2 files changed, 503 insertions, 0 deletions
diff --git a/src/expvar/expvar.go b/src/expvar/expvar.go
new file mode 100644
index 000000000..9b6dab487
--- /dev/null
+++ b/src/expvar/expvar.go
@@ -0,0 +1,336 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package expvar provides a standardized interface to public variables, such
+// as operation counters in servers. It exposes these variables via HTTP at
+// /debug/vars in JSON format.
+//
+// Operations to set or modify these public variables are atomic.
+//
+// In addition to adding the HTTP handler, this package registers the
+// following variables:
+//
+//	cmdline   os.Args
+//	memstats  runtime.Memstats
+//
+// The package is sometimes only imported for the side effect of
+// registering its HTTP handler and the above variables.  To use it
+// this way, link this package into your program:
+//	import _ "expvar"
+//
+package expvar
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+	"os"
+	"runtime"
+	"sort"
+	"strconv"
+	"sync"
+)
+
+// Var is an abstract type for all exported variables.
+type Var interface {
+	String() string
+}
+
+// Int is a 64-bit integer variable that satisfies the Var interface.
+type Int struct {
+	mu sync.RWMutex
+	i  int64
+}
+
+func (v *Int) String() string {
+	v.mu.RLock()
+	defer v.mu.RUnlock()
+	return strconv.FormatInt(v.i, 10)
+}
+
+func (v *Int) Add(delta int64) {
+	v.mu.Lock()
+	defer v.mu.Unlock()
+	v.i += delta
+}
+
+func (v *Int) Set(value int64) {
+	v.mu.Lock()
+	defer v.mu.Unlock()
+	v.i = value
+}
+
+// Float is a 64-bit float variable that satisfies the Var interface.
+type Float struct {
+	mu sync.RWMutex
+	f  float64
+}
+
+func (v *Float) String() string {
+	v.mu.RLock()
+	defer v.mu.RUnlock()
+	return strconv.FormatFloat(v.f, 'g', -1, 64)
+}
+
+// Add adds delta to v.
+func (v *Float) Add(delta float64) {
+	v.mu.Lock()
+	defer v.mu.Unlock()
+	v.f += delta
+}
+
+// Set sets v to value.
+func (v *Float) Set(value float64) {
+	v.mu.Lock()
+	defer v.mu.Unlock()
+	v.f = value
+}
+
+// Map is a string-to-Var map variable that satisfies the Var interface.
+type Map struct {
+	mu   sync.RWMutex
+	m    map[string]Var
+	keys []string // sorted
+}
+
+// KeyValue represents a single entry in a Map.
+type KeyValue struct {
+	Key   string
+	Value Var
+}
+
+func (v *Map) String() string {
+	v.mu.RLock()
+	defer v.mu.RUnlock()
+	var b bytes.Buffer
+	fmt.Fprintf(&b, "{")
+	first := true
+	v.doLocked(func(kv KeyValue) {
+		if !first {
+			fmt.Fprintf(&b, ", ")
+		}
+		fmt.Fprintf(&b, "%q: %v", kv.Key, kv.Value)
+		first = false
+	})
+	fmt.Fprintf(&b, "}")
+	return b.String()
+}
+
+func (v *Map) Init() *Map {
+	v.m = make(map[string]Var)
+	return v
+}
+
+// updateKeys updates the sorted list of keys in v.keys.
+// must be called with v.mu held.
+func (v *Map) updateKeys() {
+	if len(v.m) == len(v.keys) {
+		// No new key.
+		return
+	}
+	v.keys = v.keys[:0]
+	for k := range v.m {
+		v.keys = append(v.keys, k)
+	}
+	sort.Strings(v.keys)
+}
+
+func (v *Map) Get(key string) Var {
+	v.mu.RLock()
+	defer v.mu.RUnlock()
+	return v.m[key]
+}
+
+func (v *Map) Set(key string, av Var) {
+	v.mu.Lock()
+	defer v.mu.Unlock()
+	v.m[key] = av
+	v.updateKeys()
+}
+
+func (v *Map) Add(key string, delta int64) {
+	v.mu.RLock()
+	av, ok := v.m[key]
+	v.mu.RUnlock()
+	if !ok {
+		// check again under the write lock
+		v.mu.Lock()
+		av, ok = v.m[key]
+		if !ok {
+			av = new(Int)
+			v.m[key] = av
+			v.updateKeys()
+		}
+		v.mu.Unlock()
+	}
+
+	// Add to Int; ignore otherwise.
+	if iv, ok := av.(*Int); ok {
+		iv.Add(delta)
+	}
+}
+
+// AddFloat adds delta to the *Float value stored under the given map key.
