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Expose stale-reading age in Prometheus metrics #327

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30 changes: 30 additions & 0 deletions packages/cli/src/commands/metrics.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -98,6 +98,10 @@ function activeChannels(channels: DeviceChannel[]): DeviceChannel[] {
return channels.filter((ch) => ch.enabled !== false);
}

function ageSeconds(timestamp: Date): number {
return Math.max(0, Math.floor((Date.now() - timestamp.getTime()) / 1000));
}

function channelLabels(device: Device, channel: DeviceChannel): Record<string, string | null> {
return {
serial: device.serial,
Expand All @@ -119,8 +123,18 @@ export function renderMetrics(snapshot: MetricsSnapshot): string {
const alarmHigh: Sample[] = [];
const alarmLow: Sample[] = [];
const battery: Sample[] = [];
const deviceTelemetryAge: Sample[] = [];
const channelTelemetryAge: Sample[] = [];

for (const { device, channels } of snapshot.devices) {
const deviceTimestamp = device.latestReading ?? device.lastTelemetrySaved ?? device.lastSeen;
if (deviceTimestamp) {
deviceTelemetryAge.push({
labels: { serial: device.serial, device: device.label || device.serial },
value: ageSeconds(deviceTimestamp),
});
}

if (device.battery != null) {
battery.push({
labels: { serial: device.serial, device: device.label || device.serial },
Expand All @@ -133,6 +147,10 @@ export function renderMetrics(snapshot: MetricsSnapshot): string {
if (channel.value != null) {
temperature.push({ labels, value: channel.value });
}
const channelTimestamp = channel.lastTelemetrySaved ?? channel.lastSeen;
if (channelTimestamp) {
channelTelemetryAge.push({ labels, value: ageSeconds(channelTimestamp) });
}
if (channel.minimum?.value != null) {
minimum.push({ labels, value: channel.minimum.value });
}
Expand Down Expand Up @@ -197,6 +215,18 @@ export function renderMetrics(snapshot: MetricsSnapshot): string {
type: "gauge",
samples: battery,
},
{
name: "thermoworks_device_telemetry_age_seconds",
help: "Seconds since the newest device telemetry timestamp.",
type: "gauge",
samples: deviceTelemetryAge,
},
{
name: "thermoworks_channel_telemetry_age_seconds",
help: "Seconds since the newest channel telemetry timestamp.",
type: "gauge",
samples: channelTelemetryAge,
},
];

const lines = metrics.flatMap(renderMetric);
Expand Down
58 changes: 53 additions & 5 deletions packages/cli/tests/metrics.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -37,9 +37,9 @@ function makeDevice(overrides: Partial<Device> & { serial: string }): Device {
temperatureDeltaTrigger: null,
pendingLoad: null,
batteryAlertSent: null,
lastSeen: null,
lastTelemetrySaved: null,
latestReading: null,
lastSeen: overrides.lastSeen ?? null,
lastTelemetrySaved: overrides.lastTelemetrySaved ?? null,
latestReading: overrides.latestReading ?? null,
lastWifiConnection: null,
lastBluetoothConnection: null,
sessionStart: null,
Expand Down Expand Up @@ -70,8 +70,8 @@ function makeChannel(overrides: Partial<DeviceChannel> = {}): DeviceChannel {
number: overrides.number ?? null,
enabled: overrides.enabled ?? null,
color: null,
lastSeen: null,
lastTelemetrySaved: null,
lastSeen: overrides.lastSeen ?? null,
lastTelemetrySaved: overrides.lastTelemetrySaved ?? null,
lastEventId: null,
showAvgTemp: null,
estimatedAlarmStatus: null,
Expand Down Expand Up @@ -296,6 +296,54 @@ describe("renderMetrics", () => {
});
});

it("emits telemetry age metrics when timestamps are present", () => {
vi.useFakeTimers();
vi.setSystemTime(new Date("2026-01-15T12:10:00Z"));
try {
const devices: DeviceWithChannels[] = [
{
device: makeDevice({
serial: "S1",
label: "Smoker",
latestReading: new Date("2026-01-15T12:08:00Z"),
}),
channels: [
makeChannel({
label: "Pit",
number: "1",
lastTelemetrySaved: new Date("2026-01-15T12:09:30Z"),
}),
],
},
];

const text = renderMetrics({ up: true, scrapeErrors: 0, devices });

expect(text).toContain(
'thermoworks_device_telemetry_age_seconds{serial="S1",device="Smoker"} 120',
);
expect(text).toContain(
'thermoworks_channel_telemetry_age_seconds{serial="S1",device="Smoker",channel="1",label="Pit"} 30',
);
} finally {
vi.useRealTimers();
}
});

it("skips telemetry age metrics when timestamps are missing", () => {
const devices: DeviceWithChannels[] = [
{
device: makeDevice({ serial: "S1", label: "Smoker" }),
channels: [makeChannel({ label: "Pit", number: "1" })],
},
];

const text = renderMetrics({ up: true, scrapeErrors: 0, devices });

expect(text).not.toContain("thermoworks_device_telemetry_age_seconds{");
expect(text).not.toContain("thermoworks_channel_telemetry_age_seconds{");
});

// =============================================================================
// createMetricsServer (real HTTP)
// =============================================================================
Expand Down
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