Add cache middleware

.gitignore

@@ -0,0 +1,2 @@
+*/Godeps/*
+!*/Godeps/Godeps.json

cache/cache.go

@@ -0,0 +1,154 @@
+package cache
+
+import (
+	"bytes"
+	"crypto/sha1"
+	"errors"
+	"github.com/gin-gonic/gin"
+	"net/url"
+	"net/http"
+	"io"
+	"time"
+)
+
+const (
+	DEFAULT = time.Duration(0)
+	FOREVER = time.Duration(-1)
+	CACHE_MIDDLEWARE_KEY = "gincontrib.cache"
+)
+
+var (
+	PageCachePrefix = "gincontrib.page.cahe"
+	ErrCacheMiss = errors.New("cache: key not found.")
+	ErrNotStored = errors.New("cache: not stored.")
+	ErrNotSupport = errors.New("cache: not support.")
+)
+
+type CacheStore interface {
+	Get(key string, value interface{}) error
+	Set(key string, value interface{}, expire time.Duration) error
+	Add(key string, value interface{}, expire time.Duration) error
+	Replace(key string, data interface{}, expire time.Duration) error
+	Delete(key string) error
+	Increment(key string, data uint64) (uint64, error)
+	Decrement(key string, data uint64) (uint64, error)
+	Flush() error
+}
+
+type responseCache struct {
+	status int
+	header http.Header
+	data []byte
+}
+
+type cachedWriter struct {
+	gin.ResponseWriter
+	status int
+	written bool
+	store CacheStore
+	expire time.Duration
+	key string
+}
+
+func urlEscape(prefix string, u string) string {
+	key := url.QueryEscape(u)
+	if len(key) > 200 {
+		h := sha1.New()
+		io.WriteString(h, u)
+		key = string(h.Sum(nil))
+	}
+	var buffer bytes.Buffer
+	buffer.WriteString(prefix)
+	buffer.WriteString(":")
+	buffer.WriteString(key)
+	return buffer.String()
+}
+
+func newCachedWriter(store CacheStore, expire time.Duration, writer gin.ResponseWriter, key string) *cachedWriter {
+	return &cachedWriter{writer, 0, false, store, expire, key}
+}
+
+func (w *cachedWriter) WriteHeader(code int) {
+	w.status = code
+	w.written = true
+	w.ResponseWriter.WriteHeader(code)
+}
+
+func (w *cachedWriter) Status() int {
+	return w.status
+}
+
+func (w *cachedWriter) Written() bool {
+	return w.written
+}
+
+func (w *cachedWriter) Write(data []byte) (int, error) {
+	ret, err := w.ResponseWriter.Write(data)
+	if err == nil {
+		//cache response 
+		store := w.store
+		val := responseCache{
+			w.status,
+			w.Header(),
+			data,
+		}
+		err  = store.Set(w.key, val, w.expire)
+		if err != nil {
+			// need logger
+		}
+	}
+	return ret, err
+}
+
+// Cache Middleware 
+func Cache(store *CacheStore) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		c.Set(CACHE_MIDDLEWARE_KEY, store)
+		c.Next()
+	}
+}
+
+func SiteCache(store CacheStore, expire time.Duration) gin.HandlerFunc {
+
+	return func(c *gin.Context) {
+		var cache responseCache
+		url := c.Req.URL
+		key := urlEscape(PageCachePrefix, url.RequestURI())
+		if err := store.Get(key, &cache); err != nil {
+			c.Next()
+		} else {
+			c.Writer.WriteHeader(cache.status)
+			for k, vals := range cache.header {
+				for _, v := range vals {
+					c.Writer.Header().Add(k, v)
+				}
+			}
+			c.Writer.Write(cache.data)
+		}
+	}
+}
+
+// Cache Decorator
+func CachePage(store CacheStore, expire time.Duration, handle gin.HandlerFunc) gin.HandlerFunc {
+
+	return func(c *gin.Context) {
+		var cache responseCache
+		url := c.Req.URL
+		key := urlEscape(PageCachePrefix, url.RequestURI())
+		if err := store.Get(key, &cache); err != nil {
+			// replace writer
+			writer := newCachedWriter(store, expire, c.Writer, key)
+			c.Writer = writer
+			handle(c)
+		} else {
+			c.Writer.WriteHeader(cache.status)
+			for k, vals := range cache.header {
+				for _, v := range vals {
+					c.Writer.Header().Add(k, v)
+				}
+			}
+			c.Writer.Write(cache.data)
+		}
+	}
+}
+

