Improve context package

You shouldn't have to import both:

  github.com/docker/distribution/context
  golang.org/x/net/context

just to use the distribution tools and implement the distribution interfaces.

By pulling the Context interface from golang.org/x/net/context into the
context package within the distribution project, you no longer have to import
both packages.

Note: You do not have to change anything anywhere else yet! All current uses
of both packages together will still work correctly because the Context
interface from either package is identical.

I've also made some other minor changes:

- Added a RemoteIP function. It's like RemoteAddr but discards the port suffix
- Added `.String()` to the response duration context value so that JSON log
  formatting shows human-parseable duration and not just number of nano-seconds
- Added WithMapContext(...) to the context package. This is a useful function
  so I pulled it out of the main.go in cmd/registry so that it can be used
  elsewhere.

Docker-DCO-1.1-Signed-off-by: Josh Hawn <josh.hawn@docker.com> (github: jlhawn)

.gitignore

@@ -31,3 +31,7 @@ bin/*
 
 # Cover profiles
 *.out
+
+# Editor/IDE specific files.
+*.sublime-project
+*.sublime-workspace

cmd/registry/main.go

@@ -224,7 +224,7 @@ func configureLogging(ctx context.Context, config *configuration.Configuration)
 			fields = append(fields, k)
 		}
 
-		ctx = withMapContext(ctx, config.Log.Fields)
+		ctx = ctxu.WithValues(ctx, config.Log.Fields)
 		ctx = ctxu.WithLogger(ctx, ctxu.GetLogger(ctx, fields...))
 	}
 
@@ -241,36 +241,6 @@ func logLevel(level configuration.Loglevel) log.Level {
 	return l
 }
 
-// stringMapContext is a simple context implementation that checks a map for a
-// key, falling back to a parent if not present.
-type stringMapContext struct {
-	context.Context
-	m map[string]string
-}
-
-// withMapContext returns a context that proxies lookups through a map.
-func withMapContext(ctx context.Context, m map[string]string) context.Context {
-	mo := make(map[string]string, len(m)) // make our own copy.
-	for k, v := range m {
-		mo[k] = v
-	}
-
-	return stringMapContext{
-		Context: ctx,
-		m:       mo,
-	}
-}
-
-func (smc stringMapContext) Value(key interface{}) interface{} {
-	if ks, ok := key.(string); ok {
-		if v, ok := smc.m[ks]; ok {
-			return v
-		}
-	}
-
-	return smc.Context.Value(key)
-}
-
 // debugServer starts the debug server with pprof, expvar among other
 // endpoints. The addr should not be exposed externally. For most of these to
 // work, tls cannot be enabled on the endpoint, so it is generally separate.

configuration/configuration.go

@@ -28,7 +28,7 @@ type Configuration struct {
 
 		// Fields allows users to specify static string fields to include in
 		// the logger context.
-		Fields map[string]string `yaml:"fields"`
+		Fields map[string]interface{} `yaml:"fields"`
 	}
 
 	// Loglevel is the level at which registry operations are logged. This is

configuration/configuration_test.go

@@ -19,9 +19,9 @@ var configStruct = Configuration{
 	Log: struct {
 		Level     Loglevel               `yaml:"level"`
 		Formatter string                 `yaml:"formatter"`
-		Fields    map[string]string `yaml:"fields"`
+		Fields    map[string]interface{} `yaml:"fields"`
 	}{
-		Fields: map[string]string{"environment": "test"},
+		Fields: map[string]interface{}{"environment": "test"},
 	},
 	Loglevel: "info",
 	Storage: Storage{
@@ -340,7 +340,7 @@ func copyConfig(config Configuration) *Configuration {
 	configCopy.Version = MajorMinorVersion(config.Version.Major(), config.Version.Minor())
 	configCopy.Loglevel = config.Loglevel
 	configCopy.Log = config.Log
-	configCopy.Log.Fields = make(map[string]string, len(config.Log.Fields))
+	configCopy.Log.Fields = make(map[string]interface{}, len(config.Log.Fields))
 	for k, v := range config.Log.Fields {
 		configCopy.Log.Fields[k] = v
 	}

context/context.go

@@ -0,0 +1,53 @@
+package context
+
+import (
+	"golang.org/x/net/context"
+)
+
+// Context is a copy of Context from the golang.org/x/net/context package.
+type Context interface {
+	context.Context
+}
+
+// Background returns a non-nil, empty Context.
+func Background() Context {
+	return context.Background()
+}
+
+// WithValue returns a copy of parent in which the value associated with key is
+// val. Use context Values only for request-scoped data that transits processes
+// and APIs, not for passing optional parameters to functions.
+func WithValue(parent Context, key, val interface{}) Context {
+	return context.WithValue(parent, key, val)
+}
+
+// stringMapContext is a simple context implementation that checks a map for a
+// key, falling back to a parent if not present.
+type stringMapContext struct {
+	context.Context
+	m map[string]interface{}
+}
+
+// WithValues returns a context that proxies lookups through a map. Only
+// supports string keys.
+func WithValues(ctx context.Context, m map[string]interface{}) context.Context {
+	mo := make(map[string]interface{}, len(m)) // make our own copy.
+	for k, v := range m {
+		mo[k] = v
+	}
+
+	return stringMapContext{
+		Context: ctx,
+		m:       mo,
+	}
+}
+
+func (smc stringMapContext) Value(key interface{}) interface{} {
+	if ks, ok := key.(string); ok {
+		if v, ok := smc.m[ks]; ok {
+			return v
+		}
+	}
+
+	return smc.Context.Value(key)
+}

