mgmt/resources/timer.go

// Mgmt
// Copyright (C) 2013-2016+ James Shubin and the project contributors
// Written by James Shubin <james@shubin.ca> and the project contributors
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program 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 Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package resources

import (
	"encoding/gob"
	"log"
	"time"

	"github.com/purpleidea/mgmt/event"
)

func init() {
	gob.Register(&TimerRes{})
}

// TimerRes is a timer resource for time based events.
type TimerRes struct {
	BaseRes  `yaml:",inline"`
	Interval int `yaml:"interval"` // Interval : Interval between runs

	ticker *time.Ticker
}

// TimerUID is the UID struct for TimerRes.
type TimerUID struct {
	BaseUID
	name string
}

// NewTimerRes is a constructor for this resource. It also calls Init() for you.
func NewTimerRes(name string, interval int) (*TimerRes, error) {
	obj := &TimerRes{
		BaseRes: BaseRes{
			Name: name,
		},
		Interval: interval,
	}
	return obj, obj.Init()
}

// Init runs some startup code for this resource.
func (obj *TimerRes) Init() error {
	obj.BaseRes.kind = "Timer"
	return obj.BaseRes.Init() // call base init, b/c we're overrriding
}

// Validate the params that are passed to TimerRes
// Currently we are getting only an interval in seconds
// which gets validated by go compiler
func (obj *TimerRes) Validate() error {
	return nil
}

// newTicker creates a new ticker
func (obj *TimerRes) newTicker() *time.Ticker {
	return time.NewTicker(time.Duration(obj.Interval) * time.Second)
}

// Watch is the primary listener for this resource and it outputs events.
func (obj *TimerRes) Watch(processChan chan event.Event) error {
	if obj.IsWatching() {
		return nil
	}
	obj.SetWatching(true)
	defer obj.SetWatching(false)
	cuid := obj.converger.Register()
	defer cuid.Unregister()

	var startup bool
	Startup := func(block bool) <-chan time.Time {
		if block {
			return nil // blocks forever
			//return make(chan time.Time) // blocks forever
		}
		return time.After(time.Duration(500) * time.Millisecond) // 1/2 the resolution of converged timeout
	}

	// create a time.Ticker for the given interval
	obj.ticker = obj.newTicker()
	defer obj.ticker.Stop()

	var send = false

	for {
		obj.SetState(ResStateWatching)
		select {
		case <-obj.ticker.C: // received the timer event
			send = true
			log.Printf("%s[%s]: received tick", obj.Kind(), obj.GetName())

		case event := <-obj.Events():
			cuid.SetConverged(false)
			if exit, _ := obj.ReadEvent(&event); exit {
				return nil
			}

		case <-cuid.ConvergedTimer():
			cuid.SetConverged(true)
			continue

		case <-Startup(startup):
			cuid.SetConverged(false)
			send = true
		}
		if send {
			startup = true // startup finished
			send = false
			if exit, err := obj.DoSend(processChan, "timer ticked"); exit || err != nil {
				return err // we exit or bubble up a NACK...
			}
		}
	}
}

// CheckApply method for Timer resource. Triggers a timer reset on notify.
func (obj *TimerRes) CheckApply(apply bool) (bool, error) {
	// because there are no checks to run, this resource has a less
	// traditional pattern than what is seen in most resources...
	if !obj.Refresh() { // this works for apply || !apply
		return true, nil // state is always okay if no refresh to do
	} else if !apply { // we had a refresh to do
		return false, nil // therefore state is wrong
	}

	// reset the timer since apply && refresh
	obj.ticker.Stop()
	obj.ticker = obj.newTicker()
	return false, nil
}

// GetUIDs includes all params to make a unique identification of this object.
// Most resources only return one, although some resources can return multiple.
func (obj *TimerRes) GetUIDs() []ResUID {
	x := &TimerUID{
		BaseUID: BaseUID{
			name: obj.GetName(),
			kind: obj.Kind(),
		},
		name: obj.Name,
	}
	return []ResUID{x}
}

// AutoEdges returns the AutoEdge interface. In this case no autoedges are used.
func (obj *TimerRes) AutoEdges() AutoEdge {
	return nil
}

// Compare two resources and return if they are equivalent.
func (obj *TimerRes) Compare(res Res) bool {
	switch res.(type) {
	case *TimerRes:
		res := res.(*TimerRes)
		if !obj.BaseRes.Compare(res) {
			return false
		}
		if obj.Name != res.Name {
			return false
		}
		if obj.Interval != res.Interval {
			return false
		}
	default:
		return false
	}
	return true
}