Silent Cron Job Failure Left Production Monitor Dead for Five Days Undetected

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A developer running WhatsApp automation for businesses discovered that a watchdog cron job, designed to alert when messaging sessions dropped silently, had never executed once despite appearing correctly configured. The crontab stored the job as expected, and a separate log file showed recent successful entries — but those entries turned out to be from manual test runs on installation day, not scheduled executions. The root cause was a sudo permission or output-redirect issue causing the cron job to emit errors on stderr every ten minutes, which cron attempted to email but discarded silently due to no mail server being installed. A key diagnostic clue was the syslog message 'No MTA installed, discarding output' appearing alongside every CMD entry, indicating the job was running but failing to capture output as intended. The incident highlights that a populated log file and a visible crontab entry do not confirm a scheduled job is actually executing successfully.

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