GET /overview slow: costMs=

Error message

GET /overview slow: costMs={} thread={} heapUsedMB={} heapTotalMB={} heapMaxMB={}

What it means

OverviewServlet.doGet logs this when handling GET /overview took more than 500ms (costMs > 500). The log includes heap statistics (used/total/max MB) to help diagnose whether memory pressure caused the slowness.

Solutions

Read the heapUsedMB/heapMaxMB values in the log — if usage is near max, increase JVM -Xmx for the node
Reduce the number of jobs or scale out the cluster
Enable/inspect GC logs to confirm GC pauses as the cause
Lower monitoring poll rate and avoid concurrent heavy REST queries

Defensive patterns

Strategy: retry

Validate before calling

// check handler cost via the response header
const cost = Number(resp.headers.get('X-Handler-Cost-Ms') || 0);
if (cost > 500) console.warn('overview slow, reduce poll rate');

Try / catch

try {
  const resp = await fetch(baseUrl + '/overview');
  if (!resp.ok || Number(resp.headers.get('X-Handler-Cost-Ms')) > 500) {
    await sleep(backoffMs);
  }
} catch (e) { /* exponential backoff retry */ }

Prevention

Size JVM heap generously (-Xmx) on coordinator nodes
Enable GC logging to correlate slow handlers with GC pauses
Avoid stacking many concurrent REST queries during heavy scheduling
Scale out if job count grows beyond node capacity

When it happens

Trigger: GET /overview handler execution exceeding 500ms — typically due to JVM GC pauses, heap pressure, or expensive job-status collection on the coordinator.

Common situations: Clusters with many running jobs making overview aggregation expensive; nodes near heap exhaustion (full GCs); slow disk/CPU contention on the master node.

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/62b6dab50b8d9c82. 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:87

                                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);
        }
    }
}

View on GitHub (pinned to cf67b549a7)