Golang Context.Done方法代码示例

// Subscribe returns a channel of blocks for the given |keys|. |blockChannel|
// is closed if the |ctx| times out or is cancelled, or after sending len(keys)
// blocks.
func (ps *impl) Subscribe(ctx context.Context, keys ...*cid.Cid) <-chan blocks.Block {

	blocksCh := make(chan blocks.Block, len(keys))
	valuesCh := make(chan interface{}, len(keys)) // provide our own channel to control buffer, prevent blocking
	if len(keys) == 0 {
		close(blocksCh)
		return blocksCh
	}
	ps.wrapped.AddSubOnceEach(valuesCh, toStrings(keys)...)
	go func() {
		defer close(blocksCh)
		defer ps.wrapped.Unsub(valuesCh) // with a len(keys) buffer, this is an optimization
		for {
			select {
			case <-ctx.Done():
				return
			case val, ok := <-valuesCh:
				if !ok {
					return
				}
				block, ok := val.(blocks.Block)
				if !ok {
					return
				}
				select {
				case <-ctx.Done():
					return
				case blocksCh <- block: // continue
				}
			}
		}
	}()

	return blocksCh
}

// ScanFiles takes a chanel of files
func ScanFilesToBytes(ctx context.Context, in chan File) chan Content {

	out := make(chan Content)

	go func() {

		defer close(out)

		for {
			select {
			case value, open := <-in:
				if !open {
					return
				}
				if value.Err != nil {
					out <- Content{"", nil, kerr.Wrap("PQUCOUYLJE", value.Err)}
					return
				}
				bytes, err := ProcessFile(value.File)
				// process returns Bytes == nil for non json files, so we should skip them
				if bytes != nil || err != nil {
					out <- Content{value.File, bytes, err}
				}
			case <-ctx.Done():
				out <- Content{"", nil, kerr.Wrap("AFBJCTFOKX", ctx.Err())}
				return
			}
		}

	}()

	return out

}

func (ps *PingService) Ping(ctx context.Context, p peer.ID) (<-chan time.Duration, error) {
	s, err := ps.Host.NewStream(ctx, p, ID)
	if err != nil {
		return nil, err
	}

	out := make(chan time.Duration)
	go func() {
		defer close(out)
		defer s.Close()
		for {
			select {
			case <-ctx.Done():
				return
			default:
				t, err := ping(s)
				if err != nil {
					log.Debugf("ping error: %s", err)
					return
				}

				ps.Host.Peerstore().RecordLatency(p, t)
				select {
				case out <- t:
				case <-ctx.Done():
					return
				}
			}
		}
	}()

	return out, nil
}

func (e *offlineExchange) GetBlocks(ctx context.Context, ks []*cid.Cid) (<-chan blocks.Block, error) {
	out := make(chan blocks.Block, 0)
	go func() {
		defer close(out)
		var misses []*cid.Cid
		for _, k := range ks {
			hit, err := e.bs.Get(k)
			if err != nil {
				misses = append(misses, k)
				// a long line of misses should abort when context is cancelled.
				select {
				// TODO case send misses down channel
				case <-ctx.Done():
					return
				default:
					continue
				}
			}
			select {
			case out <- hit:
			case <-ctx.Done():
				return
			}
		}
	}()
	return out, nil
}

// FindProvidersAsync returns a channel of providers for the given key
func (bsnet *impl) FindProvidersAsync(ctx context.Context, k *cid.Cid, max int) <-chan peer.ID {

	// Since routing queries are expensive, give bitswap the peers to which we
	// have open connections. Note that this may cause issues if bitswap starts
	// precisely tracking which peers provide certain keys. This optimization
	// would be misleading. In the long run, this may not be the most
	// appropriate place for this optimization, but it won't cause any harm in
	// the short term.
	connectedPeers := bsnet.host.Network().Peers()
	out := make(chan peer.ID, len(connectedPeers)) // just enough buffer for these connectedPeers
	for _, id := range connectedPeers {
		if id == bsnet.host.ID() {
			continue // ignore self as provider
		}
		out <- id
	}

	go func() {
		defer close(out)
		providers := bsnet.routing.FindProvidersAsync(ctx, k, max)
		for info := range providers {
			if info.ID == bsnet.host.ID() {
				continue // ignore self as provider
			}
			bsnet.host.Peerstore().AddAddrs(info.ID, info.Addrs, pstore.TempAddrTTL)
			select {
			case <-ctx.Done():
				return
			case out <- info.ID:
			}
		}
	}()
	return out
}