+func (v *Map) AddFloat(key string, delta float64) {
+	v.mu.RLock()
+	av, ok := v.m[key]
+	v.mu.RUnlock()
+	if !ok {
+		// check again under the write lock
+		v.mu.Lock()
+		av, ok = v.m[key]
+		if !ok {
+			av = new(Float)
+			v.m[key] = av
+			v.updateKeys()
+		}
+		v.mu.Unlock()
+	}
+
+	// Add to Float; ignore otherwise.
+	if iv, ok := av.(*Float); ok {
+		iv.Add(delta)
+	}
+}
+
+// Do calls f for each entry in the map.
+// The map is locked during the iteration,
+// but existing entries may be concurrently updated.
+func (v *Map) Do(f func(KeyValue)) {
+	v.mu.RLock()
+	defer v.mu.RUnlock()
+	v.doLocked(f)
+}
+
+// doLocked calls f for each entry in the map.
+// v.mu must be held for reads.
+func (v *Map) doLocked(f func(KeyValue)) {
+	for _, k := range v.keys {
+		f(KeyValue{k, v.m[k]})
+	}
+}
+
+// String is a string variable, and satisfies the Var interface.
+type String struct {
+	mu sync.RWMutex
+	s  string
+}
+
+func (v *String) String() string {
+	v.mu.RLock()
+	defer v.mu.RUnlock()
+	return strconv.Quote(v.s)
+}
+
+func (v *String) Set(value string) {
+	v.mu.Lock()
+	defer v.mu.Unlock()
+	v.s = value
+}
+
+// Func implements Var by calling the function
+// and formatting the returned value using JSON.
+type Func func() interface{}
+
+func (f Func) String() string {
+	v, _ := json.Marshal(f())
+	return string(v)
+}
+
+// All published variables.
+var (
+	mutex   sync.RWMutex
+	vars    = make(map[string]Var)
+	varKeys []string // sorted
+)
+
+// Publish declares a named exported variable. This should be called from a
+// package's init function when it creates its Vars. If the name is already
+// registered then this will log.Panic.
+func Publish(name string, v Var) {
+	mutex.Lock()
+	defer mutex.Unlock()
+	if _, existing := vars[name]; existing {
+		log.Panicln("Reuse of exported var name:", name)
+	}
+	vars[name] = v
+	varKeys = append(varKeys, name)
+	sort.Strings(varKeys)
+}
+
+// Get retrieves a named exported variable.
+func Get(name string) Var {
+	mutex.RLock()
+	defer mutex.RUnlock()
+	return vars[name]
+}
+
+// Convenience functions for creating new exported variables.
+
+func NewInt(name string) *Int {
+	v := new(Int)
+	Publish(name, v)
+	return v
+}
+
+func NewFloat(name string) *Float {
+	v := new(Float)
+	Publish(name, v)
+	return v
+}
+
+func NewMap(name string) *Map {
+	v := new(Map).Init()
+	Publish(name, v)
+	return v
+}
+
+func NewString(name string) *String {
+	v := new(String)
+	Publish(name, v)
+	return v
+}
+
+// Do calls f for each exported variable.
+// The global variable map is locked during the iteration,
+// but existing entries may be concurrently updated.
+func Do(f func(KeyValue)) {
+	mutex.RLock()
+	defer mutex.RUnlock()
+	for _, k := range varKeys {
+		f(KeyValue{k, vars[k]})
+	}
+}
+
+func expvarHandler(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "application/json; charset=utf-8")
+	fmt.Fprintf(w, "{\n")
+	first := true
+	Do(func(kv KeyValue) {
+		if !first {
+			fmt.Fprintf(w, ",\n")
+		}
+		first = false
+		fmt.Fprintf(w, "%q: %s", kv.Key, kv.Value)
+	})
+	fmt.Fprintf(w, "\n}\n")
+}
+
+func cmdline() interface{} {
+	return os.Args
+}
+
+func memstats() interface{} {
+	stats := new(runtime.MemStats)
+	runtime.ReadMemStats(stats)
+	return *stats
+}
+
+func init() {
+	http.HandleFunc("/debug/vars", expvarHandler)
+	Publish("cmdline", Func(cmdline))
+	Publish("memstats", Func(memstats))
+}
diff --git a/src/expvar/expvar_test.go b/src/expvar/expvar_test.go
new file mode 100644
index 000000000..765e3b757
--- /dev/null
+++ b/src/expvar/expvar_test.go
@@ -0,0 +1,167 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package expvar
+
+import (
+	"bytes"
+	"encoding/json"
+	"net/http/httptest"
+	"strconv"
+	"testing"
+)
+
+// RemoveAll removes all exported variables.
+// This is for tests only.
+func RemoveAll() {
+	mutex.Lock()
+	defer mutex.Unlock()
+	vars = make(map[string]Var)
+	varKeys = nil
+}
+
+func TestInt(t *testing.T) {
+	RemoveAll()
+	reqs := NewInt("requests")
+	if reqs.i != 0 {
+		t.Errorf("reqs.i = %v, want 0", reqs.i)
+	}
+	if reqs != Get("requests").(*Int) {
+		t.Errorf("Get() failed.")
