Add Google Cloud Storage replica

replica_client.go

@@ -0,0 +1,48 @@
+package litestream
+
+import (
+	"context"
+	"io"
+)
+
+// ReplicaClient represents client to connect to a Replica.
+type ReplicaClient interface {
+	// Returns the type of client.
+	Type() string
+
+	// Returns a list of available generations.
+	Generations(ctx context.Context) ([]string, error)
+
+	// Deletes all snapshots & WAL segments within a generation.
+	DeleteGeneration(ctx context.Context, generation string) error
+
+	// Returns an iterator of all snapshots within a generation on the replica.
+	Snapshots(ctx context.Context, generation string) (SnapshotIterator, error)
+
+	// Writes LZ4 compressed snapshot data to the replica at a given index
+	// within a generation. Returns metadata for the snapshot.
+	WriteSnapshot(ctx context.Context, generation string, index int, r io.Reader) (SnapshotInfo, error)
+
+	// Deletes a snapshot with the given generation & index.
+	DeleteSnapshot(ctx context.Context, generation string, index int) error
+
+	// Returns a reader that contains LZ4 compressed snapshot data for a
+	// given index within a generation. Returns an os.ErrNotFound error if
+	// the snapshot does not exist.
+	SnapshotReader(ctx context.Context, generation string, index int) (io.ReadCloser, error)
+
+	// Returns an iterator of all WAL segments within a generation on the replica.
+	WALSegments(ctx context.Context, generation string) (WALSegmentIterator, error)
+
+	// Writes an LZ4 compressed WAL segment at a given position.
+	// Returns metadata for the written segment.
+	WriteWALSegment(ctx context.Context, pos Pos, r io.Reader) (WALSegmentInfo, error)
+
+	// Deletes one or more WAL segments at the given positions.
+	DeleteWALSegments(ctx context.Context, a []Pos) error
+
+	// Returns a reader that contains an LZ4 compressed WAL segment at a given
+	// index/offset within a generation. Returns an os.ErrNotFound error if the
+	// WAL segment does not exist.
+	WALSegmentReader(ctx context.Context, pos Pos) (io.ReadCloser, error)
+}