path: root/swarm/network/stream/stream.go

// Copyright 2018 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package stream

import (
    "context"
    "errors"
    "fmt"
    "math"
    "reflect"
    "sync"
    "time"

    "github.com/ethereum/go-ethereum/metrics"
    "github.com/ethereum/go-ethereum/p2p"
    "github.com/ethereum/go-ethereum/p2p/enode"
    "github.com/ethereum/go-ethereum/p2p/protocols"
    "github.com/ethereum/go-ethereum/rpc"
    "github.com/ethereum/go-ethereum/swarm/log"
    "github.com/ethereum/go-ethereum/swarm/network"
    "github.com/ethereum/go-ethereum/swarm/network/stream/intervals"
    "github.com/ethereum/go-ethereum/swarm/state"
    "github.com/ethereum/go-ethereum/swarm/storage"
)

const (
    Low uint8 = iota
    Mid
    High
    Top
    PriorityQueue    = 4    // number of priority queues - Low, Mid, High, Top
    PriorityQueueCap = 4096 // queue capacity
    HashSize         = 32
)

// Enumerate options for syncing and retrieval
type SyncingOption int
type RetrievalOption int

// Syncing options
const (
    // Syncing disabled
    SyncingDisabled SyncingOption = iota
    // Register the client and the server but not subscribe
    SyncingRegisterOnly
    // Both client and server funcs are registered, subscribe sent automatically
    SyncingAutoSubscribe
)

const (
    // Retrieval disabled. Used mostly for tests to isolate syncing features (i.e. syncing only)
    RetrievalDisabled RetrievalOption = iota
    // Only the client side of the retrieve request is registered.
    // (light nodes do not serve retrieve requests)
    // once the client is registered, subscription to retrieve request stream is always sent
    RetrievalClientOnly
    // Both client and server funcs are registered, subscribe sent automatically
    RetrievalEnabled
)

// subscriptionFunc is used to determine what to do in order to perform subscriptions
// usually we would start to really subscribe to nodes, but for tests other functionality may be needed
// (see TestRequestPeerSubscriptions in streamer_test.go)
var subscriptionFunc func(r *Registry, p *network.Peer, bin uint8, subs map[enode.ID]map[Stream]struct{}) bool = doRequestSubscription

// Registry registry for outgoing and incoming streamer constructors
type Registry struct {
    addr           enode.ID
    api            *API
    skipCheck      bool
    clientMu       sync.RWMutex
    serverMu       sync.RWMutex
    peersMu        sync.RWMutex
    serverFuncs    map[string]func(*Peer, string, bool) (Server, error)
    clientFuncs    map[string]func(*Peer, string, bool) (Client, error)
    peers          map[enode.ID]*Peer
    delivery       *Delivery
    intervalsStore state.Store
    autoRetrieval  bool // automatically subscribe to retrieve request stream
    maxPeerServers int
    spec           *protocols.Spec   //this protocol's spec
    balance        protocols.Balance //implements protocols.Balance, for accounting
    prices         protocols.Prices  //implements protocols.Prices, provides prices to accounting
}

// RegistryOptions holds optional values for NewRegistry constructor.
type RegistryOptions struct {
    SkipCheck       bool
    Syncing         SyncingOption   // Defines syncing behavior
    Retrieval       RetrievalOption // Defines retrieval behavior
    SyncUpdateDelay time.Duration
    MaxPeerServers  int // The limit of servers for each peer in registry
}

// NewRegistry is Streamer constructor
func NewRegistry(localID enode.ID, delivery *Delivery, syncChunkStore storage.SyncChunkStore, intervalsStore state.Store, options *RegistryOptions, balance protocols.Balance) *Registry {
    if options == nil {
        options = &RegistryOptions{}
    }
    if options.SyncUpdateDelay <= 0 {
        options.SyncUpdateDelay = 15 * time.Second
    }
    // check if retrieval has been disabled
    retrieval := options.Retrieval != RetrievalDisabled

    streamer := &Registry{
        addr:           localID,
        skipCheck:      options.SkipCheck,
        serverFuncs:    make(map[string]func(*Peer, string, bool) (Server, error)),
        clientFuncs:    make(map[string]func(*Peer, string, bool) (Client, error)),
        peers:          make(map[enode.ID]*Peer),
        delivery:       delivery,
        intervalsStore: intervalsStore,
        autoRetrieval:  retrieval,
        maxPeerServers: options.MaxPeerServers,
        balance:        balance,
    }

