systemd: specific units for icpu

systemd-icpu/daemon-reload.service

@@ -0,0 +1,24 @@
+[Unit]
+Description=MARS global single-threaded daemon-reloead
+Documentation=https://github.com/schoebel/mars/docu/mars-manual.pdf
+
+## The trick is to "misuse" this service (which exists only once)
+## for inhibiting startup of "systemctl daemon-real" in parallel to
+## itself.
+## In addition, Before= and After= depencencies may be used for
+## runtime exclusion of parallelism from/with other services.
+## This appears to necessary in some places, where races have
+## between daemon-reload and startup of other service have been observed.
+Before=mars-trigger.service
+
+[Service]
+# Important for blocking parallelism with itself
+Type=oneshot
+RemainAfterExit=no
+# Important for avoiding failures: do not send any signals
+KillMode=none
+
+ExecStart=/usr/bin/systemctl daemon-reload
+
+[Install]
+WantedBy=mars.service

systemd-icpu/mars-@escvar{res}-trigger.path

@@ -0,0 +1,17 @@
+[Unit]
+Description=MARS per-resource watcher for /mars/resource-@{res}/systemd-trigger
+Documentation=https://github.com/schoebel/mars/docu/mars-manual.pdf
+Requires=mars-trigger.path
+After=mars-trigger.path
+
+## Markers for the template processor
+# ALWAYS_START
+
+[Path]
+PathExists=/mars/resource-@{res}/systemd-trigger
+PathChanged=/mars/resource-@{res}/systemd-trigger
+PathModified=/mars/resource-@{res}/systemd-trigger
+Unit=mars-@escvar{res}-trigger.service
+
+[Install]
+WantedBy=mars.service

systemd-icpu/mars-@escvar{res}-trigger.service

@@ -0,0 +1,36 @@
+[Unit]
+Description=MARS per-resource trigger from /mars/resource-@{res}/systemd-trigger
+Documentation=https://github.com/schoebel/mars/docu/mars-manual.pdf
+
+## Prohibit parallelism with any daemon-reload
+After=daemon-reload.service
+
+## The per-resource trigger is the _only_ one which is allowed
+## to remotely start / stop any units dealing with resources.
+## Otherwise, races or conflicting start / stop operations might
+## occur, leading to deadlocks / failures / etc.
+##
+## General rule: each *.path watcher can only start its corresponding
+## *-trigger.service at most _once_ in parallel (provided that the actions
+## caused by "marsadm systemd-trigger-extern" are not forking into background).
+## So there is never any parallelism of _any_ unit with exactly _itself_
+## (although _different_ units are allowed to run in parallel to each other,
+## of course).
+
+## Do not start both the global and any of the per-resource triggers
+## in parallel.
+## It could lead to various races between global and per-resource units.
+## In contrast, different per-resource triggers are not mutually exclusive.
+After=mars-trigger.service
+
+[Service]
+# Important for blocking parallelism with itself
+Type=oneshot
+RemainAfterExit=no
+# Important for avoiding failures: do not send any signals
+KillMode=none
+# Important: the resource argument will keep remote triggers disjoint
+ExecStart=/usr/bin/marsadm systemd-trigger-extern @{res}
+
+[Install]
+WantedBy=mars.service

systemd-icpu/mars-trigger.path

@@ -0,0 +1,20 @@
+[Unit]
+Description=MARS global watcher /mars/userspace/systemd-trigger
+Documentation=https://github.com/schoebel/mars/docu/mars-user-manual.pdf
+
+## Global path watcher for calling mars-trigger.service
+
+## Markers for the template processor
+# ALWAYS_START
+
+BindsTo=mars.service
+After=mars.service
+
+[Path]
+PathExists=/mars/userspace/systemd-trigger
+PathChanged=/mars/userspace/systemd-trigger
+PathModified=/mars/userspace/systemd-trigger
+Unit=mars-trigger.service
+
+[Install]
+WantedBy=mars.service

systemd-icpu/mars-trigger.service

@@ -0,0 +1,26 @@
+[Unit]
+Description=MARS global trigger from /mars/userspace/systemd-trigger
+Documentation=https://github.com/schoebel/mars/docu/mars-manual.pdf
+
+## Prohibit parallelism with any daemon-reload
+After=daemon-reload.service
+
+## The global trigger calls "marsadm systemd-trigger-extern" _without_
+## resource argument.
+## The global variant will only generate any new templates, but will not
+## activate/deactivate them (except when they are new).
+## This is necessary for race avoidance with per-resource triggers.
+## Only the per-resource triggers (see mars-@{res}-trigger.service)
+## are allowed to actually start/stop any units dealing with resources.
+
+[Service]
+# Important for blocking parallelism with itself
+Type=oneshot
+RemainAfterExit=no
+# Important for avoiding failures: do not send any signals
+KillMode=none
+# Important: no resource argument must be given here
+ExecStart=/usr/bin/marsadm systemd-trigger-extern
+
+[Install]
+WantedBy=mars.service

systemd-icpu/mars.path

@@ -0,0 +1,13 @@
+[Unit]
+Description=MARS block layer HA (activation by appearance of /mars/uuid)
+Documentation=https://github.com/schoebel/mars/docu/mars-user-manual.pdf
+
+## Markers for the template processor
+# ALWAYS_START
+
+[Path]
+PathExists=/mars/uuid
+Unit=mars.service
+
+[Install]
+WantedBy=mars.service

systemd-icpu/mars.service

@@ -0,0 +1,26 @@
+[Unit]
+Description=MARS block layer HA (kernel module)
+Documentation=https://github.com/schoebel/mars/docu/mars-user-manual.pdf
+
+## Markers for the template processor
+# ALWAYS_START
+
+BindsTo=mars.mount
+After=mars.mount
+RequiresMountsFor=/mars/uuid
+
+Wants=network-online.target
+
+StopWhenUnneeded=false
+IgnoreOnIsolate=true
+
+[Service]
+Type=oneshot
+# Important for avoiding failures: do not send any signals
+KillMode=none
+RemainAfterExit=yes
+ExecStart=/sbin/modprobe mars
+ExecStop=/sbin/rmmod mars
+
+[Install]
+WantedBy=mars.mount

systemd-icpu/modprobe-mars.sh

@@ -0,0 +1,23 @@
+#!/bin/bash
+
+# do no longer start any systemd-controlled resources via nodeagent init
+
+for res in $(
+    marsadm get-systemd-unit all |\
+	grep "^nodeagent" |\
+	awk '{ print $1; }' |\
+	sed 's/nodeagent-//' |\
+	cut -d. -f1 |\
+	sed 's/\\x2d/-/g'
+); do
+  # workaround "nodeagent status --target"
+  nodeagent stop $res || echo ignore the error
+done
+
+modprobe mars
+rc=$?
+
+sleep 3
+marsadm systemd-trigger
+
+exit $rc

systemd-icpu/nodeagent-@escvar{res}.script

@@ -0,0 +1,114 @@
+#!/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