context/http.go

@@ -11,7 +11,6 @@ import (
 	"code.google.com/p/go-uuid/uuid"
 	log "github.com/Sirupsen/logrus"
 	"github.com/gorilla/mux"
-	"golang.org/x/net/context"
 )
 
 // Common errors used with this package.
@@ -50,12 +49,25 @@ func RemoteAddr(r *http.Request) string {
 	return r.RemoteAddr
 }
 
+// RemoteIP extracts the remote IP of the request, taking into
+// account proxy headers.
+func RemoteIP(r *http.Request) string {
+	addr := RemoteAddr(r)
+
+	// Try parsing it as "IP:port"
+	if ip, _, err := net.SplitHostPort(addr); err == nil {
+		return ip
+	}
+
+	return addr
+}
+
 // WithRequest places the request on the context. The context of the request
 // is assigned a unique id, available at "http.request.id". The request itself
 // is available at "http.request". Other common attributes are available under
 // the prefix "http.request.". If a request is already present on the context,
 // this method will panic.
-func WithRequest(ctx context.Context, r *http.Request) context.Context {
+func WithRequest(ctx Context, r *http.Request) Context {
 	if ctx.Value("http.request") != nil {
 		// NOTE(stevvooe): This needs to be considered a programming error. It
 		// is unlikely that we'd want to have more than one request in
@@ -74,7 +86,7 @@ func WithRequest(ctx context.Context, r *http.Request) context.Context {
 // GetRequest returns the http request in the given context. Returns
 // ErrNoRequestContext if the context does not have an http request associated
 // with it.
-func GetRequest(ctx context.Context) (*http.Request, error) {
+func GetRequest(ctx Context) (*http.Request, error) {
 	if r, ok := ctx.Value("http.request").(*http.Request); r != nil && ok {
 		return r, nil
 	}
@@ -83,13 +95,13 @@ func GetRequest(ctx context.Context) (*http.Request, error) {
 
 // GetRequestID attempts to resolve the current request id, if possible. An
 // error is return if it is not available on the context.
-func GetRequestID(ctx context.Context) string {
+func GetRequestID(ctx Context) string {
 	return GetStringValue(ctx, "http.request.id")
 }
 
 // WithResponseWriter returns a new context and response writer that makes
 // interesting response statistics available within the context.
-func WithResponseWriter(ctx context.Context, w http.ResponseWriter) (context.Context, http.ResponseWriter) {
+func WithResponseWriter(ctx Context, w http.ResponseWriter) (Context, http.ResponseWriter) {
 	irw := &instrumentedResponseWriter{
 		ResponseWriter: w,
 		Context:        ctx,
@@ -107,7 +119,7 @@ var getVarsFromRequest = mux.Vars
 // example, if looking for the variable "name", it can be accessed as
 // "vars.name". Implementations that are accessing values need not know that
 // the underlying context is implemented with gorilla/mux vars.
-func WithVars(ctx context.Context, r *http.Request) context.Context {
+func WithVars(ctx Context, r *http.Request) Context {
 	return &muxVarsContext{
 		Context: ctx,
 		vars:    getVarsFromRequest(r),
@@ -117,7 +129,7 @@ func WithVars(ctx context.Context, r *http.Request) context.Context {
 // GetRequestLogger returns a logger that contains fields from the request in
 // the current context. If the request is not available in the context, no
 // fields will display. Request loggers can safely be pushed onto the context.
-func GetRequestLogger(ctx context.Context) Logger {
+func GetRequestLogger(ctx Context) Logger {
 	return GetLogger(ctx,
 		"http.request.id",
 		"http.request.method",
@@ -133,7 +145,7 @@ func GetRequestLogger(ctx context.Context) Logger {
 // Because the values are read at call time, pushing a logger returned from
 // this function on the context will lead to missing or invalid data. Only
 // call this at the end of a request, after the response has been written.
-func GetResponseLogger(ctx context.Context) Logger {
+func GetResponseLogger(ctx Context) Logger {
 	l := getLogrusLogger(ctx,
 		"http.response.written",
 		"http.response.status",
@@ -142,7 +154,7 @@ func GetResponseLogger(ctx context.Context) Logger {
 	duration := Since(ctx, "http.request.startedat")
 
 	if duration > 0 {
-		l = l.WithField("http.response.duration", duration)
+		l = l.WithField("http.response.duration", duration.String())
 	}
 
 	return l
@@ -150,7 +162,7 @@ func GetResponseLogger(ctx context.Context) Logger {
 