    streamer.setupSpec()

    streamer.api = NewAPI(streamer)
    delivery.getPeer = streamer.getPeer

    // if retrieval is enabled, register the server func, so that retrieve requests will be served (non-light nodes only)
    if options.Retrieval == RetrievalEnabled {
        streamer.RegisterServerFunc(swarmChunkServerStreamName, func(_ *Peer, _ string, live bool) (Server, error) {
            if !live {
                return nil, errors.New("only live retrieval requests supported")
            }
            return NewSwarmChunkServer(delivery.chunkStore), nil
        })
    }

    // if retrieval is not disabled, register the client func (both light nodes and normal nodes can issue retrieve requests)
    if options.Retrieval != RetrievalDisabled {
        streamer.RegisterClientFunc(swarmChunkServerStreamName, func(p *Peer, t string, live bool) (Client, error) {
            return NewSwarmSyncerClient(p, syncChunkStore, NewStream(swarmChunkServerStreamName, t, live))
        })
    }

    // If syncing is not disabled, the syncing functions are registered (both client and server)
    if options.Syncing != SyncingDisabled {
        RegisterSwarmSyncerServer(streamer, syncChunkStore)
        RegisterSwarmSyncerClient(streamer, syncChunkStore)
    }

    // if syncing is set to automatically subscribe to the syncing stream, start the subscription process
    if options.Syncing == SyncingAutoSubscribe {
        // latestIntC function ensures that
        //   - receiving from the in chan is not blocked by processing inside the for loop
        //   - the latest int value is delivered to the loop after the processing is done
        // In context of NeighbourhoodDepthC:
        // after the syncing is done updating inside the loop, we do not need to update on the intermediate
        // depth changes, only to the latest one
        latestIntC := func(in <-chan int) <-chan int {
            out := make(chan int, 1)

            go func() {
                defer close(out)

                for i := range in {
                    select {
                    case <-out:
                    default:
                    }
                    out <- i
                }
            }()

            return out
        }

        go func() {
            // wait for kademlia table to be healthy
            time.Sleep(options.SyncUpdateDelay)

            kad := streamer.delivery.kad
            depthC := latestIntC(kad.NeighbourhoodDepthC())
            addressBookSizeC := latestIntC(kad.AddrCountC())

            // initial requests for syncing subscription to peers
            streamer.updateSyncing()

            for depth := range depthC {
                log.Debug("Kademlia neighbourhood depth change", "depth", depth)

                // Prevent too early sync subscriptions by waiting until there are no
                // new peers connecting. Sync streams updating will be done after no
                // peers are connected for at least SyncUpdateDelay period.
                timer := time.NewTimer(options.SyncUpdateDelay)
                // Hard limit to sync update delay, preventing long delays
                // on a very dynamic network
                maxTimer := time.NewTimer(3 * time.Minute)
            loop:
                for {
                    select {
                    case <-maxTimer.C:
                        // force syncing update when a hard timeout is reached
                        log.Trace("Sync subscriptions update on hard timeout")
                        // request for syncing subscription to new peers
                        streamer.updateSyncing()
                        break loop
                    case <-timer.C:
                        // start syncing as no new peers has been added to kademlia
                        // for some time
                        log.Trace("Sync subscriptions update")
                        // request for syncing subscription to new peers
                        streamer.updateSyncing()
                        break loop
                    case size := <-addressBookSizeC:
                        log.Trace("Kademlia address book size changed on depth change", "size", size)
                        // new peers has been added to kademlia,
                        // reset the timer to prevent early sync subscriptions
                        if !timer.Stop() {
                            <-timer.C
                        }
                        timer.Reset(options.SyncUpdateDelay)
                    }
                }
                timer.Stop()
                maxTimer.Stop()
            }
        }()
    }

    return streamer
}

// This is an accounted protocol, therefore we need to provide a pricing Hook to the spec
// For simulations to be able to run multiple nodes and not override the hook's balance,
// we need to construct a spec instance per node instance
func (r *Registry) setupSpec() {
    // first create the "bare" spec
    r.createSpec()
    // now create the pricing object
    r.createPriceOracle()
    // if balance is nil, this node has been started without swap support (swapEnabled flag is false)
    if r.balance != nil && !reflect.ValueOf(r.balance).IsNil() {
        // swap is enabled, so setup the hook
        r.spec.Hook = protocols.NewAccounting(r.balance, r.prices)
    }
}

