Integration of FLoM with a scheduler, for example Jenkins

Sometimes you want to integrate the flom command with a job scheduler like for example Jenkins.
When the flom command is executed by another program, you can face the below issue:

• the scheduler, for some reason, send a signal (kill command) to flom and all the processes in the same process group
• flom terminates immediately, but the command monitored by flom takes some time to clean up
• the resource locked by the first flom command is now available for another flom command
• a second process accesses the same resource before the completion of the first one

In the above scenario, the second process monitored by flom can corrupt the data that are still updated by the first process.
To avoid this type of issues, flom command can ignore one or more signals while it is waiting for the termination of the monitored command: this behaviour avoids the premature termination of the first flom command.

The below example shows the standard behaviour of the flom command:

tiian@ubuntu1004:~$ flom -- sleep 1d &
[1] 1228
tiian@ubuntu1004:~$ ps j -A | grep 'flom\|sleep\|PGID' | grep -v grep
 PPID   PID  PGID   SID TTY      TPGID STAT   UID   TIME COMMAND
 1175  1228  1228  1175 pts/0     1234 S     1000   0:00 flom -- sleep 1d
    1  1231  1230  1230 ?           -1 Sl    1000   0:00 flom -- sleep 1d
 1228  1233  1228  1175 pts/0     1234 S     1000   0:00 sleep 1d
tiian@ubuntu1004:~$ kill -SIGTERM -- -1228
tiian@ubuntu1004:~$ 
[1]+  Terminated              flom -- sleep 1d

flom command has been Terminated because it received the TERM signal.
In the below example, the --ignore-signal option is used:

tiian@ubuntu1004:~$ flom --ignore-signal=SIGTERM -- sleep 1d &
[1] 1246
tiian@ubuntu1004:~$ ps j -A | grep 'flom\|sleep\|PGID' | grep -v grep
 PPID   PID  PGID   SID TTY      TPGID STAT   UID   TIME COMMAND
 1175  1246  1246  1175 pts/0     1253 S     1000   0:00 flom --ignore-signal=SIGTERM -- sleep 1d
    1  1249  1248  1248 ?           -1 Sl    1000   0:00 flom --ignore-signal=SIGTERM -- sleep 1d
 1246  1252  1246  1175 pts/0     1253 S     1000   0:00 sleep 1d
tiian@ubuntu1004:~$ kill -SIGTERM -- -1246
tiian@ubuntu1004:~$ 
[1]+  Done                    flom --ignore-signal=SIGTERM -- sleep 1d

flom command has completed its execution because it ignored the TERM signal: this guarantees that flom command completes after the monitored process (in this example “sleep 1d”) and that the locked resource is released at the right time.

Integration of FLoM and Jenkins

As explained here:

When a Jenkins job is cancelled, it sends TERM to the process group of the process it spawns, and immediately disconnects, reporting “Finished: ABORTED,” regardless of the state of the job.
This causes the spawned process and all its subprocesses (unless they are spawned in new process groups) to receive TERM.

To obtain proper integration between FLoM and Jenkins, you should use the --ignore-signal command line option or the equivalent Monitor/IgnoredSignals configuration key.