louislam/uptime-kuma · error · Error

No heartbeat in the time window

Error message

No heartbeat in the time window

What it means

Thrown by a push-type monitor on the overdue branch: a previous heartbeat exists but more than beatInterval*1000+bufferTime ms have passed since it, or the previous beat was already down/pending. bean.duration is computed from msSinceLastBeat.

Source

Thrown at server/model/monitor.js:760

                    log.debug(
                        "monitor",
                        `[${this.name}] Checking monitor at ${dayjs().format("YYYY-MM-DD HH:mm:ss.SSS")}`
                    );
                    const bufferTime = 1000; // 1s buffer to accommodate clock differences

                    if (previousBeat) {
                        const msSinceLastBeat = dayjs.utc().valueOf() - dayjs.utc(previousBeat.time).valueOf();

                        log.debug("monitor", `[${this.name}] msSinceLastBeat = ${msSinceLastBeat}`);

                        // If the previous beat was down or pending we use the regular
                        // beatInterval/retryInterval in the setTimeout further below
                        if (
                            previousBeat.status !== (this.isUpsideDown() ? DOWN : UP) ||
                            msSinceLastBeat > beatInterval * 1000 + bufferTime
                        ) {
                            bean.duration = Math.round(msSinceLastBeat / 1000);
                            throw new Error("No heartbeat in the time window");
                        } else {
                            let timeout = beatInterval * 1000 - msSinceLastBeat;
                            if (timeout < 0) {
                                timeout = bufferTime;
                            } else {
                                timeout += bufferTime;
                            }
                            // No need to insert successful heartbeat for push type, so end here
                            retries = 0;
                            log.debug("monitor", `[${this.name}] timeout = ${timeout}`);
                            this.heartbeatInterval = setTimeout(safeBeat, timeout);
                            return;
                        }
                    } else {
                        bean.duration = beatInterval;
                        throw new Error("No heartbeat in the time window");
                    }
                } else if (this.type === "docker") {

View on GitHub (pinned to 6b5ea01557)

Solutions

1. Check the pusher's logs to confirm it is still POSTing to /metrics/push/<token>
2. Verify the push URL and secret in the pusher exactly match the monitor
3. Ensure the source host has network egress to the Uptime Kuma instance
4. Increase the monitor interval if the source legitimately pushes less often

// A missed push window is reported as a DOWN heartbeat; retry at the source.
// Ensure the pusher has retry/backoff so transient network failures do not skip a push.
pushWithRetry(url, payload, { retries: 3, backoffMs: 2000 });

When it happens

Trigger: A push monitor's push endpoint has not been called for longer than its interval plus the buffer window.

Common situations: Source-side cron/systemd timer died; firewall/network blocks the push; push URL secret changed so pushes 404; source host offline.

Related errors

• ${bean.msg}, but keyword is ${present|not} in [${data}]
• JSON query does not pass (comparing ${response} ${this.jsonP
• Failed to load docker host config
• Flip UP to DOWN
• JSON query does not pass (comparing ${response} ${monitor.js

AI-assisted analysis of louislam/uptime-kuma@6b5ea01557 (2026-08-12). Data as JSON: /api/errors/02a8cc83317f1ded. Report an issue: GitHub.