Add node autoflush service and target

Add a systemd service to manage node flush/unflush, useful during
system startup and shutdown to avoid requiring administrator
intervention for this to occur. This is optional and the service is
not enabled by default, and the postinst script informs the
administrator of this.

Also adds a systemd target to collect the two service units together
and provide an easy way to flush+shutdown or startup+unflush the
entire PVC system.

Closes #28

debian/pvc-daemon.install

@@ -1,4 +1,6 @@
 node-daemon/pvcd.py usr/share/pvc
-node-daemon/pvcd.service lib/systemd/system
 node-daemon/pvcd.sample.yaml etc/pvc
 node-daemon/pvcd usr/share/pvc
+node-daemon/pvcd.target lib/systemd/system
+node-daemon/pvcd.service lib/systemd/system
+node-daemon/pvc-flush.service lib/systemd/system

debian/pvc-daemon.postinst

@@ -1,10 +1,17 @@
 #!/bin/sh
 
-# Enable the service
+# Enable the service and target
 systemctl enable /lib/systemd/system/pvcd.service
+systemctl enable /lib/systemd/system/pvcd.target
 
-if systemctl is-active --quiet pvcd.service; then
-    echo "The PVC node daemon has not been restarted; this is up to the administrator."
-else
-    echo "The PVC node daemon has not been started; create a config file at /etc/pvc/pvcd.conf then start it."
+# Inform administrator of the autoflush daemon if it is not enabled
+if ! systemctl is-active --quiet pvc-flush.service; then
+    echo "The PVC autoflush daemon (pvc-flush.service) is not enabled by default; enable it to perform automatic flush/unflush actions on host shutdown/startup."
+fi
+
+# Inform administrator of the service restart/startup not occurring automatically
+if systemctl is-active --quiet pvcd.service; then
+    echo "The PVC node daemon (pvcd.service) has not been restarted; this is up to the administrator."
+else
+    echo "The PVC node daemon (pvcd.service) has not been started; create a config file at /etc/pvc/pvcd.yaml then start it."
 fi

debian/pvc-daemon.prerm

@@ -1,4 +1,6 @@
 #!/bin/sh
 
-# Disable the service
+# Disable the services
+systemctl disable pvc-flush.service
 systemctl disable pvcd.service
+systemctl disable pvcd.target

node-daemon/pvc-flush.service

@@ -0,0 +1,15 @@
+# Parallel Virtual Cluster autoflush daemon
+
+[Unit]
+Description = Parallel Virtual Cluster autoflush daemon
+After = pvcd.service
+
+[Service]
+Type = oneshot
+WorkingDirectory = /usr/share/pvc
+ExecStart = /usr/bin/pvc node unflush
+ExecStop = /usr/bin/pvc node flush
+Restart = never
+
+[Install]
+WantedBy = pvcd.target

node-daemon/pvcd.service

@@ -1,4 +1,5 @@
 # Parallel Virtual Cluster node daemon unit file
+
 [Unit]
 Description = Parallel Virtual Cluster node daemon
 After = network-online.target libvirtd.service zookeeper.service
@@ -12,4 +13,4 @@ ExecStart = /usr/share/pvc/pvcd.py
 Restart = on-failure
 
 [Install]
-WantedBy = multi-user.target
+WantedBy = pvcd.target

node-daemon/pvcd.target

@@ -0,0 +1,7 @@
+# Parallel Virtual Cluster startup target
+
+[Unit]
+Description = Parallel Virtual Cluster target for managing all services collectively
+
+[Install]
+WantedBy = multi-user.target