Package org.apache.http.impl.client

Class AIMDBackoffManager

  • All Implemented Interfaces:
    BackoffManager
    public class AIMDBackoffManager
extends java.lang.Object
implements BackoffManager

    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

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void backOff​(HttpRoute route)
      Called when we have decided that the result of using a connection should be interpreted as a backoff signal.
      void probe​(HttpRoute route)
      Called when we have determined that the result of using a connection has succeeded and that we may probe for more connections.
      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.
      void setCooldownMillis​(long l)
      Sets the amount of time, in milliseconds, to wait between adjustments in pool sizes for a given host, to allow enough time for the adjustments to take effect.
      void setPerHostConnectionCap​(int cap)
      Sets the absolute maximum per-host connection pool size to probe up to; defaults to 2 (the default per-host max).

      • Methods inherited from class java.lang.Object

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

    • Constructor Detail

      • AIMDBackoffManager

        public AIMDBackoffManager​(ConnPoolControl<HttpRoute> connPerRoute)
        Creates an AIMDBackoffManager to manage per-host connection pool sizes represented by the given ConnPoolControl.
        Parameters:
        connPerRoute - per-host routing maximums to be managed

    • Method Detail

      • backOff

        public void backOff​(HttpRoute route)
        Description copied from interface: BackoffManager
        Called when we have decided that the result of using a connection should be interpreted as a backoff signal.
        Specified by:
        backOff in interface BackoffManager

      • probe

        public void probe​(HttpRoute route)
        Description copied from interface: BackoffManager
        Called when we have determined that the result of using a connection has succeeded and that we may probe for more connections.
        Specified by:
        probe in interface BackoffManager

      • 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.

      • setCooldownMillis

        public void setCooldownMillis​(long l)
        Sets the amount of time, in milliseconds, to wait between adjustments in pool sizes for a given host, to allow enough time for the adjustments to take effect. Defaults to 5000L (5 seconds).
        Parameters:
        l - must be positive

      • setPerHostConnectionCap

        public void setPerHostConnectionCap​(int cap)
        Sets the absolute maximum per-host connection pool size to probe up to; defaults to 2 (the default per-host max).
        Parameters:
        cap - must be >= 1