// RegisterClient registers an incoming streamer constructor
func (r *Registry) RegisterClientFunc(stream string, f func(*Peer, string, bool) (Client, error)) {
    r.clientMu.Lock()
    defer r.clientMu.Unlock()

    r.clientFuncs[stream] = f
}

// RegisterServer registers an outgoing streamer constructor
func (r *Registry) RegisterServerFunc(stream string, f func(*Peer, string, bool) (Server, error)) {
    r.serverMu.Lock()
    defer r.serverMu.Unlock()

    r.serverFuncs[stream] = f
}

// GetClient accessor for incoming streamer constructors
func (r *Registry) GetClientFunc(stream string) (func(*Peer, string, bool) (Client, error), error) {
    r.clientMu.RLock()
    defer r.clientMu.RUnlock()

    f := r.clientFuncs[stream]
    if f == nil {
        return nil, fmt.Errorf("stream %v not registered", stream)
    }
    return f, nil
}

// GetServer accessor for incoming streamer constructors
func (r *Registry) GetServerFunc(stream string) (func(*Peer, string, bool) (Server, error), error) {
    r.serverMu.RLock()
    defer r.serverMu.RUnlock()

    f := r.serverFuncs[stream]
    if f == nil {
        return nil, fmt.Errorf("stream %v not registered", stream)
    }
    return f, nil
}

func (r *Registry) RequestSubscription(peerId enode.ID, s Stream, h *Range, prio uint8) error {
    // check if the stream is registered
    if _, err := r.GetServerFunc(s.Name); err != nil {
        return err
    }

    peer := r.getPeer(peerId)
    if peer == nil {
        return fmt.Errorf("peer not found %v", peerId)
    }

    if _, err := peer.getServer(s); err != nil {
        if e, ok := err.(*notFoundError); ok && e.t == "server" {
            // request subscription only if the server for this stream is not created
            log.Debug("RequestSubscription ", "peer", peerId, "stream", s, "history", h)
            return peer.Send(context.TODO(), &RequestSubscriptionMsg{
                Stream:   s,
                History:  h,
                Priority: prio,
            })
        }
        return err
    }
    log.Trace("RequestSubscription: already subscribed", "peer", peerId, "stream", s, "history", h)
    return nil
}

// Subscribe initiates the streamer
func (r *Registry) Subscribe(peerId enode.ID, s Stream, h *Range, priority uint8) error {
    // check if the stream is registered
    if _, err := r.GetClientFunc(s.Name); err != nil {
        return err
    }

    peer := r.getPeer(peerId)
    if peer == nil {
        return fmt.Errorf("peer not found %v", peerId)
    }

    var to uint64
    if !s.Live && h != nil {
        to = h.To
    }

    err := peer.setClientParams(s, newClientParams(priority, to))
    if err != nil {
        return err
    }
    if s.Live && h != nil {
        if err := peer.setClientParams(
            getHistoryStream(s),
            newClientParams(getHistoryPriority(priority), h.To),
        ); err != nil {
            return err
        }
    }

    msg := &SubscribeMsg{
        Stream:   s,
        History:  h,
        Priority: priority,
    }
    log.Debug("Subscribe ", "peer", peerId, "stream", s, "history", h)

    return peer.SendPriority(context.TODO(), msg, priority)
}

func (r *Registry) Unsubscribe(peerId enode.ID, s Stream) error {
    peer := r.getPeer(peerId)
    if peer == nil {
        return fmt.Errorf("peer not found %v", peerId)
    }

    msg := &UnsubscribeMsg{
        Stream: s,
    }
    log.Debug("Unsubscribe ", "peer", peerId, "stream", s)

    if err := peer.Send(context.TODO(), msg); err != nil {
        return err
    }
    return peer.removeClient(s)
}

