use std library context.Context (#131)

Signed-off-by: Bobby DeSimone <[email protected]>

groupcache.go

@@ -25,6 +25,7 @@ limitations under the License.
 package groupcache
 
 import (
+ "context"
  "errors"
  "math/rand"
  "strconv"
@@ -44,13 +45,13 @@ type Getter interface {
  // uniquely describe the loaded data, without an implicit
  // current time, and without relying on cache expiration
  // mechanisms.
- Get(ctx Context, key string, dest Sink) error
+ Get(ctx context.Context, key string, dest Sink) error
 }
 
 // A GetterFunc implements Getter with a function.
-type GetterFunc func(ctx Context, key string, dest Sink) error
+type GetterFunc func(ctx context.Context, key string, dest Sink) error
 
-func (f GetterFunc) Get(ctx Context, key string, dest Sink) error {
+func (f GetterFunc) Get(ctx context.Context, key string, dest Sink) error {
  return f(ctx, key, dest)
 }
 
@@ -204,7 +205,7 @@ func (g *Group) initPeers() {
  }
 }
 
-func (g *Group) Get(ctx Context, key string, dest Sink) error {
+func (g *Group) Get(ctx context.Context, key string, dest Sink) error {
  g.peersOnce.Do(g.initPeers)
  g.Stats.Gets.Add(1)
  if dest == nil {
@@ -233,7 +234,7 @@ func (g *Group) Get(ctx Context, key string, dest Sink) error {
 }
 
 // load loads key either by invoking the getter locally or by sending it to another machine.
-func (g *Group) load(ctx Context, key string, dest Sink) (value ByteView, destPopulated bool, err error) {
+func (g *Group) load(ctx context.Context, key string, dest Sink) (value ByteView, destPopulated bool, err error) {
  g.Stats.Loads.Add(1)
  viewi, err := g.loadGroup.Do(key, func() (interface{}, error) {
  // Check the cache again because singleflight can only dedup calls
@@ -292,15 +293,15 @@ func (g *Group) load(ctx Context, key string, dest Sink) (value ByteView, destPo
  return
 }
 
-func (g *Group) getLocally(ctx Context, key string, dest Sink) (ByteView, error) {
+func (g *Group) getLocally(ctx context.Context, key string, dest Sink) (ByteView, error) {
  err := g.getter.Get(ctx, key, dest)
  if err != nil {
  return ByteView{}, err
  }
  return dest.view()
 }
 
-func (g *Group) getFromPeer(ctx Context, peer ProtoGetter, key string) (ByteView, error) {
+func (g *Group) getFromPeer(ctx context.Context, peer ProtoGetter, key string) (ByteView, error) {
  req := &pb.GetRequest{
  Group: &g.name,
  Key: &key,

groupcache_test.go

@@ -19,6 +19,7 @@ limitations under the License.
 package groupcache
 
 import (
+ "context"
  "errors"
  "fmt"
  "hash/crc32"
@@ -41,7 +42,7 @@ var (
 
  stringc = make(chan string)
 
- dummyCtx Context
+ dummyCtx = context.TODO()
 
  // cacheFills is the number of times stringGroup or
  // protoGroup's Getter have been called. Read using the
@@ -58,15 +59,15 @@ const (
 )
 
 func testSetup() {
- stringGroup = NewGroup(stringGroupName, cacheSize, GetterFunc(func(_ Context, key string, dest Sink) error {
+ stringGroup = NewGroup(stringGroupName, cacheSize, GetterFunc(func(_ context.Context, key string, dest Sink) error {
  if key == fromChan {
  key = <-stringc
  }
  cacheFills.Add(1)
  return dest.SetString("ECHO:" + key)
  }))
 
- protoGroup = NewGroup(protoGroupName, cacheSize, GetterFunc(func(_ Context, key string, dest Sink) error {
+ protoGroup = NewGroup(protoGroupName, cacheSize, GetterFunc(func(_ context.Context, key string, dest Sink) error {
  if key == fromChan {
  key = <-stringc
  }
@@ -230,7 +231,7 @@ type fakePeer struct {
  fail bool
 }
 
