path: root/core/ticker.go

// Copyright 2018 The dexon-consensus Authors
// This file is part of the dexon-consensus library.
//
// The dexon-consensus 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 dexon-consensus 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 dexon-consensus library. If not, see
// <http://www.gnu.org/licenses/>.

package core

import (
    "context"
    "fmt"
    "sync"
    "time"

    "github.com/dexon-foundation/dexon-consensus/core/utils"
)

// TickerType is the type of ticker.
type TickerType int

// TickerType enum.
const (
    TickerBA TickerType = iota
    TickerDKG
    TickerCRS
)

// defaultTicker is a wrapper to implement ticker interface based on
// time.Ticker.
type defaultTicker struct {
    ticker     *time.Ticker
    tickerChan chan time.Time
    duration   time.Duration
    ctx        context.Context
    ctxCancel  context.CancelFunc
    waitGroup  sync.WaitGroup
}

// newDefaultTicker constructs an defaultTicker instance by giving an interval.
func newDefaultTicker(lambda time.Duration) *defaultTicker {
    ticker := &defaultTicker{duration: lambda}
    ticker.init()
    return ticker
}

// Tick implements Tick method of ticker interface.
func (t *defaultTicker) Tick() <-chan time.Time {
    return t.tickerChan
}

// Stop implements Stop method of ticker interface.
func (t *defaultTicker) Stop() {
    t.ticker.Stop()
    t.ctxCancel()
    t.waitGroup.Wait()
    t.ctx = nil
    t.ctxCancel = nil
    close(t.tickerChan)
    t.tickerChan = nil
}

// Restart implements Stop method of ticker interface.
func (t *defaultTicker) Restart() {
    t.Stop()
    t.init()
}

func (t *defaultTicker) init() {
    t.ticker = time.NewTicker(t.duration)
    t.tickerChan = make(chan time.Time)
    t.ctx, t.ctxCancel = context.WithCancel(context.Background())
    t.waitGroup.Add(1)
    go t.monitor()
}

func (t *defaultTicker) monitor() {
    defer t.waitGroup.Done()
loop:
    for {
        select {
        case <-t.ctx.Done():
            break loop
        case v := <-t.ticker.C:
            select {
            case t.tickerChan <- v:
            default:
            }
        }
    }
}

// newTicker is a helper to setup a ticker by giving an Governance. If
// the governace object implements a ticker generator, a ticker from that
// generator would be returned, else constructs a default one.
func newTicker(gov Governance, round uint64, tickerType TickerType) (t Ticker) {
    type tickerGenerator interface {
        NewTicker(TickerType) Ticker
    }

    if gen, ok := gov.(tickerGenerator); ok {
        t = gen.NewTicker(tickerType)
    }
    if t == nil {
        var duration time.Duration
        switch tickerType {
        case TickerBA:
            duration = utils.GetConfigWithPanic(gov, round, nil).LambdaBA
        case TickerDKG:
            duration = utils.GetConfigWithPanic(gov, round, nil).LambdaDKG
        default:
            panic(fmt.Errorf("unknown ticker type: %d", tickerType))
        }
        t = newDefaultTicker(duration)
    }
    return
}