Restarting Edgent if the JVM crashes

The startapp.sh script can be setup to run as a cron job every minute in order to monitor a JVM running an Edgent application and restart Edgent if the JVM crashes. The script checks whether the pid of the JVM indicates a process which is still running. If the pid is not there, it executes the command to start the application in the first place.

A crontab entry file contains information which cron uses to schedule the job. The sample startapp.cron file is configured to execute the org.apache.edgent.samples.topology.TerminateAfterNTuples sample application, which terminates the JVM after processing a preset number of tuples.

See README.md in the samples root directory for information on building the samples.

To setup cron to restart the sample application every minute:

1. Create the startapp.cron file from the startapp.cron.template file:

   $ ./mkcrontab

2. Install startapp.cron:

   $ crontab ./startapp.cron

   Note: if you wish to have your ~/.profile executed you must explicitly do so in the crontab entry or in a script called by the entry.

3. To see the set crontab entries:

   $ crontab -l

4. To remove the current crontab entries:

   $ crontab -r