Add AroundRoundTrip option, trim the API

Author: bep

httpcache.go

@@ -45,9 +45,9 @@ func cacheKey(req *http.Request) string {
 	}
 }
 
-// CachedResponse returns the cached http.Response for req if present, and nil
+// cachedResponse returns the cached http.Response for req if present, and nil
 // otherwise.
-func CachedResponse(c Cache, req *http.Request) (resp *http.Response, err error) {
+func cachedResponse(c Cache, req *http.Request) (resp *http.Response, err error) {
 	cachedVal, ok := c.Get(cacheKey(req))
 	if !ok {
 		return
@@ -57,37 +57,37 @@ func CachedResponse(c Cache, req *http.Request) (resp *http.Response, err error)
 	return http.ReadResponse(bufio.NewReader(b), req)
 }
 
-// MemoryCache is an implemtation of Cache that stores responses in an in-memory map.
-type MemoryCache struct {
+// memoryCache is an implemtation of Cache that stores responses in an in-memory map.
+type memoryCache struct {
 	mu    sync.RWMutex
 	items map[string][]byte
 }
 
 // Get returns the []byte representation of the response and true if present, false if not
-func (c *MemoryCache) Get(key string) (resp []byte, ok bool) {
+func (c *memoryCache) Get(key string) (resp []byte, ok bool) {
 	c.mu.RLock()
 	resp, ok = c.items[key]
 	c.mu.RUnlock()
 	return resp, ok
 }
 
 // Set saves response resp to the cache with key
-func (c *MemoryCache) Set(key string, resp []byte) {
+func (c *memoryCache) Set(key string, resp []byte) {
 	c.mu.Lock()
 	c.items[key] = resp
 	c.mu.Unlock()
 }
 
 // Delete removes key from the cache
-func (c *MemoryCache) Delete(key string) {
+func (c *memoryCache) Delete(key string) {
 	c.mu.Lock()
 	delete(c.items, key)
 	c.mu.Unlock()
 }
 
-// NewMemoryCache returns a new Cache that will store items in an in-memory map
-func NewMemoryCache() *MemoryCache {
-	c := &MemoryCache{items: map[string][]byte{}}
+// newMemoryCache returns a new Cache that will store items in an in-memory map
+func newMemoryCache() *memoryCache {
+	c := &memoryCache{items: map[string][]byte{}}
 	return c
 }
 
@@ -98,20 +98,18 @@ type Transport struct {
 	// The RoundTripper interface actually used to make requests
 	// If nil, http.DefaultTransport is used
 	Transport http.RoundTripper
-	Cache     Cache
+
+	// The Cache interface used to store and retrieve responses.
+	Cache Cache
+
 	// If true, responses returned from the cache will be given an extra header, X-From-Cache
 	MarkCachedResponses bool
-}
 
-// NewTransport returns a new Transport with the
-// provided Cache implementation and MarkCachedResponses set to true
-func NewTransport(c Cache) *Transport {
-	return &Transport{Cache: c, MarkCachedResponses: true}
-}
-
-// Client returns an *http.Client that caches responses.
-func (t *Transport) Client() *http.Client {
-	return &http.Client{Transport: t}
+	// AroundRoundTrip is an optional func.
+	// If set, the Transport will call AroundRoundTrip at the start of RoundTrip
+	// and defer the returned func until the end of RoundTrip.
+	// Typically used to implement a lock that is held for the duration of the RoundTrip.
+	AroundRoundTrip func(key string) func()
 }
 
 // varyMatches will return false unless all of the cached values for the headers listed in Vary
@@ -136,10 +134,13 @@ func varyMatches(cachedResp *http.Response, req *http.Request) bool {
 // will be returned.
 func (t *Transport) RoundTrip(req *http.Request) (resp *http.Response, err error) {
 	cacheKey := cacheKey(req)
+	if f := t.AroundRoundTrip; f != nil {
+		defer f(cacheKey)()
+	}
 	cacheable := (req.Method == "GET" || req.Method == "HEAD") && req.Header.Get("range") == ""
 	var cachedResp *http.Response
 	if cacheable {
-		cachedResp, err = CachedResponse(t.Cache, req)
+		cachedResp, err = cachedResponse(t.Cache, req)
 	} else {
 		// Need to invalidate an existing value
 		t.Cache.Delete(cacheKey)
@@ -254,8 +255,8 @@ func (t *Transport) RoundTrip(req *http.Request) (resp *http.Response, err error
 // ErrNoDateHeader indicates that the HTTP headers contained no Date header.
 var ErrNoDateHeader = errors.New("no Date header")
 
