etcd: enable optional log file for embedded etcd log output

In this commit we add an extra config for enabling logging to an
external file when using embedded etcd. This can be useful when running
integration tests to see more details about etcd related issues.

kvdb/backend.go

@@ -256,7 +256,7 @@ func GetTestBackend(path, name string) (Backend, func(), error) {
 		}
 		return db, empty, nil
 	} else if TestBackend == EtcdBackendName {
-		etcdConfig, cancel, err := StartEtcdTestBackend(path, 0, 0)
+		etcdConfig, cancel, err := StartEtcdTestBackend(path, 0, 0, "")
 		if err != nil {
 			return nil, empty, err
 		}

kvdb/etcd/config.go

@@ -10,6 +10,8 @@ type Config struct {
 
 	EmbeddedPeerPort uint16 `long:"embedded_peer_port" description:"Peer port to use for the embedded instance. Note: use for testing only."`
 
+	EmbeddedLogFile string `long:"embedded_log_file" description:"Optional log file to use for embedded instance logs. note: use for testing only."`
+
 	Host string `long:"host" description:"Etcd database host."`
 
 	User string `long:"user" description:"Etcd database user."`

kvdb/etcd/embed.go

@@ -60,8 +60,8 @@ func getFreePort() int {
 // NewEmbeddedEtcdInstance creates an embedded etcd instance for testing,
 // listening on random open ports. Returns the backend config and a cleanup
 // func that will stop the etcd instance.
-func NewEmbeddedEtcdInstance(path string, clientPort, peerPort uint16) (
-	*Config, func(), error) {
+func NewEmbeddedEtcdInstance(path string, clientPort, peerPort uint16,
+	logFile string) (*Config, func(), error) {
 
 	cfg := embed.NewConfig()
 	cfg.Dir = path
@@ -70,7 +70,12 @@ func NewEmbeddedEtcdInstance(path string, clientPort, peerPort uint16) (
 	cfg.MaxTxnOps = 8192
 	cfg.MaxRequestBytes = 16384 * 1024
 	cfg.Logger = "zap"
-	cfg.LogLevel = "error"
+	if logFile != "" {
+		cfg.LogLevel = "info"
+		cfg.LogOutputs = []string{logFile}
+	} else {
+		cfg.LogLevel = "error"
+	}
 
 	// Listen on random free ports if no ports were specified.
 	if clientPort == 0 {

kvdb/etcd/fixture.go

@@ -34,7 +34,7 @@ type EtcdTestFixture struct {
 func NewTestEtcdInstance(t *testing.T, path string) (*Config, func()) {
 	t.Helper()
 
-	config, cleanup, err := NewEmbeddedEtcdInstance(path, 0, 0)
+	config, cleanup, err := NewEmbeddedEtcdInstance(path, 0, 0, "")
 	if err != nil {
 		t.Fatalf("error while staring embedded etcd instance: %v", err)
 	}

kvdb/kvdb_etcd.go

@@ -12,10 +12,10 @@ const TestBackend = EtcdBackendName
 
 // GetEtcdTestBackend creates an embedded etcd backend for testing
 // storig the database at the passed path.
-func StartEtcdTestBackend(path string, clientPort, peerPort uint16) (
-	*etcd.Config, func(), error) {
+func StartEtcdTestBackend(path string, clientPort, peerPort uint16,
+	logFile string) (*etcd.Config, func(), error) {
 
 	return etcd.NewEmbeddedEtcdInstance(
-		path, clientPort, peerPort,
+		path, clientPort, peerPort, logFile,
 	)
 }

kvdb/kvdb_no_etcd.go

@@ -15,8 +15,8 @@ const TestBackend = BoltBackendName
 var errEtcdNotAvailable = fmt.Errorf("etcd backend not available")
 
 // StartEtcdTestBackend  is a stub returning nil, and errEtcdNotAvailable error.
-func StartEtcdTestBackend(path string, clientPort, peerPort uint16) (
-	*etcd.Config, func(), error) {
+func StartEtcdTestBackend(path string, clientPort, peerPort uint16,
+	logFile string) (*etcd.Config, func(), error) {
 
 	return nil, func() {}, errEtcdNotAvailable
 }

lncfg/db.go

@@ -92,7 +92,7 @@ func (db *DB) Init(ctx context.Context, dbPath string) error {
 	if db.Backend == EtcdBackend && db.Etcd.Embedded {
 		cfg, _, err := kvdb.StartEtcdTestBackend(
 			dbPath, db.Etcd.EmbeddedClientPort,
-			db.Etcd.EmbeddedPeerPort,
+			db.Etcd.EmbeddedPeerPort, db.Etcd.EmbeddedLogFile,
 		)
 		if err != nil {
 			return err

lntest/itest/lnd_etcd_failover_test.go

@@ -70,7 +70,7 @@ func testEtcdFailoverCase(net *lntest.NetworkHarness, ht *harnessTest,
 	tmpDir, err := ioutil.TempDir("", "etcd")
 	etcdCfg, cleanup, err := kvdb.StartEtcdTestBackend(
 		tmpDir, uint16(lntest.NextAvailablePort()),
-		uint16(lntest.NextAvailablePort()),
+		uint16(lntest.NextAvailablePort()), "",
 	)
 	if err != nil {
 		ht.Fatalf("Failed to start etcd instance: %v", err)

sample-lnd.conf

@@ -1131,6 +1131,10 @@ litecoin.node=ltcd
 ; If non zero, LND will use this as peer port for the embedded etcd instance.
 ; db.etcd.embedded_peer_port=1235
 
+; If set the embedded etcd instance will log to the specified file. Useful when
+; testing with embedded etcd.
+; db.etcd.embedded_log_file=/path/etcd.log
+
 
 [cluster]