etcd: decouple embedded etcd instance startup

This refactor changes how we instantiate the etcd based Backend to allow
separate initialization and startup for the embedded instance.

channeldb/kvdb/backend.go

@@ -1,6 +1,7 @@
 package kvdb
 
 import (
+	"context"
 	"encoding/binary"
 	"fmt"
 	"io/ioutil"
@@ -253,7 +254,14 @@ func GetTestBackend(path, name string) (Backend, func(), error) {
 		}
 		return db, empty, nil
 	} else if TestBackend == EtcdBackendName {
-		return GetEtcdTestBackend(path, 0, 0)
+		etcdConfig, cancel, err := StartEtcdTestBackend(path, 0, 0)
+		if err != nil {
+			return nil, empty, err
+		}
+		backend, err := Open(
+			EtcdBackendName, context.TODO(), etcdConfig,
+		)
+		return backend, cancel, err
 	}
 
 	return nil, nil, fmt.Errorf("unknown backend")

channeldb/kvdb/kvdb_etcd.go

@@ -3,8 +3,6 @@
 package kvdb
 
 import (
-	"context"
-
 	"github.com/lightningnetwork/lnd/channeldb/kvdb/etcd"
 )
 
@@ -12,33 +10,12 @@ import (
 // defined, allowing testing our database code with etcd backend.
 const TestBackend = EtcdBackendName
 
-// GetEtcdBackend returns an etcd backend configured according to the
-// passed etcdConfig.
-func GetEtcdBackend(ctx context.Context, etcdConfig *etcd.Config) (
-	Backend, error) {
-
-	return Open(EtcdBackendName, etcdConfig)
-}
-
 // GetEtcdTestBackend creates an embedded etcd backend for testing
 // storig the database at the passed path.
-func GetEtcdTestBackend(path string, clientPort, peerPort uint16) (
-	Backend, func(), error) {
+func StartEtcdTestBackend(path string, clientPort, peerPort uint16) (
+	*etcd.Config, func(), error) {
 
-	empty := func() {}
-
-	config, cleanup, err := etcd.NewEmbeddedEtcdInstance(
+	return etcd.NewEmbeddedEtcdInstance(
 		path, clientPort, peerPort,
 	)
-	if err != nil {
-		return nil, empty, err
-	}
-
-	backend, err := Open(EtcdBackendName, context.Background(), config)
-	if err != nil {
-		cleanup()
-		return nil, empty, err
-	}
-
-	return backend, cleanup, nil
 }

channeldb/kvdb/kvdb_no_etcd.go

@@ -3,7 +3,6 @@
 package kvdb
 
 import (
-	"context"
 	"fmt"
 
 	"github.com/lightningnetwork/lnd/channeldb/kvdb/etcd"
@@ -15,17 +14,9 @@ const TestBackend = BoltBackendName
 
 var errEtcdNotAvailable = fmt.Errorf("etcd backend not available")
 
-// GetEtcdBackend is a stub returning nil and errEtcdNotAvailable error.
-func GetEtcdBackend(ctx context.Context, etcdConfig *etcd.Config) (
-	Backend, error) {
-
-	return nil, errEtcdNotAvailable
-}
-
-// GetTestEtcdBackend  is a stub returning nil, an empty closure and an
-// errEtcdNotAvailable error.
-func GetEtcdTestBackend(path string, clientPort, peerPort uint16) (
-	Backend, func(), error) {
+// StartEtcdTestBackend  is a stub returning nil, and errEtcdNotAvailable error.
+func StartEtcdTestBackend(path string, clientPort, peerPort uint16) (
+	*etcd.Config, func(), error) {
 
 	return nil, func() {}, errEtcdNotAvailable
 }