-func (p *fakePeer) Get(_ Context, in *pb.GetRequest, out *pb.GetResponse) error {
+func (p *fakePeer) Get(_ context.Context, in *pb.GetRequest, out *pb.GetResponse) error {
  p.hits++
  if p.fail {
  return errors.New("simulated error from peer")
@@ -259,7 +260,7 @@ func TestPeers(t *testing.T) {
  peerList := fakePeers([]ProtoGetter{peer0, peer1, peer2, nil})
  const cacheSize = 0 // disabled
  localHits := 0
- getter := func(_ Context, key string, dest Sink) error {
+ getter := func(_ context.Context, key string, dest Sink) error {
  localHits++
  return dest.SetString("got:" + key)
  }
@@ -387,7 +388,7 @@ func (g *orderedFlightGroup) Do(key string, fn func() (interface{}, error)) (int
 func TestNoDedup(t *testing.T) {
  const testkey = "testkey"
  const testval = "testval"
- g := newGroup("testgroup", 1024, GetterFunc(func(_ Context, key string, dest Sink) error {
+ g := newGroup("testgroup", 1024, GetterFunc(func(_ context.Context, key string, dest Sink) error {
  return dest.SetString(testval)
  }), nil)
 

http.go

@@ -18,6 +18,7 @@ package groupcache
 
 import (
  "bytes"
+ "context"
  "fmt"
  "io"
  "net/http"
@@ -38,13 +39,13 @@ const defaultReplicas = 50
 type HTTPPool struct {
  // Context optionally specifies a context for the server to use when it
  // receives a request.
- // If nil, the server uses a nil Context.
- Context func(*http.Request) Context
+ // If nil, the server uses the request's context
+ Context func(*http.Request) context.Context
 
  // Transport optionally specifies an http.RoundTripper for the client
  // to use when it makes a request.
  // If nil, the client uses http.DefaultTransport.
- Transport func(Context) http.RoundTripper
+ Transport func(context.Context) http.RoundTripper
 
  // this peer's base URL, e.g. "https://example.net:8000"
  self string
@@ -157,9 +158,11 @@ func (p *HTTPPool) ServeHTTP(w http.ResponseWriter, r *http.Request) {
  http.Error(w, "no such group: "+groupName, http.StatusNotFound)
  return
  }
- var ctx Context
+ var ctx context.Context
  if p.Context != nil {
  ctx = p.Context(r)
+ } else {
+ ctx = r.Context()
  }
 
  group.Stats.ServerRequests.Add(1)
@@ -181,15 +184,15 @@ func (p *HTTPPool) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 }
 
 type httpGetter struct {
- transport func(Context) http.RoundTripper
+ transport func(context.Context) http.RoundTripper
  baseURL string
 }
 
 var bufferPool = sync.Pool{
  New: func() interface{} { return new(bytes.Buffer) },
 }
 
-func (h *httpGetter) Get(context Context, in *pb.GetRequest, out *pb.GetResponse) error {
+func (h *httpGetter) Get(context context.Context, in *pb.GetRequest, out *pb.GetResponse) error {
  u := fmt.Sprintf(
  "%v%v/%v",
  h.baseURL,

http_test.go

@@ -17,6 +17,7 @@ limitations under the License.
 package groupcache
 
 import (
+ "context"
  "errors"
  "flag"
  "log"
@@ -85,7 +86,7 @@ func TestHTTPPool(t *testing.T) {
  // Dummy getter function. Gets should go to children only.
  // The only time this process will handle a get is when the
  // children can't be contacted for some reason.
- getter := GetterFunc(func(ctx Context, key string, dest Sink) error {
+ getter := GetterFunc(func(ctx context.Context, key string, dest Sink) error {
  return errors.New("parent getter called; something's wrong")
  })
  g := NewGroup("httpPoolTest", 1<<20, getter)
@@ -116,7 +117,7 @@ func beChildForTestHTTPPool() {
  p := NewHTTPPool("http:https://" + addrs[*peerIndex])
  p.Set(addrToURL(addrs)...)
 
- getter := GetterFunc(func(ctx Context, key string, dest Sink) error {
+ getter := GetterFunc(func(ctx context.Context, key string, dest Sink) error {
  dest.SetString(strconv.Itoa(*peerIndex) + ":" + key)
  return nil
  })

peers.go

@@ -19,17 +19,14 @@ limitations under the License.
 package groupcache
 
 import (
+ "context"
+
  pb "github.com/golang/groupcache/groupcachepb"
 )
 
-// Context is an opaque value passed through calls to the
-// ProtoGetter. It may be nil if your ProtoGetter implementation does
-// not require a context.
-type Context interface{}
-
 // ProtoGetter is the interface that must be implemented by a peer.
 type ProtoGetter interface {
- Get(context Context, in *pb.GetRequest, out *pb.GetResponse) error
+ Get(context context.Context, in *pb.GetRequest, out *pb.GetResponse) error
 }
 
 // PeerPicker is the interface that must be implemented to locate