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// 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
}
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