--- /dev/null
+// Copyright 2014 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 context defines the Context type, which carries deadlines,
+// cancelation signals, and other request-scoped values across API boundaries
+// and between processes.
+//
+// Incoming requests to a server should create a Context, and outgoing calls to
+// servers should accept a Context. The chain of function calls between must
+// propagate the Context, optionally replacing it with a modified copy created
+// using WithDeadline, WithTimeout, WithCancel, or WithValue.
+//
+// Programs that use Contexts should follow these rules to keep interfaces
+// consistent across packages and enable static analysis tools to check context
+// propagation:
+//
+// Do not store Contexts inside a struct type; instead, pass a Context
+// explicitly to each function that needs it. The Context should be the first
+// parameter, typically named ctx:
+//
+// func DoSomething(ctx context.Context, arg Arg) error {
+// // ... use ctx ...
+// }
+//
+// Do not pass a nil Context, even if a function permits it. Pass context.TODO
+// if you are unsure about which Context to use.
+//
+// Use context Values only for request-scoped data that transits processes and
+// APIs, not for passing optional parameters to functions.
+//
+// The same Context may be passed to functions running in different goroutines;
+// Contexts are safe for simultaneous use by multiple goroutines.
+//
+// See http://blog.golang.org/context for example code for a server that uses
+// Contexts.
+package context
+
+import (
+ "errors"
+ "fmt"
+ "sync"
+ "time"
+)
+
+// A Context carries a deadline, a cancelation signal, and other values across
+// API boundaries.
+//
+// Context's methods may be called by multiple goroutines simultaneously.
+type Context interface {
+ // Deadline returns the time when work done on behalf of this context
+ // should be canceled. Deadline returns ok==false when no deadline is
+ // set. Successive calls to Deadline return the same results.
+ Deadline() (deadline time.Time, ok bool)
+
+ // Done returns a channel that's closed when work done on behalf of this
+ // context should be canceled. Done may return nil if this context can
+ // never be canceled. Successive calls to Done return the same value.
+ //
+ // WithCancel arranges for Done to be closed when cancel is called;
+ // WithDeadline arranges for Done to be closed when the deadline
+ // expires; WithTimeout arranges for Done to be closed when the timeout
+ // elapses.
+ //
+ // Done is provided for use in select statements:
+ //
+ // // Stream generates values with DoSomething and sends them to out
+ // // until DoSomething returns an error or ctx.Done is closed.
+ // func Stream(ctx context.Context, out <-chan Value) error {
+ // for {
+ // v, err := DoSomething(ctx)
+ // if err != nil {
+ // return err
+ // }
+ // select {
+ // case <-ctx.Done():
+ // return ctx.Err()
+ // case out <- v:
+ // }
+ // }
+ // }
+ //
+ // See http://blog.golang.org/pipelines for more examples of how to use
+ // a Done channel for cancelation.
+ Done() <-chan struct{}
+
+ // Err returns a non-nil error value after Done is closed. Err returns
+ // Canceled if the context was canceled or DeadlineExceeded if the
+ // context's deadline passed. No other values for Err are defined.
+ // After Done is closed, successive calls to Err return the same value.
+ Err() error
+
+ // Value returns the value associated with this context for key, or nil
+ // if no value is associated with key. Successive calls to Value with
+ // the same key returns the same result.
+ //
+ // Use context values only for request-scoped data that transits
+ // processes and API boundaries, not for passing optional parameters to
+ // functions.
+ //
+ // A key identifies a specific value in a Context. Functions that wish
+ // to store values in Context typically allocate a key in a global
+ // variable then use that key as the argument to context.WithValue and
+ // Context.Value. A key can be any type that supports equality;
+ // packages should define keys as an unexported type to avoid
+ // collisions.
+ //
+ // Packages that define a Context key should provide type-safe accessors
+ // for the values stores using that key:
+ //
+ // // Package user defines a User type that's stored in Contexts.
+ // package user
+ //
+ // import "context"
+ //
+ // // User is the type of value stored in the Contexts.
+ // type User struct {...}
+ //
+ // // key is an unexported type for keys defined in this package.
+ // // This prevents collisions with keys defined in other packages.
+ // type key int
+ //
+ // // userKey is the key for user.User values in Contexts. It is
+ // // unexported; clients use user.NewContext and user.FromContext
+ // // instead of using this key directly.
