Update cache for badges

Author: boyter

cmd/badges/main.go

@@ -20,7 +20,7 @@ import (
 )
 
 var uniqueCode = "unique_code"
-var cache = NewSimpleCache(1000)
+var cache = NewSimpleCache(1000, 86400)
 var countingSemaphore = make(chan bool, 1)
 
 func main() {

cmd/badges/simplecache.go

@@ -9,101 +9,153 @@ import (
 type cacheEntry struct {
 	entry []byte
 	hits  int
+	age   int64
 }
 
 type SimpleCache struct {
-	maxItems int
-	items    map[string]cacheEntry
-	lock     sync.Mutex
+	maxItems          int
+	items             map[string]cacheEntry
+	lock              sync.Mutex
+	getUnix           func() int64
+	ageOutTimeSeconds int64
 }
 
-func NewSimpleCache(maxItems int) *SimpleCache {
+func NewSimpleCache(maxItems int, ageOutTimeSeconds int64) *SimpleCache {
 	simpleCache := SimpleCache{
 		maxItems: maxItems,
 		items:    map[string]cacheEntry{},
 		lock:     sync.Mutex{},
+		getUnix: func() int64 {
+			return time.Now().Unix()
+		},
+		ageOutTimeSeconds: ageOutTimeSeconds,
 	}
 	simpleCache.runAgeItems()
 	return &simpleCache
 }
 
-func (cache *SimpleCache) runAgeItems() {
+func (c *SimpleCache) runAgeItems() {
 	go func() {
-		for {
-			// maps are randomly ordered, so only decrementing 50 at a time should be acceptable
-			count := 50
-			cache.lock.Lock()
-			for k, v := range cache.items {
-				if v.hits > 0 {
-					v.hits--
-					cache.items[k] = v
-				}
-				count--
-				if count <= 0 {
-					break
-				}
-			}
-			cache.lock.Unlock()
-			time.Sleep(10 * time.Second)
-		}
+		time.Sleep(10 * time.Second)
+		c.adjustLfu()
+		c.ageOut()
 	}()
 }
 
-func (cache *SimpleCache) Add(cacheKey string, entry []byte) {
-	cache.expireItems()
+func (c *SimpleCache) adjustLfu() {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+
+	// maps are randomly ordered, so only decrementing 50 at a time should be acceptable
+	count := 50
 
-	cache.lock.Lock()
-	defer cache.lock.Unlock()
+	for k, v := range c.items {
+		if v.hits > 0 {
+			v.hits--
+			c.items[k] = v
+		}
+		count--
+		if count <= 0 {
+			break
+		}
+	}
+}
 
-	cache.items[cacheKey] = cacheEntry{
+func (c *SimpleCache) Add(cacheKey string, entry []byte) {
+	c.evictItems()
+
+	c.lock.Lock()
+	defer c.lock.Unlock()
+
+	c.items[cacheKey] = cacheEntry{
 		entry: entry,
 		hits:  1,
+		age:   c.getUnix(),
 	}
 }
 
-func (cache *SimpleCache) Get(cacheKey string) ([]byte, bool) {
-	cache.lock.Lock()
-	defer cache.lock.Unlock()
+func (c *SimpleCache) Get(cacheKey string) ([]byte, bool) {
+	c.lock.Lock()
+	defer c.lock.Unlock()
 
-	item, ok := cache.items[cacheKey]
+	item, ok := c.items[cacheKey]
 
 	if ok {
 		if item.hits < 100 {
 			item.hits++
 		}
-		cache.items[cacheKey] = item
+		c.items[cacheKey] = item
 		return item.entry, true
 	}
 
 	return nil, false
 }
 
-// ExpireItems is called before any insert operation because we need to ensure we have less than
+// evictItems is called before any insert operation because we need to ensure we have less than
 // the total number of items
-func (cache *SimpleCache) expireItems() {
-	cache.lock.Lock()
-	defer cache.lock.Unlock()
+func (c *SimpleCache) evictItems() {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+
+	// insert process only needs to expire if we have too much
+	// as such if we haven't hit the limit return
+	if len(c.items) < c.maxItems {
+		return
+	}
 
 	count := 10
-	if len(cache.items) >= cache.maxItems {
-		lfuKey := ""
-		lfuLowestCount := math.MaxInt
 
