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…block - Tip-leader routing: a request pinned to a block above every routed upstream's known head is tried first on the tier:fallback upstreams whose head already reached it (their newHeads keep their pollers current), then on the routed list. It takes the per-request escalation, so other hedge legs and retries do not escape; the sweep that took it still escapes once to the fallbacks it has not tried. No-op when a routed head is unknown or at the block, for consensus, and with failover off. Leaders must match the use-upstream selector and their enforced availability bounds. Counted in erpc_network_tip_leader_route_total. - Hedge keeper: once a request has escalated, an all-missing ErrUpstreamsExhausted is not kept, so a leg that only re-swept the routed upstreams cannot cancel a leg still waiting on a fallback. If every leg misses, the hedge returns the last result. - Future-block short-circuit (served-tip): skip the synthetic null when a reachable fallback already has the block, except for consensus.
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…tion Same outcome as the previous commit, with fewer moving parts: - Fallbacks whose polled head has the block join the request's upstream list, and tiering now runs before the has-the-block partition, so an upstream that has the block goes first whatever its tier. This is ordering, not an escalation: drops leaderRouted, the shared MarkEscalatedToFallbacks handling, the maxLoopIterations bump and NormalizedRequest.EscalatedToFallbacks. The once-per-request escape is unchanged; use-upstream is enforced by NextUpstream as for any upstream. - The future-block short-circuit is skipped when a tip leader was added, instead of rescanning the fallbacks. - The hedge keeper no longer keeps an all-missing ErrUpstreamsExhausted at all, rather than only after escalation: a sibling leg may be on an upstream this leg never tried, which already happens in the plain escape path with no tip leader (TestFailover_HedgeKeepsEscalatedSibling and TestFailover_HedgeKeepsSlowFallbackAfterFastFallbackMiss fail on 05126d0). If every leg ends that way the hedge still returns the last one to the retry layer. Tests unchanged; TestFailover_* pass, including under -race. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Summary
tier:fallbackupstreams whose head already reached it, then on the routed list. When a fallback'snewHeadsleads, clients call at blocks the routed upstreams don't have yet, and today those calls fail on the routed upstreams first. Counted inerpc_network_tip_leader_route_total.ErrUpstreamsExhaustedis no longer kept, so a hedge leg that only re-swept the routed upstreams can't cancel the leg still waiting on a fallback.Still one escalation per request. No-op for consensus, with failover off, or when a routed head is unknown or at the block. Leaders respect
use-upstreamand their availability bounds.Test plan
TestFailover_TipLeaderRoutingand related tests (15 scenarios), each failing without its fix;TestFailover_*passes under-racego test ./erpc/ ./common/ ./upstream/ ./telemetry/: onlyTestNetwork_Forward/ForwardLlamaRPCEndpointRateLimitResponseSinglefails, identically on 05126d0