com.aliyun.apache.hc.client5.http.impl.classic.AIMDBackoffManager Maven / Gradle / Ivy
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*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
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* The {@code 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
*/
@Contract(threading = ThreadingBehavior.SAFE)
public class AIMDBackoffManager extends AbstractBackoff {
/**
* Constructs an {@code AIMDBackoffManager} with the specified
* {@link ConnPoolControl} and {@link Clock}.
*
* This constructor is primarily used for testing purposes, allowing the
* injection of a custom {@link Clock} implementation.
*
* @param connPerRoute the {@link ConnPoolControl} that manages
* per-host routing maximums
*/
public AIMDBackoffManager(final ConnPoolControl connPerRoute) {
super(connPerRoute);
}
/**
* Returns the backed-off pool size based on the current pool size.
* The new pool size is calculated as the floor of (backoffFactor * curr).
*
* @param curr the current pool size
* @return the backed-off pool size, with a minimum value of 1
*/
protected int getBackedOffPoolSize(final int curr) {
if (curr <= 1) {
return 1;
}
return (int) (Math.floor(getBackoffFactor().get() * curr));
}
/**
* Sets the factor to use when backing off; the new
* per-host limit will be roughly the current max times
* this factor. {@code 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.
* @param d must be between 0.0 and 1.0, exclusive.
*/
@Override
public void setBackoffFactor(final double d) {
Args.check(d > 0.0 && d < 1.0, "Backoff factor must be 0.0 < f < 1.0");
getBackoffFactor().set(d);
}
}