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dns_cache: unconditionally floor failure backoff at min_refresh_interval_ #134

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dns_cache: unconditionally floor failure backoff at min_refresh_interval_ #134

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Copilot Apr 23, 2026
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dns_cache: simplify failure backoff floor - unconditional min_refresh…
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18 changes: 6 additions & 12 deletions source/extensions/common/dynamic_forward_proxy/dns_cache_impl.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -570,25 +570,19 @@ void DnsCacheImpl::finishResolve(const std::string& host,
const auto elapsed = now - primary_host_info->host_info_->lastUsedTime();
std::chrono::milliseconds refresh_interval(
primary_host_info->failure_backoff_strategy_->nextBackOffMs());
const auto uncapped_refresh_interval = refresh_interval;
if (elapsed >= host_ttl_) {
refresh_interval = std::chrono::milliseconds(0);
} else {
const auto until_eviction =
std::chrono::duration_cast<std::chrono::milliseconds>(host_ttl_ - elapsed);
refresh_interval = std::min(refresh_interval, until_eviction);
}
// If (and only if) the host_ttl cap above reduced the failure backoff, floor the
// resulting interval at min_refresh_interval_ (dns_min_refresh_rate). The cap bounds
// eviction delay; this floor prevents arming a ms-scale alarm that can kick rapid-fire
// resolves and race with dispatcher/resolver teardown in integration tests (observed
// as a LeakSanitizer leak in proxy_filter_integration_test DoubleResolution). When the
// cap does not kick in, the user-configured failure backoff is passed through unchanged.
if (refresh_interval < uncapped_refresh_interval) {
const auto min_refresh_ms =
std::chrono::duration_cast<std::chrono::milliseconds>(min_refresh_interval_);
refresh_interval = std::max(refresh_interval, min_refresh_ms);
}
// Floor the result at min_refresh_interval_ (dns_min_refresh_rate) to prevent arming
// a ms-scale alarm that can kick rapid-fire resolves and race with dispatcher/resolver
// teardown in integration tests (observed as a LeakSanitizer leak in
// proxy_filter_integration_test DoubleResolution).
refresh_interval = std::max(refresh_interval,
std::chrono::duration_cast<std::chrono::milliseconds>(min_refresh_interval_));
primary_host_info->refresh_timer_->enableTimer(refresh_interval);
ENVOY_LOG(debug, "DNS refresh rate reset for host '{}', (failure) refresh rate {} ms", host,
refresh_interval.count());
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