From 72275e97d281f6b4dfb2cd1188db1e7ec5cbb198 Mon Sep 17 00:00:00 2001
From: George Robinson <george.robinson@grafana.com>
Date: Tue, 8 Nov 2022 22:05:15 +0000
Subject: [PATCH] Use fnv64 for InmemCacheService (#58468)

---
 pkg/services/screenshot/cache.go       |  6 +++---
 pkg/services/screenshot/option.go      | 12 ++++++++++++
 pkg/services/screenshot/option_test.go | 24 ++++++++++++++++++++++++
 3 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/pkg/services/screenshot/cache.go b/pkg/services/screenshot/cache.go
index 83447efbc3b..516cc886dfa 100644
--- a/pkg/services/screenshot/cache.go
+++ b/pkg/services/screenshot/cache.go
@@ -2,7 +2,7 @@ package screenshot
 
 import (
 	"context"
-	"fmt"
+	"encoding/base64"
 	"time"
 
 	gocache "github.com/patrickmn/go-cache"
@@ -46,7 +46,7 @@ func NewInmemCacheService(expiration time.Duration, r prometheus.Registerer) Cac
 }
 
 func (s *InmemCacheService) Get(_ context.Context, opts ScreenshotOptions) (*Screenshot, bool) {
-	k := fmt.Sprintf("%s-%d-%s", opts.DashboardUID, opts.PanelID, opts.Theme)
+	k := base64.StdEncoding.EncodeToString(opts.Hash())
 	if v, ok := s.cache.Get(k); ok {
 		defer s.cacheHits.Inc()
 		return v.(*Screenshot), true
@@ -56,7 +56,7 @@ func (s *InmemCacheService) Get(_ context.Context, opts ScreenshotOptions) (*Scr
 }
 
 func (s *InmemCacheService) Set(_ context.Context, opts ScreenshotOptions, screenshot *Screenshot) error {
-	k := fmt.Sprintf("%s-%d-%s", opts.DashboardUID, opts.PanelID, opts.Theme)
+	k := base64.StdEncoding.EncodeToString(opts.Hash())
 	s.cache.Set(k, screenshot, 0)
 	return nil
 }
diff --git a/pkg/services/screenshot/option.go b/pkg/services/screenshot/option.go
index 063b1d850d5..e84d2ed3a55 100644
--- a/pkg/services/screenshot/option.go
+++ b/pkg/services/screenshot/option.go
@@ -1,6 +1,8 @@
 package screenshot
 
 import (
+	"hash/fnv"
+	"strconv"
 	"time"
 
 	"github.com/grafana/grafana/pkg/models"
@@ -41,3 +43,13 @@ func (s ScreenshotOptions) SetDefaults() ScreenshotOptions {
 	}
 	return s
 }
+
+func (s ScreenshotOptions) Hash() []byte {
+	h := fnv.New64()
+	_, _ = h.Write([]byte(s.DashboardUID))
+	_, _ = h.Write([]byte(strconv.FormatInt(s.PanelID, 10)))
+	_, _ = h.Write([]byte(strconv.FormatInt(int64(s.Width), 10)))
+	_, _ = h.Write([]byte(strconv.FormatInt(int64(s.Height), 10)))
+	_, _ = h.Write([]byte(s.Theme))
+	return h.Sum(nil)
+}
diff --git a/pkg/services/screenshot/option_test.go b/pkg/services/screenshot/option_test.go
index f2c8c542fff..50552c1431b 100644
--- a/pkg/services/screenshot/option_test.go
+++ b/pkg/services/screenshot/option_test.go
@@ -53,3 +53,27 @@ func TestScreenshotOptions(t *testing.T) {
 		Timeout: DefaultTimeout + 1,
 	}, o)
 }
+
+func TestScreenshotOptions_Hash(t *testing.T) {
+	o := ScreenshotOptions{}
+	assert.Equal(t, []byte{0xd9, 0x83, 0x82, 0x18, 0x6c, 0x3d, 0x7d, 0x47}, o.Hash())
+
+	o = o.SetDefaults()
+	assert.Equal(t, []byte{0x6, 0x7, 0x97, 0x6, 0x53, 0xf, 0x8b, 0xf1}, o.Hash())
+
+	o.Width = 100
+	o = o.SetDefaults()
+	assert.Equal(t, []byte{0x25, 0x50, 0xb4, 0x4b, 0x43, 0xcd, 0x3, 0x49}, o.Hash())
+
+	o.Height = 100
+	o = o.SetDefaults()
+	assert.Equal(t, []byte{0x51, 0xe2, 0x6f, 0x2c, 0x62, 0x7b, 0x3b, 0xc5}, o.Hash())
+
+	o.Theme = "Not a theme"
+	o = o.SetDefaults()
+	assert.Equal(t, []byte{0x51, 0xe2, 0x6f, 0x2c, 0x62, 0x7b, 0x3b, 0xc5}, o.Hash())
+
+	// the timeout should not change the sum
+	o.Timeout = DefaultTimeout + 1
+	assert.Equal(t, []byte{0x51, 0xe2, 0x6f, 0x2c, 0x62, 0x7b, 0x3b, 0xc5}, o.Hash())
+}