p2p/simulations: add mocker functionality (#15207)

This commit adds mocker functionality to p2p/simulations. A
mocker allows to starting/stopping of nodes via the HTTP API.

p2p/simulations/mocker.go

@@ -0,0 +1,192 @@
+// 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 simulations simulates p2p networks.
+// A mocker simulates starting and stopping real nodes in a network.
+package simulations
+
+import (
+	"fmt"
+	"math/rand"
+	"sync"
+	"time"
+
+	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/p2p/discover"
+)
+
+//a map of mocker names to its function
+var mockerList = map[string]func(net *Network, quit chan struct{}, nodeCount int){
+	"startStop":     startStop,
+	"probabilistic": probabilistic,
+	"boot":          boot,
+}
+
+//Lookup a mocker by its name, returns the mockerFn
+func LookupMocker(mockerType string) func(net *Network, quit chan struct{}, nodeCount int) {
+	return mockerList[mockerType]
+}
+
+//Get a list of mockers (keys of the map)
+//Useful for frontend to build available mocker selection
+func GetMockerList() []string {
+	list := make([]string, 0, len(mockerList))
+	for k := range mockerList {
+		list = append(list, k)
+	}
+	return list
+}
+
+//The boot mockerFn only connects the node in a ring and doesn't do anything else
+func boot(net *Network, quit chan struct{}, nodeCount int) {
+	_, err := connectNodesInRing(net, nodeCount)
+	if err != nil {
+		panic("Could not startup node network for mocker")
+	}
+}
+
+//The startStop mockerFn stops and starts nodes in a defined period (ticker)
+func startStop(net *Network, quit chan struct{}, nodeCount int) {
+	nodes, err := connectNodesInRing(net, nodeCount)
+	if err != nil {
+		panic("Could not startup node network for mocker")
+	}
+	tick := time.NewTicker(10 * time.Second)
+	defer tick.Stop()
+	for {
+		select {
+		case <-quit:
+			log.Info("Terminating simulation loop")
+			return
+		case <-tick.C:
+			id := nodes[rand.Intn(len(nodes))]
+			log.Info("stopping node", "id", id)
+			if err := net.Stop(id); err != nil {
+				log.Error("error stopping node", "id", id, "err", err)
+				return
+			}
+
+			select {
+			case <-quit:
+				log.Info("Terminating simulation loop")
+				return
+			case <-time.After(3 * time.Second):
+			}
+
+			log.Debug("starting node", "id", id)
+			if err := net.Start(id); err != nil {
+				log.Error("error starting node", "id", id, "err", err)
+				return
+			}
+		}
+	}
+}
+
+//The probabilistic mocker func has a more probabilistic pattern
+//(the implementation could probably be improved):
+//nodes are connected in a ring, then a varying number of random nodes is selected,
+//mocker then stops and starts them in random intervals, and continues the loop
+func probabilistic(net *Network, quit chan struct{}, nodeCount int) {
+	nodes, err := connectNodesInRing(net, nodeCount)
+	if err != nil {
+		panic("Could not startup node network for mocker")
+	}
+	for {
+		select {
+		case <-quit:
+			log.Info("Terminating simulation loop")
+			return
+		default:
+		}
+		var lowid, highid int
+		var wg sync.WaitGroup
+		randWait := time.Duration(rand.Intn(5000)+1000) * time.Millisecond
+		rand1 := rand.Intn(nodeCount - 1)
+		rand2 := rand.Intn(nodeCount - 1)
+		if rand1 < rand2 {
+			lowid = rand1
+			highid = rand2
+		} else if rand1 > rand2 {
+			highid = rand1
+			lowid = rand2
+		} else {
+			if rand1 == 0 {
+				rand2 = 9
+			} else if rand1 == 9 {
+				rand1 = 0
+			}
+			lowid = rand1
+			highid = rand2
+		}
+		var steps = highid - lowid
+		wg.Add(steps)
+		for i := lowid; i < highid; i++ {
+			select {
+			case <-quit:
+				log.Info("Terminating simulation loop")
+				return
+			case <-time.After(randWait):
+			}
+			log.Debug(fmt.Sprintf("node %v shutting down", nodes[i]))
+			err := net.Stop(nodes[i])
+			if err != nil {
+				log.Error(fmt.Sprintf("Error stopping node %s", nodes[i]))
+				wg.Done()
+				continue
+			}
+			go func(id discover.NodeID) {
+				time.Sleep(randWait)
+				err := net.Start(id)
+				if err != nil {
+					log.Error(fmt.Sprintf("Error starting node %s", id))
+				}
+				wg.Done()
+			}(nodes[i])
+		}
+		wg.Wait()
+	}
+
+}
+
+//connect nodeCount number of nodes in a ring
+func connectNodesInRing(net *Network, nodeCount int) ([]discover.NodeID, error) {
+	ids := make([]discover.NodeID, nodeCount)
+	for i := 0; i < nodeCount; i++ {
+		node, err := net.NewNode()
+		if err != nil {
+			log.Error("Error creating a node! %s", err)
+			return nil, err
+		}
+		ids[i] = node.ID()
+	}
+
+	for _, id := range ids {
+		if err := net.Start(id); err != nil {
+			log.Error("Error starting a node! %s", err)
+			return nil, err
+		}
+		log.Debug(fmt.Sprintf("node %v starting up", id))
+	}
+	for i, id := range ids {
+		peerID := ids[(i+1)%len(ids)]
+		if err := net.Connect(id, peerID); err != nil {
+			log.Error("Error connecting a node to a peer! %s", err)
+			return nil, err
+		}
+	}
+
+	return ids, nil
+}