etcd: make max message size configurable

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 {