JS7 JobScheduler

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Introduction

  • Traps are used in shell jobs for the situation that the job should not be aborted immediately, but should be terminated having performed some cleanup operations, for example
    • to remove temporary files created by the job,
    • to disconnect from a database.
  • Traps are available for the Unix Shell, not for Windows.

Example:

Download: jduCleanupTrap.json

The implementation of a cleanup trap in a JS7 job script can look like this:

Example for a cleanup trap
#!/bin/bash

# define trap to forward receipt of the SIGTERM signal to a child process
trap 'kill -TERM $CHILD_PID' SIGTERM

# create shell script for background execution
TRAP_SCRIPT=$HOME/test-trap.sh
cat << 'EOF' > $TRAP_SCRIPT
#!/bin/bash

exitOnSigterm()
{
    exec &> /dev/tty
    local signal="$1"
    echo "($(date +%T.%3N)) $(basename $0): trap received signal \"$signal\", cleaning up..."
    if [[ "$CHILD_PID" != "" && -d /proc/$CHILD_PID ]]; then
        procInfo="$(ps -ef | /bin/grep -e PPID -e $CHILD_PID | /bin/grep -v /bin/grep)"
        echo -e "($(date +%T.%3N)) $(basename $0): trap found child process $CHILD_PID:\n$procInfo\n"
        cleanupTemporaryFiles "trap" "$CHILD_PID"
        # traps are not required to kill child processes: the Agent kills child processes
        # /bin/kill -s TERM "$CHILD_PID"
    fi
}

cleanupTemporaryFiles()
{
    exec &> /dev/tty
    tempFile="/tmp/temporary_file.$2"
    if [ -f "$tempFile" ]; then
        rm -f $tempFile
        echo "($(date +%T.%3N)) $(basename $0): cleanup performed by $1 for temporary file: $tempFile"
    fi
}

# add trap to call function on receipt of SIGTERM signal
trap 'exitOnSigterm "SIGTERM"' SIGTERM

# run sleep command in background and create a temporary file for later removal
sleep 120 &
CHILD_PID="$!"
touch /tmp/temporary_file.$CHILD_PID

# wait for completion of shell script or for execution of trap
wait "$CHILD_PID"

# cleanup is performed by trap or by shell script
cleanupTemporaryFiles "shell script" "$CHILD_PID"

exit
EOF

# run shell script in background
chmod +x $TRAP_SCRIPT
$TRAP_SCRIPT &

# wait for completion of shell script or for execution of trap
CHILD_PID="$!"
echo "waiting for completion of child process with pid $CHILD_PID"
wait "$CHILD_PID"

# echo "one more sleep"
# sleep 120

exit $?


Explanation:

  • Line x - x: the 



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