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430 lines
14 KiB
430 lines
14 KiB
package pex
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import (
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"fmt"
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"runtime/debug"
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"sync"
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"time"
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"github.com/tendermint/tendermint/internal/p2p"
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"github.com/tendermint/tendermint/internal/p2p/conn"
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"github.com/tendermint/tendermint/libs/log"
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tmmath "github.com/tendermint/tendermint/libs/math"
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"github.com/tendermint/tendermint/libs/service"
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protop2p "github.com/tendermint/tendermint/proto/tendermint/p2p"
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"github.com/tendermint/tendermint/types"
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)
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var (
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_ service.Service = (*Reactor)(nil)
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_ p2p.Wrapper = (*protop2p.PexMessage)(nil)
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)
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const (
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// PexChannel is a channel for PEX messages
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PexChannel = 0x00
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// over-estimate of max NetAddress size
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// hexID (40) + IP (16) + Port (2) + Name (100) ...
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// NOTE: dont use massive DNS name ..
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maxAddressSize = 256
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// max addresses returned by GetSelection
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// NOTE: this must match "maxMsgSize"
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maxGetSelection = 250
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// NOTE: amplification factor!
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// small request results in up to maxMsgSize response
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maxMsgSize = maxAddressSize * maxGetSelection
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// the minimum time one peer can send another request to the same peer
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minReceiveRequestInterval = 100 * time.Millisecond
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// the maximum amount of addresses that can be included in a response
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maxAddresses uint16 = 100
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// How long to wait when there are no peers available before trying again
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noAvailablePeersWaitPeriod = 1 * time.Second
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// indicates the ping rate of the pex reactor when the peer store is full.
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// The reactor should still look to add new peers in order to flush out low
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// scoring peers that are still in the peer store
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fullCapacityInterval = 10 * time.Minute
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)
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// TODO: We should decide whether we want channel descriptors to be housed
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// within each reactor (as they are now) or, considering that the reactor doesn't
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// really need to care about the channel descriptors, if they should be housed
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// in the node module.
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func ChannelDescriptor() *conn.ChannelDescriptor {
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return &conn.ChannelDescriptor{
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ID: PexChannel,
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MessageType: new(protop2p.PexMessage),
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Priority: 1,
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SendQueueCapacity: 10,
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RecvMessageCapacity: maxMsgSize,
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RecvBufferCapacity: 128,
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}
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}
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// The peer exchange or PEX reactor supports the peer manager by sending
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// requests to other peers for addresses that can be given to the peer manager
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// and at the same time advertises addresses to peers that need more.
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//
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// The reactor is able to tweak the intensity of it's search by decreasing or
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// increasing the interval between each request. It tracks connected peers via
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// a linked list, sending a request to the node at the front of the list and
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// adding it to the back of the list once a response is received.
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type Reactor struct {
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service.BaseService
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peerManager *p2p.PeerManager
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pexCh *p2p.Channel
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peerUpdates *p2p.PeerUpdates
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closeCh chan struct{}
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// list of available peers to loop through and send peer requests to
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availablePeers map[types.NodeID]struct{}
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mtx sync.RWMutex
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// requestsSent keeps track of which peers the PEX reactor has sent requests
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// to. This prevents the sending of spurious responses.
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// NOTE: If a node never responds, they will remain in this map until a
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// peer down status update is sent
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requestsSent map[types.NodeID]struct{}
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// lastReceivedRequests keeps track of when peers send a request to prevent
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// peers from sending requests too often (as defined by
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// minReceiveRequestInterval).
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lastReceivedRequests map[types.NodeID]time.Time
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// the time when another request will be sent
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nextRequestTime time.Time
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// keep track of how many new peers to existing peers we have received to
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// extrapolate the size of the network
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newPeers uint32
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totalPeers uint32
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// discoveryRatio is the inverse ratio of new peers to old peers squared.
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// This is multiplied by the minimum duration to calculate how long to wait
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// between each request.
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discoveryRatio float32
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}
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// NewReactor returns a reference to a new reactor.
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func NewReactor(
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logger log.Logger,
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peerManager *p2p.PeerManager,
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pexCh *p2p.Channel,
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peerUpdates *p2p.PeerUpdates,
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) *Reactor {
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r := &Reactor{
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peerManager: peerManager,
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pexCh: pexCh,
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peerUpdates: peerUpdates,
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closeCh: make(chan struct{}),
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availablePeers: make(map[types.NodeID]struct{}),
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requestsSent: make(map[types.NodeID]struct{}),
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lastReceivedRequests: make(map[types.NodeID]time.Time),
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}
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r.BaseService = *service.NewBaseService(logger, "PEX", r)
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return r
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}
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// OnStart starts separate go routines for each p2p Channel and listens for
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// envelopes on each. In addition, it also listens for peer updates and handles
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// messages on that p2p channel accordingly. The caller must be sure to execute
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// OnStop to ensure the outbound p2p Channels are closed.
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func (r *Reactor) OnStart() error {
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go r.processPexCh()
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go r.processPeerUpdates()
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return nil
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}
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// OnStop stops the reactor by signaling to all spawned goroutines to exit and
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// blocking until they all exit.
