interface implementations to use context.Context
- Change top level usage to propagate context to lover level functions
Context propagation is needed for stopping transfers and passing other
request-scoped values.
This stops the cache cleaner running unnecessarily and saves
resources.
This also helps with issue #2227 which was caused by a second mount
deleting objects in the first mounts cache.
Before this change Open("name", os.O_RDONLY|os.O_TRUNC) would have
truncated the file. This is what Linux does, but is counterintuitive.
POSIX states this is undefined, so return an error in this case
instead. This preserves the invariant O_RDONLY => file is not
changed.
Background: cmd/mount/file.go Open() function does a Seek(0, 1) to see
if the file handle is seekable to set a FUSE hint. Before this change
the file was downloaded before it needed to be which was inefficient
(and broke beta.rclone.org because HEAD requests caused downloads!).
This adds new flags to mount, cmount, serve *
--cache-max-age duration Max age of objects in the cache. (default 1h0m0s)
--cache-mode string Cache mode off|minimal|writes|full (default "off")
--cache-poll-interval duration Interval to poll the cache for stale objects. (default 1m0s)
