org.apache.hc.client5.http.impl.classic

Class AIMDBackoffManager

java.lang.Object

org.apache.hc.client5.http.impl.classic.AbstractBackoff

org.apache.hc.client5.http.impl.classic.AIMDBackoffManager

All Implemented Interfaces:

BackoffManager

@Contract(threading=SAFE)
public class AIMDBackoffManager
extends AbstractBackoff

The AIMDBackoffManager applies an additive increase, multiplicative decrease (AIMD) to managing a dynamic limit to the number of connections allowed to a given host. You may want to experiment with the settings for the cooldown periods and the backoff factor to get the adaptive behavior you want.

Generally speaking, shorter cooldowns will lead to more steady-state variability but faster reaction times, while longer cooldowns will lead to more stable equilibrium behavior but slower reaction times.

Similarly, higher backoff factors promote greater utilization of available capacity at the expense of fairness among clients. Lower backoff factors allow equal distribution of capacity among clients (fairness) to happen faster, at the expense of having more server capacity unused in the short term.

Since:

4.2

Constructor Summary

Constructors

Constructor and Description
AIMDBackoffManager(org.apache.hc.core5.pool.ConnPoolControl<HttpRoute> connPerRoute) Constructs an AIMDBackoffManager with the specified ConnPoolControl and Clock.

Method Summary

Modifier and Type	Method and Description
protected int	getBackedOffPoolSize(int curr) Returns the backed-off pool size based on the current pool size.
void	setBackoffFactor(double d) Sets the factor to use when backing off; the new per-host limit will be roughly the current max times this factor.

Methods inherited from class org.apache.hc.client5.http.impl.classic.AbstractBackoff

backOff, getBackoffFactor, getCap, getConnPerRoute, getCoolDown, getLastRouteBackoffs, getLastRouteProbes, getLastUpdate, getTimeInterval, probe, setCoolDown, setPerHostConnectionCap

Methods inherited from class java.lang.Object

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

Constructor Detail

AIMDBackoffManager

public AIMDBackoffManager(org.apache.hc.core5.pool.ConnPoolControl<HttpRoute> connPerRoute)

Constructs an AIMDBackoffManager with the specified ConnPoolControl and Clock.

This constructor is primarily used for testing purposes, allowing the injection of a custom Clock implementation.

Parameters:

connPerRoute - the ConnPoolControl that manages per-host routing maximums

Method Detail

getBackedOffPoolSize

protected int getBackedOffPoolSize(int curr)

Returns the backed-off pool size based on the current pool size. The new pool size is calculated as the floor of (backoffFactor * curr).

Specified by:

getBackedOffPoolSize in class AbstractBackoff

Parameters:

curr - the current pool size

Returns:

the backed-off pool size, with a minimum value of 1

setBackoffFactor

public void setBackoffFactor(double d)

Sets the factor to use when backing off; the new per-host limit will be roughly the current max times this factor. Math.floor is applied in the case of non-integer outcomes to ensure we actually decrease the pool size. Pool sizes are never decreased below 1, however. Defaults to 0.5.

Parameters:

d - must be between 0.0 and 1.0, exclusive.