Add Cleanup to snapshot API

Cleanup is an optional method a snapshotter may implement.
Cleanup can be used to cleanup resources after a snapshot
has been removed. This function allows a snapshotter to defer
longer resource cleanup until after snapshot removals are
completed. Adding this to the API allows proxy snapshotters
to leverage this enhancement.

Signed-off-by: Derek McGowan <derek@mcgstyle.net>

snapshots/proxy/proxy.go

@@ -184,6 +184,13 @@ func (p *proxySnapshotter) Close() error {
 	return nil
 }
 
+func (p *proxySnapshotter) Cleanup(ctx context.Context) error {
+	_, err := p.client.Cleanup(ctx, &snapshotsapi.CleanupRequest{
+		Snapshotter: p.snapshotterName,
+	})
+	return errdefs.FromGRPC(err)
+}
+
 func toKind(kind snapshotsapi.Kind) snapshots.Kind {
 	if kind == snapshotsapi.KindActive {
 		return snapshots.KindActive

snapshots/snapshotter.go

@@ -341,6 +341,17 @@ type Snapshotter interface {
 	Close() error
 }
 
+// Cleaner defines a type capable of performing asynchronous resource cleanup.
+// The Cleaner interface should be used by snapshotters which implement fast
+// removal and deferred resource cleanup. This prevents snapshots from needing
+// to perform lengthy resource cleanup before acknowledging a snapshot key
+// has been removed and available for re-use. This is also useful when
+// performing multi-key removal with the intent of cleaning up all the
+// resources after each snapshot key has been removed.
+type Cleaner interface {
+	Cleanup(ctx context.Context) error
+}
+
 // Opt allows setting mutable snapshot properties on creation
 type Opt func(info *Info) error