Allow for proper garbage collection pooling bytes.Buffer (#6266)

cmd/rpc/client.go

@@ -17,7 +17,6 @@
 package rpc
 
 import (
-	"bytes"
 	"context"
 	"crypto/tls"
 	"encoding/gob"
@@ -48,22 +47,25 @@ func (client *Client) Call(serviceMethod string, args, reply interface{}) error
 		return fmt.Errorf("rpc reply must be a pointer type, but found %v", replyKind)
 	}
 
-	data, err := gobEncode(args)
-	if err != nil {
+	argBuf := bufPool.Get()
+	defer bufPool.Put(argBuf)
+
+	if err := gobEncodeBuf(args, argBuf); err != nil {
 		return err
 	}
 
 	callRequest := CallRequest{
 		Method:   serviceMethod,
-		ArgBytes: data,
+		ArgBytes: argBuf.Bytes(),
 	}
 
-	var buf bytes.Buffer
-	if err = gob.NewEncoder(&buf).Encode(callRequest); err != nil {
+	reqBuf := bufPool.Get()
+	defer bufPool.Put(reqBuf)
+	if err := gob.NewEncoder(reqBuf).Encode(callRequest); err != nil {
 		return err
 	}
 
-	response, err := client.httpClient.Post(client.serviceURL.String(), "", &buf)
+	response, err := client.httpClient.Post(client.serviceURL.String(), "", reqBuf)
 	if err != nil {
 		return err
 	}

cmd/rpc/pool.go

@@ -0,0 +1,48 @@
+/*
+ * Minio Cloud Storage, (C) 2018 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package rpc
+
+import (
+	"bytes"
+	"sync"
+)
+
+// A Pool is a type-safe wrapper around a sync.Pool.
+type Pool struct {
+	p *sync.Pool
+}
+
+// NewPool constructs a new Pool.
+func NewPool() Pool {
+	return Pool{p: &sync.Pool{
+		New: func() interface{} {
+			return &bytes.Buffer{}
+		},
+	}}
+}
+
+// Get retrieves a bytes.Buffer from the pool, creating one if necessary.
+func (p Pool) Get() *bytes.Buffer {
+	buf := p.p.Get().(*bytes.Buffer)
+	return buf
+}
+
+// Put - returns a bytes.Buffer to the pool.
+func (p Pool) Put(buf *bytes.Buffer) {
+	buf.Reset()
+	p.p.Put(buf)
+}

cmd/rpc/server.go

@@ -40,14 +40,10 @@ var errorType = reflect.TypeOf((*error)(nil)).Elem()
 // reflect.Type of Authenticator interface.
 var authenticatorType = reflect.TypeOf((*Authenticator)(nil)).Elem()
 
-func gobEncode(e interface{}) ([]byte, error) {
-	var buf bytes.Buffer
+var bufPool = NewPool()
 
-	if err := gob.NewEncoder(&buf).Encode(e); err != nil {
-		return nil, err
-	}
-
-	return buf.Bytes(), nil
+func gobEncodeBuf(e interface{}, buf *bytes.Buffer) error {
+	return gob.NewEncoder(buf).Encode(e)
 }
 
 func gobDecode(data []byte, e interface{}) error {
@@ -146,21 +142,21 @@ func (server *Server) RegisterName(name string, receiver interface{}) error {
 }
 
 // call - call service method in receiver.
-func (server *Server) call(serviceMethod string, argBytes []byte) (replyBytes []byte, err error) {
+func (server *Server) call(serviceMethod string, argBytes []byte, replyBytes *bytes.Buffer) (err error) {
 	tokens := strings.SplitN(serviceMethod, ".", 2)
 	if len(tokens) != 2 {
-		return nil, fmt.Errorf("invalid service/method request ill-formed %v", serviceMethod)
+		return fmt.Errorf("invalid service/method request ill-formed %v", serviceMethod)
 	}
 
