Function collectQueryStats

proxy/stats.go:95–141

collectQueryStats gathers the statistics from the wrapped upstreams. resolver is an upstream DNS resolver that successfully resolved the request, if any. Provided upstreams must be of type [*upstreamWithStats]. unwrapped is the unwrapped resolver, see [upstreamWithStats.upstream]. The returned st

(
	mode UpstreamMode,
	resolver upstream.Upstream,
	upstreams []upstream.Upstream,
	fallbacks []upstream.Upstream,
)

// statistics depend on whether the DNS request was successfully resolved and
// the upstream mode, see [DNSContext.QueryStatistics].
func collectQueryStats(
	mode UpstreamMode,
	resolver upstream.Upstream,
	upstreams []upstream.Upstream,
	fallbacks []upstream.Upstream,
) (unwrapped upstream.Upstream, stats *QueryStatistics) {
	var wrapped *upstreamWithStats
	if resolver != nil {
		var ok bool
		wrapped, ok = resolver.(*upstreamWithStats)
		if !ok {
			// Should never happen.
			panic(fmt.Errorf("unexpected type %T", resolver))
		}

		unwrapped = wrapped.upstream
	}

	// The DNS query was not resolved.
	if wrapped == nil {
		return nil, &QueryStatistics{
			main:     collectUpstreamStats(upstreams...),
			fallback: collectUpstreamStats(fallbacks...),
		}
	}

	// The DNS query was successfully resolved by main resolver and the upstream
	// mode is [UpstreamModeFastestAddr].
	if mode == UpstreamModeFastestAddr && len(fallbacks) == 0 {
		return unwrapped, &QueryStatistics{
			main: collectUpstreamStats(upstreams...),
		}
	}

	// The DNS query was resolved by fallback resolver.
	if len(fallbacks) > 0 {
		return unwrapped, &QueryStatistics{
			main:     collectUpstreamStats(upstreams...),
			fallback: collectUpstreamStats(wrapped),
		}
	}

	// The DNS query was successfully resolved by main resolver.
	return unwrapped, &QueryStatistics{
		main: collectUpstreamStats(wrapped),
	}
}

// UpstreamStatistics contains the DNS query statistics.
type UpstreamStatistics struct {