+ // var userKey key = 0
+ //
+ // // NewContext returns a new Context that carries value u.
+ // func NewContext(ctx context.Context, u *User) context.Context {
+ // return context.WithValue(ctx, userKey, u)
+ // }
+ //
+ // // FromContext returns the User value stored in ctx, if any.
+ // func FromContext(ctx context.Context) (*User, bool) {
+ // u, ok := ctx.Value(userKey).(*User)
+ // return u, ok
+ // }
+ Value(key interface{}) interface{}
+}
+
+// Canceled is the error returned by Context.Err when the context is canceled.
+var Canceled = errors.New("context canceled")
+
+// DeadlineExceeded is the error returned by Context.Err when the context's
+// deadline passes.
+var DeadlineExceeded = errors.New("context deadline exceeded")
+
+// An emptyCtx is never canceled, has no values, and has no deadline. It is not
+// struct{}, since vars of this type must have distinct addresses.
+type emptyCtx int
+
+func (*emptyCtx) Deadline() (deadline time.Time, ok bool) {
+ return
+}
+
+func (*emptyCtx) Done() <-chan struct{} {
+ return nil
+}
+
+func (*emptyCtx) Err() error {
+ return nil
+}
+
+func (*emptyCtx) Value(key interface{}) interface{} {
+ return nil
+}
+
+func (e *emptyCtx) String() string {
+ switch e {
+ case background:
+ return "context.Background"
+ case todo:
+ return "context.TODO"
+ }
+ return "unknown empty Context"
+}
+
+var (
+ background = new(emptyCtx)
+ todo = new(emptyCtx)
+)
+
+// Background returns a non-nil, empty Context. It is never canceled, has no
+// values, and has no deadline. It is typically used by the main function,
+// initialization, and tests, and as the top-level Context for incoming
+// requests.
+func Background() Context {
+ return background
+}
+
+// TODO returns a non-nil, empty Context. Code should use context.TODO when
+// it's unclear which Context to use or it is not yet available (because the
+// surrounding function has not yet been extended to accept a Context
+// parameter). TODO is recognized by static analysis tools that determine
+// whether Contexts are propagated correctly in a program.
+func TODO() Context {
+ return todo
+}
+
+// A CancelFunc tells an operation to abandon its work.
+// A CancelFunc does not wait for the work to stop.
+// After the first call, subsequent calls to a CancelFunc do nothing.
+type CancelFunc func()
+
+// WithCancel returns a copy of parent with a new Done channel. The returned
+// context's Done channel is closed when the returned cancel function is called
+// or when the parent context's Done channel is closed, whichever happens first.
+//
+// Canceling this context releases resources associated with it, so code should
+// call cancel as soon as the operations running in this Context complete.
+func WithCancel(parent Context) (ctx Context, cancel CancelFunc) {
+ c := newCancelCtx(parent)
+ propagateCancel(parent, &c)
+ return &c, func() { c.cancel(true, Canceled) }
+}
+
+// newCancelCtx returns an initialized cancelCtx.
+func newCancelCtx(parent Context) cancelCtx {
+ return cancelCtx{
+ Context: parent,
+ done: make(chan struct{}),
+ }
+}
+
+// propagateCancel arranges for child to be canceled when parent is.
+func propagateCancel(parent Context, child canceler) {
+ if parent.Done() == nil {
+ return // parent is never canceled
+ }
+ if p, ok := parentCancelCtx(parent); ok {
+ p.mu.Lock()
+ if p.err != nil {
+ // parent has already been canceled
+ child.cancel(false, p.err)
+ } else {
+ if p.children == nil {
+ p.children = make(map[canceler]bool)
+ }
+ p.children[child] = true
+ }
+ p.mu.Unlock()
+ } else {
+ go func() {
+ select {
+ case <-parent.Done():
+ child.cancel(false, parent.Err())
+ case <-child.Done():
+ }
+ }()
+ }
+}
+
+// parentCancelCtx follows a chain of parent references until it finds a
+// *cancelCtx. This function understands how each of the concrete types in this
+// package represents its parent.
+func parentCancelCtx(parent Context) (*cancelCtx, bool) {
+ for {
+ switch c := parent.(type) {
+ case *cancelCtx:
+ return c, true
+ case *timerCtx:
+ return &c.cancelCtx, true
+ case *valueCtx:
+ parent = c.Context
+ default:
+ return nil, false
+ }
+ }
+}
+
+// removeChild removes a context from its parent.
