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321 lines
10 KiB
321 lines
10 KiB
package evidence
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import (
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"context"
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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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clist "github.com/tendermint/tendermint/internal/libs/clist"
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"github.com/tendermint/tendermint/internal/p2p"
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"github.com/tendermint/tendermint/libs/log"
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"github.com/tendermint/tendermint/libs/service"
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tmproto "github.com/tendermint/tendermint/proto/tendermint/types"
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"github.com/tendermint/tendermint/types"
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)
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var _ service.Service = (*Reactor)(nil)
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const (
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EvidenceChannel = p2p.ChannelID(0x38)
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maxMsgSize = 1048576 // 1MB TODO make it configurable
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// broadcast all uncommitted evidence this often. This sets when the reactor
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// goes back to the start of the list and begins sending the evidence again.
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// Most evidence should be committed in the very next block that is why we wait
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// just over the block production rate before sending evidence again.
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broadcastEvidenceIntervalS = 10
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)
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// GetChannelDescriptor produces an instance of a descriptor for this
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// package's required channels.
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func GetChannelDescriptor() *p2p.ChannelDescriptor {
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return &p2p.ChannelDescriptor{
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ID: EvidenceChannel,
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MessageType: new(tmproto.Evidence),
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Priority: 6,
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RecvMessageCapacity: maxMsgSize,
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RecvBufferCapacity: 32,
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}
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}
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// Reactor handles evpool evidence broadcasting amongst peers.
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type Reactor struct {
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service.BaseService
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logger log.Logger
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evpool *Pool
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evidenceCh *p2p.Channel
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peerUpdates *p2p.PeerUpdates
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mtx sync.Mutex
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peerRoutines map[types.NodeID]context.CancelFunc
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}
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// NewReactor returns a reference to a new evidence reactor, which implements the
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// service.Service interface. It accepts a p2p Channel dedicated for handling
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// envelopes with EvidenceList messages.
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func NewReactor(
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ctx context.Context,
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logger log.Logger,
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chCreator p2p.ChannelCreator,
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peerUpdates *p2p.PeerUpdates,
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evpool *Pool,
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) (*Reactor, error) {
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evidenceCh, err := chCreator(ctx, GetChannelDescriptor())
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if err != nil {
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return nil, err
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}
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r := &Reactor{
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logger: logger,
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evpool: evpool,
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evidenceCh: evidenceCh,
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peerUpdates: peerUpdates,
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peerRoutines: make(map[types.NodeID]context.CancelFunc),
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}
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r.BaseService = *service.NewBaseService(logger, "Evidence", r)
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return r, err
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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. No error is returned.
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func (r *Reactor) OnStart(ctx context.Context) error {
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go r.processEvidenceCh(ctx)
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go r.processPeerUpdates(ctx)
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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 the evidence db
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r.evpool.Close()
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}
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// handleEvidenceMessage handles envelopes sent from peers on the EvidenceChannel.
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// It returns an error only if the Envelope.Message is unknown for this channel
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// or if the given evidence is invalid. This should never be called outside of
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// handleMessage.
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func (r *Reactor) handleEvidenceMessage(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 *tmproto.Evidence:
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// Process the evidence received from a peer
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// Evidence is sent and received one by one
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ev, err := types.EvidenceFromProto(msg)
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if err != nil {
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logger.Error("failed to convert evidence", "err", err)
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return err
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}
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if err := r.evpool.AddEvidence(ev); err != nil {
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// If we're given invalid evidence by the peer, notify the router that
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// we should remove this peer by returning an error.
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if _, ok := err.(*types.ErrInvalidEvidence); ok {
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return err
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}
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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 message", "message", envelope.Message, "peer", envelope.From)
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switch chID {
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case EvidenceChannel:
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err = r.handleEvidenceMessage(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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// processEvidenceCh implements a blocking event loop where we listen for p2p
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// Envelope messages from the evidenceCh.
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func (r *Reactor) processEvidenceCh(ctx context.Context) {
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iter := r.evidenceCh.Receive(ctx)
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for iter.Next(ctx) {
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envelope := iter.Envelope()
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if err := r.handleMessage(r.evidenceCh.ID, envelope); err != nil {
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r.logger.Error("failed to process message", "ch_id", r.evidenceCh.ID, "envelope", envelope, "err", err)
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if serr := r.evidenceCh.SendError(ctx, p2p.PeerError{
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NodeID: envelope.From,
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Err: err,
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}); serr != nil {
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return
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}
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}
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}
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}
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// processPeerUpdate processes a PeerUpdate. For new or live peers it will check
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// if an evidence broadcasting goroutine needs to be started. For down or
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// removed peers, it will check if an evidence broadcasting goroutine
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// exists and signal that it should exit.
