Function isRetriableOriginFetchError

cmd/cache-proxy/proxy.go:531–564

(err error)

func (p *CacheProxy) fetchFromPeer(holder string, flight bool, cacheKey string, r *http.Request) (fetchResult, bool) {
	n, ok := p.peers.FetchFromPeer(r.Context(), holder, cacheKey, flight, func(body io.Reader) (int64, error) {
		return p.store.PutStream(cacheKey, body)
	})
	if !ok {
		return fetchResult{}, false
	}
	cacheBytesServed.WithLabelValues("peer").Add(float64(n))
	return fetchResult{size: n, source: "peer"}, true
}

// fetchOrigin forwards the request verbatim (headers, Host, signature) to the
// real origin and streams a successful body straight to the on-disk cache,
// returning the stored size and Content-Type. The SigV4 signature remains valid
// because the URL and Host header are unchanged. Streaming to disk (rather than
// io.ReadAll into a []byte) is what keeps proxy memory flat under concurrent
// large range reads. A non-2xx response is NOT cached — its (capped) error body
// is captured and returned as an originStatusError for verbatim forwarding.
func (p *CacheProxy) fetchOrigin(cacheKey string, r *http.Request) (int64, string, error) {
	_, originSpan := proxyTracer.Start(r.Context(), "cache.origin_fetch")
	defer originSpan.End()

	var size int64
	var contentType string
	err := p.retryOriginFetch(r, originSpan, func() error {
		var attemptErr error
		size, contentType, attemptErr = p.fetchOriginOnce(cacheKey, r)
		return attemptErr
	})
	if err != nil {
		return 0, "", err
	}
	originSpan.SetAttributes(attribute.Int64("duckgres.bytes", size))
	return size, contentType, nil
}

// retryOriginFetch runs attempt (one origin fetch) up to
// originRetryMaxAttempts times with jittered exponential backoff, while the
// error is retriable (isRetriableOriginFetchError) and the request context is