systemd: Fix -Dpid arg passing to systemd usage service (#3210)

* systemd: Fix -Dpid arg passing to systemd usage service

This fixes regression introduced by refactoring PR #3163 where `-Dpid`
was incorrectly passed string `$$` instead of parent PID integer.

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>

* fix systemd limitation, exec using /bin/sh instead and wrap in ${} syntax

https://www.freedesktop.org/software/systemd/man/systemd.service.html#Command%20lines

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>

* usage: don't hide exception from Gabriel's https://github.com/apache/cloudstack/pull/3207/files#diff-062fcf5ae32de59dfd6cd4f780e1d7cd

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>

Author: yadvr

packaging/systemd/cloudstack-usage.default

@@ -15,8 +15,11 @@
 # specific language governing permissions and limitations
 # under the License.
 
-JAVA_OPTS="-Dpid=$$ -Xms256m -Xmx2048m"
+JAVA_OPTS="-Xms256m -Xmx2048m"
 
 CLASSPATH="/usr/share/cloudstack-usage/*:/usr/share/cloudstack-usage/lib/*:/usr/share/cloudstack-mysql-ha/lib/*:/etc/cloudstack/usage:/usr/share/java/mysql-connector-java.jar"
 
 JAVA_CLASS=com.cloud.usage.UsageServer
+
+# Enable the following to enable remote socket based debugging:
+#JAVA_DEBUG="-agentlib:jdwp=transport=dt_socket,address=8001,server=y,suspend=n"

packaging/systemd/cloudstack-usage.service

@@ -24,7 +24,8 @@ After=network.target network-online.target
 [Service]
 Type=simple
 EnvironmentFile=/etc/default/cloudstack-usage
-ExecStart=/usr/bin/java $JAVA_OPTS -cp $CLASSPATH $JAVA_CLASS
+Environment=JAVA_PID=$$
+ExecStart=/bin/sh -ec '/usr/bin/java -Dpid=${JAVA_PID} $JAVA_OPTS $JAVA_DEBUG -cp $CLASSPATH $JAVA_CLASS'
 Restart=always
 RestartSec=10s
 

usage/src/com/cloud/usage/UsageServer.java

@@ -51,11 +51,7 @@ public void start() {
 
         appContext = new ClassPathXmlApplicationContext("usageApplicationContext.xml");
 
-        try {
-            ComponentContext.initComponentsLifeCycle();
-        } catch (Exception e) {
-            e.printStackTrace();
-        }
+        ComponentContext.initComponentsLifeCycle();
 
         mgr = appContext.getBean(UsageManager.class);