jaegertracing/jaeger · warning

failed writing HTTP response: %w

Error message

failed writing HTTP response: %w

What it means

writeJSON serializes an API response and writes it to the http.ResponseWriter; if the marshal-and-write step fails, it responds 500 with "failed writing HTTP response". The library throws it so handler authors and operators can distinguish response-serialization/IO failures from query failures.

Source

Thrown at cmd/jaeger/internal/extension/jaegerquery/internal/http_handler.go:421

	http.Error(w, string(resp), statusCode)
	return true
}

func (aH *APIHandler) writeJSON(w http.ResponseWriter, r *http.Request, response any) {
	prettyPrintValue := r.URL.Query().Get(prettyPrintParam)
	prettyPrint := prettyPrintValue != "" && prettyPrintValue != "false"

	var marshal jsonMarshaler
	switch response.(type) {
	case proto.Message:
		marshal = newProtoJSONMarshaler(prettyPrint)
	default:
		marshal = newStructJSONMarshaler(prettyPrint)
	}

	w.Header().Set("Content-Type", "application/json")
	if err := marshal(w, response); err != nil {
		aH.handleError(w, fmt.Errorf("failed writing HTTP response: %w", err), http.StatusInternalServerError)
	}
}

func (aH *APIHandler) getQualityMetrics(w http.ResponseWriter, r *http.Request) {
	data := qualitymetrics.GetSampleData()
	aH.writeJSON(w, r, &data)
}

View on GitHub (pinned to 806f444784)

Solutions

1. Check server/proxy logs for the wrapped cause (e.g. broken pipe, connection reset) — most cases are a client-side disconnect, not a Jaeger bug.
2. Retry the query with a smaller time range or limit to reduce the response size.
3. If persistent, inspect proxies/load balancers for idle-timeout or body-size limits between the client and jaeger-query.

resp, err := http.Get(url)
if err != nil { return err }
defer resp.Body.Close()
if resp.StatusCode == http.StatusInternalServerError {
    body, _ := io.ReadAll(resp.Body)
    log.Printf("query endpoint failed writing response: %s", body) // check wrapped cause in server logs
}

When it happens

Trigger: Any HTTP query endpoint (transformOTLP, /api/dependencies, deep dependencies, metrics, getTrace, archiveTrace) where the marshaled response cannot be written to the client, or a non-standard marshaler fails while encoding.

Common situations: Client disconnected mid-response (broken pipe) on a large trace or long dependencies query; reverse proxy closing the connection; response body larger than an intermediary's limits.

Related errors

• failed marshalling HTTP response to JSON: %w
• access denied
• no http.RoundTripper provided
• bad request
• unmarshalling ElasticSearch documents failed

AI-assisted analysis of jaegertracing/jaeger@806f444784 (2026-09-01). Data as JSON: /api/errors/b83d973891a1de54. Report an issue: GitHub.