UnusedBlobs now directly reads the list of existing blobs from the
repository index. This removes the need for the blobStatusExists flag,
which in turn allows converting the blobRefs map into a BlobSet.
By construction these two errors always show up in pairs: 'size could
not be found' is printed when the blob is not found in the repository
index. That blob is also part of the `blobs` array. Later on, check
iterates over that array and checks whether the blob is marked as
existing. Which cannot be the case as that mark is generated by
iterating over the repository index.
The merged warning no longer reports the blob index within a file. That
information could also be derived by printing the affected tree using
`cat` and searching for the blob.
If a data blob and a tree blob with the same ID (= same content) exist,
then the checker did not report a data or tree blob as unused when the
blob of the other type was still in use.
The `DuplicateTree` flag is necessary to ensure that failures cannot be
swallowed. The old checker implementation ignores errors from LoadTree
if the corresponding tree was already checked.
Backups traverse the file tree in depth-first order and saves trees on
the way back up. This results in tree packs filled in a way comparable
to the reverse Polish notation. In order to check tree blobs in that
order, the treeFilter would have to delay the forwarding of tree nodes
until all children of it are processed which would complicate the
implementation.
Therefore do the next similar thing and traverse the tree in depth-first
order, but process trees already on the way down. The tree blob ids are
added in reverse order to the backlog, which is once again reverted when
removing the ids from the back of the backlog.
The blobRefs map and the processedTrees IDSet are merged to reduce the
memory usage. The blobRefs map now uses separate flags to track blob
usage as data or tree blob. This prevents skipping of trees whose
content is identical to an already processed data blob. A third flag
tracks whether a blob exists or not, which removes the need for the
blobs IDSet.
Even though the checkTreeWorker skips already processed chunks,
filterTrees did queue the same tree blob on every occurence. This
becomes a serious performance bottleneck for larger number of snapshots
that cover mostly the same directories. Therefore decode a tree blob
exactly once.
I was running "golangci-lint" and found this two warnings
internal/checker/checker.go:135:18: (*Checker).LoadIndex$3 - result 0 (error) is always nil (unparam)
final := func() error {
^
internal/repository/repository.go:457:18: (*Repository).LoadIndex$3 - result 0 (error) is always nil (unparam)
final := func() error {
^
It turns out that these functions are used only in "RunWorkers(...)",
which is used only two times in whole project right after this "final"
functions.
And because these "final" functions always return "nil", I've
descided, that it would be better to remove requriments for "final" func
to return error to avoid magick "return nil" at their end.
As mentioned in issue [#1560](https://github.com/restic/restic/pull/1560#issuecomment-364689346)
this changes the signature for `backend.Save()`. It now takes a
parameter of interface type `RewindReader`, so that the backend
implementations or our `RetryBackend` middleware can reset the reader to
the beginning and then retry an upload operation.
The `RewindReader` interface also provides a `Length()` method, which is
used in the backend to get the size of the data to be saved. This
removes several ugly hacks we had to do to pull the size back out of the
`io.Reader` passed to `Save()` before. In the `s3` and `rest` backend
this is actively used.
