Golang Context.Err方法代码示例

// GetBlocks returns a channel where the caller may receive blocks that
// correspond to the provided |keys|. Returns an error if BitSwap is unable to
// begin this request within the deadline enforced by the context.
//
// NB: Your request remains open until the context expires. To conserve
// resources, provide a context with a reasonably short deadline (ie. not one
// that lasts throughout the lifetime of the server)
func (bs *Bitswap) GetBlocks(ctx context.Context, keys []key.Key) (<-chan *blocks.Block, error) {
	select {
	case <-bs.process.Closing():
		return nil, errors.New("bitswap is closed")
	default:
	}
	promise := bs.notifications.Subscribe(ctx, keys...)

	for _, k := range keys {
		log.Event(ctx, "Bitswap.GetBlockRequest.Start", &k)
	}

	bs.wm.WantBlocks(keys)

	req := &blockRequest{
		keys: keys,
		ctx:  ctx,
	}
	select {
	case bs.findKeys <- req:
		return promise, nil
	case <-ctx.Done():
		return nil, ctx.Err()
	}
}

func (ds *dagService) GetMany(ctx context.Context, keys []key.Key) <-chan *NodeOption {
	out := make(chan *NodeOption, len(keys))
	blocks := ds.Blocks.GetBlocks(ctx, keys)
	var count int

	go func() {
		defer close(out)
		for {
			select {
			case b, ok := <-blocks:
				if !ok {
					if count != len(keys) {
						out <- &NodeOption{Err: fmt.Errorf("failed to fetch all nodes")}
					}
					return
				}
				nd, err := DecodeProtobuf(b.Data())
				if err != nil {
					out <- &NodeOption{Err: err}
					return
				}
				nd.cached = b.Key().ToMultihash()

				// buffered, no need to select
				out <- &NodeOption{Node: nd}
				count++

			case <-ctx.Done():
				out <- &NodeOption{Err: ctx.Err()}
				return
			}
		}
	}()
	return out
}

func readMsgCtx(ctx context.Context, r msgio.Reader, p proto.Message) ([]byte, error) {
	var msg []byte

	// read in a goroutine so we can exit when our context is cancelled.
	done := make(chan error)
	go func() {
		var err error
		msg, err = r.ReadMsg()
		select {
		case done <- err:
		case <-ctx.Done():
		}
	}()

	select {
	case <-ctx.Done():
		return nil, ctx.Err()
	case e := <-done:
		if e != nil {
			return nil, e
		}
	}

	return msg, proto.Unmarshal(msg, p)
}

func waitOnErrChan(ctx context.Context, errs chan error) error {
	select {
	case err := <-errs:
		return err
	case <-ctx.Done():
		return ctx.Err()
	}
}

func EnumerateChildrenAsync(ctx context.Context, ds DAGService, root *Node, set key.KeySet) error {
	toprocess := make(chan []key.Key, 8)
	nodes := make(chan *NodeOption, 8)

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

	go fetchNodes(ctx, ds, toprocess, nodes)

	nodes <- &NodeOption{Node: root}
	live := 1

	for {
		select {
		case opt, ok := <-nodes:
			if !ok {
				return nil
			}

			if opt.Err != nil {
				return opt.Err
			}

			nd := opt.Node

			// a node has been fetched
			live--

			var keys []key.Key
			for _, lnk := range nd.Links {
				k := key.Key(lnk.Hash)
				if !set.Has(k) {
					set.Add(k)
					live++
					keys = append(keys, k)
				}
			}

			if live == 0 {
				return nil
			}

			if len(keys) > 0 {
				select {
				case toprocess <- keys:
				case <-ctx.Done():
					return ctx.Err()
				}
			}
		case <-ctx.Done():
			return ctx.Err()
		}
	}
}

// Fsync flushes the content in the file to disk, but does not
// update the dag tree internally
func (fi *FileNode) Fsync(ctx context.Context, req *fuse.FsyncRequest) error {
	errs := make(chan error, 1)
	go func() {
		errs <- fi.fi.Sync()
	}()
	select {
	case err := <-errs:
		return err
	case <-ctx.Done():
		return ctx.Err()
	}
}

// Run runs the query at hand. pass in a list of peers to use first.
func (q *dhtQuery) Run(ctx context.Context, peers []peer.ID) (*dhtQueryResult, error) {
	select {
	case <-ctx.Done():
		return nil, ctx.Err()
	default:
	}

