etcd: make max message size configurable

go.mod

@@ -46,7 +46,7 @@ require (
 	github.com/lightningnetwork/lnd/cert v1.1.0
 	github.com/lightningnetwork/lnd/clock v1.1.0
 	github.com/lightningnetwork/lnd/healthcheck v1.2.0
-	github.com/lightningnetwork/lnd/kvdb v1.2.1
+	github.com/lightningnetwork/lnd/kvdb v1.2.3
 	github.com/lightningnetwork/lnd/queue v1.1.0
 	github.com/lightningnetwork/lnd/ticker v1.1.0
 	github.com/ltcsuite/ltcd v0.0.0-20190101042124-f37f8bf35796

kvdb/etcd/config.go

@@ -30,6 +30,8 @@ type Config struct {
 
 	CollectStats bool `long:"collect_stats" description:"Whether to collect etcd commit stats."`
 
+	MaxMsgSize int `long:"max_msg_size" description:"The maximum message size in bytes that we may send to etcd."`
+
 	// SingleWriter should be set to true if we intend to only allow a
 	// single writer to the database at a time.
 	SingleWriter bool

kvdb/etcd/db.go

@@ -141,7 +141,7 @@ func newEtcdBackend(ctx context.Context, cfg Config) (*db, error) {
 		DialTimeout:        etcdConnectionTimeout,
 		Username:           cfg.User,
 		Password:           cfg.Pass,
-		MaxCallSendMsgSize: 16384*1024 - 1,
+		MaxCallSendMsgSize: cfg.MaxMsgSize,
 	}
 
 	if !cfg.DisableTLS {

lncfg/db.go

@@ -73,6 +73,10 @@ func DefaultDB() *DB {
 			AutoCompactMinAge: kvdb.DefaultBoltAutoCompactMinAge,
 			DBTimeout:         kvdb.DefaultDBTimeout,
 		},
+		Etcd: &etcd.Config{
+			// Allow at most 32 MiB messages by default.
+			MaxMsgSize: 32768 * 1024,
+		},
 		Postgres: &postgres.Config{
 			MaxConnections: defaultPostgresMaxConnections,
 		},

sample-lnd.conf

@@ -1169,6 +1169,9 @@ litecoin.node=ltcd
 ; testing with embedded etcd.
 ; db.etcd.embedded_log_file=/path/etcd.log
 
+; The maximum message size in bytes that we may send to etcd. Defaults to 32 MiB.
+; db.etcd.max_msg_size=33554432
+
 [postgres]
 ; Postgres connection string.
 ; db.postgres.dsn=postgres://lnd:lnd@localhost:45432/lnd?sslmode=disable