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func (r *Reactor) OnStop() {
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// Close closeCh to signal to all spawned goroutines to gracefully exit. All
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// p2p Channels should execute Close().
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close(r.closeCh)
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// Wait for all p2p Channels to be closed before returning. This ensures we
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// can easily reason about synchronization of all p2p Channels and ensure no
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// panics will occur.
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<-r.pexCh.Done()
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<-r.peerUpdates.Done()
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}
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// processPexCh implements a blocking event loop where we listen for p2p
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// Envelope messages from the pexCh.
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func (r *Reactor) processPexCh() {
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defer r.pexCh.Close()
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for {
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select {
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case <-r.closeCh:
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r.Logger.Debug("stopped listening on PEX channel; closing...")
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return
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// outbound requests for new peers
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case <-r.waitUntilNextRequest():
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r.sendRequestForPeers()
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// inbound requests for new peers or responses to requests sent by this
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// reactor
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case envelope := <-r.pexCh.In:
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if err := r.handleMessage(r.pexCh.ID, envelope); err != nil {
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r.Logger.Error("failed to process message", "ch_id", r.pexCh.ID, "envelope", envelope, "err", err)
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r.pexCh.Error <- p2p.PeerError{
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NodeID: envelope.From,
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Err: err,
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}
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}
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}
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}
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}
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// processPeerUpdates initiates a blocking process where we listen for and handle
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// PeerUpdate messages. When the reactor is stopped, we will catch the signal and
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// close the p2p PeerUpdatesCh gracefully.
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func (r *Reactor) processPeerUpdates() {
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defer r.peerUpdates.Close()
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for {
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select {
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case peerUpdate := <-r.peerUpdates.Updates():
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r.processPeerUpdate(peerUpdate)
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case <-r.closeCh:
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r.Logger.Debug("stopped listening on peer updates channel; closing...")
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return
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}
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}
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}
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// handlePexMessage handles envelopes sent from peers on the PexChannel.
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func (r *Reactor) handlePexMessage(envelope p2p.Envelope) error {
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logger := r.Logger.With("peer", envelope.From)
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switch msg := envelope.Message.(type) {
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case *protop2p.PexRequest:
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// check if the peer hasn't sent a prior request too close to this one
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// in time
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if err := r.markPeerRequest(envelope.From); err != nil {
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return err
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}
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// request peers from the peer manager and parse the NodeAddresses into
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// URL strings
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nodeAddresses := r.peerManager.Advertise(envelope.From, maxAddresses)
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pexAddresses := make([]protop2p.PexAddress, len(nodeAddresses))
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for idx, addr := range nodeAddresses {
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pexAddresses[idx] = protop2p.PexAddress{
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URL: addr.String(),
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}
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}
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r.pexCh.Out <- p2p.Envelope{
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To: envelope.From,
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Message: &protop2p.PexResponse{Addresses: pexAddresses},
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}
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case *protop2p.PexResponse:
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// check if the response matches a request that was made to that peer
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if err := r.markPeerResponse(envelope.From); err != nil {
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return err
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}
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// check the size of the response
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if len(msg.Addresses) > int(maxAddresses) {
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return fmt.Errorf("peer sent too many addresses (max: %d, got: %d)",
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maxAddresses,
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len(msg.Addresses),
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)
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}
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for _, pexAddress := range msg.Addresses {
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peerAddress, err := p2p.ParseNodeAddress(pexAddress.URL)
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if err != nil {
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continue
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}
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added, err := r.peerManager.Add(peerAddress)
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if err != nil {
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logger.Error("failed to add PEX address", "address", peerAddress, "err", err)
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}
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if added {
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r.newPeers++
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logger.Debug("added PEX address", "address", peerAddress)
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}
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r.totalPeers++
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}
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default:
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return fmt.Errorf("received unknown message: %T", msg)
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}
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return nil
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}
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// handleMessage handles an Envelope sent from a peer on a specific p2p Channel.
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// It will handle errors and any possible panics gracefully. A caller can handle
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// any error returned by sending a PeerError on the respective channel.
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func (r *Reactor) handleMessage(chID p2p.ChannelID, envelope p2p.Envelope) (err error) {
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defer func() {
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if e := recover(); e != nil {
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err = fmt.Errorf("panic in processing message: %v", e)
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r.Logger.Error(
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"recovering from processing message panic",
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"err", err,
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"stack", string(debug.Stack()),
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)
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}
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}()
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r.Logger.Debug("received PEX message", "peer", envelope.From)
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switch chID {
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case p2p.ChannelID(PexChannel):
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err = r.handlePexMessage(envelope)
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default:
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err = fmt.Errorf("unknown channel ID (%d) for envelope (%v)", chID, envelope)
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}
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return err
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}
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// processPeerUpdate processes a PeerUpdate. For added peers, PeerStatusUp, we
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// send a request for addresses.
