refactor: enhanced uuid

- more allocation friendly uuid string function
- use buffered rand.Reader to reduce syscalls
- uuid benchmarks

Signed-off-by: Marcus Brandenburger <bur@zurich.ibm.com>

Author: mbrandenburger

pkg/utils/uuid.go

@@ -8,8 +8,18 @@ package utils
 
 import (
 	"crypto/rand"
+	"encoding/hex"
 	"fmt"
 	"io"
+	"sync"
+)
+
+const randPoolSize = 16 * 16
+
+var (
+	poolMu  sync.Mutex
+	poolPos = randPoolSize     // protected with poolMu
+	pool    [randPoolSize]byte // protected with poolMu
 )
 
 var randChar = &poolRandReader{
@@ -38,10 +48,19 @@ func (r *poolRandReader) Read(p []byte) (int, error) {
 // GenerateBytesUUID returns a UUID based on RFC 4122 returning the generated bytes
 func GenerateBytesUUID() []byte {
 	uuid := make([]byte, 16)
-	_, err := io.ReadFull(rand.Reader, uuid)
-	if err != nil {
-		panic(fmt.Sprintf("Error generating UUID: %s", err))
+
+	poolMu.Lock()
+	if poolPos == randPoolSize {
+		_, err := io.ReadFull(rand.Reader, pool[:])
+		if err != nil {
+			poolMu.Unlock()
+			panic(fmt.Sprintf("Error generating UUID: %s", err))
+		}
+		poolPos = 0
 	}
+	copy(uuid[:], pool[poolPos:(poolPos+16)])
+	poolPos += 16
+	poolMu.Unlock()
 
 	// variant bits; see section 4.1.1
 	uuid[8] = uuid[8]&^0xc0 | 0x80
@@ -59,7 +78,17 @@ func GenerateUUID() string {
 }
 
 func idBytesToStr(id []byte) string {
-	return fmt.Sprintf("%x-%x-%x-%x-%x", id[0:4], id[4:6], id[6:8], id[8:10], id[10:])
+	dst := make([]byte, 36)
+	hex.Encode(dst[0:8], id[0:4])
+	dst[8] = '-'
+	hex.Encode(dst[9:13], id[4:6])
+	dst[13] = '-'
+	hex.Encode(dst[14:18], id[6:8])
+	dst[18] = '-'
+	hex.Encode(dst[19:23], id[8:10])
+	dst[23] = '-'
+	hex.Encode(dst[24:], id[10:16])
+	return string(dst)
 }
 
 // GenerateUUIDOnlyLetters returns a UUID without digits

pkg/utils/uuid_test.go

@@ -15,3 +15,24 @@ import (
 func TestUUIDLettersOnly(t *testing.T) {
 	assert.Regexp(t, "^[a-zA-Z]{16}$", GenerateUUIDOnlyLetters())
 }
+
+func BenchmarkUUID(b *testing.B) {
+	b.Run("GenerateBytesUUID", func(b *testing.B) {
+		for b.Loop() {
+			_ = GenerateBytesUUID()
+		}
+	})
+
+	b.Run("GenerateUUID", func(b *testing.B) {
+		for b.Loop() {
+			_ = GenerateUUID()
+		}
+	})
+
+	b.Run("idBytesToStr", func(b *testing.B) {
+		k := GenerateBytesUUID()
+		for b.Loop() {
+			_ = idBytesToStr(k)
+		}
+	})
+}