func storageLoop(ctx context.Context, local *localNode, remotes *remoteNodes, notify <-chan struct{}, reply chan<- []*net.UDPAddr, done chan<- struct{}, client *s3.S3, bucket, prefix, localKey string, log *Log) {
	defer func() {
		updateStorage(local.empty(), client, bucket, localKey, log)
		close(done)
	}()

	timer := time.NewTimer(randomStorageInterval())

	for {
		var scan bool

		select {
		case <-notify:
			scan = false

		case <-timer.C:
			timer.Reset(randomStorageInterval())
			scan = true

		case <-ctx.Done():
			timer.Stop()
			return
		}

		if err := updateStorage(local, client, bucket, localKey, log); err != nil {
			log.Error(err)
		}

		if scan {
			if err := scanStorage(local, remotes, reply, client, bucket, prefix, log); err != nil {
				log.Error(err)
			}
		}
	}
}

func (ds *dagService) GetMany(ctx context.Context, keys []*cid.Cid) <-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 := decodeBlock(b)
				if err != nil {
					out <- &NodeOption{Err: err}
					return
				}

				out <- &NodeOption{Node: nd}
				count++

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

func paintLines(ctx context.Context, r io.Reader, source string) {
	scanner := bufio.NewScanner(r)
	doneC := ctx.Done()
	for scanner.Scan() {
		lsp.Println(source, scanner.Text())
		select {
		case <-doneC:
			break
		default:
			// do nothing
		}
	}

	if err := ctx.Err(); err != nil {
		errC <- err
		return
	}

	if err := scanner.Err(); err != nil {
		errC <- err
		return
	}

	errC <- nil
}

// bloomCached returns Blockstore that caches Has requests using Bloom filter
// Size is size of bloom filter in bytes
func bloomCached(bs Blockstore, ctx context.Context, bloomSize, hashCount int) (*bloomcache, error) {
	bl, err := bloom.New(float64(bloomSize), float64(hashCount))
	if err != nil {
		return nil, err
	}
	bc := &bloomcache{blockstore: bs, bloom: bl}
	bc.hits = metrics.NewCtx(ctx, "bloom.hits_total",
		"Number of cache hits in bloom cache").Counter()
	bc.total = metrics.NewCtx(ctx, "bloom_total",
		"Total number of requests to bloom cache").Counter()

	bc.Invalidate()
	go bc.Rebuild(ctx)
	if metrics.Active() {
		go func() {
			fill := metrics.NewCtx(ctx, "bloom_fill_ratio",
				"Ratio of bloom filter fullnes, (updated once a minute)").Gauge()

			<-bc.rebuildChan
			t := time.NewTicker(1 * time.Minute)
			for {
				select {
				case <-ctx.Done():
					t.Stop()
					return
				case <-t.C:
					fill.Set(bc.bloom.FillRatio())
				}
			}
		}()
	}
	return bc, nil
}

func (e *apiClient) PerformRequests(ctx context.Context, queries []QueryToSend) (*tsdb.QueryResult, error) {
	queryResult := &tsdb.QueryResult{}

	queryCount := len(queries)
	jobsChan := make(chan QueryToSend, queryCount)
	resultChan := make(chan []*tsdb.TimeSeries, queryCount)
	errorsChan := make(chan error, 1)
	for w := 1; w <= MaxWorker; w++ {
		go e.spawnWorker(ctx, w, jobsChan, resultChan, errorsChan)
	}

	for _, v := range queries {
		jobsChan <- v
	}
	close(jobsChan)

	resultCounter := 0
	for {
		select {
		case timeseries := <-resultChan:
			queryResult.Series = append(queryResult.Series, timeseries...)
			resultCounter++

			if resultCounter == queryCount {
				close(resultChan)
				return queryResult, nil
			}
		case err := <-errorsChan:
			return nil, err
		case <-ctx.Done():
			return nil, ctx.Err()
		}
	}
}

func (mq *msgQueue) doWork(ctx context.Context) {
	if mq.sender == nil {
		err := mq.openSender(ctx)
		if err != nil {
			log.Infof("cant open message sender to peer %s: %s", mq.p, err)
			// TODO: cant connect, what now?
			return
		}
	}