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func (r *Reactor) processPeerUpdate(peerUpdate p2p.PeerUpdate) {
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r.Logger.Debug("received PEX peer update", "peer", peerUpdate.NodeID, "status", peerUpdate.Status)
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r.mtx.Lock()
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defer r.mtx.Unlock()
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switch peerUpdate.Status {
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case p2p.PeerStatusUp:
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r.availablePeers[peerUpdate.NodeID] = struct{}{}
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case p2p.PeerStatusDown:
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delete(r.availablePeers, peerUpdate.NodeID)
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delete(r.requestsSent, peerUpdate.NodeID)
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delete(r.lastReceivedRequests, peerUpdate.NodeID)
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default:
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}
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}
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func (r *Reactor) waitUntilNextRequest() <-chan time.Time {
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return time.After(time.Until(r.nextRequestTime))
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}
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// sendRequestForPeers pops the first peerID off the list and sends the
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// peer a request for more peer addresses. The function then moves the
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// peer into the requestsSent bucket and calculates when the next request
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// time should be
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func (r *Reactor) sendRequestForPeers() {
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r.mtx.Lock()
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defer r.mtx.Unlock()
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if len(r.availablePeers) == 0 {
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// no peers are available
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r.Logger.Debug("no available peers to send request to, waiting...")
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r.nextRequestTime = time.Now().Add(noAvailablePeersWaitPeriod)
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return
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}
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var peerID types.NodeID
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// use range to get a random peer.
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for peerID = range r.availablePeers {
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break
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}
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// send out the pex request
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r.pexCh.Out <- p2p.Envelope{
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To: peerID,
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Message: &protop2p.PexRequest{},
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}
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// remove the peer from the abvailable peers list and mark it in the requestsSent map
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delete(r.availablePeers, peerID)
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r.requestsSent[peerID] = struct{}{}
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r.calculateNextRequestTime()
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r.Logger.Debug("peer request sent", "next_request_time", r.nextRequestTime)
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}
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// calculateNextRequestTime implements something of a proportional controller
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// to estimate how often the reactor should be requesting new peer addresses.
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// The dependent variable in this calculation is the ratio of new peers to
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// all peers that the reactor receives. The interval is thus calculated as the
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// inverse squared. In the beginning, all peers should be new peers.
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// We expect this ratio to be near 1 and thus the interval to be as short
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// as possible. As the node becomes more familiar with the network the ratio of
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// new nodes will plummet to a very small number, meaning the interval expands
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// to its upper bound.
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// CONTRACT: Must use a write lock as nextRequestTime is updated
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func (r *Reactor) calculateNextRequestTime() {
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// check if the peer store is full. If so then there is no need
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// to send peer requests too often
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if ratio := r.peerManager.PeerRatio(); ratio >= 0.95 {
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r.Logger.Debug("peer manager near full ratio, sleeping...",
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"sleep_period", fullCapacityInterval, "ratio", ratio)
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r.nextRequestTime = time.Now().Add(fullCapacityInterval)
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return
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}
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// baseTime represents the shortest interval that we can send peer requests
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// in. For example if we have 10 peers and we can't send a message to the
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// same peer every 500ms, then we can send a request every 50ms. In practice
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// we use a safety margin of 2, ergo 100ms
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peers := tmmath.MinInt(len(r.availablePeers), 50)
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baseTime := minReceiveRequestInterval
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if peers > 0 {
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baseTime = minReceiveRequestInterval * 2 / time.Duration(peers)
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}
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if r.totalPeers > 0 || r.discoveryRatio == 0 {
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// find the ratio of new peers. NOTE: We add 1 to both sides to avoid
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// divide by zero problems
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ratio := float32(r.totalPeers+1) / float32(r.newPeers+1)
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// square the ratio in order to get non linear time intervals
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// NOTE: The longest possible interval for a network with 100 or more peers
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// where a node is connected to 50 of them is 2 minutes.
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r.discoveryRatio = ratio * ratio
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r.newPeers = 0
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r.totalPeers = 0
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}
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// NOTE: As ratio is always >= 1, discovery ratio is >= 1. Therefore we don't need to worry
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// about the next request time being less than the minimum time
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r.nextRequestTime = time.Now().Add(baseTime * time.Duration(r.discoveryRatio))
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}
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func (r *Reactor) markPeerRequest(peer types.NodeID) error {
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r.mtx.Lock()
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defer r.mtx.Unlock()
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if lastRequestTime, ok := r.lastReceivedRequests[peer]; ok {
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if time.Now().Before(lastRequestTime.Add(minReceiveRequestInterval)) {
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return fmt.Errorf("peer sent a request too close after a prior one. Minimum interval: %v",
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minReceiveRequestInterval)
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}
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}
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r.lastReceivedRequests[peer] = time.Now()
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return nil
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}
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func (r *Reactor) markPeerResponse(peer types.NodeID) error {
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r.mtx.Lock()
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defer r.mtx.Unlock()
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// check if a request to this peer was sent
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if _, ok := r.requestsSent[peer]; !ok {
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return fmt.Errorf("peer sent a PEX response when none was requested (%v)", peer)
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}
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delete(r.requestsSent, peer)
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// attach to the back of the list so that the peer can be used again for
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// future requests
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r.availablePeers[peer] = struct{}{}
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return nil
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}
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