GUIDE · AZURE FUNCTIONS · TIMER TRIGGER · FREE

Monitor Azure Functions timer triggers — detect missed and failed scheduled runs

Azure Functions timer triggers fire on a 6-field NCRONTAB schedule. When a function throws or the host is down, Application Insights logs the exception — but sends no notification unless you've configured alerts, which is non-trivial to set up. A missed run (host offline during the scheduled window) produces nothing at all. One ping call at the end of a successful function execution is the simplest reliable detection.

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Setup: one HTTP call, about a minute

Snippets for Python v2, C# isolated worker, and Node.js.

Create a heartbeat monitor in LastPing

In the console, create a monitor. Azure Functions timer uses 6-field NCRONTAB (prepend a seconds field to standard cron). Use the same expression as your function's schedule binding. All times in the NCRONTAB are UTC.

# Azure NCRONTAB — 6 fields: second minute hour day month day-of-week # "0 0 3 * * *" → 03:00:00 UTC daily # "0 */30 * * * *" → every 30 minutes # "0 0 9 * * 1-5" → 09:00 UTC weekdays https://ping.lastping.dev/<your-monitor-id>

Python v2 function — ping on success

Store the monitor ID in an app setting (LASTPING_MONITOR_ID) and call the ping at the end of the successful path.

import os, urllib.request import azure.functions as func app = func.FunctionApp() PING_URL = f"https://ping.lastping.dev/{os.environ['LASTPING_MONITOR_ID']}" @app.timer_trigger(schedule="0 0 3 * * *", arg_name="mytimer", run_on_startup=False, use_monitor=True) def nightly_job(mytimer: func.TimerRequest) -> None: urllib.request.urlopen(f"{PING_URL}/start", timeout=10) # overrun detection try: do_work() urllib.request.urlopen(PING_URL, timeout=10) except Exception: urllib.request.urlopen(f"{PING_URL}/fail", timeout=10) raise

C# isolated worker — ping on success

using Microsoft.Azure.Functions.Worker; using System.Net.Http; public class NightlyJob { private static readonly HttpClient _http = new(); private static readonly string _pingUrl = $"https://ping.lastping.dev/{Environment.GetEnvironmentVariable("LASTPING_MONITOR_ID")}"; [Function("NightlyJob")] public async Task Run([TimerTrigger("0 0 3 * * *", RunOnStartup = false)] TimerInfo timer) { await _http.GetAsync($"{_pingUrl}/start"); // arm overrun detection try { await DoWorkAsync(); await _http.GetAsync(_pingUrl); } catch { await _http.GetAsync($"{_pingUrl}/fail"); throw; } } }

Node.js v4 function — ping on success

const { app } = require('@azure/functions'); const PING_URL = `https://ping.lastping.dev/${process.env.LASTPING_MONITOR_ID}`; app.timer('nightlyJob', { schedule: '0 0 3 * * *', runOnStartup: false, handler: async (myTimer, context) => { await fetch(`${PING_URL}/start`); try { await doWork(); await fetch(PING_URL); } catch (err) { await fetch(`${PING_URL}/fail`); throw err; } } });

Add the app setting in Azure

In the Azure portal: Function App → Configuration → Application settings → + New application setting. Or via Azure CLI:

az functionapp config appsettings set \ --name my-function-app \ --resource-group my-rg \ --settings LASTPING_MONITOR_ID=<your-monitor-id>

What this catches

  • Unhandled exception — /fail fires; incident opens immediately.
  • Function host offline during scheduled window — no invocation, no ping → incident opens on silence.
  • Function timeout (default 5 min, up to 60 min) — /start arrived, function killed before success → overrun incident.
  • Deployment broke the function — host restarts and misses the trigger window → silence → incident.
  • Recovery — next successful run closes the incident automatically.

Running on AWS? See AWS Lambda + EventBridge. On GCP? See Google Cloud Scheduler. For the broader concept, see dead-man's switch explained. For AI agent heartbeat monitoring, see the LastPing MCP server.

Questions people ask

Front-loaded answers — the most important fact first.

  • What cron format does Azure Functions use?

    Azure Functions uses 6-field NCRONTAB where the first field is seconds: {second} {minute} {hour} {day} {month} {day-of-week}. Example: 0 0 3 * * * = 03:00:00 UTC daily. All times are UTC; there is no per-binding timezone setting (set the function app's WEBSITE_TIME_ZONE app setting to change the host timezone).

  • Does Azure Functions alert on a missed timer trigger?

    No. A missed trigger (host offline during the scheduled window) produces nothing by default. If use_monitor=True (Python) or UseMonitor=true (C#) is set, missed invocations are caught up on next host start — but no notification is sent. Dead-man's-switch monitoring catches the gap.

  • What is the difference between RunOnStartup and UseMonitor?

    RunOnStartup=True fires the function immediately when the host starts, regardless of schedule — useful in development, dangerous in production (causes extra invocations on every deployment). UseMonitor=True enables Azure's built-in missed-run catch-up: if the host was offline when the schedule fired, it fires on next startup. Use RunOnStartup=False, UseMonitor=True in production.

  • Is this free?

    Yes. LastPing is free and fully hosted with no monitor cap and no paid tier. See vs Healthchecks.io and vs Cronitor.

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Azure timer triggers fail silently. Add one line to know immediately.

One HTTP call at the end of your function. First alert in under a minute — and LastPing monitors itself the same way.

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