Heartbeats
Cron job monitoring for the jobs that fail by not running.
A broken backup job doesn't error - it just stops running, and nobody notices until the restore. Give each job a heartbeat URL: one curl when it finishes, and CertSentry alerts you when the pings stop arriving.
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The coverage
What this watch covers
One line to instrument
Append && curl -fsS <your ping URL> to the job. The first ping arms the monitor; from then on, silence past the deadline raises an alert.
Interval plus grace
Tell the watch how often the job should run and how much lateness is acceptable, per job. A nightly backup with a generous grace won't page you over a slow disk.
Failures can speak too
Jobs that catch their own errors can hit the failure endpoint to alert immediately - with the missed-ping deadline as the dead man's switch either way.
Made for renewal jobs
Point your certbot deploy hook at a heartbeat and pair it with the certificate monitor for the same host - you'll know both that renewal ran and that the new certificate is actually being served.
Questions
Common questions
How is this different from uptime monitoring?
Uptime checks reach in from outside; heartbeats let the job report in from inside. Anything that runs on a schedule - cron, systemd timers, CI jobs, queue workers - can carry one.
What if the job runs but fails?
Have it hit the failure endpoint instead and the alert fires immediately. If the process dies before it can report anything, the missed deadline catches it.
When does the alert clear?
On the next successful ping. Recovery notifications go to the same channels as the alert.
Do heartbeats need my server to be reachable from outside?
No - the request goes from your job to CertSentry, so jobs behind NAT, in private subnets or on a laptop all work.
The rest of the watch
Also on watch
- SSL certificatesExpiry ladder alerts, broken-cert detection and a TLS grade per check.
- Domain expiryRegistry-sourced expiry dates with the 30-to-1-day warning ladder.
- DNS changesDaily snapshots of six record types, alerting only on confirmed changes.
- UptimeChecks from 7 regions; down only when two regions agree, twice.
- Certificate TransparencyDaily CT log sweeps; an alert on any new certificate for your domain.
- DMARC reportsParsed aggregate reports, new-sender alerts and failure-rate warnings.
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