This is especially useful if ssh asks for a password or if closing the
initial connection could return an error due to a problematic server
implementation.
rclone can exit early for example when the connection to rclone is
relayed for example via ssh: `-o rclone.program='ssh user@example.org
forced-command'`
For backends which are able to atomically replace files, we just can
overwrite the old copy, if it is necessary to retry an upload. This has
the benefit of issuing one operation less and might be beneficial if a
backend storage, due to bugs or similar, could mix up the order of the
upload and delete calls.
When hard deleting the latest file version on B2, this uncovers earlier
versions. If an upload required retries, multiple version might exist
for a file. Thus to reliably delete a file, we have to remove all
versions of it.
pkg/sftp.Client.MkdirAll(d) does a Stat to determine if d exists and is
a directory, then a recursive call to create the parent, so the calls
for data/?? each take three round trips. Doing a Mkdir first should
eliminate two round trips for 255/256 data directories as well as all
but one of the top-level directories.
Also, we can do all of the calls concurrently. This may reintroduce some
of the Stat calls when multiple goroutines try to create the same
parent, but at the default number of connections, that should not be
much of a problem.
... called backend/sema. I resisted the temptation to call the main
type sema.Phore. Also, semaphores are now passed by value to skip a
level of indirection when using them.
github.com/pkg/errors is no longer getting updates, because Go 1.13
went with the more flexible errors.{As,Is} function. Use those instead:
errors from pkg/errors already support the Unwrap interface used by 1.13
error handling. Also:
* check for io.EOF with a straight ==. That value should not be wrapped,
and the chunker (whose error is checked in the cases changed) does not
wrap it.
* Give custom Error methods pointer receivers, so there's no ambiguity
when type-switching since the value type will no longer implement error.
* Make restic.ErrAlreadyLocked private, and rename it to
alreadyLockedError to match the stdlib convention that error type
names end in Error.
* Same with rest.ErrIsNotExist => rest.notExistError.
* Make s3.Backend.IsAccessDenied a private function.
Apparently SMB/CIFS on Linux/macOS returns somewhat random errnos when
trying to sync a windows share which does not support calling fsync for
a directory.
When resolving snapshotIDs in FindFilteredSnapshots either
FindLatestSnapshot or FindSnapshot is called. Both operations issue a
list operation to the backend. When for example passing a long list of
snapshot ids to `forget` this could lead to a large number of list
operations.
These commands filter the snapshots according to some criteria which
essentially requires loading the index before filtering the snapshots.
Thus create a copy of the snapshots list beforehand and use it later on.
Create a temporary file with a sufficiently random name to essentially
avoid any chance of conflicts. Once the upload has finished remove the
temporary suffix. Interrupted upload thus will be ignored by restic.
The missing eof with http2 when a response included a content-length
header but no data, has been fixed in golang 1.17.3/1.16.10. Therefore
just drop the canary test and schedule it for removal once go 1.18 is
required as minimum version by restic.
When deleting a file, B2 sometimes returns a "500 Service Unavailable"
error but nevertheless correctly deletes the file. Due to retries in
the B2 library blazer, we sometimes also see a "400 File not present"
error. The retries of restic for the delete request then fail with
"404 File with such name does not exist.".
As we have to rely on request retries in a distributed system to handle
temporary errors, also consider a delete request to be successful if the
file is reported as not existing. This should be safe as B2 claims to
provide a strongly consistent bucket listing and thus a missing file
shouldn't mysteriously show up again later on.
