Package org.asynchttpclient.netty.channel

Class FailedIpCooldownHolder

  • public final class FailedIpCooldownHolder
extends Object
    Per-host failed-IP cooldown applied to a request's resolved addresses before a new connection is opened, independently of the configured LoadBalance mode.

    When a connection attempt to an address fails, markFailed(String, InetSocketAddress) puts that address in a short cooldown. While the cooldown is active reorder(String, List) moves the address to the back of the returned list rather than dropping it, so it is still available as a last-resort failover target and is re-probed once the window elapses. This bounds the cost of an IP that silently black-holes packets (drops them with no RST): without the cooldown every new connection targeting it would burn a full connectTimeout before failing over; with it, only the occasional re-probe pays that cost. (An IP that actively refuses the connection fails over immediately and cheaply, with or without the cooldown.) Liveness remains governed at the DNS/resolver level — the cooldown is only a short-lived dampener, not a health checker.

    The cooldown only re-orders the resolved addresses; it never removes one, so failover always has somewhere to go. It tracks TCP connect failures only (TLS/handshake failures are not fed back here), matching where address-level failover happens.

    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 — it simply forgets any cooldowns the next time the host is seen.

    Thread-safe.

    • Constructor Detail

      • FailedIpCooldownHolder

        public FailedIpCooldownHolder()

      • FailedIpCooldownHolder

        public FailedIpCooldownHolder​(long cooldownNanos,
                              LongSupplier nanoClock)

    • Method Detail

      • reorder

        public List<InetSocketAddress> reorder​(String host,
                                       List<InetSocketAddress> addresses)
        Re-orders addresses so that any address currently in cooldown is moved to the back (otherwise preserving the incoming order).
        Parameters:
        host - the connection's target host (the key the matching markFailed(java.lang.String, java.net.InetSocketAddress) calls use)
        addresses - the resolved socket addresses, in their incoming order
        Returns:
        the same list instance when there is nothing to do (size <= 1, or no address is in cooldown), otherwise a new list with the cooling addresses moved to the back

      • markFailed

        public void markFailed​(String host,
                       InetSocketAddress address)
        Records that a connection attempt to address (for host) failed, so subsequent reorder(java.lang.String, java.util.List<java.net.InetSocketAddress>) calls move it to the back for DEFAULT_FAILED_IP_COOLDOWN. No-op when the host is not (or no longer) tracked — we never resurrect an evicted entry, which keeps the failure path from growing the map for hosts that are not actively being connected to.