thanos-io/thanos · error

snappy decode error

Error message

snappy decode error

What it means

Logged (and returned as HTTP 400) when s2.Decode fails on the request body of a remote-write v1 endpoint: the snappy-compressed payload is corrupt or not actually snappy/s2-encoded. The compressed bytes were read successfully; only decompression failed, so the client is at fault.

Solutions

1. Ensure the sender snappy-encodes the body (remote-write v1).
2. Check for double compression or corruption in transit.
3. 400: do not retry the unchanged payload.

When it happens

Trigger: Thrown at pkg/receive/handler.go:835 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of thanos-io/thanos@35b8b99117 (2026-09-07). Data as JSON: /api/errors/c69ad2570937bc9f. Report an issue: GitHub.

Appendix: source

Thrown at pkg/receive/handler.go:835

	compressed := bytes.Buffer{}
	if r.ContentLength >= 0 {
		if !requestLimiter.AllowSizeBytes(tenantHTTP, r.ContentLength) {
			http.Error(w, "write request too large", http.StatusRequestEntityTooLarge)
			return
		}
		compressed.Grow(int(r.ContentLength))
	} else {
		compressed.Grow(512)
	}
	_, err = io.Copy(&compressed, r.Body)
	if err != nil {
		http.Error(w, errors.Wrap(err, "read compressed request body").Error(), http.StatusInternalServerError)
		return
	}
	reqBuf, err := s2.Decode(nil, compressed.Bytes())
	if err != nil {
		level.Error(tLogger).Log("msg", "snappy decode error", "err", err)
		http.Error(w, errors.Wrap(err, "snappy decode error").Error(), http.StatusBadRequest)
		return
	}

	if !requestLimiter.AllowSizeBytes(tenantHTTP, int64(len(reqBuf))) {
		http.Error(w, "write request too large", http.StatusRequestEntityTooLarge)
		return
	}

	rwVersion, err := determineRWVersion(r)
	if err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}

	switch rwVersion {
	case 1:
		// NOTE: Due to zero copy ZLabels, Labels used from WriteRequests keeps memory
		// from the whole request. Ensure that we always copy those when we want to

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