p2p: add network simulation framework (#14982)

This commit introduces a network simulation framework which
can be used to run simulated networks of devp2p nodes. The
intention is to use this for testing protocols, performing
benchmarks and visualising emergent network behaviour.

3 files changed, 263 insertions, 0 deletions

diff --git a/p2p/simulations/examples/README.md b/p2p/simulations/examples/README.md
new file mode 100644
index 000000000..822a48dcb
--- /dev/null
+++ b/p2p/simulations/examples/README.md
@@ -0,0 +1,39 @@
+# devp2p simulation examples
+
+## ping-pong
+
+`ping-pong.go` implements a simulation network which contains nodes running a
+simple "ping-pong" protocol where nodes send a ping message to all their
+connected peers every 10s and receive pong messages in return.
+
+To run the simulation, run `go run ping-pong.go` in one terminal to start the
+simulation API and `./ping-pong.sh` in another to start and connect the nodes:
+
+```
+$ go run ping-pong.go
+INFO [08-15|13:53:49] using sim adapter
+INFO [08-15|13:53:49] starting simulation server on 0.0.0.0:8888...
+```
+
+```
+$ ./ping-pong.sh
+---> 13:58:12 creating 10 nodes
+Created node01
+Started node01
+...
+Created node10
+Started node10
+---> 13:58:13 connecting node01 to all other nodes
+Connected node01 to node02
+...
+Connected node01 to node10
+---> 13:58:14 done
+```
+
+Use the `--adapter` flag to choose the adapter type:
+
+```
+$ go run ping-pong.go --adapter exec
+INFO [08-15|14:01:14] using exec adapter                       tmpdir=/var/folders/k6/wpsgfg4n23ddbc6f5cnw5qg00000gn/T/p2p-example992833779
+INFO [08-15|14:01:14] starting simulation server on 0.0.0.0:8888...
+```
diff --git a/p2p/simulations/examples/ping-pong.go b/p2p/simulations/examples/ping-pong.go
new file mode 100644
index 000000000..6a0ead53a
--- /dev/null
+++ b/p2p/simulations/examples/ping-pong.go
@@ -0,0 +1,184 @@
+// Copyright 2017 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 main
+
+import (
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"os"
+	"sync/atomic"
+	"time"
+
+	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/node"
+	"github.com/ethereum/go-ethereum/p2p"
+	"github.com/ethereum/go-ethereum/p2p/discover"
+	"github.com/ethereum/go-ethereum/p2p/simulations"
+	"github.com/ethereum/go-ethereum/p2p/simulations/adapters"
+	"github.com/ethereum/go-ethereum/rpc"
+)
+
+var adapterType = flag.String("adapter", "sim", `node adapter to use (one of "sim", "exec" or "docker")`)
+
+// main() starts a simulation network which contains nodes running a simple
+// ping-pong protocol
+func main() {
+	flag.Parse()
+
+	// set the log level to Trace
+	log.Root().SetHandler(log.LvlFilterHandler(log.LvlTrace, log.StreamHandler(os.Stderr, log.TerminalFormat(false))))
+
+	// register a single ping-pong service
+	services := map[string]adapters.ServiceFunc{
+		"ping-pong": func(ctx *adapters.ServiceContext) (node.Service, error) {
+			return newPingPongService(ctx.Config.ID), nil
+		},
+	}
+	adapters.RegisterServices(services)
+
+	// create the NodeAdapter
+	var adapter adapters.NodeAdapter
+
+	switch *adapterType {
+
+	case "sim":
+		log.Info("using sim adapter")
+		adapter = adapters.NewSimAdapter(services)
+
+	case "exec":
+		tmpdir, err := ioutil.TempDir("", "p2p-example")
+		if err != nil {
+			log.Crit("error creating temp dir", "err", err)
+		}
+		defer os.RemoveAll(tmpdir)
+		log.Info("using exec adapter", "tmpdir", tmpdir)
+		adapter = adapters.NewExecAdapter(tmpdir)
+
+	case "docker":
+		log.Info("using docker adapter")
+		var err error
+		adapter, err = adapters.NewDockerAdapter()