+func removeChild(parent Context, child canceler) {
+ p, ok := parentCancelCtx(parent)
+ if !ok {
+ return
+ }
+ p.mu.Lock()
+ if p.children != nil {
+ delete(p.children, child)
+ }
+ p.mu.Unlock()
+}
+
+// A canceler is a context type that can be canceled directly. The
+// implementations are *cancelCtx and *timerCtx.
+type canceler interface {
+ cancel(removeFromParent bool, err error)
+ Done() <-chan struct{}
+}
+
+// A cancelCtx can be canceled. When canceled, it also cancels any children
+// that implement canceler.
+type cancelCtx struct {
+ Context
+
+ done chan struct{} // closed by the first cancel call.
+
+ mu sync.Mutex
+ children map[canceler]bool // set to nil by the first cancel call
+ err error // set to non-nil by the first cancel call
+}
+
+func (c *cancelCtx) Done() <-chan struct{} {
+ return c.done
+}
+
+func (c *cancelCtx) Err() error {
+ c.mu.Lock()
+ defer c.mu.Unlock()
+ return c.err
+}
+
+func (c *cancelCtx) String() string {
+ return fmt.Sprintf("%v.WithCancel", c.Context)
+}
+
+// cancel closes c.done, cancels each of c's children, and, if
+// removeFromParent is true, removes c from its parent's children.
+func (c *cancelCtx) cancel(removeFromParent bool, err error) {
+ if err == nil {
+ panic("context: internal error: missing cancel error")
+ }
+ c.mu.Lock()
+ if c.err != nil {
+ c.mu.Unlock()
+ return // already canceled
+ }
+ c.err = err
+ close(c.done)
+ for child := range c.children {
+ // NOTE: acquiring the child's lock while holding parent's lock.
+ child.cancel(false, err)
+ }
+ c.children = nil
+ c.mu.Unlock()
+
+ if removeFromParent {
+ removeChild(c.Context, c)
+ }
+}
+
+// WithDeadline returns a copy of the parent context with the deadline adjusted
+// to be no later than d. If the parent's deadline is already earlier than d,
+// WithDeadline(parent, d) is semantically equivalent to parent. The returned
+// context's Done channel is closed when the deadline expires, when the returned
+// cancel function is called, or when the parent context's Done channel is
+// closed, whichever happens first.
+//
+// Canceling this context releases resources associated with it, so code should
+// call cancel as soon as the operations running in this Context complete.
+func WithDeadline(parent Context, deadline time.Time) (Context, CancelFunc) {
+ if cur, ok := parent.Deadline(); ok && cur.Before(deadline) {
+ // The current deadline is already sooner than the new one.
+ return WithCancel(parent)
+ }
+ c := &timerCtx{
+ cancelCtx: newCancelCtx(parent),
+ deadline: deadline,
+ }
+ propagateCancel(parent, c)
+ d := deadline.Sub(time.Now())
+ if d <= 0 {
+ c.cancel(true, DeadlineExceeded) // deadline has already passed
+ return c, func() { c.cancel(true, Canceled) }
+ }
+ c.mu.Lock()
+ defer c.mu.Unlock()
+ if c.err == nil {
+ c.timer = time.AfterFunc(d, func() {
+ c.cancel(true, DeadlineExceeded)
+ })
+ }
+ return c, func() { c.cancel(true, Canceled) }
+}
+
+// A timerCtx carries a timer and a deadline. It embeds a cancelCtx to
+// implement Done and Err. It implements cancel by stopping its timer then
+// delegating to cancelCtx.cancel.
+type timerCtx struct {
+ cancelCtx
+ timer *time.Timer // Under cancelCtx.mu.
+
+ deadline time.Time
+}
+
+func (c *timerCtx) Deadline() (deadline time.Time, ok bool) {
+ return c.deadline, true
+}
+
+func (c *timerCtx) String() string {
+ return fmt.Sprintf("%v.WithDeadline(%s [%s])", c.cancelCtx.Context, c.deadline, c.deadline.Sub(time.Now()))
+}
+
+func (c *timerCtx) cancel(removeFromParent bool, err error) {
+ c.cancelCtx.cancel(false, err)
+ if removeFromParent {
+ // Remove this timerCtx from its parent cancelCtx's children.
