pub struct PeakEwmaTracker { /* private fields */ }Expand description
Peak-EWMA latency tracker (DW-090): one per endpoint when the
upstream’s algorithm is peak_ewma. Holds the current EWMA cost
(cost_ns, in nanoseconds) and the timestamp of the last update
(stamp, in nanoseconds since the Unix epoch) as atomics so
UpstreamLb::record_latency is lock-free on the hot path. Carried
across rebuilds by address:port (exactly like inflight and
health): the live tracker survives a config reload so a latency
history accumulated under one generation is not thrown away by the
next.
The Finagle peak-EWMA formula (see UpstreamLb::record_latency):
a new RTT that EXCEEDS the current cost replaces it outright (the
“peak” — a slow response is remembered in full so the balancer
degrades an outlier immediately), otherwise the cost decays toward
the new RTT at rate w = exp(-td / tau) where td is the time
since the last update and tau is the decay window. Selection
scores endpoints by cost_ns * (inflight + 1) (lowest wins).
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impl !Freeze for PeakEwmaTracker
impl RefUnwindSafe for PeakEwmaTracker
impl Send for PeakEwmaTracker
impl Sync for PeakEwmaTracker
impl Unpin for PeakEwmaTracker
impl UnwindSafe for PeakEwmaTracker
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