 // httpRequestContext makes information about a request available to context.
 type httpRequestContext struct {
-	context.Context
+	Context
 
 	startedAt time.Time
 	id        string
@@ -209,7 +221,7 @@ fallback:
 }
 
 type muxVarsContext struct {
-	context.Context
+	Context
 	vars map[string]string
 }
 
@@ -235,7 +247,7 @@ func (ctx *muxVarsContext) Value(key interface{}) interface{} {
 // context.
 type instrumentedResponseWriter struct {
 	http.ResponseWriter
-	context.Context
+	Context
 
 	mu      sync.Mutex
 	status  int

context/http_test.go

@@ -8,8 +8,6 @@ import (
 	"reflect"
 	"testing"
 	"time"
-
-	"golang.org/x/net/context"
 )
 
 func TestWithRequest(t *testing.T) {
@@ -23,7 +21,7 @@ func TestWithRequest(t *testing.T) {
 	req.Header.Set("Referer", "foo.com/referer")
 	req.Header.Set("User-Agent", "test/0.1")
 
-	ctx := WithRequest(context.Background(), &req)
+	ctx := WithRequest(Background(), &req)
 	for _, testcase := range []struct {
 		key      string
 		expected interface{}
@@ -132,7 +130,7 @@ func (trw *testResponseWriter) Flush() {
 
 func TestWithResponseWriter(t *testing.T) {
 	trw := testResponseWriter{}
-	ctx, rw := WithResponseWriter(context.Background(), &trw)
+	ctx, rw := WithResponseWriter(Background(), &trw)
 
 	if ctx.Value("http.response") != &trw {
 		t.Fatalf("response not available in context: %v != %v", ctx.Value("http.response"), &trw)
@@ -183,7 +181,7 @@ func TestWithVars(t *testing.T) {
 		return vars
 	}
 
-	ctx := WithVars(context.Background(), &req)
+	ctx := WithVars(Background(), &req)
 	for _, testcase := range []struct {
 		key      string
 		expected interface{}

context/logger.go

@@ -4,7 +4,6 @@ import (
 	"fmt"
 
 	"github.com/Sirupsen/logrus"
-	"golang.org/x/net/context"
 )
 
 // Logger provides a leveled-logging interface.
@@ -41,8 +40,8 @@ type Logger interface {
 }
 
 // WithLogger creates a new context with provided logger.
-func WithLogger(ctx context.Context, logger Logger) context.Context {
+func WithLogger(ctx Context, logger Logger) Context {
-	return context.WithValue(ctx, "logger", logger)
+	return WithValue(ctx, "logger", logger)
 }
 
 // GetLogger returns the logger from the current context, if present. If one
@@ -51,7 +50,7 @@ func WithLogger(ctx context.Context, logger Logger) context.Context {
 // argument passed to GetLogger will be passed to fmt.Sprint when expanded as
 // a logging key field. If context keys are integer constants, for example,
 // its recommended that a String method is implemented.
-func GetLogger(ctx context.Context, keys ...interface{}) Logger {
+func GetLogger(ctx Context, keys ...interface{}) Logger {
 	return getLogrusLogger(ctx, keys...)
 }
 
@@ -59,7 +58,7 @@ func GetLogger(ctx context.Context, keys ...interface{}) Logger {
 // are provided, they will be resolved on the context and included in the
 // logger. Only use this function if specific logrus functionality is
 // required.
-func getLogrusLogger(ctx context.Context, keys ...interface{}) *logrus.Entry {
+func getLogrusLogger(ctx Context, keys ...interface{}) *logrus.Entry {
 	var logger *logrus.Entry
 
 	// Get a logger, if it is present.

context/util.go

@@ -2,14 +2,12 @@ package context
 
 import (
 	"time"
-
-	"golang.org/x/net/context"
 )
 
 // Since looks up key, which should be a time.Time, and returns the duration
 // since that time. If the key is not found, the value returned will be zero.
 // This is helpful when inferring metrics related to context execution times.
-func Since(ctx context.Context, key interface{}) time.Duration {
+func Since(ctx Context, key interface{}) time.Duration {
 	startedAtI := ctx.Value(key)
 	if startedAtI != nil {
 		if startedAt, ok := startedAtI.(time.Time); ok {
@@ -22,7 +20,7 @@ func Since(ctx context.Context, key interface{}) time.Duration {
 
 // GetStringValue returns a string value from the context. The empty string
 // will be returned if not found.
-func GetStringValue(ctx context.Context, key string) (value string) {
+func GetStringValue(ctx Context, key string) (value string) {
 	stringi := ctx.Value(key)
 	if stringi != nil {
 		if valuev, ok := stringi.(string); ok {