+ removeChild(c.cancelCtx.Context, c)
+ }
+ c.mu.Lock()
+ if c.timer != nil {
+ c.timer.Stop()
+ c.timer = nil
+ }
+ c.mu.Unlock()
+}
+
+// WithTimeout returns WithDeadline(parent, time.Now().Add(timeout)).
+//
+// Canceling this context releases resources associated with it, so code should
+// call cancel as soon as the operations running in this Context complete:
+//
+// func slowOperationWithTimeout(ctx context.Context) (Result, error) {
+// ctx, cancel := context.WithTimeout(ctx, 100*time.Millisecond)
+// defer cancel() // releases resources if slowOperation completes before timeout elapses
+// return slowOperation(ctx)
+// }
+func WithTimeout(parent Context, timeout time.Duration) (Context, CancelFunc) {
+ return WithDeadline(parent, time.Now().Add(timeout))
+}
+
+// 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 interface{}, val interface{}) Context {
+ return &valueCtx{parent, key, val}
+}
+
+// A valueCtx carries a key-value pair. It implements Value for that key and
+// delegates all other calls to the embedded Context.
+type valueCtx struct {
+ Context
+ key, val interface{}
+}
+
+func (c *valueCtx) String() string {
+ return fmt.Sprintf("%v.WithValue(%#v, %#v)", c.Context, c.key, c.val)
+}
+
+func (c *valueCtx) Value(key interface{}) interface{} {
+ if c.key == key {
+ return c.val
+ }
+ return c.Context.Value(key)
+}
--- /dev/null
+// Copyright 2014 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 context
+
+import (
+ "fmt"
+ "math/rand"
+ "runtime"
+ "strings"
+ "sync"
+ "testing"
+ "time"
+)
+
+// otherContext is a Context that's not one of the types defined in context.go.
+// This lets us test code paths that differ based on the underlying type of the
+// Context.
+type otherContext struct {
+ Context
+}
+
+func TestBackground(t *testing.T) {
+ c := Background()
+ if c == nil {
+ t.Fatalf("Background returned nil")
+ }
+ select {
+ case x := <-c.Done():
+ t.Errorf("<-c.Done() == %v want nothing (it should block)", x)
+ default:
+ }
+ if got, want := fmt.Sprint(c), "context.Background"; got != want {
+ t.Errorf("Background().String() = %q want %q", got, want)
+ }
+}
+
+func TestTODO(t *testing.T) {
+ c := TODO()
+ if c == nil {
+ t.Fatalf("TODO returned nil")
+ }
+ select {
+ case x := <-c.Done():
+ t.Errorf("<-c.Done() == %v want nothing (it should block)", x)
+ default:
+ }
+ if got, want := fmt.Sprint(c), "context.TODO"; got != want {
+ t.Errorf("TODO().String() = %q want %q", got, want)
+ }
+}
+
+func TestWithCancel(t *testing.T) {
+ c1, cancel := WithCancel(Background())
+
+ if got, want := fmt.Sprint(c1), "context.Background.WithCancel"; got != want {
+ t.Errorf("c1.String() = %q want %q", got, want)
+ }
+
+ o := otherContext{c1}
+ c2, _ := WithCancel(o)
+ contexts := []Context{c1, o, c2}
+
+ for i, c := range contexts {
+ if d := c.Done(); d == nil {
+ t.Errorf("c[%d].Done() == %v want non-nil", i, d)
+ }
+ if e := c.Err(); e != nil {
+ t.Errorf("c[%d].Err() == %v want nil", i, e)
+ }
+
+ select {
+ case x := <-c.Done():
+ t.Errorf("<-c.Done() == %v want nothing (it should block)", x)
+ default:
+ }
+ }
+
+ cancel()
+ time.Sleep(100 * time.Millisecond) // let cancelation propagate
+
+ for i, c := range contexts {
+ select {
+ case <-c.Done():
+ default:
+ t.Errorf("<-c[%d].Done() blocked, but shouldn't have", i)
+ }
+ if e := c.Err(); e != Canceled {
+ t.Errorf("c[%d].Err() == %v want %v", i, e, Canceled)
+ }
+ }
+}
+
+func TestParentFinishesChild(t *testing.T) {
+ // Context tree:
+ // parent -> cancelChild
+ // parent -> valueChild -> timerChild
+ parent, cancel := WithCancel(Background())
+ cancelChild, stop := WithCancel(parent)
+ defer stop()
+ valueChild := WithValue(parent, "key", "value")
+ timerChild, stop := WithTimeout(valueChild, 10000*time.Hour)
+ defer stop()
+
+ select {
+ case x := <-parent.Done():
+ t.Errorf("<-parent.Done() == %v want nothing (it should block)", x)
+ case x := <-cancelChild.Done():
+ t.Errorf("<-cancelChild.Done() == %v want nothing (it should block)", x)
+ case x := <-timerChild.Done():
+ t.Errorf("<-timerChild.Done() == %v want nothing (it should block)", x)
+ case x := <-valueChild.Done():
+ t.Errorf("<-valueChild.Done() == %v want nothing (it should block)", x)
+ default:
+ }
+
+ // The parent's children should contain the two cancelable children.
