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load_fact.go
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load_fact.go
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// Mgmt
// Copyright (C) 2013-2018+ 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 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
package core // TODO: should this be in its own individual package?
import (
"time"
"github.com/purpleidea/mgmt/lang/funcs/facts"
"github.com/purpleidea/mgmt/lang/types"
errwrap "github.com/pkg/errors"
)
const (
loadSignature = "struct{x1 float; x5 float; x15 float}"
)
func init() {
facts.Register("load", func() facts.Fact { return &LoadFact{} }) // must register the fact and name
}
// LoadFact is a fact which returns the current system load.
type LoadFact struct {
init *facts.Init
closeChan chan struct{}
}
// Validate makes sure we've built our struct properly. It is usually unused for
// normal facts that users can use directly.
//func (obj *LoadFact) Validate() error {
// return nil
//}
// Info returns some static info about itself.
func (obj *LoadFact) Info() *facts.Info {
return &facts.Info{
Output: types.NewType(loadSignature),
}
}
// Init runs some startup code for this fact.
func (obj *LoadFact) Init(init *facts.Init) error {
obj.init = init
obj.closeChan = make(chan struct{})
return nil
}
// Stream returns the changing values that this fact has over time.
func (obj *LoadFact) Stream() error {
defer close(obj.init.Output) // always signal when we're done
// it seems the different values only update once every 5
// seconds, so that's as often as we need to refresh this!
// TODO: lookup this value if it's something configurable
ticker := time.NewTicker(time.Duration(5) * time.Second)
// streams must generate an initial event on startup
startChan := make(chan struct{}) // start signal
close(startChan) // kick it off!
defer ticker.Stop()
for {
select {
case <-startChan: // kick the loop once at start
startChan = nil // disable
case <-ticker.C: // received the timer event
// pass
case <-obj.closeChan:
return nil
}
x1, x5, x15, err := load()
if err != nil {
return errwrap.Wrapf(err, "could not read load values")
}
st := types.NewStruct(types.NewType(loadSignature))
for k, v := range map[string]float64{"x1": x1, "x5": x5, "x15": x15} {
if err := st.Set(k, &types.FloatValue{V: v}); err != nil {
return errwrap.Wrapf(err, "struct could not set key: `%s`", k)
}
}
select {
case obj.init.Output <- st:
// send
case <-obj.closeChan:
return nil
}
}
}
// Close runs some shutdown code for this fact and turns off the stream.
func (obj *LoadFact) Close() error {
close(obj.closeChan)
return nil
}