// Quit sends the QuitMsg to the peer to remove the
// stream peer client and terminate the streaming.
func (r *Registry) Quit(peerId enode.ID, s Stream) error {
    peer := r.getPeer(peerId)
    if peer == nil {
        log.Debug("stream quit: peer not found", "peer", peerId, "stream", s)
        // if the peer is not found, abort the request
        return nil
    }

    msg := &QuitMsg{
        Stream: s,
    }
    log.Debug("Quit ", "peer", peerId, "stream", s)

    return peer.Send(context.TODO(), msg)
}

func (r *Registry) Close() error {
    return r.intervalsStore.Close()
}

func (r *Registry) getPeer(peerId enode.ID) *Peer {
    r.peersMu.RLock()
    defer r.peersMu.RUnlock()

    return r.peers[peerId]
}

func (r *Registry) setPeer(peer *Peer) {
    r.peersMu.Lock()
    r.peers[peer.ID()] = peer
    metrics.GetOrRegisterGauge("registry.peers", nil).Update(int64(len(r.peers)))
    r.peersMu.Unlock()
}

func (r *Registry) deletePeer(peer *Peer) {
    r.peersMu.Lock()
    delete(r.peers, peer.ID())
    metrics.GetOrRegisterGauge("registry.peers", nil).Update(int64(len(r.peers)))
    r.peersMu.Unlock()
}

func (r *Registry) peersCount() (c int) {
    r.peersMu.Lock()
    c = len(r.peers)
    r.peersMu.Unlock()
    return
}

// Run protocol run function
func (r *Registry) Run(p *network.BzzPeer) error {
    sp := NewPeer(p.Peer, r)
    r.setPeer(sp)
    defer r.deletePeer(sp)
    defer close(sp.quit)
    defer sp.close()

    if r.autoRetrieval && !p.LightNode {
        err := r.Subscribe(p.ID(), NewStream(swarmChunkServerStreamName, "", true), nil, Top)
        if err != nil {
            return err
        }
    }

    return sp.Run(sp.HandleMsg)
}

// updateSyncing subscribes to SYNC streams by iterating over the
// kademlia connections and bins. If there are existing SYNC streams
// and they are no longer required after iteration, request to Quit
// them will be send to appropriate peers.
func (r *Registry) updateSyncing() {
    kad := r.delivery.kad
    // map of all SYNC streams for all peers
    // used at the and of the function to remove servers
    // that are not needed anymore
    subs := make(map[enode.ID]map[Stream]struct{})
    r.peersMu.RLock()
    for id, peer := range r.peers {
        peer.serverMu.RLock()
        for stream := range peer.servers {
            if stream.Name == "SYNC" {
                if _, ok := subs[id]; !ok {
                    subs[id] = make(map[Stream]struct{})
                }
                subs[id][stream] = struct{}{}
            }
        }
        peer.serverMu.RUnlock()
    }
    r.peersMu.RUnlock()

    // start requesting subscriptions from peers
    r.requestPeerSubscriptions(kad, subs)

    // remove SYNC servers that do not need to be subscribed
    for id, streams := range subs {
        if len(streams) == 0 {
            continue
        }
        peer := r.getPeer(id)
        if peer == nil {
            continue
        }
        for stream := range streams {
            log.Debug("Remove sync server", "peer", id, "stream", stream)
            err := r.Quit(peer.ID(), stream)
            if err != nil && err != p2p.ErrShuttingDown {
                log.Error("quit", "err", err, "peer", peer.ID(), "stream", stream)
            }
        }
    }
}

// requestPeerSubscriptions calls on each live peer in the kademlia table
// and sends a `RequestSubscription` to peers according to their bin
// and their relationship with kademlia's depth.
// Also check `TestRequestPeerSubscriptions` in order to understand the
// expected behavior.
// The function expects:
//   * the kademlia
//   * a map of subscriptions
//   * the actual function to subscribe
//     (in case of the test, it doesn't do real subscriptions)
func (r *Registry) requestPeerSubscriptions(kad *network.Kademlia, subs map[enode.ID]map[Stream]struct{}) {

