This patch provides the support of synchronous cache space recovery
to allow read threads to recover from ENOSPC errors when cache space
can be recovered from cache items that are not in use or safe to be
reset/emptied .
The patch complements the existing cache cleaning process in two ways.
Firstly, the existing cache cleaning process is time-driven that runs
periodically. The cache space can run out while the cache cleaner
thread is still waiting for its next scheduled run. The io threads
encountering ENOSPC return an internal error to the applications
in this case even when cache space can be recovered to avoid this
error. This patch addresses this problem by having the read threads
kick the cache cleaner thread in this condition to recover cache
space preventing unnecessary ENOSPC errors from being seen by the
applications.
Secondly, this patch enhances the cache cleaner to support cache
item reset. Currently the cache purge process removes cache
items that are not in use. This may not be sufficient when the
total size of the working set exceeds the cache directory's
capacity. Like in the current code, this patch starts the purge
process by removing cache files that are not in use. Cache items
whose access times are older than vfs-cache-max-age are removed first.
After that, other not-in-use items are removed in LRU order until
vfs-cache-max-size is reached. If the vfs-cache-max-size (the quota)
is still not reached at this time, this patch adds a cache reset
step to reset/empty cache files that are still in use but not
dirtied. This enables application processes to continue without
seeing an error even when the working set depletes the cache space
as long as there is not a large write working set hoarding the
entire cache space.
By design this patch does not add ENOSPC error recovery for write
IOs. Rclone does not empty a write cache item until the file data
is written back to the backend upon close. Allowing more cache
space to be consumed by dirty cache items when the cache space is
already running low would increase the risk of exhausting the cache
space in a way that the vfs mount becomes unreadable.
This adds the missing WSAECONNREFUSED error to the list of errors we
can retry under Windows.
> Connection refused. No connection could be made because the target
> computer actively refused it.
It also adds any relevant errors I could see in the error code list.
See: https://forum.rclone.org/t/failing-to-upload-large-file-to-b2/17085
For few commands, RClone counts a error multiple times. This was fixed by
creating a new error type which keeps a flag to remember if the error has
already been counted or not. The CountError function now wraps the original
error eith the above new error type and returns it.
It was reported that v1.49.4 which was accidentally compiled with
go1.13 instead of go1.12 produced errors like this:
Failed to get StartPageToken: Get https://www.googleapis.com/drive/v3/changes/startPageToken?XXX: stream error: stream ID 1789; INTERNAL_ERROR
IO error: open file failed: Get https://www.googleapis.com/drive/v3/files/XXX?alt=media: stream error: stream ID 1781; INTERNAL_ERROR
These are errors from the http2 library. It appears that go1.13 when
communicating with google drive defaults to http2 whereas with go1.12
it doesn't.
It is unclear what is causing these errors, but retrying them since
they don't happen very often seems like a valid strategy.
This was fixed in v1.49.5 by compiling with go1.12 - this fix is
designed to work with go1.13
See: https://forum.rclone.org/t/1-49-4-plex-internal-errors-on-google-drive/12108/
The error "tls: bad record MAC" is very likely to be caused by
hardware issues. It indicates that a packet got corrupted somewhere.
As a work around, this change treats it as retriable error which
allows the chunk to get retried and the transfer to continue.
The purpose of this is to make it easier to maintain and eventually to
allow the rclone backends to be re-used in other projects without
having to use the rclone configuration system.
The new code layout is documented in CONTRIBUTING.