+ pc := parent.(*cancelCtx)
+ cc := cancelChild.(*cancelCtx)
+ tc := timerChild.(*timerCtx)
+ pc.mu.Lock()
+ if len(pc.children) != 2 || !pc.children[cc] || !pc.children[tc] {
+ t.Errorf("bad linkage: pc.children = %v, want %v and %v",
+ pc.children, cc, tc)
+ }
+ pc.mu.Unlock()
+
+ if p, ok := parentCancelCtx(cc.Context); !ok || p != pc {
+ t.Errorf("bad linkage: parentCancelCtx(cancelChild.Context) = %v, %v want %v, true", p, ok, pc)
+ }
+ if p, ok := parentCancelCtx(tc.Context); !ok || p != pc {
+ t.Errorf("bad linkage: parentCancelCtx(timerChild.Context) = %v, %v want %v, true", p, ok, pc)
+ }
+
+ cancel()
+
+ pc.mu.Lock()
+ if len(pc.children) != 0 {
+ t.Errorf("pc.cancel didn't clear pc.children = %v", pc.children)
+ }
+ pc.mu.Unlock()
+
+ // parent and children should all be finished.
+ check := func(ctx Context, name string) {
+ select {
+ case <-ctx.Done():
+ default:
+ t.Errorf("<-%s.Done() blocked, but shouldn't have", name)
+ }
+ if e := ctx.Err(); e != Canceled {
+ t.Errorf("%s.Err() == %v want %v", name, e, Canceled)
+ }
+ }
+ check(parent, "parent")
+ check(cancelChild, "cancelChild")
+ check(valueChild, "valueChild")
+ check(timerChild, "timerChild")
+
+ // WithCancel should return a canceled context on a canceled parent.
+ precanceledChild := WithValue(parent, "key", "value")
+ select {
+ case <-precanceledChild.Done():
+ default:
+ t.Errorf("<-precanceledChild.Done() blocked, but shouldn't have")
+ }
+ if e := precanceledChild.Err(); e != Canceled {
+ t.Errorf("precanceledChild.Err() == %v want %v", e, Canceled)
+ }
+}
+
+func TestChildFinishesFirst(t *testing.T) {
+ cancelable, stop := WithCancel(Background())
+ defer stop()
+ for _, parent := range []Context{Background(), cancelable} {
+ child, cancel := WithCancel(parent)
+
+ select {
+ case x := <-parent.Done():
+ t.Errorf("<-parent.Done() == %v want nothing (it should block)", x)
+ case x := <-child.Done():
+ t.Errorf("<-child.Done() == %v want nothing (it should block)", x)
+ default:
+ }
+
+ cc := child.(*cancelCtx)
+ pc, pcok := parent.(*cancelCtx) // pcok == false when parent == Background()
+ if p, ok := parentCancelCtx(cc.Context); ok != pcok || (ok && pc != p) {
+ t.Errorf("bad linkage: parentCancelCtx(cc.Context) = %v, %v want %v, %v", p, ok, pc, pcok)
+ }
+
+ if pcok {
+ pc.mu.Lock()
+ if len(pc.children) != 1 || !pc.children[cc] {
+ t.Errorf("bad linkage: pc.children = %v, cc = %v", pc.children, cc)
+ }
+ pc.mu.Unlock()
+ }
+
+ cancel()
+
+ if pcok {
+ pc.mu.Lock()
+ if len(pc.children) != 0 {
+ t.Errorf("child's cancel didn't remove self from pc.children = %v", pc.children)
+ }
+ pc.mu.Unlock()
+ }
+
+ // child should be finished.
