com.alibaba.csp.sentinel.slots.block.flow.controller

Class WarmUpController

java.lang.Object

com.alibaba.csp.sentinel.slots.block.flow.controller.WarmUpController

All Implemented Interfaces:

TrafficShapingController

Direct Known Subclasses:

WarmUpRateLimiterController

public class WarmUpController
extends Object
implements TrafficShapingController

The principle idea comes from Guava. However, the calculation of Guava is rate-based, which means that we need to translate rate to QPS.

Requests arriving at the pulse may drag down long idle systems even though it has a much larger handling capability in stable period. It usually happens in scenarios that require extra time for initialization, e.g. DB establishes a connection, connects to a remote service, and so on. That’s why we need “warm up”.

Sentinel's "warm-up" implementation is based on the Guava's algorithm. However, Guava’s implementation focuses on adjusting the request interval, which is similar to leaky bucket. Sentinel pays more attention to controlling the count of incoming requests per second without calculating its interval, which resembles token bucket algorithm.

The remaining tokens in the bucket is used to measure the system utility. Suppose a system can handle b requests per second. Every second b tokens will be added into the bucket until the bucket is full. And when system processes a request, it takes a token from the bucket. The more tokens left in the bucket, the lower the utilization of the system; when the token in the token bucket is above a certain threshold, we call it in a "saturation" state.

Base on Guava’s theory, there is a linear equation we can write this in the form y = m * x + b where y (a.k.a y(x)), or qps(q)), is our expected QPS given a saturated period (e.g. 3 minutes in), m is the rate of change from our cold (minimum) rate to our stable (maximum) rate, x (or q) is the occupied token.

Author:

jialiang.linjl

Field Summary

Fields

Modifier and Type	Field and Description
protected double	count
protected AtomicLong	lastFilledTime
protected double	slope
protected AtomicLong	storedTokens
protected int	warningToken

Constructor Summary

Constructors

Constructor and Description
WarmUpController(double count, int warmUpPeriodInSec)
WarmUpController(double count, int warmUpPeriodInSec, int coldFactor)

Method Summary

Modifier and Type	Method and Description
boolean	canPass(Node node, int acquireCount) Check whether given resource entry can pass with provided count.
boolean	canPass(Node node, int acquireCount, boolean prioritized) Check whether given resource entry can pass with provided count.
protected void	syncToken(long passQps)

Methods inherited from class java.lang.Object

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

Field Detail

count

protected double count

warningToken

protected int warningToken

slope

protected double slope

storedTokens

protected AtomicLong storedTokens

lastFilledTime

protected AtomicLong lastFilledTime

Constructor Detail

WarmUpController

public WarmUpController(double count,
                        int warmUpPeriodInSec,
                        int coldFactor)

WarmUpController

public WarmUpController(double count,
                        int warmUpPeriodInSec)

Method Detail

canPass

public boolean canPass(Node node,
                       int acquireCount)

Description copied from interface: TrafficShapingController

Check whether given resource entry can pass with provided count.

Specified by:

canPass in interface TrafficShapingController

Parameters:

node - resource node

acquireCount - count to acquire

Returns:

true if the resource entry can pass; false if it should be blocked

canPass

public boolean canPass(Node node,
                       int acquireCount,
                       boolean prioritized)

Description copied from interface: TrafficShapingController

Check whether given resource entry can pass with provided count.

Specified by:

canPass in interface TrafficShapingController

Parameters:

node - resource node

acquireCount - count to acquire

prioritized - whether the request is prioritized

Returns:

true if the resource entry can pass; false if it should be blocked

syncToken

protected void syncToken(long passQps)