path: root/p2p/simulations/simulation.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
}