+ select {
+ case <-child.Done():
+ default:
+ t.Errorf("<-child.Done() blocked, but shouldn't have")
+ }
+ if e := child.Err(); e != Canceled {
+ t.Errorf("child.Err() == %v want %v", e, Canceled)
+ }
+
+ // parent should not be finished.
+ select {
+ case x := <-parent.Done():
+ t.Errorf("<-parent.Done() == %v want nothing (it should block)", x)
+ default:
+ }
+ if e := parent.Err(); e != nil {
+ t.Errorf("parent.Err() == %v want nil", e)
+ }
+ }
+}
+
+func testDeadline(c Context, wait time.Duration, t *testing.T) {
+ select {
+ case <-time.After(wait):
+ t.Fatalf("context should have timed out")
+ case <-c.Done():
+ }
+ if e := c.Err(); e != DeadlineExceeded {
+ t.Errorf("c.Err() == %v want %v", e, DeadlineExceeded)
+ }
+}
+
+func TestDeadline(t *testing.T) {
+ c, _ := WithDeadline(Background(), time.Now().Add(100*time.Millisecond))
+ if got, prefix := fmt.Sprint(c), "context.Background.WithDeadline("; !strings.HasPrefix(got, prefix) {
+ t.Errorf("c.String() = %q want prefix %q", got, prefix)
+ }
+ testDeadline(c, 200*time.Millisecond, t)
+
+ c, _ = WithDeadline(Background(), time.Now().Add(100*time.Millisecond))
+ o := otherContext{c}
+ testDeadline(o, 200*time.Millisecond, t)
+
+ c, _ = WithDeadline(Background(), time.Now().Add(100*time.Millisecond))
+ o = otherContext{c}
+ c, _ = WithDeadline(o, time.Now().Add(300*time.Millisecond))
+ testDeadline(c, 200*time.Millisecond, t)
+}
+
+func TestTimeout(t *testing.T) {
+ c, _ := WithTimeout(Background(), 100*time.Millisecond)
+ if got, prefix := fmt.Sprint(c), "context.Background.WithDeadline("; !strings.HasPrefix(got, prefix) {
+ t.Errorf("c.String() = %q want prefix %q", got, prefix)
+ }
+ testDeadline(c, 200*time.Millisecond, t)
+
+ c, _ = WithTimeout(Background(), 100*time.Millisecond)
+ o := otherContext{c}
+ testDeadline(o, 200*time.Millisecond, t)
+
+ c, _ = WithTimeout(Background(), 100*time.Millisecond)
+ o = otherContext{c}
+ c, _ = WithTimeout(o, 300*time.Millisecond)
+ testDeadline(c, 200*time.Millisecond, t)
+}
+
+func TestCanceledTimeout(t *testing.T) {
+ c, _ := WithTimeout(Background(), 200*time.Millisecond)
+ o := otherContext{c}
+ c, cancel := WithTimeout(o, 400*time.Millisecond)
+ cancel()
+ time.Sleep(100 * time.Millisecond) // let cancelation propagate
+ select {
+ case <-c.Done():
+ default:
+ t.Errorf("<-c.Done() blocked, but shouldn't have")
+ }
+ if e := c.Err(); e != Canceled {
+ t.Errorf("c.Err() == %v want %v", e, Canceled)
+ }
+}
+
+type key1 int
+type key2 int
+
+var k1 = key1(1)
+var k2 = key2(1) // same int as k1, different type
+var k3 = key2(3) // same type as k2, different int
+
+func TestValues(t *testing.T) {
+ check := func(c Context, nm, v1, v2, v3 string) {
+ if v, ok := c.Value(k1).(string); ok == (len(v1) == 0) || v != v1 {
+ t.Errorf(`%s.Value(k1).(string) = %q, %t want %q, %t`, nm, v, ok, v1, len(v1) != 0)
+ }
+ if v, ok := c.Value(k2).(string); ok == (len(v2) == 0) || v != v2 {
+ t.Errorf(`%s.Value(k2).(string) = %q, %t want %q, %t`, nm, v, ok, v2, len(v2) != 0)
+ }
+ if v, ok := c.Value(k3).(string); ok == (len(v3) == 0) || v != v3 {
