Golang context.WithCancel函数代码示例

func TestDoubleGet(t *testing.T) {
	net := tn.VirtualNetwork(mockrouting.NewServer(), delay.Fixed(kNetworkDelay))
	sg := NewTestSessionGenerator(net)
	defer sg.Close()
	bg := blocksutil.NewBlockGenerator()

	t.Log("Test a one node trying to get one block from another")

	instances := sg.Instances(2)
	blocks := bg.Blocks(1)

	ctx1, cancel1 := context.WithCancel(context.Background())

	blkch1, err := instances[1].Exchange.GetBlocks(ctx1, []key.Key{blocks[0].Key()})
	if err != nil {
		t.Fatal(err)
	}

	ctx2, cancel2 := context.WithCancel(context.Background())
	defer cancel2()

	blkch2, err := instances[1].Exchange.GetBlocks(ctx2, []key.Key{blocks[0].Key()})
	if err != nil {
		t.Fatal(err)
	}

	// ensure both requests make it into the wantlist at the same time
	time.Sleep(time.Millisecond * 100)
	cancel1()

	_, ok := <-blkch1
	if ok {
		t.Fatal("expected channel to be closed")
	}

	err = instances[0].Exchange.HasBlock(blocks[0])
	if err != nil {
		t.Fatal(err)
	}

	blk, ok := <-blkch2
	if !ok {
		t.Fatal("expected to get the block here")
	}
	t.Log(blk)

	for _, inst := range instances {
		err := inst.Exchange.Close()
		if err != nil {
			t.Fatal(err)
		}
	}
}

func RunSupernodePutRecordGetRecord(conf testutil.LatencyConfig) error {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	servers, clients, err := InitializeSupernodeNetwork(ctx, 2, 2, conf)
	if err != nil {
		return err
	}
	for _, n := range append(servers, clients...) {
		defer n.Close()
	}

	putter := clients[0]
	getter := clients[1]

	k := key.Key("key")
	note := []byte("a note from putter")

	if err := putter.Routing.PutValue(ctx, k, note); err != nil {
		return fmt.Errorf("failed to put value: %s", err)
	}

	received, err := getter.Routing.GetValue(ctx, k)
	if err != nil {
		return fmt.Errorf("failed to get value: %s", err)
	}

	if 0 != bytes.Compare(note, received) {
		return errors.New("record doesn't match")
	}
	cancel()
	return nil
}

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 TestWritePostCancel(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	piper, pipew := io.Pipe()
	w := NewWriter(ctx, pipew)

	buf := []byte("abcdefghij")
	buf2 := make([]byte, 10)
	done := make(chan ioret)

	go func() {
		n, err := w.Write(buf)
		done <- ioret{n, err}
	}()

	piper.Read(buf2)

	select {
	case ret := <-done:
		if ret.n != 10 {
			t.Error("ret.n should be 10", ret.n)
		}
		if ret.err != nil {
			t.Error("ret.err should be nil", ret.err)
		}
		if string(buf2) != "abcdefghij" {
			t.Error("write contents differ")
		}
	case <-time.After(20 * time.Millisecond):
		t.Fatal("failed to write")
	}

	go func() {
		n, err := w.Write(buf)
		done <- ioret{n, err}
	}()

	cancel()

	select {
	case ret := <-done:
		if ret.n != 0 {
			t.Error("ret.n should be 0", ret.n)
		}
		if ret.err == nil {
			t.Error("ret.err should be ctx error", ret.err)
		}
	case <-time.After(20 * time.Millisecond):
		t.Fatal("failed to stop writing after cancel")
	}

	copy(buf, []byte("aaaaaaaaaa"))

	piper.Read(buf2)

	if string(buf2) == "aaaaaaaaaa" {
		t.Error("buffer was read from after ctx cancel")
	} else if string(buf2) != "abcdefghij" {
		t.Error("write contents differ from expected")
	}
}

func TestBasic(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	ds, rt := setupRoot(ctx, t)

	rootdir := rt.GetValue().(*Directory)

	// test making a basic dir
	_, err := rootdir.Mkdir("a")
	if err != nil {
		t.Fatal(err)
	}

	path := "a/b/c/d/e/f/g"
	d := mkdirP(t, rootdir, path)

	fi := getRandFile(t, ds, 1000)

