Cronjobs with DFOS

Certain steps of the daily workflow can be called automatically day by day and hence qualify for the unix cronjob functionality. DFOS offers the tool dfosCron as a wrapper script to launch certain dfos tools as cronjob. Details about the tool are described here.

As a reference, the current dfos cronjob file operational for FLAMES/GIRAFFE is available here.

Here we describe how cronjobs (not just dfosCron but in principle any kind of job) are installed and managed under linux/unix.

Installation of cronjobs

Install a dfos cronjob:

• call 'crontab -e' which opens you an editor session of the cronjob file (there is no other access to that file!)
• enter the following as a new line:
  
  09 * * * * export TZ=Europe/Berlin; $HOME/bin/dfosCron -t ngasMonitor
  
  and exit.
• this will call the ngasMonitor every full hour; if you omit the TZ command, cronjobs will run under UT instead; you have to give the explicit path since cronjobs don't read .qcrc or .dfosrc.
• All dfosCron cronjobs will log into $DFO_MON_DIR/CRON_LOGS which will be created for you. There will be log files CRON_<date>.log where <date> is the date of execution.

Monitor and test cronjobs

Type 'crontab -l' to see the active cronjobs.

dfosCron is written such that it writes any regular output (log information) into the CRON files (see above). Any irregular output (error messages) would go to stdout which does not exist for cronjobs, however. That output is instead sent as an email to the user. While this is useful in the rare case of a failure, it should not become routine behaviour of the tool. Hence the user may want to test the cronjob before it is made operational.

There are two essential test:

• test the shell script functionality
• test the cronjob functionality

The script functionality itself is best checked by calling the tool from the command line, e.g.

dfosCron -t ngasMonitor

The cronjob functionality is best tested by a test run. Call crontab -e with a time close in the future, and check its results (in the log file and maybe in the email queue). The critical part is that cronjobs do not source the initialization files like .login, .qcrc etc. which are sourced at any user login. The tool dfosCron explicitly sources .qcrc and .dfosrc, hoping that all environment variables, as well as the PATH and DISPLAY information is properly set afterwards. Since there seem to be slight differences in the way DFO account are setup, this test is critical.