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//
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// FIXME: The peer may be behind in which case it would simply ignore the
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// evidence and treat it as invalid. This would cause the peer to disconnect.
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// The peer may also receive the same piece of evidence multiple times if it
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// connects/disconnects frequently from the broadcasting peer(s).
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//
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// REF: https://github.com/tendermint/tendermint/issues/4727
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func (r *Reactor) processPeerUpdate(ctx context.Context, peerUpdate p2p.PeerUpdate) {
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r.logger.Debug("received 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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// Do not allow starting new evidence broadcast loops after reactor shutdown
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// has been initiated. This can happen after we've manually closed all
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// peer broadcast loops, but the router still sends in-flight peer updates.
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if !r.IsRunning() {
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return
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}
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// Check if we've already started a goroutine for this peer, if not we create
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// a new done channel so we can explicitly close the goroutine if the peer
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// is later removed, we increment the waitgroup so the reactor can stop
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// safely, and finally start the goroutine to broadcast evidence to that peer.
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_, ok := r.peerRoutines[peerUpdate.NodeID]
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if !ok {
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pctx, pcancel := context.WithCancel(ctx)
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r.peerRoutines[peerUpdate.NodeID] = pcancel
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go r.broadcastEvidenceLoop(pctx, peerUpdate.NodeID)
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}
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case p2p.PeerStatusDown:
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// Check if we've started an evidence broadcasting goroutine for this peer.
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// If we have, we signal to terminate the goroutine via the channel's closure.
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// This will internally decrement the peer waitgroup and remove the peer
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// from the map of peer evidence broadcasting goroutines.
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closer, ok := r.peerRoutines[peerUpdate.NodeID]
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if ok {
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closer()
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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(ctx context.Context) {
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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(ctx, peerUpdate)
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case <-ctx.Done():
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return
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}
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}
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}
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// broadcastEvidenceLoop starts a blocking process that continuously reads pieces
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// of evidence off of a linked-list and sends the evidence in a p2p Envelope to
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// the given peer by ID. This should be invoked in a goroutine per unique peer
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// ID via an appropriate PeerUpdate. The goroutine can be signaled to gracefully
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// exit by either explicitly closing the provided doneCh or by the reactor
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// signaling to stop.
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//
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// TODO: This should be refactored so that we do not blindly gossip evidence
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// that the peer has already received or may not be ready for.
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//
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// REF: https://github.com/tendermint/tendermint/issues/4727
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func (r *Reactor) broadcastEvidenceLoop(ctx context.Context, peerID types.NodeID) {
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var next *clist.CElement
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defer func() {
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r.mtx.Lock()
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delete(r.peerRoutines, peerID)
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r.mtx.Unlock()
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if e := recover(); e != nil {
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r.logger.Error(
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"recovering from broadcasting evidence loop",
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"err", e,
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"stack", string(debug.Stack()),
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)
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}
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}()
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timer := time.NewTimer(0)
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defer timer.Stop()
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for {
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// This happens because the CElement we were looking at got garbage
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// collected (removed). That is, .NextWaitChan() returned nil. So we can go
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// ahead and start from the beginning.
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if next == nil {
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select {
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case <-r.evpool.EvidenceWaitChan(): // wait until next evidence is available
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if next = r.evpool.EvidenceFront(); next == nil {
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continue
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}
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case <-ctx.Done():
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return
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}
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}
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ev := next.Value.(types.Evidence)
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evProto, err := types.EvidenceToProto(ev)
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if err != nil {
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panic(fmt.Errorf("failed to convert evidence: %w", err))
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}
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// Send the evidence to the corresponding peer. Note, the peer may be behind
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// and thus would not be able to process the evidence correctly. Also, the
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// peer may receive this piece of evidence multiple times if it added and
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// removed frequently from the broadcasting peer.
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if err := r.evidenceCh.Send(ctx, p2p.Envelope{
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To: peerID,
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Message: evProto,
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}); err != nil {
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return
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}
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r.logger.Debug("gossiped evidence to peer", "evidence", ev, "peer", peerID)
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select {
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case <-timer.C:
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// start from the beginning after broadcastEvidenceIntervalS seconds
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timer.Reset(time.Second * broadcastEvidenceIntervalS)
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next = nil
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case <-next.NextWaitChan():
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next = next.Next()
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case <-ctx.Done():
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return
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}
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}
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}
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