-		for k, v := range cache.items {
-			v.hits--
-			cache.items[k] = v
-			if v.hits < lfuLowestCount {
-				lfuKey = k
-				lfuLowestCount = v.hits
-			}
-
-			// we only want to process X random elements so we don't spin forever
-			count--
-			if count <= 0 {
-				break
-			}
+	lfuKey := ""
+	lfuLowestCount := math.MaxInt
+
+	for k, v := range c.items {
+		v.hits--
+		c.items[k] = v
+		if v.hits < lfuLowestCount {
+			lfuKey = k
+			lfuLowestCount = v.hits
 		}
 
-		delete(cache.items, lfuKey)
+		// we only want to process X random elements so we don't spin forever
+		// however we also exit if the count is <= 0
+		count--
+		if count <= 0 || lfuLowestCount <= 0 {
+			break
+		}
+	}
+
+	delete(c.items, lfuKey)
+}
+
+// ageOut is called on a schedule to evict the oldest entry so long as
+// its older than the configured cache time
+func (c *SimpleCache) ageOut() {
+	// we also want to age out things eventually to avoid https://github.com/boyter/scc/discussions/435
+	// as such loop though and the first one that's older than a day with 0 hits is removed
+
+	c.lock.Lock()
+	defer c.lock.Unlock()
+
+	count := 10
+	lfuKey := ""
+	lfuOldest := int64(math.MaxInt)
+
+	// maps are un-ordered so this is acceptable
+	for k, v := range c.items {
+		c.items[k] = v
+		if v.age < lfuOldest {
+			lfuKey = k
+			lfuOldest = v.age
+		}
+
+		count--
+		if count <= 0 {
+			break
+		}
+	}
+
+	// evict the oldest but only if its older than it should be
+	if lfuOldest <= c.getUnix()-c.ageOutTimeSeconds {
+		delete(c.items, lfuKey)
 	}
 }

cmd/badges/simplecache_test.go

@@ -2,11 +2,13 @@ package main
 
 import (
 	"fmt"
+	"sync"
 	"testing"
+	"time"
 )
 
 func TestSimpleCache_Add(t *testing.T) {
-	simpleCache := NewSimpleCache(5)
+	simpleCache := NewSimpleCache(5, 60)
 
 	for i := 0; i < 5; i++ {
 		simpleCache.Add(fmt.Sprintf("%d", i), []byte{})
@@ -22,7 +24,7 @@ func TestSimpleCache_Add(t *testing.T) {
 }
 
 func TestSimpleCache_Multiple(t *testing.T) {
-	simpleCache := NewSimpleCache(10)
+	simpleCache := NewSimpleCache(10, 60)
 
 	for i := 0; i < 500; i++ {
 		simpleCache.Add(fmt.Sprintf("%d", i), []byte{})
@@ -36,7 +38,7 @@ func TestSimpleCache_Multiple(t *testing.T) {
 }
 
 func TestSimpleCache_MultipleLarge(t *testing.T) {
-	simpleCache := NewSimpleCache(1000)
+	simpleCache := NewSimpleCache(1000, 60)
 
 	for i := 0; i < 500000; i++ {
 		simpleCache.Add(fmt.Sprintf("%d", i), []byte{})
@@ -50,3 +52,51 @@ func TestSimpleCache_MultipleLarge(t *testing.T) {
 		t.Errorf("expected 999 items got %v", len(simpleCache.items))
 	}
 }
+
+func TestSimpleCache_AgeOut(t *testing.T) {
+	simpleCache := &SimpleCache{
+		maxItems: 100,
+		items:    map[string]cacheEntry{},
+		lock:     sync.Mutex{},
+		getUnix: func() int64 {
+			return 0
+		},
+		ageOutTimeSeconds: 10,
+	}
+
+	for i := 0; i < 10; i++ {
+		simpleCache.Add(fmt.Sprintf("%d", i), []byte{})
+	}
+
+	// advance time
+	simpleCache.getUnix = func() int64 {
+		return 10000
+	}
+	// simulate eviction over time
+	for i := 0; i < 10; i++ {
+		simpleCache.ageOut()
+	}
+
+	if len(simpleCache.items) != 0 {
+		t.Errorf("expected 0 items got %v", len(simpleCache.items))
+	}
+}
+
+func TestSimpleCache_AgeOutTime(t *testing.T) {
+	simpleCache := NewSimpleCache(100, 1)
+
+	for i := 0; i < 10; i++ {
+		simpleCache.Add(fmt.Sprintf("%d", i), []byte{})
+	}
+
+	time.Sleep(1 * time.Second)
+
+	// simulate eviction over time
+	for i := 0; i < 10; i++ {
+		simpleCache.ageOut()
+	}
+
+	if len(simpleCache.items) != 0 {
+		t.Errorf("expected 0 items got %v", len(simpleCache.items))
+	}
+}