+		if err != nil {
+			log.Crit("error creating docker adapter", "err", err)
+		}
+
+	default:
+		log.Crit(fmt.Sprintf("unknown node adapter %q", *adapterType))
+	}
+
+	// start the HTTP API
+	log.Info("starting simulation server on 0.0.0.0:8888...")
+	network := simulations.NewNetwork(adapter, &simulations.NetworkConfig{
+		DefaultService: "ping-pong",
+	})
+	if err := http.ListenAndServe(":8888", simulations.NewServer(network)); err != nil {
+		log.Crit("error starting simulation server", "err", err)
+	}
+}
+
+// pingPongService runs a ping-pong protocol between nodes where each node
+// sends a ping to all its connected peers every 10s and receives a pong in
+// return
+type pingPongService struct {
+	id       discover.NodeID
+	log      log.Logger
+	received int64
+}
+
+func newPingPongService(id discover.NodeID) *pingPongService {
+	return &pingPongService{
+		id:  id,
+		log: log.New("node.id", id),
+	}
+}
+
+func (p *pingPongService) Protocols() []p2p.Protocol {
+	return []p2p.Protocol{{
+		Name:     "ping-pong",
+		Version:  1,
+		Length:   2,
+		Run:      p.Run,
+		NodeInfo: p.Info,
+	}}
+}
+
+func (p *pingPongService) APIs() []rpc.API {
+	return nil
+}
+
+func (p *pingPongService) Start(server *p2p.Server) error {
+	p.log.Info("ping-pong service starting")
+	return nil
+}
+
+func (p *pingPongService) Stop() error {
+	p.log.Info("ping-pong service stopping")
+	return nil
+}
+
+func (p *pingPongService) Info() interface{} {
+	return struct {
+		Received int64 `json:"received"`
+	}{
+		atomic.LoadInt64(&p.received),
+	}
+}
+
+const (
+	pingMsgCode = iota
+	pongMsgCode
+)
+
+// Run implements the ping-pong protocol which sends ping messages to the peer
+// at 10s intervals, and responds to pings with pong messages.
+func (p *pingPongService) Run(peer *p2p.Peer, rw p2p.MsgReadWriter) error {
+	log := p.log.New("peer.id", peer.ID())
+
+	errC := make(chan error)
+	go func() {
+		for range time.Tick(10 * time.Second) {
+			log.Info("sending ping")
+			if err := p2p.Send(rw, pingMsgCode, "PING"); err != nil {
+				errC <- err
+				return
+			}
+		}
+	}()
+	go func() {
+		for {
+			msg, err := rw.ReadMsg()
+			if err != nil {
+				errC <- err
+				return
+			}
+			payload, err := ioutil.ReadAll(msg.Payload)
+			if err != nil {
+				errC <- err
+				return
+			}
+			log.Info("received message", "msg.code", msg.Code, "msg.payload", string(payload))
+			atomic.AddInt64(&p.received, 1)
+			if msg.Code == pingMsgCode {
+				log.Info("sending pong")
+				go p2p.Send(rw, pongMsgCode, "PONG")
+			}
+		}
+	}()
+	return <-errC
+}
diff --git a/p2p/simulations/examples/ping-pong.sh b/p2p/simulations/examples/ping-pong.sh
new file mode 100755
index 000000000..47936bd9a
--- /dev/null
+++ b/p2p/simulations/examples/ping-pong.sh
@@ -0,0 +1,40 @@
+#!/bin/bash
+#
+# Boot a ping-pong network simulation using the HTTP API started by ping-pong.go
+
+set -e
+
+main() {
+  if ! which p2psim &>/dev/null; then
+    fail "missing p2psim binary (you need to build cmd/p2psim and put it in \$PATH)"
+  fi
+
+  info "creating 10 nodes"
+  for i in $(seq 1 10); do
+    p2psim node create --name "$(node_name $i)"
+    p2psim node start "$(node_name $i)"
+  done
+
+  info "connecting node01 to all other nodes"
+  for i in $(seq 2 10); do
+    p2psim node connect "node01" "$(node_name $i)"
+  done
+
+  info "done"
+}
+
+node_name() {
+  local num=$1
+  echo "node$(printf '%02d' $num)"
+}
+
+info() {
+  echo -e "\033[1;32m---> $(date +%H:%M:%S) ${@}\033[0m"
+}
+
+fail() {
+  echo -e "\033[1;31mERROR: ${@}\033[0m" >&2
+  exit 1
+}
+
+main "$@"