logical/framework: WAL entry supports "kind"

logical/framework/backend.go

@@ -34,7 +34,7 @@ type Backend struct {
 	// Rollback is called when a WAL entry (see wal.go) has to be rolled
 	// back. It is called with the data from the entry. Boolean true should
 	// be returned on success. Errors should just be logged.
-	Rollback func(data interface{}) bool
+	Rollback func(kind string, data interface{}) bool
 
 	once    sync.Once
 	pathsRe []*regexp.Regexp
@@ -193,13 +193,13 @@ func (b *Backend) handleRollback(
 	}
 
 	for _, k := range keys {
-		data, err := GetWAL(req.Storage, k)
+		kind, data, err := GetWAL(req.Storage, k)
 		if err != nil {
 			merr = multierror.Append(merr, err)
 			continue
 		}
 
-		if b.Rollback(data) {
+		if b.Rollback(kind, data) {
 			if err := DeleteWAL(req.Storage, k); err != nil {
 				merr = multierror.Append(merr, err)
 			}

logical/framework/backend_test.go

@@ -138,7 +138,7 @@ func TestBackendHandleRequest_help(t *testing.T) {
 
 func TestBackendHandleRequest_rollback(t *testing.T) {
 	var called uint32
-	callback := func(data interface{}) bool {
+	callback := func(kind string, data interface{}) bool {
 		if data == "foo" {
 			atomic.AddUint32(&called, 1)
 		}
@@ -151,7 +151,7 @@ func TestBackendHandleRequest_rollback(t *testing.T) {
 	}
 
 	storage := new(logical.InmemStorage)
-	if _, err := PutWAL(storage, "foo"); err != nil {
+	if _, err := PutWAL(storage, "kind", "foo"); err != nil {
 		t.Fatalf("err: %s", err)
 	}
 

logical/framework/wal.go

@@ -12,6 +12,10 @@ const WALPrefix = "wal/"
 
 // PutWAL writes some data to the WAL.
 //
+// The kind parameter is used by the framework to allow users to store
+// multiple kinds of WAL data and to easily disambiguate what data they're
+// expecting.
+//
 // Data within the WAL that is uncommitted (CommitWAL hasn't be called)
 // will be given to the rollback callback when an rollback operation is
 // received, allowing the backend to clean up some partial states.
@@ -21,8 +25,11 @@ const WALPrefix = "wal/"
 // This returns a unique ID that can be used to reference this WAL data.
 // WAL data cannot be modified. You can only add to the WAL and commit existing
 // WAL entries.
-func PutWAL(s logical.Storage, data interface{}) (string, error) {
-	value, err := json.Marshal(data)
+func PutWAL(s logical.Storage, kind string, data interface{}) (string, error) {
+	value, err := json.Marshal(map[string]interface{}{
+		"kind": kind,
+		"data": data,
+	})
 	if err != nil {
 		return "", err
 	}
@@ -40,21 +47,23 @@ func PutWAL(s logical.Storage, data interface{}) (string, error) {
 
 // GetWAL reads a specific entry from the WAL. If the entry doesn't exist,
 // then nil value is returned.
-func GetWAL(s logical.Storage, id string) (interface{}, error) {
+//
+// The kind, value, and error are returned.
+func GetWAL(s logical.Storage, id string) (string, interface{}, error) {
 	entry, err := s.Get(WALPrefix + id)
 	if err != nil {
-		return nil, err
+		return "", nil, err
 	}
 	if entry == nil {
-		return nil, nil
+		return "", nil, nil
 	}
 
-	var result interface{}
+	var result map[string]interface{}
 	if err := json.Unmarshal(entry.Value, &result); err != nil {
-		return nil, err
+		return "", nil, err
 	}
 
-	return result, nil
+	return result["kind"].(string), result["data"], nil
 }
 
 // DeleteWAL commits the WAL entry with the given ID. Once comitted,

logical/framework/wal_test.go

@@ -20,7 +20,7 @@ func TestWAL(t *testing.T) {
 	}
 
 	// Write an entry to the WAL
-	id, err := PutWAL(s, "bar")
+	id, err := PutWAL(s, "foo", "bar")
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
@@ -35,10 +35,13 @@ func TestWAL(t *testing.T) {
 	}
 
 	// Should be able to get the value
-	v, err := GetWAL(s, id)
+	kind, v, err := GetWAL(s, id)
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}
+	if kind != "foo" {
+		t.Fatalf("bad: %#v", kind)
+	}
 	if v != "bar" {
 		t.Fatalf("bad: %#v", v)
 	}
@@ -47,7 +50,7 @@ func TestWAL(t *testing.T) {
 	if err := DeleteWAL(s, id); err != nil {
 		t.Fatalf("err: %s", err)
 	}
-	v, err = GetWAL(s, id)
+	_, v, err = GetWAL(s, id)
 	if err != nil {
 		t.Fatalf("err: %s", err)
 	}