physical: Factory constructor style for backends

physical/consul.go

@@ -1,17 +1,14 @@
 package physical
 
-import "github.com/hashicorp/consul/api"
-
 // ConsulBackend is a physical backend that stores data at specific
 // prefix within Consul. It is used for most production situations as
 // it allows Vault to run on multiple machines in a highly-available manner.
 type ConsulBackend struct {
 }
 
-// NewConsulBackend constructs a Consul backend using the given API client
+// newConsulBackend constructs a Consul backend using the given API client
 // and the prefix in the KV store.
-func NewConsulBackend(client *api.Client, prefix string) (*ConsulBackend, error) {
+func newConsulBackend(conf map[string]string) (Backend, error) {
 	// TODO
-	c := &ConsulBackend{}
-	return c, nil
+	return nil, nil
 }

physical/file.go

@@ -6,9 +6,8 @@ package physical
 type FileBackend struct {
 }
 
-// NewFileBackend constructs a Filebackend using the given directory
-func NewFileBackend(dir string) (*FileBackend, error) {
+// newFileBackend constructs a Filebackend using the given directory
+func newFileBackend(conf map[string]string) (Backend, error) {
 	// TODO:
-	f := &FileBackend{}
-	return f, nil
+	return nil, nil
 }

physical/inmem.go

@@ -16,7 +16,7 @@ type InmemBackend struct {
 }
 
 // NewInmem constructs a new in-memory backend
-func NewInmem() *InmemBackend {
+func newInmem() *InmemBackend {
 	in := &InmemBackend{
 		root: radix.New(),
 	}

physical/inmem_test.go

@@ -3,7 +3,7 @@ package physical
 import "testing"
 
 func TestInmem(t *testing.T) {
-	inm := NewInmem()
+	inm := newInmem()
 	testBackend(t, inm)
 	testBackend_ListPrefix(t, inm)
 }

physical/physical.go

@@ -1,5 +1,7 @@
 package physical
 
+import "fmt"
+
 // Backend is the interface required for a physical
 // backend. A physical backend is used to durably store
 // datd outside of Vault. As such, it is completely untrusted,
@@ -26,3 +28,26 @@ type Entry struct {
 	Key   string
 	Value []byte
 }
+
+// Factory is the factory function to create a physical backend.
+type Factory func(map[string]string) (Backend, error)
+
+// NewBackend returns a new Bckend with the given type and configuration.
+// The backend is looked up in the BuiltinBackends variable.
+func NewBackend(t string, conf map[string]string) (Backend, error) {
+	f, ok := BuiltinBackends[t]
+	if !ok {
+		return nil, fmt.Errorf("unknown physical backend type: %s", t)
+	}
+	return f(conf)
+}
+
+// BuiltinBackends is the list of built-in physical backends that can
+// be used with NewBackend.
+var BuiltinBackends = map[string]Factory{
+	"inmem": func(map[string]string) (Backend, error) {
+		return newInmem(), nil
+	},
+	"consul": newConsulBackend,
+	"file":   newFileBackend,
+}

physical/physical_test.go

@@ -5,6 +5,22 @@ import (
 	"testing"
 )
 
+func testNewBackend(t *testing.T) {
+	_, err := NewBackend("foobar", nil)
+	if err == nil {
+		t.Fatalf("expected error")
+	}
+
+	b, err := NewBackend("inmem", nil)
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+
+	if b == nil {
+		t.Fatalf("expected backend")
+	}
+}
+
 func testBackend(t *testing.T, b Backend) {
 	// Should be empty
 	keys, err := b.List("")