cache/cache_test.go

@@ -0,0 +1,203 @@
+package cache
+
+import (
+	"math"
+	"testing"
+	"time"
+)
+
+type cacheFactory func(*testing.T, time.Duration) CacheStore
+
+// Test typical cache interactions
+func typicalGetSet(t *testing.T, newCache cacheFactory) {
+	var err error
+	cache := newCache(t, time.Hour)
+
+	value := "foo"
+	if err = cache.Set("value", value, DEFAULT); err != nil {
+		t.Errorf("Error setting a value: %s", err)
+	}
+
+	value = ""
+	err = cache.Get("value", &value)
+	if err != nil {
+		t.Errorf("Error getting a value: %s", err)
+	}
+	if value != "foo" {
+		t.Errorf("Expected to get foo back, got %s", value)
+	}
+}
+
+// Test the increment-decrement cases
+func incrDecr(t *testing.T, newCache cacheFactory) {
+	var err error
+	cache := newCache(t, time.Hour)
+
+	// Normal increment / decrement operation.
+	if err = cache.Set("int", 10, DEFAULT); err != nil {
+		t.Errorf("Error setting int: %s", err)
+	}
+	newValue, err := cache.Increment("int", 50)
+	if err != nil {
+		t.Errorf("Error incrementing int: %s", err)
+	}
+	if newValue != 60 {
+		t.Errorf("Expected 60, was %d", newValue)
+	}
+
+	if newValue, err = cache.Decrement("int", 50); err != nil {
+		t.Errorf("Error decrementing: %s", err)
+	}
+	if newValue != 10 {
+		t.Errorf("Expected 10, was %d", newValue)
+	}
+
+	// Increment wraparound
+	newValue, err = cache.Increment("int", math.MaxUint64-5)
+	if err != nil {
+		t.Errorf("Error wrapping around: %s", err)
+	}
+	if newValue != 4 {
+		t.Errorf("Expected wraparound 4, got %d", newValue)
+	}
+
+	// Decrement capped at 0
+	newValue, err = cache.Decrement("int", 25)
+	if err != nil {
+		t.Errorf("Error decrementing below 0: %s", err)
+	}
+	if newValue != 0 {
+		t.Errorf("Expected capped at 0, got %d", newValue)
+	}
+}
+
+func expiration(t *testing.T, newCache cacheFactory) {
+	// memcached does not support expiration times less than 1 second.
+	var err error
+	cache := newCache(t, time.Second)
+	// Test Set w/ DEFAULT
+	value := 10
+	cache.Set("int", value, DEFAULT)
+	time.Sleep(2 * time.Second)
+	err = cache.Get("int", &value)
+	if err != ErrCacheMiss {
+		t.Errorf("Expected CacheMiss, but got: %s", err)
+	}
+
+	// Test Set w/ short time
+	cache.Set("int", value, time.Second)
+	time.Sleep(2 * time.Second)
+	err = cache.Get("int", &value)
+	if err != ErrCacheMiss {
+		t.Errorf("Expected CacheMiss, but got: %s", err)
+	}
+
+	// Test Set w/ longer time.
+	cache.Set("int", value, time.Hour)
+	time.Sleep(2 * time.Second)
+	err = cache.Get("int", &value)
+	if err != nil {
+		t.Errorf("Expected to get the value, but got: %s", err)
+	}
+
+	// Test Set w/ forever.
+	cache.Set("int", value, FOREVER)
+	time.Sleep(2 * time.Second)
+	err = cache.Get("int", &value)
+	if err != nil {
+		t.Errorf("Expected to get the value, but got: %s", err)
+	}
+}
+
+func emptyCache(t *testing.T, newCache cacheFactory) {
+	var err error
+	cache := newCache(t, time.Hour)
+
+	err = cache.Get("notexist", 0)
+	if err == nil {
+		t.Errorf("Error expected for non-existent key")
+	}
+	if err != ErrCacheMiss {
+		t.Errorf("Expected ErrCacheMiss for non-existent key: %s", err)
+	}
+
+	err = cache.Delete("notexist")
+	if err != ErrCacheMiss {
+		t.Errorf("Expected ErrCacheMiss for non-existent key: %s", err)
+	}
+
+	_, err = cache.Increment("notexist", 1)
+	if err != ErrCacheMiss {
+		t.Errorf("Expected cache miss incrementing non-existent key: %s", err)
+	}
+
+	_, err = cache.Decrement("notexist", 1)
+	if err != ErrCacheMiss {
+		t.Errorf("Expected cache miss decrementing non-existent key: %s", err)
+	}
+}
+
+func testReplace(t *testing.T, newCache cacheFactory) {
+	var err error
+	cache := newCache(t, time.Hour)
+
+	// Replace in an empty cache.
+	if err = cache.Replace("notexist", 1, FOREVER); err != ErrNotStored {
+		t.Errorf("Replace in empty cache: expected ErrNotStored, got: %s", err)
+	}
+
+	// Set a value of 1, and replace it with 2
+	if err = cache.Set("int", 1, time.Second); err != nil {
+		t.Errorf("Unexpected error: %s", err)
+	}
+
+	if err = cache.Replace("int", 2, time.Second); err != nil {
+		t.Errorf("Unexpected error: %s", err)
+	}
+	var i int
+	if err = cache.Get("int", &i); err != nil {
+		t.Errorf("Unexpected error getting a replaced item: %s", err)
+	}
+	if i != 2 {
+		t.Errorf("Expected 2, got %d", i)
+	}
+
+	// Wait for it to expire and replace with 3 (unsuccessfully).
+	time.Sleep(2 * time.Second)
+	if err = cache.Replace("int", 3, time.Second); err != ErrNotStored {
+		t.Errorf("Expected ErrNotStored, got: %s", err)
+	}
+	if err = cache.Get("int", &i); err != ErrCacheMiss {
+		t.Errorf("Expected cache miss, got: %s", err)
+	}
+}
+
+func testAdd(t *testing.T, newCache cacheFactory) {
+	var err error
+	cache := newCache(t, time.Hour)
+	// Add to an empty cache.
+	if err = cache.Add("int", 1, time.Second); err != nil {
+		t.Errorf("Unexpected error adding to empty cache: %s", err)
+	}
+
+	// Try to add again. (fail)
+	if err = cache.Add("int", 2, time.Second); err != ErrNotStored {
+		t.Errorf("Expected ErrNotStored adding dupe to cache: %s", err)
+	}
+
+	// Wait for it to expire, and add again.
+	time.Sleep(2 * time.Second)
+	if err = cache.Add("int", 3, time.Second); err != nil {
+		t.Errorf("Unexpected error adding to cache: %s", err)
+	}
+
+	// Get and verify the value.
+	var i int
+	if err = cache.Get("int", &i); err != nil {
+		t.Errorf("Unexpected error: %s", err)
+	}
+	if i != 3 {
+		t.Errorf("Expected 3, got: %d", i)
+	}
+}
+