    var startPo int
    var endPo int
    var ok bool

    // kademlia's depth
    kadDepth := kad.NeighbourhoodDepth()
    // request subscriptions for all nodes and bins
    // nil as base takes the node's base; we need to pass 255 as `EachConn` runs
    // from deepest bins backwards
    kad.EachConn(nil, 255, func(p *network.Peer, po int) bool {
        // nodes that do not provide stream protocol
        // should not be subscribed, e.g. bootnodes
        if !p.HasCap("stream") {
            return true
        }
        //if the peer's bin is shallower than the kademlia depth,
        //only the peer's bin should be subscribed
        if po < kadDepth {
            startPo = po
            endPo = po
        } else {
            //if the peer's bin is equal or deeper than the kademlia depth,
            //each bin from the depth up to k.MaxProxDisplay should be subscribed
            startPo = kadDepth
            endPo = kad.MaxProxDisplay
        }

        for bin := startPo; bin <= endPo; bin++ {
            //do the actual subscription
            ok = subscriptionFunc(r, p, uint8(bin), subs)
        }
        return ok
    })
}

// doRequestSubscription sends the actual RequestSubscription to the peer
func doRequestSubscription(r *Registry, p *network.Peer, bin uint8, subs map[enode.ID]map[Stream]struct{}) bool {
    log.Debug("Requesting subscription by registry:", "registry", r.addr, "peer", p.ID(), "bin", bin)
    // bin is always less then 256 and it is safe to convert it to type uint8
    stream := NewStream("SYNC", FormatSyncBinKey(bin), true)
    if streams, ok := subs[p.ID()]; ok {
        // delete live and history streams from the map, so that it won't be removed with a Quit request
        delete(streams, stream)
        delete(streams, getHistoryStream(stream))
    }
    err := r.RequestSubscription(p.ID(), stream, NewRange(0, 0), High)
    if err != nil {
        log.Debug("Request subscription", "err", err, "peer", p.ID(), "stream", stream)
        return false
    }
    return true
}

func (r *Registry) runProtocol(p *p2p.Peer, rw p2p.MsgReadWriter) error {
    peer := protocols.NewPeer(p, rw, r.spec)
    bp := network.NewBzzPeer(peer)
    np := network.NewPeer(bp, r.delivery.kad)
    r.delivery.kad.On(np)
    defer r.delivery.kad.Off(np)
    return r.Run(bp)
}

// HandleMsg is the message handler that delegates incoming messages
func (p *Peer) HandleMsg(ctx context.Context, msg interface{}) error {
    switch msg := msg.(type) {

    case *SubscribeMsg:
        return p.handleSubscribeMsg(ctx, msg)

    case *SubscribeErrorMsg:
        return p.handleSubscribeErrorMsg(msg)

    case *UnsubscribeMsg:
        return p.handleUnsubscribeMsg(msg)

    case *OfferedHashesMsg:
        return p.handleOfferedHashesMsg(ctx, msg)

    case *TakeoverProofMsg:
        return p.handleTakeoverProofMsg(ctx, msg)

    case *WantedHashesMsg:
        return p.handleWantedHashesMsg(ctx, msg)

    case *ChunkDeliveryMsgRetrieval:
        // handling chunk delivery is the same for retrieval and syncing, so let's cast the msg
        return p.streamer.delivery.handleChunkDeliveryMsg(ctx, p, ((*ChunkDeliveryMsg)(msg)))

    case *ChunkDeliveryMsgSyncing:
        // handling chunk delivery is the same for retrieval and syncing, so let's cast the msg
        return p.streamer.delivery.handleChunkDeliveryMsg(ctx, p, ((*ChunkDeliveryMsg)(msg)))

    case *RetrieveRequestMsg:
        return p.streamer.delivery.handleRetrieveRequestMsg(ctx, p, msg)

    case *RequestSubscriptionMsg:
        return p.handleRequestSubscription(ctx, msg)

    case *QuitMsg:
        return p.handleQuitMsg(msg)

    default:
        return fmt.Errorf("unknown message type: %T", msg)
    }
}

type server struct {
    Server
    stream       Stream
    priority     uint8
    currentBatch []byte
    sessionIndex uint64
}