-// Date parses and returns the value of the Date header.
-func Date(respHeaders http.Header) (date time.Time, err error) {
+// date parses and returns the value of the date header.
+func date(respHeaders http.Header) (date time.Time, err error) {
 	dateHeader := respHeaders.Get("date")
 	if dateHeader == "" {
 		err = ErrNoDateHeader
@@ -299,7 +300,7 @@ func getFreshness(respHeaders, reqHeaders http.Header) (freshness int) {
 		return fresh
 	}
 
-	date, err := Date(respHeaders)
+	date, err := date(respHeaders)
 	if err != nil {
 		return stale
 	}
@@ -398,7 +399,7 @@ func canStaleOnError(respHeaders, reqHeaders http.Header) bool {
 	}
 
 	if lifetime >= 0 {
-		date, err := Date(respHeaders)
+		date, err := date(respHeaders)
 		if err != nil {
 			return false
 		}
@@ -541,9 +542,9 @@ func (r *cachingReadCloser) Close() error {
 	return r.R.Close()
 }
 
-// NewMemoryCacheTransport returns a new Transport using the in-memory cache implementation
-func NewMemoryCacheTransport() *Transport {
-	c := NewMemoryCache()
-	t := NewTransport(c)
+// newMemoryCacheTransport returns a new Transport using the in-memory cache implementation
+func newMemoryCacheTransport() *Transport {
+	c := newMemoryCache()
+	t := &Transport{Cache: c, MarkCachedResponses: true}
 	return t
 }

httpcache_test.go

@@ -37,7 +37,7 @@ func TestMain(m *testing.M) {
 }
 
 func setup() {
-	tp := NewMemoryCacheTransport()
+	tp := newMemoryCacheTransport()
 	client := http.Client{Transport: tp}
 	s.transport = tp
 	s.client = client
@@ -165,7 +165,7 @@ func teardown() {
 }
 
 func resetTest() {
-	s.transport.Cache = NewMemoryCache()
+	s.transport.Cache = newMemoryCache()
 	clock = &realClock{}
 }
 
@@ -1206,7 +1206,7 @@ func TestStaleIfErrorRequest(t *testing.T) {
 		},
 		err: nil,
 	}
-	tp := NewMemoryCacheTransport()
+	tp := newMemoryCacheTransport()
 	tp.Transport = &tmock
 
 	// First time, response is cached on success
@@ -1251,7 +1251,7 @@ func TestStaleIfErrorRequestLifetime(t *testing.T) {
 		},
 		err: nil,
 	}
-	tp := NewMemoryCacheTransport()
+	tp := newMemoryCacheTransport()
 	tp.Transport = &tmock
 
 	// First time, response is cached on success
@@ -1314,7 +1314,7 @@ func TestStaleIfErrorResponse(t *testing.T) {
 		},
 		err: nil,
 	}
-	tp := NewMemoryCacheTransport()
+	tp := newMemoryCacheTransport()
 	tp.Transport = &tmock
 
 	// First time, response is cached on success
@@ -1358,7 +1358,7 @@ func TestStaleIfErrorResponseLifetime(t *testing.T) {
 		},
 		err: nil,
 	}
-	tp := NewMemoryCacheTransport()
+	tp := newMemoryCacheTransport()
 	tp.Transport = &tmock
 
 	// First time, response is cached on success
@@ -1412,7 +1412,7 @@ func TestStaleIfErrorKeepsStatus(t *testing.T) {
 		},
 		err: nil,
 	}
-	tp := NewMemoryCacheTransport()
+	tp := newMemoryCacheTransport()
 	tp.Transport = &tmock
 
 	// First time, response is cached on success
@@ -1456,7 +1456,7 @@ func TestClientTimeout(t *testing.T) {
 	}
 	resetTest()
 	client := &http.Client{
-		Transport: NewMemoryCacheTransport(),
+		Transport: newMemoryCacheTransport(),
 		Timeout:   time.Second,
 	}
 	started := time.Now()