	// grab outgoing message
	mq.outlk.Lock()
	wlm := mq.out
	if wlm == nil || wlm.Empty() {
		mq.outlk.Unlock()
		return
	}
	mq.out = nil
	mq.outlk.Unlock()

	// send wantlist updates
	for { // try to send this message until we fail.
		err := mq.sender.SendMsg(wlm)
		if err == nil {
			return
		}

		log.Infof("bitswap send error: %s", err)
		mq.sender.Close()
		mq.sender = nil

		select {
		case <-mq.done:
			return
		case <-ctx.Done():
			return
		case <-time.After(time.Millisecond * 100):
			// wait 100ms in case disconnect notifications are still propogating
			log.Warning("SendMsg errored but neither 'done' nor context.Done() were set")
		}

		err = mq.openSender(ctx)
		if err != nil {
			log.Errorf("couldnt open sender again after SendMsg(%s) failed: %s", mq.p, err)
			// TODO(why): what do we do now?
			// I think the *right* answer is to probably put the message we're
			// trying to send back, and then return to waiting for new work or
			// a disconnect.
			return
		}

		// TODO: Is this the same instance for the remote peer?
		// If its not, we should resend our entire wantlist to them
		/*
			if mq.sender.InstanceID() != mq.lastSeenInstanceID {
				wlm = mq.getFullWantlistMessage()
			}
		*/
	}
}

func cgoLookupPTR(ctx context.Context, addr string) (names []string, err error, completed bool) {
	var zone string
	ip := parseIPv4(addr)
	if ip == nil {
		ip, zone = parseIPv6(addr, true)
	}
	if ip == nil {
		return nil, &DNSError{Err: "invalid address", Name: addr}, true
	}
	sa, salen := cgoSockaddr(ip, zone)
	if sa == nil {
		return nil, &DNSError{Err: "invalid address " + ip.String(), Name: addr}, true
	}
	if ctx.Done() == nil {
		names, err := cgoLookupAddrPTR(addr, sa, salen)
		return names, err, true
	}
	result := make(chan reverseLookupResult, 1)
	go cgoReverseLookup(result, addr, sa, salen)
	select {
	case r := <-result:
		return r.names, r.err, true
	case <-ctx.Done():
		return nil, mapErr(ctx.Err()), false
	}
}

func (bs *Bitswap) provideCollector(ctx context.Context) {
	defer close(bs.provideKeys)
	var toProvide []*cid.Cid
	var nextKey *cid.Cid
	var keysOut chan *cid.Cid

	for {
		select {
		case blkey, ok := <-bs.newBlocks:
			if !ok {
				log.Debug("newBlocks channel closed")
				return
			}

			if keysOut == nil {
				nextKey = blkey
				keysOut = bs.provideKeys
			} else {
				toProvide = append(toProvide, blkey)
			}
		case keysOut <- nextKey:
			if len(toProvide) > 0 {
				nextKey = toProvide[0]
				toProvide = toProvide[1:]
			} else {
				keysOut = nil
			}
		case <-ctx.Done():
			return
		}
	}
}

func (bs *Bitswap) taskWorker(ctx context.Context, id int) {
	idmap := logging.LoggableMap{"ID": id}
	defer log.Info("bitswap task worker shutting down...")
	for {
		log.Event(ctx, "Bitswap.TaskWorker.Loop", idmap)
		select {
		case nextEnvelope := <-bs.engine.Outbox():
			select {
			case envelope, ok := <-nextEnvelope:
				if !ok {
					continue
				}
				log.Event(ctx, "Bitswap.TaskWorker.Work", logging.LoggableMap{
					"ID":     id,
					"Target": envelope.Peer.Pretty(),
					"Block":  envelope.Block.Cid().String(),
				})

				bs.wm.SendBlock(ctx, envelope)
			case <-ctx.Done():
				return
			}
		case <-ctx.Done():
			return
		}
	}
}

func absFilepath(ctx context.Context, filename string) <-chan string {
	ch := make(chan string)
	go func() {
		var (
			err error
		)
		defer func() {
			if err != nil {
				<-ctx.Done()
				close(ch)
				return
			}
			select {
			case <-ctx.Done():
				close(ch)
			default:
				ch <- filename
				close(ch)
			}
		}()
		if !filepath.IsAbs(filename) {
			err = errors.New("filename is not abs")
			return
		}
		fi, err := os.Lstat(filename)
		if err != nil {
			return
		}
		if fi.IsDir() {
			err = ErrNotFile
			return
		}
	}()
	return ch
}