	// test inserting that file
	err = d.AddChild("afile", fi)
	if err != nil {
		t.Fatal(err)
	}

	err = assertFileAtPath(ds, rootdir, fi, "a/b/c/d/e/f/g/afile")
	if err != nil {
		t.Fatal(err)
	}
}

func (i *cmdInvocation) SetupInterruptHandler(ctx context.Context) (io.Closer, context.Context) {

	intrh := NewIntrHandler()
	ctx, cancelFunc := context.WithCancel(ctx)

	handlerFunc := func(count int, ih *IntrHandler) {
		switch count {
		case 1:
			fmt.Println() // Prevent un-terminated ^C character in terminal

			ih.wg.Add(1)
			go func() {
				defer ih.wg.Done()
				cancelFunc()
			}()

		default:
			fmt.Println("Received another interrupt before graceful shutdown, terminating...")
			os.Exit(-1)
		}
	}

	intrh.Handle(handlerFunc, syscall.SIGHUP, syscall.SIGINT, syscall.SIGTERM)

	return intrh, ctx
}

// 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)
}

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) 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.
}

func Unpin(n *core.IpfsNode, ctx context.Context, paths []string, recursive bool) ([]key.Key, error) {

	var unpinned []key.Key
	for _, p := range paths {
		p, err := path.ParsePath(p)
		if err != nil {
			return nil, err
		}

		k, err := core.ResolveToKey(ctx, n, p)
		if err != nil {
			return nil, err
		}

		ctx, cancel := context.WithCancel(ctx)
		defer cancel()
		err = n.Pinning.Unpin(ctx, k, recursive)
		if err != nil {
			return nil, err
		}
		unpinned = append(unpinned, k)
	}

	err := n.Pinning.Flush()
	if err != nil {
		return nil, err
	}
	return unpinned, nil
}

func Pin(n *core.IpfsNode, ctx context.Context, paths []string, recursive bool) ([]key.Key, error) {
	dagnodes := make([]*merkledag.Node, 0)
	for _, fpath := range paths {
		dagnode, err := core.Resolve(ctx, n, path.Path(fpath))
		if err != nil {
			return nil, fmt.Errorf("pin: %s", err)
		}
		dagnodes = append(dagnodes, dagnode)
	}

	var out []key.Key
	for _, dagnode := range dagnodes {
		k, err := dagnode.Key()
		if err != nil {
			return nil, err
		}

		ctx, cancel := context.WithCancel(ctx)
		defer cancel()
		err = n.Pinning.Pin(ctx, dagnode, recursive)
		if err != nil {
			return nil, fmt.Errorf("pin: %s", err)
		}
		out = append(out, k)
	}

	err := n.Pinning.Flush()
	if err != nil {
		return nil, err
	}

	return out, nil
}

func BenchmarkDagmodWrite(b *testing.B) {
	b.StopTimer()
	dserv := getMockDagServ(b)
	_, n := getNode(b, dserv, 0)
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	wrsize := 4096

	dagmod, err := NewDagModifier(ctx, n, dserv, sizeSplitterGen(512))
	if err != nil {
		b.Fatal(err)
	}

	buf := make([]byte, b.N*wrsize)
	u.NewTimeSeededRand().Read(buf)
	b.StartTimer()
	b.SetBytes(int64(wrsize))
	for i := 0; i < b.N; i++ {
		n, err := dagmod.Write(buf[i*wrsize : (i+1)*wrsize])
		if err != nil {
			b.Fatal(err)
		}
		if n != wrsize {
			b.Fatal("Wrote bad size")
		}
	}
}

func addDefaultAssets(out io.Writer, repoRoot string) error {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	r, err := fsrepo.Open(repoRoot)
	if err != nil { // NB: repo is owned by the node
		return err
	}

	nd, err := core.NewNode(ctx, &core.BuildCfg{Repo: r})
	if err != nil {
		return err
	}
	defer nd.Close()

	dkey, err := assets.SeedInitDocs(nd)
	if err != nil {
		return fmt.Errorf("init: seeding init docs failed: %s", err)
	}
	log.Debugf("init: seeded init docs %s", dkey)

	if _, err = fmt.Fprintf(out, "to get started, enter:\n"); err != nil {
		return err
	}

	_, err = fmt.Fprintf(out, "\n\tipfs cat /ipfs/%s/readme\n\n", dkey)
	return err
}

func (dm *DagModifier) readPrep() error {
	err := dm.Sync()
	if err != nil {
		return err
	}

	if dm.read == nil {
		ctx, cancel := context.WithCancel(dm.ctx)
		dr, err := uio.NewDagReader(ctx, dm.curNode, dm.dagserv)
		if err != nil {
			return err
		}

		i, err := dr.Seek(int64(dm.curWrOff), os.SEEK_SET)
		if err != nil {
			return err
		}

		if i != int64(dm.curWrOff) {
			return ErrSeekFail
		}

		dm.readCancel = cancel
		dm.read = dr
	}

	return nil
}

// InitializeKeyspace sets the ipns record for the given key to
// point to an empty directory.
func InitializeKeyspace(n *core.IpfsNode, key ci.PrivKey) error {
	emptyDir := &mdag.Node{Data: ft.FolderPBData()}
	nodek, err := n.DAG.Add(emptyDir)
	if err != nil {
		return err
	}

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

	err = n.Pinning.Pin(ctx, emptyDir, false)
	if err != nil {
		return err
	}

	err = n.Pinning.Flush()
	if err != nil {
		return err
	}

	pub := nsys.NewRoutingPublisher(n.Routing, n.Repo.Datastore())
	if err := pub.Publish(ctx, key, path.FromKey(nodek)); err != nil {
		return err
	}

	return nil
}