// setNextBatch adjusts passed interval based on session index and whether
// stream is live or history. It calls Server SetNextBatch with adjusted
// interval and returns batch hashes and their interval.
func (s *server) setNextBatch(from, to uint64) ([]byte, uint64, uint64, *HandoverProof, error) {
    if s.stream.Live {
        if from == 0 {
            from = s.sessionIndex
        }
        if to <= from || from >= s.sessionIndex {
            to = math.MaxUint64
        }
    } else {
        if (to < from && to != 0) || from > s.sessionIndex {
            return nil, 0, 0, nil, nil
        }
        if to == 0 || to > s.sessionIndex {
            to = s.sessionIndex
        }
    }
    return s.SetNextBatch(from, to)
}

// Server interface for outgoing peer Streamer
type Server interface {
    // SessionIndex is called when a server is initialized
    // to get the current cursor state of the stream data.
    // Based on this index, live and history stream intervals
    // will be adjusted before calling SetNextBatch.
    SessionIndex() (uint64, error)
    SetNextBatch(uint64, uint64) (hashes []byte, from uint64, to uint64, proof *HandoverProof, err error)
    GetData(context.Context, []byte) ([]byte, error)
    Close()
}

type client struct {
    Client
    stream    Stream
    priority  uint8
    sessionAt uint64
    to        uint64
    next      chan error
    quit      chan struct{}

    intervalsKey   string
    intervalsStore state.Store
}

func peerStreamIntervalsKey(p *Peer, s Stream) string {
    return p.ID().String() + s.String()
}

func (c client) AddInterval(start, end uint64) (err error) {
    i := &intervals.Intervals{}
    err = c.intervalsStore.Get(c.intervalsKey, i)
    if err != nil {
        return err
    }
    i.Add(start, end)
    return c.intervalsStore.Put(c.intervalsKey, i)
}

func (c client) NextInterval() (start, end uint64, err error) {
    i := &intervals.Intervals{}
    err = c.intervalsStore.Get(c.intervalsKey, i)
    if err != nil {
        return 0, 0, err
    }
    start, end = i.Next()
    return start, end, nil
}

// Client interface for incoming peer Streamer
type Client interface {
    NeedData(context.Context, []byte) func(context.Context) error
    BatchDone(Stream, uint64, []byte, []byte) func() (*TakeoverProof, error)
    Close()
}

func (c *client) nextBatch(from uint64) (nextFrom uint64, nextTo uint64) {
    if c.to > 0 && from >= c.to {
        return 0, 0
    }
    if c.stream.Live {
        return from, 0
    } else if from >= c.sessionAt {
        if c.to > 0 {
            return from, c.to
        }
        return from, math.MaxUint64
    }
    nextFrom, nextTo, err := c.NextInterval()
    if err != nil {
        log.Error("next intervals", "stream", c.stream)
        return
    }
    if nextTo > c.to {
        nextTo = c.to
    }
    if nextTo == 0 {
        nextTo = c.sessionAt
    }
    return
}

func (c *client) batchDone(p *Peer, req *OfferedHashesMsg, hashes []byte) error {
    if tf := c.BatchDone(req.Stream, req.From, hashes, req.Root); tf != nil {
        tp, err := tf()
        if err != nil {
            return err
        }
        if err := p.SendPriority(context.TODO(), tp, c.priority); err != nil {
            return err
        }
        if c.to > 0 && tp.Takeover.End >= c.to {
            return p.streamer.Unsubscribe(p.Peer.ID(), req.Stream)
        }
        return nil
    }
    // TODO: make a test case for testing if the interval is added when the batch is done
    if err := c.AddInterval(req.From, req.To); err != nil {
        return err
    }
    return nil
}

func (c *client) close() {
    select {
    case <-c.quit:
    default:
        close(c.quit)
    }
    c.Close()
}

