GET /overview dispatch delayed: dispatchDelayMs=

Error message

GET /overview dispatch delayed: dispatchDelayMs={} thread={}

What it means

A self-monitoring warning in OverviewServlet.doGet: the request spent more than 500ms waiting before dispatch (e.g. queued in the servlet thread pool or blocked upstream). It exposes the delay via the X-Dispatch-Delay-Ms header and logs the serving thread name.

Solutions

Reduce polling frequency of the /overview endpoint in your monitoring setup
Increase the REST service thread pool size in the cluster configuration
Check GC logs and heap pressure on the node — the companion heap diagnostics (costMs > 500) show memory stats
Profile what else is running on the node; offload heavy work from the master node serving the REST API

Defensive patterns

Strategy: retry

Validate before calling

// track the dispatch-delay header before continuing polling
const delayMs = Number(resp.headers.get('X-Dispatch-Delay-Ms') || 0);
if (delayMs > 500) backoff();

Try / catch

try {
  const resp = await fetch(baseUrl + '/overview');
  if (Number(resp.headers.get('X-Dispatch-Delay-Ms')) > 500) {
    await sleep(pollInterval * 2); // back off before next poll
  }
} catch (e) { /* retry with backoff */ }

Prevention

Poll /overview at moderate intervals (>= 5s)
Increase REST thread pool if many clients poll concurrently
Monitor node GC and CPU load
Alert on X-Dispatch-Delay-Ms header values rather than raw failures

When it happens

Trigger: GET /overview when the Jetty/REST thread pool is saturated or the handler thread is starved; system under heavy load, GC pauses, or many concurrent REST calls delaying dispatch.

Common situations: Large clusters where the overview handler competes with heavy engine work; monitoring systems polling /overview at high frequency; worker overload causing slow request acceptance.

Understand the failure class

Background: Request timed out: what client-side request timeouts mean across libraries (Request timed out, TIMED_OUT, APITimeoutError) — this error's family across 39 libraries.

Related errors

AI-assisted analysis of apache/seatunnel@cf67b549a7 (2026-09-10). Data as JSON: /api/errors/9c885e0052fab9e0. Report an issue: GitHub.

Appendix: source

Thrown at seatunnel-engine/seatunnel-engine-server/src/main/java/org/apache/seatunnel/engine/server/rest/servlet/OverviewServlet.java:79

        }

        long startNs = System.nanoTime();
        Map<String, String> tags = getParameterMap(req);

        JsonObject body =
                JsonUtil.toJsonObject(
                        JsonUtils.toMap(
                                JsonUtils.toJsonString(overviewService.getOverviewInfo(tags))));

        long costMs = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startNs);
        long dispatchDelayMs = receivedMs <= 0 ? -1 : Math.max(0, nowMs - receivedMs);

        resp.setHeader("X-Dispatch-Delay-Ms", String.valueOf(dispatchDelayMs));
        resp.setHeader("X-Handler-Cost-Ms", String.valueOf(costMs));

        writeJson(resp, body);
        if (dispatchDelayMs > 500) {
            log.warn(
                    "GET /overview dispatch delayed: dispatchDelayMs={} thread={}",
                    dispatchDelayMs,
                    Thread.currentThread().getName());
        }
        if (costMs > 500) {
            Runtime rt = Runtime.getRuntime();
            long usedBytes = rt.totalMemory() - rt.freeMemory();
            log.warn(
                    "GET /overview slow: costMs={} thread={} heapUsedMB={} heapTotalMB={} "
                            + "heapMaxMB={}",
                    costMs,
                    Thread.currentThread().getName(),
                    usedBytes / 1024 / 1024,
                    rt.totalMemory() / 1024 / 1024,
                    rt.maxMemory() / 1024 / 1024);
        }
    }
}

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