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208 lines
5.9 KiB
208 lines
5.9 KiB
package p2p
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import (
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"context"
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"fmt"
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"sync"
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"github.com/gogo/protobuf/proto"
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"github.com/tendermint/tendermint/types"
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)
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// Envelope contains a message with sender/receiver routing info.
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type Envelope struct {
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From types.NodeID // sender (empty if outbound)
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To types.NodeID // receiver (empty if inbound)
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Broadcast bool // send to all connected peers (ignores To)
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Message proto.Message // message payload
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ChannelID ChannelID
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}
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// Wrapper is a Protobuf message that can contain a variety of inner messages
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// (e.g. via oneof fields). If a Channel's message type implements Wrapper, the
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// Router will automatically wrap outbound messages and unwrap inbound messages,
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// such that reactors do not have to do this themselves.
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type Wrapper interface {
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proto.Message
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// Wrap will take a message and wrap it in this one if possible.
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Wrap(proto.Message) error
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// Unwrap will unwrap the inner message contained in this message.
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Unwrap() (proto.Message, error)
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}
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// PeerError is a peer error reported via Channel.Error.
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//
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// FIXME: This currently just disconnects the peer, which is too simplistic.
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// For example, some errors should be logged, some should cause disconnects,
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// and some should ban the peer.
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//
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// FIXME: This should probably be replaced by a more general PeerBehavior
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// concept that can mark good and bad behavior and contributes to peer scoring.
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// It should possibly also allow reactors to request explicit actions, e.g.
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// disconnection or banning, in addition to doing this based on aggregates.
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type PeerError struct {
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NodeID types.NodeID
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Err error
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}
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func (pe PeerError) Error() string { return fmt.Sprintf("peer=%q: %s", pe.NodeID, pe.Err.Error()) }
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func (pe PeerError) Unwrap() error { return pe.Err }
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// Channel is a bidirectional channel to exchange Protobuf messages with peers.
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// Each message is wrapped in an Envelope to specify its sender and receiver.
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type Channel struct {
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ID ChannelID
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inCh <-chan Envelope // inbound messages (peers to reactors)
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outCh chan<- Envelope // outbound messages (reactors to peers)
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errCh chan<- PeerError // peer error reporting
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messageType proto.Message // the channel's message type, used for unmarshaling
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}
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// NewChannel creates a new channel. It is primarily for internal and test
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// use, reactors should use Router.OpenChannel().
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func NewChannel(
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id ChannelID,
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messageType proto.Message,
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inCh <-chan Envelope,
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outCh chan<- Envelope,
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errCh chan<- PeerError,
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) *Channel {
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return &Channel{
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ID: id,
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messageType: messageType,
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inCh: inCh,
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outCh: outCh,
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errCh: errCh,
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}
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}
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// Send blocks until the envelope has been sent, or until ctx ends.
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// An error only occurs if the context ends before the send completes.
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func (ch *Channel) Send(ctx context.Context, envelope Envelope) error {
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select {
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case <-ctx.Done():
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return ctx.Err()
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case ch.outCh <- envelope:
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return nil
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}
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}
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// SendError blocks until the given error has been sent, or ctx ends.
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// An error only occurs if the context ends before the send completes.
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func (ch *Channel) SendError(ctx context.Context, pe PeerError) error {
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select {
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case <-ctx.Done():
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return ctx.Err()
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case ch.errCh <- pe:
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return nil
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}
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}
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// Receive returns a new unbuffered iterator to receive messages from ch.
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// The iterator runs until ctx ends.
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func (ch *Channel) Receive(ctx context.Context) *ChannelIterator {
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iter := &ChannelIterator{
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pipe: make(chan Envelope), // unbuffered
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}
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go func() {
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defer close(iter.pipe)
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iteratorWorker(ctx, ch, iter.pipe)
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}()
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return iter
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}
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// ChannelIterator provides a context-aware path for callers
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// (reactors) to process messages from the P2P layer without relying
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// on the implementation details of the P2P layer. Channel provides
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// access to it's Outbound stream as an iterator, and the
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// MergedChannelIterator makes it possible to combine multiple
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// channels into a single iterator.
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type ChannelIterator struct {
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pipe chan Envelope
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current *Envelope
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}
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func iteratorWorker(ctx context.Context, ch *Channel, pipe chan Envelope) {
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for {
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select {
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case <-ctx.Done():
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return
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case envelope := <-ch.inCh:
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select {
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case <-ctx.Done():
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return
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case pipe <- envelope:
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}
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}
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}
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}
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// Next returns true when the Envelope value has advanced, and false
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// when the context is canceled or iteration should stop. If an iterator has returned false,
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// it will never return true again.
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// in general, use Next, as in:
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//
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// for iter.Next(ctx) {
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// envelope := iter.Envelope()
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// // ... do things ...
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// }
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//
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func (iter *ChannelIterator) Next(ctx context.Context) bool {
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select {
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case <-ctx.Done():
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iter.current = nil
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return false
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case envelope, ok := <-iter.pipe:
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if !ok {
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iter.current = nil
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return false
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}
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iter.current = &envelope
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return true
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}
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}
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// Envelope returns the current Envelope object held by the
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// iterator. When the last call to Next returned true, Envelope will
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// return a non-nil object. If Next returned false then Envelope is
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// always nil.
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func (iter *ChannelIterator) Envelope() *Envelope { return iter.current }
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// MergedChannelIterator produces an iterator that merges the
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// messages from the given channels in arbitrary order.
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//
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// This allows the caller to consume messages from multiple channels
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// without needing to manage the concurrency separately.
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func MergedChannelIterator(ctx context.Context, chs ...*Channel) *ChannelIterator {
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iter := &ChannelIterator{
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pipe: make(chan Envelope), // unbuffered
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}
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wg := new(sync.WaitGroup)
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for _, ch := range chs {
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wg.Add(1)
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go func(ch *Channel) {
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defer wg.Done()
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iteratorWorker(ctx, ch, iter.pipe)
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}(ch)
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}
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done := make(chan struct{})
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go func() { defer close(done); wg.Wait() }()
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go func() {
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defer close(iter.pipe)
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// we could return early if the context is canceled,
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// but this is safer because it means the pipe stays
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// open until all of the ch worker threads end, which
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// should happen very quickly.
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<-done
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}()
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return iter
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}
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