Golang context.WithCancel函數代碼示例

func TestDoesNotDeadLockIfContextCancelledBeforePublish(t *testing.T) {

	g := blocksutil.NewBlockGenerator()
	ctx, cancel := context.WithCancel(context.Background())
	n := New()
	defer n.Shutdown()

	t.Log("generate a large number of blocks. exceed default buffer")
	bs := g.Blocks(1000)
	ks := func() []key.Key {
		var keys []key.Key
		for _, b := range bs {
			keys = append(keys, b.Key())
		}
		return keys
	}()

	_ = n.Subscribe(ctx, ks...) // ignore received channel

	t.Log("cancel context before any blocks published")
	cancel()
	for _, b := range bs {
		n.Publish(b)
	}

	t.Log("publishing the large number of blocks to the ignored channel must not deadlock")
}

func TestConsistentAccounting(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	sender := newEngine(ctx, "Ernie")
	receiver := newEngine(ctx, "Bert")

	// Send messages from Ernie to Bert
	for i := 0; i < 1000; i++ {

		m := message.New(false)
		content := []string{"this", "is", "message", "i"}
		m.AddBlock(blocks.NewBlock([]byte(strings.Join(content, " "))))

		sender.Engine.MessageSent(receiver.Peer, m)
		receiver.Engine.MessageReceived(sender.Peer, m)
	}

	// Ensure sender records the change
	if sender.Engine.numBytesSentTo(receiver.Peer) == 0 {
		t.Fatal("Sent bytes were not recorded")
	}

	// Ensure sender and receiver have the same values
	if sender.Engine.numBytesSentTo(receiver.Peer) != receiver.Engine.numBytesReceivedFrom(sender.Peer) {
		t.Fatal("Inconsistent book-keeping. Strategies don't agree")
	}

	// Ensure sender didn't record receving anything. And that the receiver
	// didn't record sending anything
	if receiver.Engine.numBytesSentTo(sender.Peer) != 0 || sender.Engine.numBytesReceivedFrom(receiver.Peer) != 0 {
		t.Fatal("Bert didn't send bytes to Ernie")
	}
}

func (bs *Bitswap) rebroadcastWorker(parent context.Context) {
	ctx, cancel := context.WithCancel(parent)
	defer cancel()

	broadcastSignal := time.NewTicker(rebroadcastDelay.Get())
	defer broadcastSignal.Stop()

	tick := time.NewTicker(10 * time.Second)
	defer tick.Stop()

	for {
		log.Event(ctx, "Bitswap.Rebroadcast.idle")
		select {
		case <-tick.C:
			n := bs.wm.wl.Len()
			if n > 0 {
				log.Debug(n, "keys in bitswap wantlist")
			}
		case <-broadcastSignal.C: // resend unfulfilled wantlist keys
			log.Event(ctx, "Bitswap.Rebroadcast.active")
			entries := bs.wm.wl.Entries()
			if len(entries) > 0 {
				bs.connectToProviders(ctx, entries)
			}
		case <-parent.Done():
			return
		}
	}
}

func (bs *Bitswap) connectToProviders(ctx context.Context, entries []wantlist.Entry) {

	ctx, cancel := context.WithCancel(ctx)
	defer cancel()

	// Get providers for all entries in wantlist (could take a while)
	wg := sync.WaitGroup{}
	for _, e := range entries {
		wg.Add(1)
		go func(k key.Key) {
			defer wg.Done()

			child, cancel := context.WithTimeout(ctx, providerRequestTimeout)
			defer cancel()
			providers := bs.network.FindProvidersAsync(child, k, maxProvidersPerRequest)
			for prov := range providers {
				go func(p peer.ID) {
					bs.network.ConnectTo(ctx, p)
				}(prov)
			}
		}(e.Key)
	}

