Merge pull request #8 from jdeppe-pivotal/master

Add a SecondaryCache which exposes the secondary part of a LayeredCache

Author: karlseguin

layeredbucket.go

@@ -11,13 +11,21 @@ type layeredBucket struct {
 }
 
 func (b *layeredBucket) get(primary, secondary string) *Item {
+	bucket := b.getSecondaryBucket(primary)
+	if bucket == nil {
+		return nil
+	}
+	return bucket.get(secondary)
+}
+
+func (b *layeredBucket) getSecondaryBucket(primary string) *bucket {
 	b.RLock()
 	bucket, exists := b.buckets[primary]
 	b.RUnlock()
 	if exists == false {
 		return nil
 	}
-	return bucket.get(secondary)
+	return bucket
 }
 
 func (b *layeredBucket) set(primary, secondary string, value interface{}, duration time.Duration) (*Item, *Item) {

layeredcache.go

@@ -64,6 +64,24 @@ func (c *LayeredCache) Get(primary, secondary string) *Item {
 	return item
 }
 
+// Get the secondary cache for a given primary key. This operation will
+// never return nil. In the case where the primary key does not exist, a
+// new, underlying, empty bucket will be created and returned.
+func (c *LayeredCache) GetOrCreateSecondaryCache(primary string) *SecondaryCache {
+	primaryBkt := c.bucket(primary)
+	bkt := primaryBkt.getSecondaryBucket(primary)
+	primaryBkt.Lock()
+	if bkt == nil {
+		bkt = &bucket{lookup: make(map[string]*Item)}
+		primaryBkt.buckets[primary] = bkt
+	}
+	primaryBkt.Unlock()
+	return &SecondaryCache{
+		bucket: bkt,
+		pCache: c,
+	}
+}
+
 // Used when the cache was created with the Track() configuration option.
 // Avoid otherwise
 func (c *LayeredCache) TrackingGet(primary, secondary string) TrackedItem {

