minimize allocations (#1472)

* server: minimize allocations on re-register

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* server: stop old instance before Init()

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* client/grpc: fix allocations in protobuf marshal

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* codec/json: fix allocations in protobuf marshal

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* remove stop from init

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* codec/grpc: expose MaxMessageSize

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* codec: use buffer pool

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* metadata: minimize reallocations

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* util/wrapper: use metadata helper

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* registry/cache: move logs to debug level

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* server: move logs to debug level

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* server: cache service only when Advertise is ip addr

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* server: use metadata.Copy

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

codec/proto/marshaler.go

@@ -1,17 +1,45 @@
 package proto
 
 import (
+	"bytes"
+
 	"github.com/golang/protobuf/proto"
+	"github.com/micro/go-micro/v2/codec"
+	"github.com/oxtoacart/bpool"
 )
 
+// create buffer pool with 16 instances each preallocated with 256 bytes
+var bufferPool = bpool.NewSizedBufferPool(16, 256)
+
 type Marshaler struct{}
 
 func (Marshaler) Marshal(v interface{}) ([]byte, error) {
-	return proto.Marshal(v.(proto.Message))
+	pb, ok := v.(proto.Message)
+	if !ok {
+		return nil, codec.ErrInvalidMessage
+	}
+
+	// looks not good, but allows to reuse underlining bytes
+	buf := bufferPool.Get()
+	pbuf := proto.NewBuffer(buf.Bytes())
+	defer func() {
+		bufferPool.Put(bytes.NewBuffer(pbuf.Bytes()))
+	}()
+
+	if err := pbuf.Marshal(pb); err != nil {
+		return nil, err
+	}
+
+	return pbuf.Bytes(), nil
 }
 
 func (Marshaler) Unmarshal(data []byte, v interface{}) error {
-	return proto.Unmarshal(data, v.(proto.Message))
+	pb, ok := v.(proto.Message)
+	if !ok {
+		return codec.ErrInvalidMessage
+	}
+
+	return proto.Unmarshal(data, pb)
 }
 
 func (Marshaler) String() string {