Crab is a dashboard system for monitoring cron jobs, or other scheduled tasks. The Crab server receives messages when tasks start or finish, and displays the status of all of the tasks via a web interface. It can also send notifications by email, for example to warn if a task fails, is missed or does not complete within its time-out period.

Tasks communicate with the Crab server by JSON messages sent by HTTP PUT requests. The finish message includes the status of the job, and any output from it. Further messages are used to import and export the client’s crontab, which the server uses to determine the intended schedule.

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