+	}
+
+	reqs.Add(1)
+	reqs.Add(3)
+	if reqs.i != 4 {
+		t.Errorf("reqs.i = %v, want 4", reqs.i)
+	}
+
+	if s := reqs.String(); s != "4" {
+		t.Errorf("reqs.String() = %q, want \"4\"", s)
+	}
+
+	reqs.Set(-2)
+	if reqs.i != -2 {
+		t.Errorf("reqs.i = %v, want -2", reqs.i)
+	}
+}
+
+func TestFloat(t *testing.T) {
+	RemoveAll()
+	reqs := NewFloat("requests-float")
+	if reqs.f != 0.0 {
+		t.Errorf("reqs.f = %v, want 0", reqs.f)
+	}
+	if reqs != Get("requests-float").(*Float) {
+		t.Errorf("Get() failed.")
+	}
+
+	reqs.Add(1.5)
+	reqs.Add(1.25)
+	if reqs.f != 2.75 {
+		t.Errorf("reqs.f = %v, want 2.75", reqs.f)
+	}
+
+	if s := reqs.String(); s != "2.75" {
+		t.Errorf("reqs.String() = %q, want \"4.64\"", s)
+	}
+
+	reqs.Add(-2)
+	if reqs.f != 0.75 {
+		t.Errorf("reqs.f = %v, want 0.75", reqs.f)
+	}
+}
+
+func TestString(t *testing.T) {
+	RemoveAll()
+	name := NewString("my-name")
+	if name.s != "" {
+		t.Errorf("name.s = %q, want \"\"", name.s)
+	}
+
+	name.Set("Mike")
+	if name.s != "Mike" {
+		t.Errorf("name.s = %q, want \"Mike\"", name.s)
+	}
+
+	if s := name.String(); s != "\"Mike\"" {
+		t.Errorf("reqs.String() = %q, want \"\"Mike\"\"", s)
+	}
+}
+
+func TestMapCounter(t *testing.T) {
+	RemoveAll()
+	colors := NewMap("bike-shed-colors")
+
+	colors.Add("red", 1)
+	colors.Add("red", 2)
+	colors.Add("blue", 4)
+	colors.AddFloat(`green "midori"`, 4.125)
+	if x := colors.m["red"].(*Int).i; x != 3 {
+		t.Errorf("colors.m[\"red\"] = %v, want 3", x)
+	}
+	if x := colors.m["blue"].(*Int).i; x != 4 {
+		t.Errorf("colors.m[\"blue\"] = %v, want 4", x)
+	}
+	if x := colors.m[`green "midori"`].(*Float).f; x != 4.125 {
+		t.Errorf("colors.m[`green \"midori\"] = %v, want 3.14", x)
+	}
+
+	// colors.String() should be '{"red":3, "blue":4}',
+	// though the order of red and blue could vary.
+	s := colors.String()
+	var j interface{}
+	err := json.Unmarshal([]byte(s), &j)
+	if err != nil {
+		t.Errorf("colors.String() isn't valid JSON: %v", err)
+	}
+	m, ok := j.(map[string]interface{})
+	if !ok {
+		t.Error("colors.String() didn't produce a map.")
+	}
+	red := m["red"]
+	x, ok := red.(float64)
+	if !ok {
+		t.Error("red.Kind() is not a number.")
+	}
+	if x != 3 {
+		t.Errorf("red = %v, want 3", x)
+	}
+}
+
+func TestFunc(t *testing.T) {
+	RemoveAll()
+	var x interface{} = []string{"a", "b"}
+	f := Func(func() interface{} { return x })
+	if s, exp := f.String(), `["a","b"]`; s != exp {
+		t.Errorf(`f.String() = %q, want %q`, s, exp)
+	}
+
+	x = 17
+	if s, exp := f.String(), `17`; s != exp {
+		t.Errorf(`f.String() = %q, want %q`, s, exp)
+	}
+}
+
+func TestHandler(t *testing.T) {
+	RemoveAll()
+	m := NewMap("map1")
+	m.Add("a", 1)
+	m.Add("z", 2)
+	m2 := NewMap("map2")
+	for i := 0; i < 9; i++ {
+		m2.Add(strconv.Itoa(i), int64(i))
+	}
+	rr := httptest.NewRecorder()
+	rr.Body = new(bytes.Buffer)
+	expvarHandler(rr, nil)
+	want := `{
+"map1": {"a": 1, "z": 2},
+"map2": {"0": 0, "1": 1, "2": 2, "3": 3, "4": 4, "5": 5, "6": 6, "7": 7, "8": 8}
+}
+`
+	if got := rr.Body.String(); got != want {
+		t.Errorf("HTTP handler wrote:\n%s\nWant:\n%s", got, want)
+	}
+}