go-pulse/p2p/simulations/simulation.go
Lewis Marshall 9feec51e2d 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.
2017-09-25 10:08:07 +02:00

158 lines
3.9 KiB
Go

// 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
import (
"context"
"time"
"github.com/ethereum/go-ethereum/p2p/discover"
)
// Simulation provides a framework for running actions in a simulated network
// and then waiting for expectations to be met
type Simulation struct {
network *Network
}
// NewSimulation returns a new simulation which runs in the given network
func NewSimulation(network *Network) *Simulation {
return &Simulation{
network: network,
}
}
// Run performs a step of the simulation by performing the step's action and
// then waiting for the step's expectation to be met
func (s *Simulation) Run(ctx context.Context, step *Step) (result *StepResult) {
result = newStepResult()
result.StartedAt = time.Now()
defer func() { result.FinishedAt = time.Now() }()
// watch network events for the duration of the step
stop := s.watchNetwork(result)
defer stop()
// perform the action
if err := step.Action(ctx); err != nil {
result.Error = err
return
}
// wait for all node expectations to either pass, error or timeout
nodes := make(map[discover.NodeID]struct{}, len(step.Expect.Nodes))
for _, id := range step.Expect.Nodes {
nodes[id] = struct{}{}
}
for len(result.Passes) < len(nodes) {
select {
case id := <-step.Trigger:
// skip if we aren't checking the node
if _, ok := nodes[id]; !ok {
continue
}
// skip if the node has already passed
if _, ok := result.Passes[id]; ok {
continue
}
// run the node expectation check
pass, err := step.Expect.Check(ctx, id)
if err != nil {
result.Error = err
return
}
if pass {
result.Passes[id] = time.Now()
}
case <-ctx.Done():
result.Error = ctx.Err()
return
}
}
return
}
func (s *Simulation) watchNetwork(result *StepResult) func() {
stop := make(chan struct{})
done := make(chan struct{})
events := make(chan *Event)
sub := s.network.Events().Subscribe(events)
go func() {
defer close(done)
defer sub.Unsubscribe()
for {
select {
case event := <-events:
result.NetworkEvents = append(result.NetworkEvents, event)
case <-stop:
return
}
}
}()
return func() {
close(stop)
<-done
}
}
type Step struct {
// Action is the action to perform for this step
Action func(context.Context) error
// Trigger is a channel which receives node ids and triggers an
// expectation check for that node
Trigger chan discover.NodeID
// Expect is the expectation to wait for when performing this step
Expect *Expectation
}
type Expectation struct {
// Nodes is a list of nodes to check
Nodes []discover.NodeID
// Check checks whether a given node meets the expectation
Check func(context.Context, discover.NodeID) (bool, error)
}
func newStepResult() *StepResult {
return &StepResult{
Passes: make(map[discover.NodeID]time.Time),
}
}
type StepResult struct {
// Error is the error encountered whilst running the step
Error error
// StartedAt is the time the step started
StartedAt time.Time
// FinishedAt is the time the step finished
FinishedAt time.Time
// Passes are the timestamps of the successful node expectations
Passes map[discover.NodeID]time.Time
// NetworkEvents are the network events which occurred during the step
NetworkEvents []*Event
}