What causes "Error queuing request: %s" in openfaas/faas?

Check queue health: kubectl get pods -n openfaas and confirm the nats pod is Running/Ready

Error queuing request: %s

Error message

Error queuing request: %s

What it means

After building the QueueRequest, MakeQueuedProxy publishes it through the configured RequestQueuer (nats-queue in the standard OpenFaaS stack). A publish failure returns 500 with 'Error queuing request: <err>'. Only a successful publish yields 202 Accepted, so this error means the async invocation was not accepted at all.

Source

Thrown at gateway/handlers/queue_proxy.go:61

		}

		vars := mux.Vars(r)
		name := vars["name"]

		req := &ftypes.QueueRequest{
			Function:    name,
			Body:        body,
			Method:      r.Method,
			QueryString: r.URL.RawQuery,
			Path:        pathTransformer.Transform(r),
			Header:      r.Header,
			Host:        r.Host,
			CallbackURL: callbackURL,
		}

		if err = queuer.Queue(req); err != nil {
			log.Printf("Error queuing request: %v", err)
			http.Error(w, fmt.Sprintf("Error queuing request: %s", err.Error()),
				http.StatusInternalServerError)
			return
		}

		w.WriteHeader(http.StatusAccepted)
	}
}

func getCallbackURLHeader(header http.Header) (*url.URL, error) {
	value := header.Get("X-Callback-Url")
	var callbackURL *url.URL

	if len(value) > 0 {
		urlVal, err := url.Parse(value)
		if err != nil {
			return callbackURL, err
		}

View on GitHub (pinned to 8d803bf9e2)

Solutions

Check queue health: kubectl get pods -n openfaas and confirm the nats pod is Running/Ready
Verify connectivity to NATS port 4222 from the cluster (nc -z nats.openfaas.svc 4222)
Reduce the async payload below the NATS max_payload limit or raise the limit
Read the embedded error text ('nats: connection closed', 'payload too large') — it names the exact failure
Restart the queue connector if its NATS connection is stale

Defensive patterns

Strategy: retry

Validate before calling

# preflight: NATS reachable before firing async requests
nc -z nats.openfaas 4222 || echo 'NATS down: /async-function/* calls will fail'

Try / catch

resp, err := client.Post(asyncURL, contentType, body)
if err != nil || resp.StatusCode == http.StatusInternalServerError {
    // queue backend unavailable: wait, then re-enqueue the whole job
    time.Sleep(backoff)
    continue
}

Prevention

Monitor the nats-streaming pod and alert before it degrades
Keep async payloads under the NATS max_payload (default 1MB)
Treat 202 Accepted as the only success signal — anything else means the job was not queued
Persist jobs locally so failed enqueues can be replayed

When it happens

Trigger: POST /async-function/{name} while the queue backend is unavailable: nats-streaming pod down or not ready, wrong NATS address or port (4222), the request body exceeding NATS max_payload (default 1MB), or the queue connector crashed.

Common situations: nats-streaming StatefulSet not running or evicted; chart installed without queue mode; NATS max_payload smaller than the async body; resource limits killing the streaming server.

Related errors

AI-assisted analysis of openfaas/faas@8d803bf9e2 (2026-08-16). Data as JSON: /api/errors/ddc49aaafdbbcb8f. Report an issue: GitHub.