Golang context.OnClosingContext函数代码示例

// Bootstrap kicks off IpfsNode bootstrapping. This function will periodically
// check the number of open connections and -- if there are too few -- initiate
// connections to well-known bootstrap peers. It also kicks off subsystem
// bootstrapping (i.e. routing).
func Bootstrap(n *IpfsNode, cfg BootstrapConfig) (io.Closer, error) {

	// make a signal to wait for one bootstrap round to complete.
	doneWithRound := make(chan struct{})

	// the periodic bootstrap function -- the connection supervisor
	periodic := func(worker goprocess.Process) {
		ctx := procctx.OnClosingContext(worker)
		defer log.EventBegin(ctx, "periodicBootstrap", n.Identity).Done()

		if err := bootstrapRound(ctx, n.PeerHost, cfg); err != nil {
			log.Event(ctx, "bootstrapError", n.Identity, lgbl.Error(err))
			log.Debugf("%s bootstrap error: %s", n.Identity, err)
		}

		<-doneWithRound
	}

	// kick off the node's periodic bootstrapping
	proc := periodicproc.Tick(cfg.Period, periodic)
	proc.Go(periodic) // run one right now.

	// kick off Routing.Bootstrap
	if n.Routing != nil {
		ctx := procctx.OnClosingContext(proc)
		if err := n.Routing.Bootstrap(ctx); err != nil {
			proc.Close()
			return nil, err
		}
	}

	doneWithRound <- struct{}{}
	close(doneWithRound) // it no longer blocks periodic
	return proc, nil
}

func (rp *Republisher) republishEntries(p goprocess.Process) error {
	ctx, cancel := context.WithCancel(gpctx.OnClosingContext(p))
	defer cancel()

	for id, _ := range rp.entries {
		log.Debugf("republishing ipns entry for %s", id)
		priv := rp.ps.PrivKey(id)

		// Look for it locally only
		_, ipnskey := namesys.IpnsKeysForID(id)
		p, seq, err := rp.getLastVal(ipnskey)
		if err != nil {
			if err == errNoEntry {
				continue
			}
			return err
		}

		// update record with same sequence number
		eol := time.Now().Add(rp.RecordLifetime)
		err = namesys.PutRecordToRouting(ctx, priv, p, seq, eol, rp.r, id)
		if err != nil {
			return err
		}
	}

	return nil
}

func (bs *Bitswap) provideWorker(px process.Process) {

	limit := make(chan struct{}, provideWorkerMax)

	limitedGoProvide := func(k key.Key, wid int) {
		defer func() {
			// replace token when done
			<-limit
		}()
		ev := logging.LoggableMap{"ID": wid}

		ctx := procctx.OnClosingContext(px) // derive ctx from px
		defer log.EventBegin(ctx, "Bitswap.ProvideWorker.Work", ev, &k).Done()

		ctx, cancel := context.WithTimeout(ctx, provideTimeout) // timeout ctx
		defer cancel()

		if err := bs.network.Provide(ctx, k); err != nil {
			log.Warning(err)
		}
	}

	// worker spawner, reads from bs.provideKeys until it closes, spawning a
	// _ratelimited_ number of workers to handle each key.
	for wid := 2; ; wid++ {
		ev := logging.LoggableMap{"ID": 1}
		log.Event(procctx.OnClosingContext(px), "Bitswap.ProvideWorker.Loop", ev)

		select {
		case <-px.Closing():
			return
		case k, ok := <-bs.provideKeys:
			if !ok {
				log.Debug("provideKeys channel closed")
				return
			}
			select {
			case <-px.Closing():
				return
			case limit <- struct{}{}:
				go limitedGoProvide(k, wid)
			}
		}
	}
}

func newQueryRunner(q *dhtQuery) *dhtQueryRunner {
	proc := process.WithParent(process.Background())
	ctx := ctxproc.OnClosingContext(proc)
	return &dhtQueryRunner{
		query:          q,
		peersToQuery:   queue.NewChanQueue(ctx, queue.NewXORDistancePQ(string(q.key))),
		peersRemaining: todoctr.NewSyncCounter(),
		peersSeen:      pset.New(),
		rateLimit:      make(chan struct{}, q.concurrency),
		proc:           proc,
	}
}

func (r *dhtQueryRunner) queryPeer(proc process.Process, p peer.ID) {
	// ok let's do this!

	// create a context from our proc.
	ctx := ctxproc.OnClosingContext(proc)

	// make sure we do this when we exit
	defer func() {
		// signal we're done proccessing peer p
		r.peersRemaining.Decrement(1)
		r.rateLimit <- struct{}{}
	}()

	// make sure we're connected to the peer.
	// FIXME abstract away into the network layer
	if conns := r.query.dht.host.Network().ConnsToPeer(p); len(conns) == 0 {
		log.Debug("not connected. dialing.")

		notif.PublishQueryEvent(r.runCtx, &notif.QueryEvent{
			Type: notif.DialingPeer,
			ID:   p,
		})
		// while we dial, we do not take up a rate limit. this is to allow
		// forward progress during potentially very high latency dials.
		r.rateLimit <- struct{}{}

		pi := peer.PeerInfo{ID: p}

		if err := r.query.dht.host.Connect(ctx, pi); err != nil {
			log.Debugf("Error connecting: %s", err)

			notif.PublishQueryEvent(r.runCtx, &notif.QueryEvent{
				Type:  notif.QueryError,
				Extra: err.Error(),
				ID:    p,
			})

			r.Lock()
			r.errs = append(r.errs, err)
			r.Unlock()
			<-r.rateLimit // need to grab it again, as we deferred.
			return
		}
		<-r.rateLimit // need to grab it again, as we deferred.
		log.Debugf("connected. dial success.")
	}

	// finally, run the query against this peer
	res, err := r.query.qfunc(ctx, p)

	if err != nil {
		log.Debugf("ERROR worker for: %v %v", p, err)
		r.Lock()
		r.errs = append(r.errs, err)
		r.Unlock()

	} else if res.success {
		log.Debugf("SUCCESS worker for: %v %s", p, res)
		r.Lock()
		r.result = res
		r.Unlock()
		go r.proc.Close() // signal to everyone that we're done.
		// must be async, as we're one of the children, and Close blocks.

	} else if len(res.closerPeers) > 0 {
		log.Debugf("PEERS CLOSER -- worker for: %v (%d closer peers)", p, len(res.closerPeers))
		for _, next := range res.closerPeers {
			if next.ID == r.query.dht.self { // dont add self.
				log.Debugf("PEERS CLOSER -- worker for: %v found self", p)
				continue
			}

			// add their addresses to the dialer's peerstore
			r.query.dht.peerstore.AddAddrs(next.ID, next.Addrs, peer.TempAddrTTL)
			r.addPeerToQuery(next.ID)
			log.Debugf("PEERS CLOSER -- worker for: %v added %v (%v)", p, next.ID, next.Addrs)
		}
	} else {
		log.Debugf("QUERY worker for: %v - not found, and no closer peers.", p)
	}
}