	wg.Wait() // make sure all our children do finish.
}

// WithDeadlineFraction returns a Context with a fraction of the
// original context's timeout. This is useful in sequential pipelines
// of work, where one might try options and fall back to others
// depending on the time available, or failure to respond. For example:
//
//  // getPicture returns a picture from our encrypted database
//  // we have a pipeline of multiple steps. we need to:
//  // - get the data from a database
//  // - decrypt it
//  // - apply many transforms
//  //
//  // we **know** that each step takes increasingly more time.
//  // The transforms are much more expensive than decryption, and
//  // decryption is more expensive than the database lookup.
//  // If our database takes too long (i.e. >0.2 of available time),
//  // there's no use in continuing.
//  func getPicture(ctx context.Context, key string) ([]byte, error) {
//    // fractional timeout contexts to the rescue!
//
//    // try the database with 0.2 of remaining time.
//    ctx1, _ := ctxext.WithDeadlineFraction(ctx, 0.2)
//    val, err := db.Get(ctx1, key)
//    if err != nil {
//      return nil, err
//    }
//
//    // try decryption with 0.3 of remaining time.
//    ctx2, _ := ctxext.WithDeadlineFraction(ctx, 0.3)
//    if val, err = decryptor.Decrypt(ctx2, val); err != nil {
//      return nil, err
//    }
//
//    // try transforms with all remaining time. hopefully it's enough!
//    return transformer.Transform(ctx, val)
//  }
//
//
func WithDeadlineFraction(ctx context.Context, fraction float64) (
	context.Context, context.CancelFunc) {

	d, found := ctx.Deadline()
	if !found { // no deadline
		return context.WithCancel(ctx)
	}

	left := d.Sub(time.Now())
	if left < 0 { // already passed...
		return context.WithCancel(ctx)
	}

	left = time.Duration(float64(left) * fraction)
	return context.WithTimeout(ctx, left)
}

// WithProcessClosing returns a context.Context derived from ctx that
// is cancelled as p is Closing (after: <-p.Closing()). It is simply:
//
//   func WithProcessClosing(ctx context.Context, p goprocess.Process) context.Context {
//     ctx, cancel := context.WithCancel(ctx)
//     go func() {
//       <-p.Closing()
//       cancel()
//     }()
//     return ctx
//   }
//
func WithProcessClosing(ctx context.Context, p goprocess.Process) context.Context {
	ctx, cancel := context.WithCancel(ctx)
	go func() {
		<-p.Closing()
		cancel()
	}()
	return ctx
}

// Context returns a context that cancels when the waitable is closing.
func Context(w Waitable) context.Context {
	ctx, cancel := context.WithCancel(context.Background())
	go func() {
		<-w.Closing()
		cancel()
	}()
	return ctx
}

// TODO does dht ensure won't receive self as a provider? probably not.
func TestCanceledContext(t *testing.T) {
	rs := NewServer()
	k := key.Key("hello")

	// avoid leaking goroutine, without using the context to signal
	// (we want the goroutine to keep trying to publish on a
	// cancelled context until we've tested it doesnt do anything.)
	done := make(chan struct{})
	defer func() { done <- struct{}{} }()

	t.Log("async'ly announce infinite stream of providers for key")
	i := 0
	go func() { // infinite stream
		for {
			select {
			case <-done:
				t.Log("exiting async worker")
				return
			default:
			}

			pi, err := testutil.RandIdentity()
			if err != nil {
				t.Error(err)
			}
			err = rs.Client(pi).Provide(context.Background(), k)
			if err != nil {
				t.Error(err)
			}
			i++
		}
	}()

	local := testutil.RandIdentityOrFatal(t)
	client := rs.Client(local)

	t.Log("warning: max is finite so this test is non-deterministic")
	t.Log("context cancellation could simply take lower priority")
	t.Log("and result in receiving the max number of results")
	max := 1000

	t.Log("cancel the context before consuming")
	ctx, cancelFunc := context.WithCancel(context.Background())
	cancelFunc()
	providers := client.FindProvidersAsync(ctx, k, max)

	numProvidersReturned := 0
	for _ = range providers {
		numProvidersReturned++
	}
	t.Log(numProvidersReturned)

	if numProvidersReturned == max {
		t.Fatal("Context cancel had no effect")
	}
}

// WARNING: this uses RandTestBogusIdentity DO NOT USE for NON TESTS!
func NewTestSessionGenerator(
	net tn.Network) SessionGenerator {
	ctx, cancel := context.WithCancel(context.TODO())
	return SessionGenerator{
		net:    net,
		seq:    0,
		ctx:    ctx, // TODO take ctx as param to Next, Instances
		cancel: cancel,
	}
}

func TestDoReturnsContextErr(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	ch := make(chan struct{})
	err := ContextDo(ctx, func() error {
		cancel()
		ch <- struct{}{} // won't return
		return nil
	})
	if err != ctx.Err() {
		t.Fail()
	}
}