 	serviceName := tokens[0]
 	if serviceName != server.serviceName {
-		return nil, fmt.Errorf("can't find service %v", serviceName)
+		return fmt.Errorf("can't find service %v", serviceName)
 	}
 
 	methodName := tokens[1]
 	method, found := server.methodMap[methodName]
 	if !found {
-		return nil, fmt.Errorf("can't find method %v", methodName)
+		return fmt.Errorf("can't find method %v", methodName)
 	}
 
 	var argv reflect.Value
@@ -175,7 +171,7 @@ func (server *Server) call(serviceMethod string, argBytes []byte) (replyBytes []
 	}
 
 	if err = gobDecode(argBytes, argv.Interface()); err != nil {
-		return nil, err
+		return err
 	}
 
 	if argIsValue {
@@ -193,7 +189,7 @@ func (server *Server) call(serviceMethod string, argBytes []byte) (replyBytes []
 		err = errInter.(error)
 	}
 	if err != nil {
-		return nil, err
+		return err
 	}
 
 	replyv := reflect.New(method.Type.In(2).Elem())
@@ -211,10 +207,10 @@ func (server *Server) call(serviceMethod string, argBytes []byte) (replyBytes []
 		err = errInter.(error)
 	}
 	if err != nil {
-		return nil, err
+		return err
 	}
 
-	return gobEncode(replyv.Interface())
+	return gobEncodeBuf(replyv.Interface(), replyBytes)
 }
 
 // CallRequest - RPC call request parameters.
@@ -242,20 +238,18 @@ func (server *Server) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 		return
 	}
 
-	var callResponse CallResponse
-	var err error
-	callResponse.ReplyBytes, err = server.call(callRequest.Method, callRequest.ArgBytes)
-	if err != nil {
+	callResponse := CallResponse{}
+	buf := bufPool.Get()
+	defer bufPool.Put(buf)
+
+	if err := server.call(callRequest.Method, callRequest.ArgBytes, buf); err != nil {
 		callResponse.Error = err.Error()
 	}
+	callResponse.ReplyBytes = buf.Bytes()
 
-	data, err := gobEncode(callResponse)
-	if err != nil {
-		w.WriteHeader(http.StatusInternalServerError)
-		return
-	}
+	gob.NewEncoder(w).Encode(callResponse)
 
-	w.Write(data)
+	w.(http.Flusher).Flush()
 }
 
 // NewServer - returns new RPC server.

cmd/rpc/server_test.go

@@ -18,6 +18,7 @@ package rpc
 
 import (
 	"bytes"
+	"encoding/gob"
 	"errors"
 	"net/http"
 	"net/http/httptest"
@@ -25,6 +26,12 @@ import (
 	"testing"
 )
 
+func gobEncode(e interface{}) ([]byte, error) {
+	var buf bytes.Buffer
+	err := gob.NewEncoder(&buf).Encode(e)
+	return buf.Bytes(), err
+}
+
 type Args struct {
 	A, B int
 }
@@ -251,7 +258,10 @@ func TestServerCall(t *testing.T) {
 	}
 
 	for i, testCase := range testCases {
-		result, err := testCase.server.call(testCase.serviceMethod, testCase.argBytes)
+		buf := bufPool.Get()
+		defer bufPool.Put(buf)
+
+		err := testCase.server.call(testCase.serviceMethod, testCase.argBytes, buf)
 		expectErr := (err != nil)
 
 		if expectErr != testCase.expectErr {
@@ -259,8 +269,8 @@ func TestServerCall(t *testing.T) {
 		}
 
 		if !testCase.expectErr {
-			if !reflect.DeepEqual(result, testCase.expectedResult) {
-				t.Fatalf("case %v: result: expected: %v, got: %v\n", i+1, testCase.expectedResult, result)
+			if !reflect.DeepEqual(buf.Bytes(), testCase.expectedResult) {
+				t.Fatalf("case %v: result: expected: %v, got: %v\n", i+1, testCase.expectedResult, buf.Bytes())
 			}
 		}
 	}