From 6f54afb45ed61a7e38fad9b65beaf23ab203d7fb Mon Sep 17 00:00:00 2001
From: Vincent Bernat <vincent@bernat.ch>
Date: Wed, 21 Dec 2022 21:23:10 +0100
Subject: [PATCH] feat: add WithOnCacheMiss option

This is similar to WithOnCacheHit. It is also triggered on error (as
this is technically a cache miss). This is useful if you want to keep
metrics about hit and miss without having another middleware.
---
 cache.go                 |  1 +
 cache_test.go            | 23 ++++++++++++++++++++++-
 examples/options/main.go | 13 ++++++++++---
 option.go                | 18 +++++++++++++++++-
 4 files changed, 50 insertions(+), 5 deletions(-)

diff --git a/cache.go b/cache.go
index 11ab064..219d470 100644
--- a/cache.go
+++ b/cache.go
@@ -88,6 +88,7 @@ func cache(
 			if err != persist.ErrCacheMiss {
 				cfg.logger.Errorf("get cache error: %s, cache key: %s", err, cacheKey)
 			}
+			cfg.missCacheCallback(c)
 		}
 
 		// cache miss, then call the backend
diff --git a/cache_test.go b/cache_test.go
index 85827a9..33f0517 100644
--- a/cache_test.go
+++ b/cache_test.go
@@ -2,17 +2,18 @@ package cache
 
 import (
 	"fmt"
-	"github.com/stretchr/testify/require"
 	"math/rand"
 	"net/http"
 	"net/http/httptest"
 	"sync"
+	"sync/atomic"
 	"testing"
 	"time"
 
 	"github.com/chenyahui/gin-cache/persist"
 	"github.com/gin-gonic/gin"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func init() {
@@ -53,6 +54,26 @@ func TestCacheByRequestPath(t *testing.T) {
 	assert.Equal(t, w1.Code, w2.Code)
 }
 
+func TestCacheHitMissCallback(t *testing.T) {
+	var cacheHitCount, cacheMissCount int32
+	memoryStore := persist.NewMemoryStore(1 * time.Minute)
+	cachePathMiddleware := CacheByRequestPath(memoryStore, 3*time.Second,
+		WithOnHitCache(func(c *gin.Context) {
+			atomic.AddInt32(&cacheHitCount, 1)
+		}),
+		WithOnMissCache(func(c *gin.Context) {
+			atomic.AddInt32(&cacheMissCount, 1)
+		}),
+	)
+
+	mockHttpRequest(cachePathMiddleware, "/cache?uid=u1", true)
+	mockHttpRequest(cachePathMiddleware, "/cache?uid=u2", true)
+	mockHttpRequest(cachePathMiddleware, "/cache?uid=u3", true)
+
+	assert.Equal(t, cacheHitCount, int32(2))
+	assert.Equal(t, cacheMissCount, int32(1))
+}
+
 func TestCacheDuration(t *testing.T) {
 	memoryStore := persist.NewMemoryStore(1 * time.Minute)
 	cacheURIMiddleware := CacheByRequestURI(memoryStore, 3*time.Second)
diff --git a/examples/options/main.go b/examples/options/main.go
index f4838a1..ddf3ae5 100644
--- a/examples/options/main.go
+++ b/examples/options/main.go
@@ -2,11 +2,12 @@ package main
 
 import (
 	"fmt"
+	"sync/atomic"
+	"time"
+
 	cache "github.com/chenyahui/gin-cache"
 	"github.com/chenyahui/gin-cache/persist"
 	"github.com/gin-gonic/gin"
-	"sync/atomic"
-	"time"
 )
 
 func main() {
@@ -14,7 +15,7 @@ func main() {
 
 	memoryStore := persist.NewMemoryStore(1 * time.Minute)
 
-	var cacheHitCount int32
+	var cacheHitCount, cacheMissCount int32
 	app.GET("/hello",
 		cache.CacheByRequestURI(
 			memoryStore,
@@ -22,6 +23,9 @@ func main() {
 			cache.WithOnHitCache(func(c *gin.Context) {
 				atomic.AddInt32(&cacheHitCount, 1)
 			}),
+			cache.WithOnMissCache(func(c *gin.Context) {
+				atomic.AddInt32(&cacheMissCount, 1)
+			}),
 		),
 		func(c *gin.Context) {
 			c.String(200, "hello world")
@@ -31,6 +35,9 @@ func main() {
 	app.GET("/get_hit_count", func(c *gin.Context) {
 		c.String(200, fmt.Sprintf("total hit count: %d", cacheHitCount))
 	})
+	app.GET("/get_miss_count", func(c *gin.Context) {
+		c.String(200, fmt.Sprintf("total miss count: %d", cacheMissCount))
+	})
 
 	if err := app.Run(":8080"); err != nil {
 		panic(err)
diff --git a/option.go b/option.go
index d303bfb..4c4f034 100644
--- a/option.go
+++ b/option.go
@@ -12,7 +12,8 @@ type Config struct {
 
 	getCacheStrategyByRequest GetCacheStrategyByRequest
 
-	hitCacheCallback OnHitCacheCallback
+	hitCacheCallback  OnHitCacheCallback
+	missCacheCallback OnMissCacheCallback
 
 	beforeReplyWithCacheCallback BeforeReplyWithCacheCallback
 
@@ -27,6 +28,7 @@ func newConfigByOpts(opts ...Option) *Config {
 	cfg := &Config{
 		logger:                       Discard{},
 		hitCacheCallback:             defaultHitCacheCallback,
+		missCacheCallback:            defaultMissCacheCallback,
 		beforeReplyWithCacheCallback: defaultBeforeReplyWithCacheCallback,
 		shareSingleFlightCallback:    defaultShareSingleFlightCallback,
 	}
@@ -86,6 +88,20 @@ func WithOnHitCache(cb OnHitCacheCallback) Option {
 	}
 }
 
+// OnMissCacheCallback define the callback when use cache
+type OnMissCacheCallback func(c *gin.Context)
+
+var defaultMissCacheCallback = func(c *gin.Context) {}
+
+// WithOnMissCache will be called when cache miss.
+func WithOnMissCache(cb OnMissCacheCallback) Option {
+	return func(c *Config) {
+		if cb != nil {
+			c.missCacheCallback = cb
+		}
+	}
+}
+
 type BeforeReplyWithCacheCallback func(c *gin.Context, cache *ResponseCache)
 
 var defaultBeforeReplyWithCacheCallback = func(c *gin.Context, cache *ResponseCache) {}