+ t.Errorf(`%s.Value(k3).(string) = %q, %t want %q, %t`, nm, v, ok, v3, len(v3) != 0)
+ }
+ }
+
+ c0 := Background()
+ check(c0, "c0", "", "", "")
+
+ c1 := WithValue(Background(), k1, "c1k1")
+ check(c1, "c1", "c1k1", "", "")
+
+ if got, want := fmt.Sprint(c1), `context.Background.WithValue(1, "c1k1")`; got != want {
+ t.Errorf("c.String() = %q want %q", got, want)
+ }
+
+ c2 := WithValue(c1, k2, "c2k2")
+ check(c2, "c2", "c1k1", "c2k2", "")
+
+ c3 := WithValue(c2, k3, "c3k3")
+ check(c3, "c2", "c1k1", "c2k2", "c3k3")
+
+ c4 := WithValue(c3, k1, nil)
+ check(c4, "c4", "", "c2k2", "c3k3")
+
+ o0 := otherContext{Background()}
+ check(o0, "o0", "", "", "")
+
+ o1 := otherContext{WithValue(Background(), k1, "c1k1")}
+ check(o1, "o1", "c1k1", "", "")
+
+ o2 := WithValue(o1, k2, "o2k2")
+ check(o2, "o2", "c1k1", "o2k2", "")
+
+ o3 := otherContext{c4}
+ check(o3, "o3", "", "c2k2", "c3k3")
+
+ o4 := WithValue(o3, k3, nil)
+ check(o4, "o4", "", "c2k2", "")
+}
+
+func TestAllocs(t *testing.T) {
+ bg := Background()
+ for _, test := range []struct {
+ desc string
+ f func()
+ limit float64
+ gccgoLimit float64
+ }{
+ {
+ desc: "Background()",
+ f: func() { Background() },
+ limit: 0,
+ gccgoLimit: 0,
+ },
+ {
+ desc: fmt.Sprintf("WithValue(bg, %v, nil)", k1),
+ f: func() {
+ c := WithValue(bg, k1, nil)
+ c.Value(k1)
+ },
+ limit: 3,
+ gccgoLimit: 3,
+ },
+ {
+ desc: "WithTimeout(bg, 15*time.Millisecond)",
+ f: func() {
+ c, _ := WithTimeout(bg, 15*time.Millisecond)
+ <-c.Done()
+ },
+ limit: 8,
+ gccgoLimit: 15,
+ },
+ {
+ desc: "WithCancel(bg)",
+ f: func() {
+ c, cancel := WithCancel(bg)
+ cancel()
+ <-c.Done()
+ },
+ limit: 5,
+ gccgoLimit: 8,
+ },
+ {
+ desc: "WithTimeout(bg, 100*time.Millisecond)",
+ f: func() {
+ c, cancel := WithTimeout(bg, 100*time.Millisecond)
+ cancel()
+ <-c.Done()
+ },
+ limit: 8,
+ gccgoLimit: 25,
+ },
+ } {
+ limit := test.limit
+ if runtime.Compiler == "gccgo" {
+ // gccgo does not yet do escape analysis.
+ // TOOD(iant): Remove this when gccgo does do escape analysis.
+ limit = test.gccgoLimit
+ }
+ if n := testing.AllocsPerRun(100, test.f); n > limit {
+ t.Errorf("%s allocs = %f want %d", test.desc, n, int(limit))
+ }
+ }
+}
+
+func TestSimultaneousCancels(t *testing.T) {
+ root, cancel := WithCancel(Background())
+ m := map[Context]CancelFunc{root: cancel}
+ q := []Context{root}
+ // Create a tree of contexts.
+ for len(q) != 0 && len(m) < 100 {
+ parent := q[0]
+ q = q[1:]
+ for i := 0; i < 4; i++ {
+ ctx, cancel := WithCancel(parent)
+ m[ctx] = cancel
+ q = append(q, ctx)
+ }
+ }
+ // Start all the cancels in a random order.
+ var wg sync.WaitGroup
+ wg.Add(len(m))
+ for _, cancel := range m {
+ go func(cancel CancelFunc) {
+ cancel()
+ wg.Done()
+ }(cancel)
+ }
+ // Wait on all the contexts in a random order.
+ for ctx := range m {
+ select {
+ case <-ctx.Done():
+ case <-time.After(1 * time.Second):
+ buf := make([]byte, 10<<10)
+ n := runtime.Stack(buf, true)
+ t.Fatalf("timed out waiting for <-ctx.Done(); stacks:\n%s", buf[:n])
+ }
+ }
+ // Wait for all the cancel functions to return.
