use std library context.Context (#131)

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

Author: desimone

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://" + 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