readme.md

@@ -151,6 +151,18 @@ cache.Delete("/users/goku", "type:xml")
 cache.DeleteAll("/users/goku")
 ```
 
+# SecondaryCache
+
+In some cases, when using a `LayeredCache`, it may be desirable to always be acting on the secondary portion of the cache entry. This could be the case where the primary key is used as a key elsewhere in your code. The `SecondaryCache` is retrieved with:
+
+```go
+cache := ccache.Layered(ccache.Configure())
+sCache := cache.GetOrCreateSecondaryCache("/users/goku")
+sCache.Set("type:json", "{value_to_cache}", time.Minute * 5)
+```
+
+The semantics for interacting with the `SecondaryCache` are exactly the same as for a regular `Cache`. However, one difference is that `Get` will not return nil, but will return an empty 'cache' for a non-existent primary key.
+
 ## Size
 By default, items added to a cache have a size of 1. This means that if you configure `MaxSize(10000)`, you'll be able to store 10000 items in the cache.
 

secondarycache.go

@@ -0,0 +1,72 @@
+package ccache
+
+import "time"
+
+type SecondaryCache struct {
+	bucket *bucket
+	pCache *LayeredCache
+}
+
+// Get the secondary key.
+// The semantics are the same as for LayeredCache.Get
+func (s *SecondaryCache) Get(secondary string) *Item {
+	return s.bucket.get(secondary)
+}
+
+// Set the secondary key to a value.
+// The semantics are the same as for LayeredCache.Set
+func (s *SecondaryCache) Set(secondary string, value interface{}, duration time.Duration) *Item {
+	item, existing := s.bucket.set(secondary, value, duration)
+	if existing != nil {
+		s.pCache.deletables <- existing
+	}
+	s.pCache.promote(item)
+	return item
+}
+
+// Fetch or set a secondary key.
+// The semantics are the same as for LayeredCache.Fetch
+func (s *SecondaryCache) Fetch(secondary string, duration time.Duration, fetch func() (interface{}, error)) (*Item, error) {
+	item := s.Get(secondary)
+	if item != nil {
+		return item, nil
+	}
+	value, err := fetch()
+	if err != nil {
+		return nil, err
+	}
+	return s.Set(secondary, value, duration), nil
+}
+
+// Delete a secondary key.
+// The semantics are the same as for LayeredCache.Delete
+func (s *SecondaryCache) Delete(secondary string) bool {
+	item := s.bucket.delete(secondary)
+	if item != nil {
+		s.pCache.deletables <- item
+		return true
+	}
+	return false
+}
+
+// Replace a secondary key.
+// The semantics are the same as for LayeredCache.Replace
+func (s *SecondaryCache) Replace(secondary string, value interface{}) bool {
+	item := s.Get(secondary)
+	if item == nil {
+		return false
+	}
+	s.Set(secondary, value, item.TTL())
+	return true
+}
+
+// Track a secondary key.
+// The semantics are the same as for LayeredCache.TrackingGet
+func (c *SecondaryCache) TrackingGet(secondary string) TrackedItem {
+	item := c.Get(secondary)
+	if item == nil {
+		return NilTracked
+	}
+	item.track()
+	return item
+}

secondarycache_test.go

@@ -0,0 +1,105 @@
+package ccache
+
+import (
+	. "github.com/karlseguin/expect"
+	"testing"
+	"time"
+	"strconv"
+)
+
+type SecondaryCacheTests struct{}
+
+func Test_SecondaryCache(t *testing.T) {
+	Expectify(new(SecondaryCacheTests), t)
+}
+
+func (_ SecondaryCacheTests) GetsANonExistantValue() {
+	cache := newLayered().GetOrCreateSecondaryCache("foo")
+	Expect(cache).Not.To.Equal(nil)
+}
+
+func (_ SecondaryCacheTests) SetANewValue() {
+	cache := newLayered()
+	cache.Set("spice", "flow", "a value", time.Minute)
+	sCache := cache.GetOrCreateSecondaryCache("spice")
+	Expect(sCache.Get("flow").Value()).To.Equal("a value")
+	Expect(sCache.Get("stop")).To.Equal(nil)
+}
+
+func (_ SecondaryCacheTests) ValueCanBeSeenInBothCaches1() {
+	cache := newLayered()
+	cache.Set("spice", "flow", "a value", time.Minute)
+	sCache := cache.GetOrCreateSecondaryCache("spice")
+	sCache.Set("orinoco", "another value", time.Minute)
+	Expect(sCache.Get("orinoco").Value()).To.Equal("another value")
+	Expect(cache.Get("spice", "orinoco").Value()).To.Equal("another value")
+}
+
+func (_ SecondaryCacheTests) ValueCanBeSeenInBothCaches2() {
+	cache := newLayered()
+	sCache := cache.GetOrCreateSecondaryCache("spice")
+	sCache.Set("flow", "a value", time.Minute)
+	Expect(sCache.Get("flow").Value()).To.Equal("a value")
+	Expect(cache.Get("spice", "flow").Value()).To.Equal("a value")
+}
+
+func (_ SecondaryCacheTests) DeletesAreReflectedInBothCaches() {
+	cache := newLayered()
+	cache.Set("spice", "flow", "a value", time.Minute)
+	cache.Set("spice", "sister", "ghanima", time.Minute)
+	sCache := cache.GetOrCreateSecondaryCache("spice")
+
+	cache.Delete("spice", "flow")
+	Expect(cache.Get("spice", "flow")).To.Equal(nil)
+	Expect(sCache.Get("flow")).To.Equal(nil)
+
+	sCache.Delete("sister")
+	Expect(cache.Get("spice", "sister")).To.Equal(nil)
+	Expect(sCache.Get("sister")).To.Equal(nil)
+}
+
+func (_ SecondaryCacheTests) ReplaceDoesNothingIfKeyDoesNotExist() {
+	cache := newLayered()
+	sCache := cache.GetOrCreateSecondaryCache("spice")
+	Expect(sCache.Replace("flow", "value-a")).To.Equal(false)
+	Expect(cache.Get("spice", "flow")).To.Equal(nil)
+}
+
+func (_ SecondaryCacheTests) ReplaceUpdatesTheValue() {
+	cache := newLayered()
+	cache.Set("spice", "flow", "value-a", time.Minute)
+	sCache := cache.GetOrCreateSecondaryCache("spice")
+	Expect(sCache.Replace("flow", "value-b")).To.Equal(true)
+	Expect(cache.Get("spice", "flow").Value().(string)).To.Equal("value-b")
+}
+
+func (_ SecondaryCacheTests) FetchReturnsAnExistingValue() {
+	cache := newLayered()
+	cache.Set("spice", "flow", "value-a", time.Minute)
+	sCache := cache.GetOrCreateSecondaryCache("spice")
+	val, _ := sCache.Fetch("flow", time.Minute, func() (interface{}, error) {return "a fetched value", nil})
+	Expect(val.Value().(string)).To.Equal("value-a")
+}
+
+func (_ SecondaryCacheTests) FetchReturnsANewValue() {
+	cache := newLayered()
+	sCache := cache.GetOrCreateSecondaryCache("spice")
+	val, _ := sCache.Fetch("flow", time.Minute, func() (interface{}, error) {return "a fetched value", nil})
+	Expect(val.Value().(string)).To.Equal("a fetched value")
+}
+
+func (_ SecondaryCacheTests) TrackerDoesNotCleanupHeldInstance() {
+	cache := Layered(Configure().ItemsToPrune(10).Track())
+	for i := 0; i < 10; i++ {
+		cache.Set(strconv.Itoa(i), "a", i, time.Minute)
+	}
+	sCache := cache.GetOrCreateSecondaryCache("0")
+	item := sCache.TrackingGet("a")
+	time.Sleep(time.Millisecond * 10)
+	cache.gc()
+	Expect(cache.Get("0", "a").Value()).To.Equal(0)
+	Expect(cache.Get("1", "a")).To.Equal(nil)
+	item.Release()
+	cache.gc()
+	Expect(cache.Get("0", "a")).To.Equal(nil)
+}