聊聊dubbo-go的DefaultHealthChecker

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本文主要研究一下dubbo-go的DefaultHealthChecker

DefaultHealthChecker

dubbo-go-v1.4.2/cluster/router/healthcheck/default_health_check.go

func init() {
	extension.SethealthChecker(constant.DEFAULT_HEALTH_CHECKER, NewDefaultHealthChecker)
}

// DefaultHealthChecker is the default implementation of HealthChecker, which determines the health status of
// the invoker based on the number of successive bad request and the current active request.
type DefaultHealthChecker struct {
	// the limit of outstanding request
	outStandingRequestConutLimit int32
	// the threshold of successive-failure-request
	requestSuccessiveFailureThreshold int32
	// value of circuit-tripped timeout factor
	circuitTrippedTimeoutFactor int32
}

NewDefaultHealthChecker

dubbo-go-v1.4.2/cluster/router/healthcheck/default_health_check.go

// NewDefaultHealthChecker constructs a new DefaultHealthChecker based on the url
func NewDefaultHealthChecker(url *common.URL) router.HealthChecker {
	return &DefaultHealthChecker{
		outStandingRequestConutLimit:      int32(url.GetParamInt(constant.OUTSTANDING_REQUEST_COUNT_LIMIT_KEY, math.MaxInt32)),
		requestSuccessiveFailureThreshold: int32(url.GetParamInt(constant.SUCCESSIVE_FAILED_REQUEST_THRESHOLD_KEY, constant.DEFAULT_SUCCESSIVE_FAILED_REQUEST_MAX_DIFF)),
		circuitTrippedTimeoutFactor:       int32(url.GetParamInt(constant.CIRCUIT_TRIPPED_TIMEOUT_FACTOR_KEY, constant.DEFAULT_CIRCUIT_TRIPPED_TIMEOUT_FACTOR)),
	}
}

IsHealthy

dubbo-go-v1.4.2/cluster/router/healthcheck/default_health_check.go

// IsHealthy evaluates the healthy state on the given Invoker based on the number of successive bad request
// and the current active request
func (c *DefaultHealthChecker) IsHealthy(invoker protocol.Invoker) bool {
	urlStatus := protocol.GetURLStatus(invoker.GetUrl())
	if c.isCircuitBreakerTripped(urlStatus) || urlStatus.GetActive() > c.GetOutStandingRequestConutLimit() {
		logger.Debugf("Invoker [%s] is currently in circuitbreaker tripped state", invoker.GetUrl().Key())
		return false
	}
	return true
}

isCircuitBreakerTripped

dubbo-go-v1.4.2/cluster/router/healthcheck/default_health_check.go

// isCircuitBreakerTripped determine whether the invoker is in the tripped state by the number of successive bad request
func (c *DefaultHealthChecker) isCircuitBreakerTripped(status *protocol.RPCStatus) bool {
	circuitBreakerTimeout := c.getCircuitBreakerTimeout(status)
	currentTime := protocol.CurrentTimeMillis()
	if circuitBreakerTimeout <= 0 {
		return false
	}
	return circuitBreakerTimeout > currentTime
}

getCircuitBreakerTimeout

dubbo-go-v1.4.2/cluster/router/healthcheck/default_health_check.go

// getCircuitBreakerTimeout get the timestamp recovered from tripped state, the unit is millisecond
func (c *DefaultHealthChecker) getCircuitBreakerTimeout(status *protocol.RPCStatus) int64 {
	sleepWindow := c.getCircuitBreakerSleepWindowTime(status)
	if sleepWindow <= 0 {
		return 0
	}
	return status.GetLastRequestFailedTimestamp() + sleepWindow
}

getCircuitBreakerSleepWindowTime

dubbo-go-v1.4.2/cluster/router/healthcheck/default_health_check.go

// getCircuitBreakerSleepWindowTime get the sleep window time of invoker, the unit is millisecond
func (c *DefaultHealthChecker) getCircuitBreakerSleepWindowTime(status *protocol.RPCStatus) int64 {

	successiveFailureCount := status.GetSuccessiveRequestFailureCount()
	diff := successiveFailureCount - c.GetRequestSuccessiveFailureThreshold()
	if diff < 0 {
		return 0
	} else if diff > constant.DEFAULT_SUCCESSIVE_FAILED_REQUEST_MAX_DIFF {
		diff = constant.DEFAULT_SUCCESSIVE_FAILED_REQUEST_MAX_DIFF
	}
	sleepWindow := (1 << diff) * c.GetCircuitTrippedTimeoutFactor()
	if sleepWindow > constant.MAX_CIRCUIT_TRIPPED_TIMEOUT_IN_MS {
		sleepWindow = constant.MAX_CIRCUIT_TRIPPED_TIMEOUT_IN_MS
	}
	return int64(sleepWindow)
}

小结

DefaultHealthChecker定义了outStandingRequestConutLimit、requestSuccessiveFailureThreshold、circuitTrippedTimeoutFactor属性;IsHealthy方法通过protocol.GetURLStatus(invoker.GetUrl())获取urlStatus,之后根据c.isCircuitBreakerTripped(urlStatus)或者urlStatus.GetActive() > c.GetOutStandingRequestConutLimit()判断是否处于circuitbreaker tripped状态

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