// clientParams store parameters for the new client
// between a subscription and initial offered hashes request handling.
type clientParams struct {
    priority uint8
    to       uint64
    // signal when the client is created
    clientCreatedC chan struct{}
}

func newClientParams(priority uint8, to uint64) *clientParams {
    return &clientParams{
        priority:       priority,
        to:             to,
        clientCreatedC: make(chan struct{}),
    }
}

func (c *clientParams) waitClient(ctx context.Context) error {
    select {
    case <-ctx.Done():
        return ctx.Err()
    case <-c.clientCreatedC:
        return nil
    }
}

func (c *clientParams) clientCreated() {
    close(c.clientCreatedC)
}

// GetSpec returns the streamer spec to callers
// This used to be a global variable but for simulations with
// multiple nodes its fields (notably the Hook) would be overwritten
func (r *Registry) GetSpec() *protocols.Spec {
    return r.spec
}

func (r *Registry) createSpec() {
    // Spec is the spec of the streamer protocol
    var spec = &protocols.Spec{
        Name:       "stream",
        Version:    8,
        MaxMsgSize: 10 * 1024 * 1024,
        Messages: []interface{}{
            UnsubscribeMsg{},
            OfferedHashesMsg{},
            WantedHashesMsg{},
            TakeoverProofMsg{},
            SubscribeMsg{},
            RetrieveRequestMsg{},
            ChunkDeliveryMsgRetrieval{},
            SubscribeErrorMsg{},
            RequestSubscriptionMsg{},
            QuitMsg{},
            ChunkDeliveryMsgSyncing{},
        },
    }
    r.spec = spec
}

// An accountable message needs some meta information attached to it
// in order to evaluate the correct price
type StreamerPrices struct {
    priceMatrix map[reflect.Type]*protocols.Price
    registry    *Registry
}

// Price implements the accounting interface and returns the price for a specific message
func (sp *StreamerPrices) Price(msg interface{}) *protocols.Price {
    t := reflect.TypeOf(msg).Elem()
    return sp.priceMatrix[t]
}

// Instead of hardcoding the price, get it
// through a function - it could be quite complex in the future
func (sp *StreamerPrices) getRetrieveRequestMsgPrice() uint64 {
    return uint64(1)
}

// Instead of hardcoding the price, get it
// through a function - it could be quite complex in the future
func (sp *StreamerPrices) getChunkDeliveryMsgRetrievalPrice() uint64 {
    return uint64(1)
}

// createPriceOracle sets up a matrix which can be queried to get
// the price for a message via the Price method
func (r *Registry) createPriceOracle() {
    sp := &StreamerPrices{
        registry: r,
    }
    sp.priceMatrix = map[reflect.Type]*protocols.Price{
        reflect.TypeOf(ChunkDeliveryMsgRetrieval{}): {
            Value:   sp.getChunkDeliveryMsgRetrievalPrice(), // arbitrary price for now
            PerByte: true,
            Payer:   protocols.Receiver,
        },
        reflect.TypeOf(RetrieveRequestMsg{}): {
            Value:   sp.getRetrieveRequestMsgPrice(), // arbitrary price for now
            PerByte: false,
            Payer:   protocols.Sender,
        },
    }
    r.prices = sp
}

func (r *Registry) Protocols() []p2p.Protocol {
    return []p2p.Protocol{
        {
            Name:    r.spec.Name,
            Version: r.spec.Version,
            Length:  r.spec.Length(),
            Run:     r.runProtocol,
        },
    }
}

func (r *Registry) APIs() []rpc.API {
    return []rpc.API{
        {
            Namespace: "stream",
            Version:   "3.0",
            Service:   r.api,
            Public:    true,
        },
    }
}

func (r *Registry) Start(server *p2p.Server) error {
    log.Info("Streamer started")
    return nil
}

func (r *Registry) Stop() error {
    return nil
}

type Range struct {
    From, To uint64
}

func NewRange(from, to uint64) *Range {
    return &Range{
        From: from,
        To:   to,
    }
}

func (r *Range) String() string {
    return fmt.Sprintf("%v-%v", r.From, r.To)
}

func getHistoryPriority(priority uint8) uint8 {
    if priority == 0 {
        return 0
    }
    return priority - 1
}

func getHistoryStream(s Stream) Stream {
    return NewStream(s.Name, s.Key, false)
}

type API struct {
    streamer *Registry
}

func NewAPI(r *Registry) *API {
    return &API{
        streamer: r,
    }
}

func (api *API) SubscribeStream(peerId enode.ID, s Stream, history *Range, priority uint8) error {
    return api.streamer.Subscribe(peerId, s, history, priority)
}

func (api *API) UnsubscribeStream(peerId enode.ID, s Stream) error {
    return api.streamer.Unsubscribe(peerId, s)
}