server: don't always Sprintf params for logger

Add Stringer to Params, if we're not printing Debug messages (which usually is
the case), it won't be called at all. Micro-optimization.

pkg/rpc/request/params.go

@@ -1,5 +1,7 @@
 package request
 
+import "fmt"
+
 type (
 	// Params represents the JSON-RPC params.
 	Params []Param
@@ -23,3 +25,7 @@ func (p Params) ValueWithType(index int, valType paramType) *Param {
 	}
 	return nil
 }
+
+func (p Params) String() string {
+	return fmt.Sprintf("%v", []Param(p))
+}

pkg/rpc/server/server.go

@@ -291,7 +291,7 @@ func (s *Server) handleRequest(req *request.In, sub *subscriber) response.Abstra
 
 	s.log.Debug("processing rpc request",
 		zap.String("method", req.Method),
-		zap.String("params", fmt.Sprintf("%v", reqParams)))
+		zap.Stringer("params", reqParams))
 
 	incCounter(req.Method)