DryCron is perfectly suited for monitoring cron jobs. All you have to do is update your cron job command to send a HTTP request to DryCron after a job completes.
Let's look at an example:
$ crontab -l # m h dom mon dow command 8 6 * * * /home/user/backup.sh
The above job runs
/home/user/backup.sh every day at 6:08. The backup
script is presumably a headless, background process. Even if it works
correctly currently, it can start silently failing in future, without
You can set up DryCron to notify you whenever the backup script does not run on time or does not complete successfully. Here are the steps to do that.
If you have not already, sign up for a free DryCron account.
In your DryCron account, add a new check.
Give the check a meaningful name. Good naming will become increasingly important as you add more checks to your account.
Edit the check's schedule:
8 6 * * *in the cron expression field
Take note of your check's unique ping URL.
Finally, edit your cron job definition and append a curl or wget call after the command:
$ crontab -e # m h dom mon dow command 8 6 * * * /home/user/backup.sh && curl -fsS --retry 5 -o /dev/null https://cron.drycat.fr/ping/your-uuid-here
Now, each time your cron job runs, it will send a HTTP request to the ping URL. Since DryCron knows the schedule of your cron job, it can calculate the dates and times when the job should run. As soon as your cron job doesn't report at an expected time, DryCron will send you a notification.
This monitoring technique takes care of various failure scenarios that could potentially go unnoticed otherwise:
The extra options in the above example tells curl to retry failed HTTP requests, and to silence output unless there is an error. Feel free to adjust the curl options to suit your needs.
/home/user/backup.shexits with an exit code 0.
If your cron job consistently pings DryCron an hour early or an hour late, the likely cause is a timezone mismatch: your machine may be using a different timezone than what is configured on DryCron.
On modern GNU/Linux systems, you can look up the time zone using the
timedatectl status command and looking for "Time zone" in its output:
$ timedatectl status Local time: C 2020-01-23 12:35:50 EET Universal time: C 2020-01-23 10:35:50 UTC RTC time: C 2020-01-23 10:35:50 Time zone: Europe/Riga (EET, +0200) System clock synchronized: yes NTP service: active RTC in local TZ: no
On a systemd-based system, you can use the
journalctl utility to see system logs,
including logs from the cron daemon.
To see live logs:
To see logs from e.g. the last hour, and only from the cron daemon:
journalctl --since "1 hour ago" -t CRON