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fault_detector.go
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fault_detector.go
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package protocols
import (
"fmt"
"time"
"github.com/antongulenko/golib"
)
const (
default_ping_check_duration = 200 * time.Millisecond
)
var (
stateUnknown = fmt.Errorf("Status was not checked yet")
)
type FaultDetectorCallback func(key interface{})
type FaultDetector interface {
Close() error
Check()
// Implemented by *FaultDetectorBase
Error() error
Online() bool
ErrorDetected(err error)
ObservedServer() Addr
AddCallback(callback FaultDetectorCallback, key interface{})
}
type faultDetectorCallbackData struct {
callback FaultDetectorCallback
key interface{}
}
type observedServer struct {
protocol Protocol
addr Addr
}
type FaultDetectorBase struct {
callbacks []faultDetectorCallbackData
lastErr error
observedServer observedServer
Closed golib.StopChan
}
func NewFaultDetectorBase(observedProtocol Protocol, server Addr) *FaultDetectorBase {
return &FaultDetectorBase{
lastErr: stateUnknown,
observedServer: observedServer{
observedProtocol,
server,
},
Closed: golib.NewStopChan(),
}
}
func (detector *FaultDetectorBase) ObservedServer() Addr {
return detector.observedServer.addr
}
func (detector *FaultDetectorBase) AddCallback(callback FaultDetectorCallback, key interface{}) {
detector.callbacks = append(detector.callbacks, faultDetectorCallbackData{callback, key})
}
func (detector *FaultDetectorBase) ErrorDetected(err error) {
detector.lastErr = err
}
func (detector *FaultDetectorBase) Online() bool {
return detector.lastErr == nil
}
func (detector *FaultDetectorBase) Error() (err error) {
lastErr := detector.lastErr
if lastErr != nil {
err = fmt.Errorf("%v on %s is currently offline: %v",
detector.observedServer.protocol.Name(), detector.observedServer.addr, lastErr)
}
return
}
func (detector *FaultDetectorBase) InvokeCallback(wasOnline bool) {
isOnline := detector.lastErr == nil
if wasOnline != isOnline && detector.lastErr != stateUnknown {
for _, data := range detector.callbacks {
data.callback(data.key)
}
}
}
func (detector *FaultDetectorBase) PerformCheck(checker func() error) {
wasOnline := detector.Online()
detector.lastErr = checker()
detector.InvokeCallback(wasOnline)
}
func (detector *FaultDetectorBase) LoopCheck(checker func(), timeout time.Duration) {
for !detector.Closed.Enabled() {
checker()
time.Sleep(timeout)
}
if detector.lastErr == nil {
detector.lastErr = fmt.Errorf("FaultDetector for %v is closed", detector.observedServer.addr)
} else {
detector.lastErr = fmt.Errorf("FaultDetector for %v is closed. Previous error: %v", detector.observedServer.addr, detector.lastErr)
}
detector.InvokeCallback(detector.lastErr == nil)
}