feat: Make extension snapshotter interface safer to use (cosmos#11825)

* Make extension snapshotter interface safer to use

Closes: cosmos#11824
Solution:
- Use new methods `SnapshotExtension`/`RestoreExtension` to handle payload stream specifically.
- Improve unit tests.

* update changelog

* Update snapshots/types/util.go

* changelog

* go linter

* Update CHANGELOG.md

Co-authored-by: Aleksandr Bezobchuk <[email protected]>

(cherry picked from commit e397434)

CHANGELOG.md

@@ -56,6 +56,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 ### API Breaking Changes
 
 * [#13673](https://github.com/cosmos/cosmos-sdk/pull/13673) The `GetFromFields` function now takes `Context` as an argument and removes `genOnly`.
+* (store) [#11825](https://github.com/cosmos/cosmos-sdk/pull/11825) Make extension snapshotter interface safer to use, renamed the util function `WriteExtensionItem` to `WriteExtensionPayload`.
 
 ## v0.45.10 - 2022-10-24
 

docs/architecture/adr-049-state-sync-hooks.md

@@ -3,10 +3,11 @@
 ## Changelog
 
 - Jan 19, 2022: Initial Draft
+- Apr 29, 2022: Safer extension snapshotter interface
 
 ## Status
 
-Draft, Under Implementation
+Implemented
 
 ## Abstract
 
@@ -107,11 +108,16 @@ func (m *Manager) RegisterExtensions(extensions ...types.ExtensionSnapshotter) e
 On top of the existing `Snapshotter` interface for the `multistore`, we add `ExtensionSnapshotter` interface for the extension snapshotters. Three more function signatures: `SnapshotFormat()`, `SupportedFormats()` and `SnapshotName()` are added to `ExtensionSnapshotter`.
 
 ```go
+// ExtensionPayloadReader read extension payloads,
+// it returns io.EOF when reached either end of stream or the extension boundaries.
+type ExtensionPayloadReader = func() ([]byte, error)
+
+// ExtensionPayloadWriter is a helper to write extension payloads to underlying stream.
+type ExtensionPayloadWriter = func([]byte) error
+
 // ExtensionSnapshotter is an extension Snapshotter that is appended to the snapshot stream.
 // ExtensionSnapshotter has an unique name and manages it's own internal formats.
 type ExtensionSnapshotter interface {
-	Snapshotter
-
 	// SnapshotName returns the name of snapshotter, it should be unique in the manager.
 	SnapshotName() string
 
@@ -120,6 +126,14 @@ type ExtensionSnapshotter interface {
 
 	// SupportedFormats returns a list of formats it can restore from.
 	SupportedFormats() []uint32
+
+	// SnapshotExtension writes extension payloads into the underlying protobuf stream.
+	SnapshotExtension(height uint64, payloadWriter ExtensionPayloadWriter) error
+
+	// RestoreExtension restores an extension state snapshot,
+	// the payload reader returns `io.EOF` when reached the extension boundaries.
+	RestoreExtension(height uint64, format uint32, payloadReader ExtensionPayloadReader) error
+
 }
 ```
 

store/snapshots/manager_test.go

@@ -70,8 +70,12 @@ func TestManager_Take(t *testing.T) {
 	snapshotter := &mockSnapshotter{
 		items: items,
 	}
-	expectChunks := snapshotItems(items)
+	extSnapshotter := newExtSnapshotter(10)
+
+	expectChunks := snapshotItems(items, extSnapshotter)
 	manager := snapshots.NewManager(store, snapshotter)
+	err := manager.RegisterExtensions(extSnapshotter)
+	require.NoError(t, err)
 
 	// nil manager should return error
 	_, err = (*snapshots.Manager)(nil).Create(1)
@@ -93,7 +97,7 @@ func TestManager_Take(t *testing.T) {
 		Height: 5,
 		Format: snapshotter.SnapshotFormat(),
 		Chunks: 1,
-		Hash:   []uint8{0xcd, 0x17, 0x9e, 0x7f, 0x28, 0xb6, 0x82, 0x90, 0xc7, 0x25, 0xf3, 0x42, 0xac, 0x65, 0x73, 0x50, 0xaa, 0xa0, 0x10, 0x5c, 0x40, 0x8c, 0xd5, 0x1, 0xed, 0x82, 0xb5, 0xca, 0x8b, 0xe0, 0x83, 0xa2},
+		Hash:   []uint8{0x89, 0xfa, 0x18, 0xbc, 0x5a, 0xe3, 0xdc, 0x36, 0xa6, 0x95, 0x5, 0x17, 0xf9, 0x2, 0x1a, 0x55, 0x36, 0x16, 0x5d, 0x4b, 0x8b, 0x2b, 0x3d, 0xfd, 0xe, 0x2f, 0xb6, 0x40, 0x6b, 0xc3, 0xbc, 0x23},
 		Metadata: types.Metadata{
 			ChunkHashes: checksums(expectChunks),
 		},
@@ -132,11 +136,9 @@ func TestManager_Prune(t *testing.T) {
 
 func TestManager_Restore(t *testing.T) {
 	store := setupStore(t)
-	target := &mockSnapshotter{
-		prunedHeights: make(map[int64]struct{}),
-	}
+	target := &mockSnapshotter{}
 	extSnapshotter := newExtSnapshotter(0)
-	manager := snapshots.NewManager(store, opts, target, nil, log.NewNopLogger())
+	manager := snapshots.NewManager(store, target)
 	err := manager.RegisterExtensions(extSnapshotter)
 	require.NoError(t, err)
 
@@ -146,7 +148,7 @@ func TestManager_Restore(t *testing.T) {
 		{7, 8, 9},
 	}
 
-	chunks := snapshotItems(expectItems)
+	chunks := snapshotItems(expectItems, newExtSnapshotter(10))
 
 	// Restore errors on invalid format
 	err = manager.Restore(types.Snapshot{
@@ -209,6 +211,7 @@ func TestManager_Restore(t *testing.T) {
 	}
 
 	assert.Equal(t, expectItems, target.items)
+	assert.Equal(t, 10, len(extSnapshotter.state))
 
 	// Starting a new restore should fail now, because the target already has contents.
 	err = manager.Restore(types.Snapshot{