144 lines
3.1 KiB
Markdown
144 lines
3.1 KiB
Markdown
# P2P Module
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P2P provides an abstraction around peer-to-peer communication.<br/>
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Communication happens via Agents that react to messages from peers.<br/>
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Each Agent has one or more Channels of communication for each Peer.<br/>
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Channels are multiplexed automatically and can be configured.<br/>
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A Switch is started upon app start, and handles Peer management.<br/>
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A PEXAgent implementation is provided to automate peer discovery.<br/>
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## Usage
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MempoolAgent started from the following template code.<br/>
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Modify the snippet below according to your needs.<br/>
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Check out the ConsensusAgent for an example of tracking peer state.<br/>
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```golang
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package mempool
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import (
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"bytes"
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"fmt"
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"io"
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"sync/atomic"
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. "github.com/tendermint/tendermint/binary"
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. "github.com/tendermint/tendermint/blocks"
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"github.com/tendermint/tendermint/p2p"
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)
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var (
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MempoolCh = byte(0x30)
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)
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// MempoolAgent handles mempool tx broadcasting amongst peers.
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type MempoolAgent struct {
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sw *p2p.Switch
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swEvents chan interface{}
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quit chan struct{}
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started uint32
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stopped uint32
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}
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func NewMempoolAgent(sw *p2p.Switch) *MempoolAgent {
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swEvents := make(chan interface{})
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sw.AddEventListener("MempoolAgent.swEvents", swEvents)
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memA := &MempoolAgent{
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sw: sw,
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swEvents: swEvents,
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quit: make(chan struct{}),
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}
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return memA
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}
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func (memA *MempoolAgent) Start() {
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if atomic.CompareAndSwapUint32(&memA.started, 0, 1) {
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log.Info("Starting MempoolAgent")
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go memA.switchEventsRoutine()
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go memA.gossipTxRoutine()
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}
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}
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func (memA *MempoolAgent) Stop() {
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if atomic.CompareAndSwapUint32(&memA.stopped, 0, 1) {
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log.Info("Stopping MempoolAgent")
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close(memA.quit)
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close(memA.swEvents)
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}
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}
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// Handle peer new/done events
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func (memA *MempoolAgent) switchEventsRoutine() {
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for {
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swEvent, ok := <-memA.swEvents
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if !ok {
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break
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}
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switch swEvent.(type) {
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case p2p.SwitchEventNewPeer:
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// event := swEvent.(p2p.SwitchEventNewPeer)
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// NOTE: set up peer state
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case p2p.SwitchEventDonePeer:
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// event := swEvent.(p2p.SwitchEventDonePeer)
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// NOTE: tear down peer state
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default:
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log.Warning("Unhandled switch event type")
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}
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}
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}
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func (memA *MempoolAgent) gossipTxRoutine() {
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OUTER_LOOP:
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for {
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// Receive incoming message on MempoolCh
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inMsg, ok := memA.sw.Receive(MempoolCh)
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if !ok {
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break OUTER_LOOP // Client has stopped
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}
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_, msg_ := decodeMessage(inMsg.Bytes)
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log.Info("gossipMempoolRoutine received %v", msg_)
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switch msg_.(type) {
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case *TxMessage:
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// msg := msg_.(*TxMessage)
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// handle msg
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default:
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// Ignore unknown message
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// memA.sw.StopPeerForError(inMsg.MConn.Peer, errInvalidMessage)
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}
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}
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// Cleanup
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}
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```
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## Channels
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Each peer connection is multiplexed into channels.
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The p2p module comes with a channel implementation used for peer
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discovery (called PEX, short for "peer exchange").
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<table>
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<tr>
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<td><b>Channel</b></td>
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<td>"PEX"</td>
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</tr>
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<tr>
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<td><b>Messages</b></td>
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<td>
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<ul>
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<li>pexRequestMsg</li>
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<li>pexResponseMsg</li>
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</ul>
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</td>
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</tr>
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</table>
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<hr />
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## Resources
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* http://www.upnp-hacks.org/upnp.html
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