org.thales.punch.libraries.netty.loadcontrol

Class RateLimiterLoadController

java.lang.Object

org.thales.punch.libraries.netty.loadcontrol.LoadController

org.thales.punch.libraries.netty.loadcontrol.RateLimiterLoadController

All Implemented Interfaces:

ILoadController

public class RateLimiterLoadController
extends LoadController
implements ILoadController

This class allows you to know when you should start refuse traffic because the application is overloaded.

It works as follows: whenever you want to accept a new incoming message in the system, you call the allow() method. If it returns true, process the message, if it returns false, dont, i.e. either drop the message or delay its injection into the application. When a processed message is acknowledged,fully processed by the application, call the update method with the corresponding processing time in millisecond.

The load controller keeps track of an average traversal time, and will start telling you to slow down if it detects an increase in the response time. However, when doing that it will keep let some messages pass so that the traversal time can still be computed, and so as not to brutally stop traffic processing.

The load controller can be in one of two state: BLOCKED: only a fraction of the traffic is accepted. NORMAL: all the traffic is accepted.

Every time it enters the BLOCKED state, the load controller computes an estimated message rate, used to compute what fraction of the traffic should be allowed to pass. The higher the increase in RTT, the smaller that fraction.

You can question the statistics of the load controller, in particular the ration of allowed message, from the beginning or in the last 10 seconds interval.

The main parameter influencing the behavior of that load comntroller is the alpha parameter used in computing the average RTT. The formula is a standard weighted moving average:

newRtt = alpha * value + + (1-alpha) * currentRTT

The smaller alpha, the less weight the latest value. In practice a 0.05 value is good enough so as to react quickly enough. If you use 0.01 or smaller, the controlled will be more defensive, and will end up refusing more traffic than it should.

Author:

dimi

Field Summary

Fields inherited from class org.thales.punch.libraries.netty.loadcontrol.LoadController

lastStatTimestamp, statsDelay

Constructor Summary

Constructors

Constructor and Description
RateLimiterLoadController(org.thales.punch.libraries.metrics.api.IMetricContext metricsContext) Create a new load controller with the default starting response time (RTT) of 30000, i.e.

Method Summary

Modifier and Type	Method and Description
void	ack(long v) update the controller statistics.
LoadController	configure(org.thales.punch.settings.api.ISettingsMap settings) Configure a load controller.
protected void	debug() dump some useful infos.
void	fail(long v) update the controller statistics.
int	getCurrentRate()
void	regulate() regulate the traffic, this method potentially take some time before returning.
RateLimiterLoadController	setAdaptative(Boolean asBoolean) activate an adaptative load control.
RateLimiterLoadController	setRate(long rate) Set the rate expressed in eps
RateLimiterLoadController	setStatsDelay(long delay) set the stats publishing delay

Methods inherited from class org.thales.punch.libraries.netty.loadcontrol.LoadController

factory, setMaxTimeoutSec

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.thales.punch.libraries.netty.loadcontrol.ILoadController

setMaxTimeoutSec

Constructor Detail

RateLimiterLoadController

public RateLimiterLoadController(org.thales.punch.libraries.metrics.api.IMetricContext metricsContext)

Create a new load controller with the default starting response time (RTT) of 30000, i.e. 30 seconds. The alpha parameter for computing the average RTT is 0.05.

Parameters:

metricsContext - the provider of metrics registry and context tags

Method Detail

setStatsDelay

public RateLimiterLoadController setStatsDelay(long delay)

set the stats publishing delay

Parameters:

delay - the delay in milliseconds

Returns:

your new instance

setRate

public RateLimiterLoadController setRate(long rate)

Set the rate expressed in eps

Parameters:

rate - the rate in event per second

Returns:

this load controller

ack

public void ack(long v)

Description copied from interface: ILoadController

update the controller statistics. If you work with a non acknowledged protocol, call this method with a 0 value.

Specified by:

ack in interface ILoadController

Overrides:

ack in class LoadController

Parameters:

v - the traversal time of a tuple, in milliseconds

fail

public void fail(long v)

Description copied from interface: ILoadController

update the controller statistics.

Specified by:

fail in interface ILoadController

Overrides:

fail in class LoadController

Parameters:

v - the traversal time of a tuple, in milliseconds

regulate

public void regulate()

Description copied from interface: ILoadController

regulate the traffic, this method potentially take some time before returning. It will slow you down as requested by your settings.

Specified by:

regulate in interface ILoadController

Overrides:

regulate in class LoadController

debug

protected void debug()

dump some useful infos.

Overrides:

debug in class LoadController

configure

public LoadController configure(org.thales.punch.settings.api.ISettingsMap settings)

Description copied from class: LoadController

Configure a load controller. Each load controller implementation use various settings. Check the implementation you use.

Overrides:

configure in class LoadController

Parameters:

settings - the caller load contraoller settings

Returns:

your rate controller

setAdaptative

public RateLimiterLoadController setAdaptative(Boolean asBoolean)

activate an adaptative load control. This refines the storm max tuple pending settings.

Parameters:

asBoolean - true to activate the adaptative behavior

Returns:

this controller

getCurrentRate

public int getCurrentRate()

Specified by:

getCurrentRate in interface ILoadController

Overrides:

getCurrentRate in class LoadController

Returns:

the current limiting rate. If the rate limiter is configured as passing through ("none"), -1 is returned