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

	runner := newQueryRunner(q)
	return runner.Run(ctx, peers)
}

func (np *nodePromise) Get(ctx context.Context) (*Node, error) {
	if np.cache != nil {
		return np.cache, nil
	}

	select {
	case blk := <-np.recv:
		np.cache = blk
	case <-np.ctx.Done():
		return nil, np.ctx.Err()
	case <-ctx.Done():
		return nil, ctx.Err()
	}
	return np.cache, nil
}

func (ms *messageSender) ctxReadMsg(ctx context.Context, mes *pb.Message) error {
	errc := make(chan error, 1)
	go func(r ggio.ReadCloser) {
		errc <- r.ReadMsg(mes)
	}(ms.r)

	t := time.NewTimer(dhtReadMessageTimeout)
	defer t.Stop()

	select {
	case err := <-errc:
		return err
	case <-ctx.Done():
		return ctx.Err()
	case <-t.C:
		return ErrReadTimeout
	}
}

func ContextDo(ctx context.Context, f func() error) error {

	ch := make(chan error)

	go func() {
		select {
		case <-ctx.Done():
		case ch <- f():
		}
	}()
	select {
	case <-ctx.Done():
		return ctx.Err()
	case val := <-ch:
		return val
	}
	return nil
}

// resolveOnce implements resolver.
// TXT records for a given domain name should contain a b58
// encoded multihash.
func (r *DNSResolver) resolveOnce(ctx context.Context, name string) (path.Path, error) {
	segments := strings.SplitN(name, "/", 2)
	domain := segments[0]

	if !isd.IsDomain(domain) {
		return "", errors.New("not a valid domain name")
	}
	log.Infof("DNSResolver resolving %s", domain)

	rootChan := make(chan lookupRes, 1)
	go workDomain(r, domain, rootChan)

	subChan := make(chan lookupRes, 1)
	go workDomain(r, "_dnslink."+domain, subChan)

	var subRes lookupRes
	select {
	case subRes = <-subChan:
	case <-ctx.Done():
		return "", ctx.Err()
	}

	var p path.Path
	if subRes.error == nil {
		p = subRes.path
	} else {
		var rootRes lookupRes
		select {
		case rootRes = <-rootChan:
		case <-ctx.Done():
			return "", ctx.Err()
		}
		if rootRes.error == nil {
			p = rootRes.path
		} else {
			return "", ErrResolveFailed
		}
	}
	if len(segments) > 1 {
		return path.FromSegments("", strings.TrimRight(p.String(), "/"), segments[1])
	} else {
		return p, nil
	}
}

func (np *nodePromise) Get(ctx context.Context) (*Node, error) {
	np.clk.Lock()
	c := np.cache
	np.clk.Unlock()
	if c != nil {
		return c, nil
	}

	select {
	case nd := <-np.recv:
		return nd, nil
	case <-np.ctx.Done():
		return nil, np.ctx.Err()
	case <-ctx.Done():
		return nil, ctx.Err()
	case err := <-np.err:
		return nil, err
	}
}

func GarbageCollect(n *core.IpfsNode, ctx context.Context) error {
	ctx, cancel := context.WithCancel(ctx)
	defer cancel() // in case error occurs during operation
	rmed, err := gc.GC(ctx, n.Blockstore, n.Pinning)
	if err != nil {
		return err
	}

	for {
		select {
		case _, ok := <-rmed:
			if !ok {
				return nil
			}
		case <-ctx.Done():
			return ctx.Err()
		}
	}

}

// nextEnvelope runs in the taskWorker goroutine. Returns an error if the
// context is cancelled before the next Envelope can be created.
func (e *Engine) nextEnvelope(ctx context.Context) (*Envelope, error) {
	for {
		nextTask := e.peerRequestQueue.Pop()
		for nextTask == nil {
			select {
			case <-ctx.Done():
				return nil, ctx.Err()
			case <-e.workSignal:
				nextTask = e.peerRequestQueue.Pop()
			case <-e.ticker.C:
				e.peerRequestQueue.thawRound()
				nextTask = e.peerRequestQueue.Pop()
			}
		}

		// with a task in hand, we're ready to prepare the envelope...

		block, err := e.bs.Get(nextTask.Entry.Key)
		if err != nil {
			// If we don't have the block, don't hold that against the peer
			// make sure to update that the task has been 'completed'
			nextTask.Done()
			continue
		}

		return &Envelope{
			Peer:  nextTask.Target,
			Block: block,
			Sent: func() {
				nextTask.Done()
				select {
				case e.workSignal <- struct{}{}:
					// work completing may mean that our queue will provide new
					// work to be done.
				default:
				}
			},
		}, nil
	}
}

func (fi *File) Read(ctx context.Context, req *fuse.ReadRequest, resp *fuse.ReadResponse) error {
	_, err := fi.fi.Seek(req.Offset, os.SEEK_SET)
	if err != nil {
		return err
	}

	fisize, err := fi.fi.Size()
	if err != nil {
		return err
	}

	select {
	case <-ctx.Done():
		return ctx.Err()
	default:
	}

	readsize := min(req.Size, int(fisize-req.Offset))
	n, err := fi.fi.CtxReadFull(ctx, resp.Data[:readsize])
	resp.Data = resp.Data[:n]
	return err
}