#!/bin/bash
# TST Nov 2020
# Tried to make any operations as idempotent as possible.
#
# At the moment, idempotent startup fails with a message like
# "Failed to start transient scope unit: Unit infongws-test06.scope already exists."
# Theoretically, I could treat the existence and/or the runtime status of said intermediate scope unit
# as an indicator for directly reporting success.
# However, I am unsure what could be the consequences when the main LXC container fails but the
# scope unit persists for whatever reason. Possibly, it could remain in a state where it could be
# neither startable nor stoppable.
# Leaving this kind of behaviour untouched for now.
# Currently, it doesn't seem to produce harm, but rather looks like a false-positive error message.
# In case somebody would be confused by this error message, some other parts of nodeagent
# (which is outside of my scope) should be fixed, in preference to trying to workaround it here.

# Markers for the template processor
# DEFAULT_START
# DEFAULT_STOP
# KEEP_RUNNING
# ALSO=mars-@escvar{res}-trigger.path
# ALSO=mars-@escvar{res}-trigger.service

op="$1"

# Ensure that pure trigger does not change anything.

systemd_want_path="/mars/resource-@{res}/systemd-want"
systemd_copy_path="/mars/resource-@{res}/userspace/systemd-want"

systemd_want="$(stat --printf="%Y\n" $systemd_want_path)"
systemd_copy="$(stat --printf="%Y\n" $systemd_copy_path)"

echo "Old timestamp: '$systemd_copy'"
echo "New timestamp: '$systemd_want'"

if (( systemd_copy && systemd_want == systemd_copy )); then
    echo "Unmodified timestamp $systemd_want_path $systemd_want"
    exit 0
fi

function report_success
{
    rsync -av $systemd_want_path $systemd_copy_path
}

mars_dev=/dev/mars/@{res}

case "$op" in
status)
    /usr/sbin/nodeagent status @{res}
    ;;

start)
    # Assumption: start and vmstart seem to be idempotent already
    if ! [[ -b $mars_dev ]]; then
	echo "ignoring, $mars_dev is not present" 
	exit 0
    fi
    if mountpoint /vol/@{res}; then
	/usr/sbin/nodeagent vmstart @{res}
    else
	/usr/sbin/nodeagent start @{res}
    fi
    rc=$?
    if (( !rc )); then
	report_success
    fi
    exit $rc
    ;;

stop)
    # The following does not work: if ! mountpoint /vol/@{res}; then ...; fi
    # In the presence of bind mounts, the main mountpoint may vanish,
    # but sub-bindmounts may persist, leaving /dev/mars/@{res} opened,
    # and consequently hindering a planned handover.
    # This is a Linux kernel feature, not a bug.
    # Thus we need to mistrust the main mountpoint /vol/@{res} .
    # For safety, check the presence of /dev/mars/@{res} instead.
    if ! [[ -b "/dev/mars/@{res}" ]]; then
	# Idempotence
	exit 0
    fi
    if ! [[ -b $mars_dev ]]; then
	echo "ignoring, $mars_dev is not present" 
	exit 0
    fi
    # Additionally, check whether the mars device is opened.
    if (( !$(marsadm view-device-opened @{res}) )); then
	# Idempotence
	exit 0
    fi

    /usr/sbin/nodeagent stop @{res}
    rc=$?

    # for safety
    if (( !rc )); then
	sleep 1
	if mountpoint /vol/@{res}; then
	    umount /vol/@{res}
	fi
	report_success
    fi
    exit $rc
    ;;

*)
    # Ignore all other ops, like enable / disable / etc
    echo "Ignore '$op'"
    exit 0
esac

exit 0