Package org.asynchttpclient.netty.channel

Class RoundRobinAddressSelector

  • public final class RoundRobinAddressSelector
extends Object
    Picks, per host and per request, which resolved IP a new connection should target first when LoadBalance.ROUND_ROBIN is enabled.

    rotate(String, List) returns the resolved addresses re-ordered so that the round-robin-selected address comes first; the remaining addresses follow (in their original order) so the connector can still fail over to them. The order is taken as-is from the resolver and is not re-sorted, so the per-host counter maps consistently to the same address across requests only when the configured InetNameResolver returns the addresses in a stable order (see LoadBalance.ROUND_ROBIN).

    This class is concerned only with rotation. Deprioritizing addresses whose connection attempts recently failed is handled separately and mode-independently by FailedIpCooldownHolder, applied on top of the rotation before a connection is opened.

    Per-host state is held in a bounded map (capped at 4096); at the cap an arbitrary entry is evicted before a new one is added, so memory stays bounded even for clients that touch very many distinct hosts. Dropping a host's state is harmless — its rotation simply restarts at the first resolved address the next time it is seen.

    Thread-safe.

    • Constructor Detail

      • RoundRobinAddressSelector

        public RoundRobinAddressSelector()

    • Method Detail

      • rotate

        public List<InetSocketAddress> rotate​(String host,
                                      List<InetSocketAddress> resolved)
        Parameters:
        host - the request's target host
        resolved - the resolved socket addresses (size >= 1), in resolver order
        Returns:
        the same list instance when there is nothing to rotate (size <= 1, or the selected index is already first), otherwise a new list whose first element is the round-robin-selected address (otherwise preserving resolver order)