containerd/snapshot/storage/metastore.go

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package storage
import (
"context"
"github.com/containerd/containerd/snapshot"
)
// MetaStore is used to store metadata related to a snapshot driver. The
// MetaStore is intended to store metadata related to name, state and
// parentage. Using the MetaStore is not required to implement a snapshot
// driver but can be used to handle the persistence and transactional
// complexities of a driver implementation.
type MetaStore interface {
// TransactionContext creates a new transaction context.
TransactionContext(ctx context.Context, writable bool) (context.Context, Transactor, error)
// Stat returns the snapshot stat Info directly from
// the metadata.
Stat(ctx context.Context, key string) (snapshot.Info, error)
// Walk iterates through all metadata for the stored
// snapshots and calls the provided function for each.
Walk(ctx context.Context, fn func(context.Context, snapshot.Info) error) error
// CreateActive creates a new active snapshot transaction referenced by
// the provided key. The new active snapshot will have the provided
// parent. If the readonly option is given, the active snapshot will be
// marked as readonly and can only be removed, and not committed. The
// provided context must contain a writable transaction.
CreateActive(ctx context.Context, key, parent string, readonly bool) (Active, error)
// GetActive returns the metadata for the active snapshot transaction
// referenced by the given key.
GetActive(ctx context.Context, key string) (Active, error)
// Remove removes a snapshot from the metastore. The provided context
// must contain a writable transaction. The string identifier for the
// snapshot is returned as well as the kind.
Remove(ctx context.Context, key string) (string, snapshot.Kind, error)
// Commit renames the active snapshot transaction referenced by `key`
// as a committed snapshot referenced by `Name`. The resulting snapshot
// will be committed and readonly. The `key` reference will no longer
// be available for lookup or removal. The returned string identifier
// for the committed snapshot is the same identifier of the original
// active snapshot.
Commit(ctx context.Context, key, name string) (string, error)
}
// Transactor is used to finalize an active transaction.
type Transactor interface {
// Commit commits any changes made during the transaction.
Commit() error
// Rollback rolls back any changes made during the transaction.
Rollback() error
}
// Active hold the metadata for an active snapshot transaction. The ParentIDs
// hold the snapshot identifiers for the committed snapshots this active is
// based on. The ParentIDs are ordered from the lowest base to highest, meaning
// they should be applied in order from the first index to the last index. The
// last index should always be considered the active snapshots immediate parent.
type Active struct {
ID string
ParentIDs []string
Readonly bool
}