Most snapshotters end up manually handling the rollback logic, either
by calling `t.Rollback()` in every failure path, setting up a custom
defer func to log on certain errors, or just deferring `t.Rollback()`
even for `snapshotter.Commit()` which *will* cause `t.Rollback()` to return
an error afaict, but it's just never checked and luckily bolt handles this
alright...
The devmapper snapshotter has a solution to this which is to have a
method that starts either a read-only or writable transaction inside
the method, and you pass in a callback to do your bidding and any
failures are rolled back, and if it's writable will handle the commit
for you. This seems like the right model to me, it removes the burden
from the snapshot author to remember to either defer/call rollback
in every method for every failure case.
This change exposes the convenience method from devmapper to the
snapshots/storage package as a method off of `storage.MetaStore` and moves
over the devmapper snapshotter to use this.
Signed-off-by: Danny Canter <danny@dcantah.dev>
The directory created by `T.TempDir` is automatically removed when the
test and all its subtests complete.
Reference: https://pkg.go.dev/testing#T.TempDir
Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>
The io/ioutil package has been deprecated as of Go 1.16, see
https://golang.org/doc/go1.16#ioutil. This commit replaces the existing
io/ioutil functions with their new definitions in io and os packages.
Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>
Updates overlay remove to simply remove the reference, adds
a cleanup method for discarding the directory.
Updates snapshot create to setup the directory structure while
in the transaction, to prevent cleanup from removing directories
which are part of a create.
Signed-off-by: Derek McGowan <derek@mcgstyle.net>
