Kill child processes of shell jobs terminating after SIGTERM

Current Situation

• The JS7 - FAQ - Does JS7 reliably kill running jobs article explains the steps performed by the Agent to terminate job processes.
• For job processes that are terminated by a SIGTERM signal any child processes will continue to run. This is the built-in behavior of Unix shells.
• Users who wish to terminate child processes can add to their job script:

  trap "wait && exit 143" TERM
  

  The trap will prevent a job process from terminating until all child processes are terminated. If the Grace Timeout is exceeded then the Agent executes the kill_task.sh | .cmd script to kill the job process and any child processes.
  Specification of the exit command in a trap is required, so is the return value of the exit command that can be used to signal abnormal termination of a job in the workflow.

Desired Behavior for use with cancel/kill and suspend/kill operations

• Users should not be forced to add a trap to their job scripts as killing of child processes is considered the default behavior.
• When killing a job process, the Agent performs the following steps:
  • collect chld process PIDs of job process
  • send SIGTERM to job process
  • wait for one of the following events, whichever arrives first:
    • wait for Grace Timeout configured with the job
    • wait for stdout/stderr to be released by the job process
  • send SIGKILL to job process if Grace Timeout is exceeded
  • send SIGTERM to child processes for which PIDs have previously been collected; send SIGTERM recursively to child processes of a child process.
  • wait for 50% of the duration of the Grace Timeout or for 1s whichever is the higher value.
  • send SIGKILL signal to remaining child processes recursively.
• The Agent drops use of the kill_task.sh | .cmd scripts. Instead, Java is used for process management.

Desired Behavior in the event of Agent crash

• If the Agent is killed, then the watchdog.sh | .cmd script will terminate remaining child processes.
• The Agent keeps track of the PIDs of job processes that have been started. The information is available from a temporary file.
• The Agent offers a Java class that is used by the watchdog.sh | .cmd script. The Java class will use the information about the PIDs of any started processes and will apply the following sequence of actions:

• • for each job process identify child processes recursively,
  • send SIGTERM to all job processes and child processes,
  • wait for 3s,
  • send SIGKILL to all remaining job processes and child processes.