+ done := make(chan struct{})
+ go func() {
+ wg.Wait()
+ close(done)
+ }()
+ select {
+ case <-done:
+ case <-time.After(1 * time.Second):
+ buf := make([]byte, 10<<10)
+ n := runtime.Stack(buf, true)
+ t.Fatalf("timed out waiting for cancel functions; stacks:\n%s", buf[:n])
+ }
+}
+
+func TestInterlockedCancels(t *testing.T) {
+ parent, cancelParent := WithCancel(Background())
+ child, cancelChild := WithCancel(parent)
+ go func() {
+ parent.Done()
+ cancelChild()
+ }()
+ cancelParent()
+ select {
+ case <-child.Done():
+ case <-time.After(1 * time.Second):
+ buf := make([]byte, 10<<10)
+ n := runtime.Stack(buf, true)
+ t.Fatalf("timed out waiting for child.Done(); stacks:\n%s", buf[:n])
+ }
+}
+
+func TestLayersCancel(t *testing.T) {
+ testLayers(t, time.Now().UnixNano(), false)
+}
+
+func TestLayersTimeout(t *testing.T) {
+ testLayers(t, time.Now().UnixNano(), true)
+}
+
+func testLayers(t *testing.T, seed int64, testTimeout bool) {
+ rand.Seed(seed)
+ errorf := func(format string, a ...interface{}) {
+ t.Errorf(fmt.Sprintf("seed=%d: %s", seed, format), a...)
+ }
+ const (
+ timeout = 200 * time.Millisecond
+ minLayers = 30
+ )
+ type value int
+ var (
+ vals []*value
+ cancels []CancelFunc
+ numTimers int
+ ctx = Background()
+ )
+ for i := 0; i < minLayers || numTimers == 0 || len(cancels) == 0 || len(vals) == 0; i++ {
+ switch rand.Intn(3) {
+ case 0:
+ v := new(value)
+ ctx = WithValue(ctx, v, v)
+ vals = append(vals, v)
+ case 1:
+ var cancel CancelFunc
+ ctx, cancel = WithCancel(ctx)
+ cancels = append(cancels, cancel)
+ case 2:
+ var cancel CancelFunc
+ ctx, cancel = WithTimeout(ctx, timeout)
+ cancels = append(cancels, cancel)
+ numTimers++
+ }
+ }
+ checkValues := func(when string) {
+ for _, key := range vals {
+ if val := ctx.Value(key).(*value); key != val {
+ errorf("%s: ctx.Value(%p) = %p want %p", when, key, val, key)
+ }
+ }
+ }
+ select {
+ case <-ctx.Done():
+ errorf("ctx should not be canceled yet")
+ default:
+ }
+ if s, prefix := fmt.Sprint(ctx), "context.Background."; !strings.HasPrefix(s, prefix) {
+ t.Errorf("ctx.String() = %q want prefix %q", s, prefix)
+ }
+ t.Log(ctx)
+ checkValues("before cancel")
+ if testTimeout {
+ select {
+ case <-ctx.Done():
+ case <-time.After(timeout + 100*time.Millisecond):
+ errorf("ctx should have timed out")
+ }
+ checkValues("after timeout")
+ } else {
+ cancel := cancels[rand.Intn(len(cancels))]
+ cancel()
+ select {
+ case <-ctx.Done():
+ default:
+ errorf("ctx should be canceled")
+ }
+ checkValues("after cancel")
+ }
+}
+
+func TestCancelRemoves(t *testing.T) {
+ checkChildren := func(when string, ctx Context, want int) {
+ if got := len(ctx.(*cancelCtx).children); got != want {
+ t.Errorf("%s: context has %d children, want %d", when, got, want)
+ }
+ }
+
+ ctx, _ := WithCancel(Background())
+ checkChildren("after creation", ctx, 0)
+ _, cancel := WithCancel(ctx)
+ checkChildren("with WithCancel child ", ctx, 1)
+ cancel()
+ checkChildren("after cancelling WithCancel child", ctx, 0)
+
+ ctx, _ = WithCancel(Background())
+ checkChildren("after creation", ctx, 0)
+ _, cancel = WithTimeout(ctx, 60*time.Minute)
+ checkChildren("with WithTimeout child ", ctx, 1)
+ cancel()
+ checkChildren("after cancelling WithTimeout child", ctx, 0)
+}