// New initializes a BitSwap instance that communicates over the provided
// BitSwapNetwork. This function registers the returned instance as the network
// delegate.
// Runs until context is cancelled.
func New(parent context.Context, p peer.ID, network bsnet.BitSwapNetwork,
	bstore blockstore.Blockstore, nice bool) exchange.Interface {

	// important to use provided parent context (since it may include important
	// loggable data). It's probably not a good idea to allow bitswap to be
	// coupled to the concerns of the IPFS daemon in this way.
	//
	// FIXME(btc) Now that bitswap manages itself using a process, it probably
	// shouldn't accept a context anymore. Clients should probably use Close()
	// exclusively. We should probably find another way to share logging data
	ctx, cancelFunc := context.WithCancel(parent)

	notif := notifications.New()
	px := process.WithTeardown(func() error {
		notif.Shutdown()
		return nil
	})

	go func() {
		<-px.Closing() // process closes first
		cancelFunc()
	}()
	go func() {
		<-ctx.Done() // parent cancelled first
		px.Close()
	}()

	bs := &Bitswap{
		self:          p,
		blockstore:    bstore,
		notifications: notif,
		engine:        decision.NewEngine(ctx, bstore), // TODO close the engine with Close() method
		network:       network,
		findKeys:      make(chan *blockRequest, sizeBatchRequestChan),
		process:       px,
		newBlocks:     make(chan *blocks.Block, HasBlockBufferSize),
		provideKeys:   make(chan key.Key),
		wm:            NewWantManager(ctx, network),
	}
	go bs.wm.Run()
	network.SetDelegate(bs)

	// Start up bitswaps async worker routines
	bs.startWorkers(px, ctx)
	return bs
}

func TestSecureHandshakeFailsWithWrongKeys(t *testing.T) {
	// t.Skip("Skipping in favor of another test")

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	c1, c2, p1, p2 := setupSingleConn(t, ctx)

	done := make(chan error)
	go secureHandshake(t, ctx, p2.PrivKey, c1, done)
	go secureHandshake(t, ctx, p1.PrivKey, c2, done)

	for i := 0; i < 2; i++ {
		if err := <-done; err == nil {
			t.Fatal("wrong keys should've errored out.")
		}
	}
}

func TestClose(t *testing.T) {
	// t.Skip("Skipping in favor of another test")

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	c1, c2, _, _ := setupSingleConn(t, ctx)

	testOneSendRecv(t, c1, c2)
	testOneSendRecv(t, c2, c1)

	c1.Close()
	testNotOneSendRecv(t, c1, c2)

	c2.Close()
	testNotOneSendRecv(t, c2, c1)
	testNotOneSendRecv(t, c1, c2)
}

func TestSecureCancelHandshake(t *testing.T) {
	// t.Skip("Skipping in favor of another test")

	ctx, cancel := context.WithCancel(context.Background())
	c1, c2, p1, p2 := setupSingleConn(t, ctx)

	done := make(chan error)
	go secureHandshake(t, ctx, p1.PrivKey, c1, done)
	<-time.After(time.Millisecond)
	cancel() // cancel ctx
	go secureHandshake(t, ctx, p2.PrivKey, c2, done)

	for i := 0; i < 2; i++ {
		if err := <-done; err == nil {
			t.Error("cancel should've errored out")
		}
	}
}

func testPing(t *testing.T, ps *PingService, p peer.ID) {
	pctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	ts, err := ps.Ping(pctx, p)
	if err != nil {
		t.Fatal(err)
	}

	for i := 0; i < 5; i++ {
		select {
		case took := <-ts:
			t.Log("ping took: ", took)
		case <-time.After(time.Second * 4):
			t.Fatal("failed to receive ping")
		}
	}

}