From 7fca02e45f38b946be5d9a41594043ca67a06090 Mon Sep 17 00:00:00 2001
From: "Sascha L. Teichmann" <sascha.teichmann@intevation.de>
Date: Tue, 28 Feb 2017 18:50:45 +0100
Subject: [PATCH] Unified pooling for redis client in hspatial requests.

---
 common/coords.go      |  4 +++
 common/redisclient.go | 58 ++++++++++++++-----------------------------
 2 files changed, 22 insertions(+), 40 deletions(-)

diff --git a/common/coords.go b/common/coords.go
index f66c365..03ec866 100644
--- a/common/coords.go
+++ b/common/coords.go
@@ -81,6 +81,10 @@ func DecodeStringFromBytes(key []byte) (pos int64, err error) {
 	return strconv.ParseInt(string(key), 10, 64)
 }
 
+func keyToBytes(key int64, buf []byte) []byte {
+	return strconv.AppendInt(buf, key, 10)
+}
+
 func StringToBytes(key int64) []byte {
 	return strconv.AppendInt(nil, key, 10)
 }
diff --git a/common/redisclient.go b/common/redisclient.go
index 3149259..cc90b71 100644
--- a/common/redisclient.go
+++ b/common/redisclient.go
@@ -41,47 +41,21 @@ var (
 	ignore      = []byte("IGNORE")
 )
 
-// stringPool is a pool to help recycle bulk strings
-// for writing. Experimented with sync.Pool and
-// channel based leaky buffers but the mutex based
-// version performs best in this case.
-type stringPool struct {
-	list [][]byte
-	sync.Mutex
+var bufPool = sync.Pool{
+	New: func() interface{} {
+		// Some fun with slices
+		buf := make([]byte, 40)
+		return [2][]byte{buf[:20:20][:0], buf[20:][:0]}
+	},
 }
 
-func (sp *stringPool) alloc() (l []byte) {
-	sp.Lock()
-	if n := len(sp.list); n > 0 {
-		l = sp.list[n-1]
-		sp.list[n-1] = nil
-		sp.list = sp.list[:n-1]
-		sp.Unlock()
-	} else {
-		sp.Unlock()
-		l = make([]byte, 0, 32)
-	}
-	return
-}
-
-func (sp *stringPool) free(b []byte) {
-	b = b[:0]
-	sp.Lock()
-	sp.list = append(sp.list, b)
-	sp.Unlock()
-}
-
-var spool stringPool
-
-func (client *RedisClient) writeBulkString(data []byte) (err error) {
-	buf := spool.alloc()
+func (client *RedisClient) writeBulkString(buf []byte, data []byte) (err error) {
 	buf = append(buf, '$')
 	buf = strconv.AppendInt(buf, int64(len(data)), 10)
 	buf = append(buf, nl...)
 	buf = append(buf, data...)
 	buf = append(buf, nl...)
 	_, err = client.conn.Write(buf)
-	spool.free(buf)
 	return
 }
 
@@ -89,16 +63,20 @@ func (client *RedisClient) writeHSpatial(p1, p2 int64) (err error) {
 	if _, err = client.conn.Write(writeArray4); err != nil {
 		return
 	}
-	if err = client.writeBulkString(hspatial); err != nil {
-		return
+	buf := bufPool.Get().([2][]byte)
+	// defer bufPool.Put(buf) // not used to avoid allocation.
+	if err = client.writeBulkString(buf[0], hspatial); err != nil {
+		goto exit
 	}
-	if err = client.writeBulkString(ignore); err != nil {
-		return
+	if err = client.writeBulkString(buf[0], ignore); err != nil {
+		goto exit
 	}
-	if err = client.writeBulkString(StringToBytes(p1)); err != nil {
-		return
+	if err = client.writeBulkString(buf[0], keyToBytes(p1, buf[1])); err != nil {
+		goto exit
 	}
-	err = client.writeBulkString(StringToBytes(p2))
+	err = client.writeBulkString(buf[0], keyToBytes(p2, buf[1]))
+exit:
+	bufPool.Put(buf)
 	return
 }